Baleen Whales - The Oceans' Gentle Giants

Author: Shena Cannon

Baleen Whales

While being the largest animals on earth, yet consume some of the smallest animals. There are 15 species of baleen whale, they are generally larger than toothed whales except for the sperm whale which is very big and has teeth. Many baleen whales migrate annually, traveling long distances between cold water feeding areas and warm water breeding areas. They can grow up to 90 feet, yet krill, small fish, and plankton sustain them. These creatures are the baleen order of whales, they have no teeth. Instead, have baleen which is a filter-feeding system that allows them to trap their favorite prey. Baleen is made out of keratin, it is the same protein that our hair and fingernails are made from. Baleen whales have been subjected to numerous anthropogenic disturbances, including whaling, ship strikes, and pollutants. These anthropogenic disturbances can cause an extreme stress response in mammals. According to Nature Communications, the physiological response to a stressor, defined as the disruption of an organism’s internal environment, or homeostasis, can lead to system-wide health effects from the scale of an individual to the population (3).

Stress Response

So what can cause baleen whales to be stressed? Cortisol is a stress hormone that is stimulated through the hypothalamic-pituitary-adrenal, this causes a stress response to activate in mammals and positively correlates with the severity of the stressor. Earplugs from baleen whales that consist of lipid and keratin-based semiannual bands of alternating dark and light laminae (growth layer groups) formed over the life span of the animal. By using the earplugs from baleen whales it determines the association of past and/or present anthropogenic stressors. According to Nature Communications, a positive relationship between activities associated with commercial whaling harvests and baseline-corrected cortisol from baleen whale earplugs spanning the 20th century (3).

Whale Hunting

For thousands of years, whaling has caused a lifetime of stress for baleen whales in the Northern Hemisphere. They were hunted and killed for different things including soap, jewelry, transmission oil, and margarine to corset material. With it being no controls on hunting, all these species eventually became depleted. Until 1982 when the International Whaling Commission “instituted a moratorium on commercial whaling and although some whale populations have since recovered to near their pre-whaling abundance, others remain compromise” (1). Most countries have stopped whaling activity.

Future of Baleen Whales

Whales are extremely important in the health of our environment and play an important role to help grow economies that rely on whale watching and other activities through tourism. Whales help the environment and the ocean’s ecosystems, regulating the flow of food to maintain a stable food chain and ensure certain animal species do not overpopulate the ocean. Even whale poop plays a large role in the environment by stabilizing the offset of carbon in the atmosphere and provides a healthier environment for both land and aquatic life forms. Whale watching has become a huge tourism activity; to get a glance at these majestic creatures in their natural habitat people have been spending billions of dollars. The growing interest in whale watching is an extremely important component for economies that want to increase their global presence and attract the interest of other countries. To conclude, whales not only play a vital role in the marine ecosystem by providing at least half of the oxygen we breathe, combat climate change, and sustain fish stocks but by following the Be Whale Wise Guidelines and giving whales the space they need and how to protect our oceans from the various forms of pollution can help these animals flourish once again.


(1) Brüniche-Olsen, A. et al. The inference of gray whale (Eschrichtius robustus) historical population attributes from whole-genome sequences. BMC Evolutionary Biology 18, (2018).

(2) Lapidese, J. Baleen Whales – The Gentle Giants of the Ocean. Oceanwide Expeditions (2018). Available at: https://oceanwide-expeditions.com/blog/baleen-whales-the-gentle-giants-of-the-ocean. (Accessed: 12th May 2021).

(3) Trumble, S. J. et al. Baleen whale cortisol levels reveal a physiological response to 20th-century whaling. Nature Communications 9, (2018).

Photo Credits

File:Humpback stellwagen edit.jpg by Whit Welles is licensed under GNU Free Documentation License and CC BY 3.0.


PIKA POWER! The tiny mammal that packs a punch against cold

Author: Alexandra Baldacci

Check the Pokedex!

Pika! Pika! You’ve probably heard this adorable call before, if not take a look at an anime called Pokemon. Specifically, a little cutie named Pikachu! Pikachu is a mouse Pokemon that can generate powerful charges of electricity and is pretty speedy. But not everyone knows that we have our own version of Pikachu living in the mountains in America! This small rodent-like mammal is called the American pika. Just like how Pikachu generates electricity, the American pika has an extremely fast metabolism. Let’s get to know our version of Pikachu!


Our Real Life Pikachu

The American pika, or Ochotona princeps, is a small rodent-like mammal. They have short, stout little bodies that are brown, black, or tan in coloration. They are about 18-20 centimeters in length, think the width of a piece of paper, with large ears and no visible tails. They live from six to seven years, but sadly many will die from the ages three to four. Their range includes Montana, Wyoming, Colorado, Idaho, Washington, Oregon, California, Nevada, Utah, New Mexico, and western Canada. They prefer to live in alpine ecosystems at the bottom of mountains where there are plenty of rocks to make dens in.

Their diet consists of grasses, weeds, tall wildflowers, and sometimes yellow-bellied marmot scat. They collect vegetation throughout the year and make hay piles by their den for the winter. They leave the greens outside to dry out in the sun to prevent the collected food from rotting. It even turns out that pikas have specific places that they like to make their hay piles!

Their mating season is in early to mid-spring, and they can breed again in the summer of the same year. The mother will carry two to six babies for a month, and once they are born, they rely on her for another month before heading out. After the babies leave the den, it only takes about three months for them to reach their adult size. Pikas have thick fur that helps keep them warm during the winter, and during the summer, they go through a molting period where their coat gets thinned. It’s like how huskies will get rid of their winter coat in giant balls of fluff when they’re brushed. Despite their ability to change the thickness of their fur, the pika is a very climate-sensitive animal. Even in the summer with their thinner coat, they can overheat if they spend too much time in the hot sun. Because they can overheat so easily they’ve become super important to scientists! Scientists have started looking at the pikas to determine how severely climate change is affecting wildlife. There is hope that they can be used as an indicator species for the impending ramifications of climate change in the future.


The Pika’s Special Ability

The main way that O. princeps has been impacted by climate change is by thermal physiological stress. Pikas need cool microclimates because they can get really hot because they metabolize food so quickly and they retain that heat. Because they possess these traits and thick coats, they can survive in the harsh alpine winter without entering torpor or hibernation. Hibernation you probably know from bears, but maybe you haven’t heard of torpor before. That’s okay! Because I can help with that. Torpor is a lot like hibernation where it’s a survival tactic used to conserve energy, but torpor is only entered in short periods of time (usually just a night) and it’s not as deep of a sleep as hibernation. Torpor is usually triggered by a limited food supply or the ambient temperature outside. Another reason why pikas can survive these cool microclimates is that their resting body temperature is only a few degrees below its lethal threshold. They can maintain this body temperature by actually slowing down their metabolism.

A study done in 1973 [3] pointed to evidence of chronic thermal stress occurring in Ochotona princeps. If an animal is under constant stress, it could undergo severe physiological consequences like suppressed immune response, severe protein loss, fat deposition, and hypertension, and behavioral changes like decreased cognitive function, inhibition of reproductive behavior, and depression. (Waterhouse, Matthew D., et al) That’s right, pikas can get depressed too. Pika populations have been on the decline, and scientists believe it has to do with physiological stress caused by climate change.

Another study done by Waterhouse, Matthew D., et al. [4] measured a corticosteroid hormone called glucocorticoids (GC) in both hair and fecal samples. Lots of scary large scientific words there, but don’t worry I’m going to break them down a bit more. GC levels are used to assess animals' overall health and fitness because when this hormone is released, it means that the animal is under stress. So this hormone triggers behavioral changes to avoid or remedy the stressor. Throughout the rest of this post, we are going to call the hormone GC, just to make it a bit easier. One study observed the relationship between GC levels in hair samples, the air temperature, sex, and the size of the pikas. The most important parts of this blog are the GC levels and the hair samples. Their results claimed that there was evidence of cold stress in the American pika. Now cold stress is when the pika's internal temperature declines to dangerous levels and causes the release of stress hormones. We know that they rest a few degrees below overheating but that doesn’t mean they can’t potentially freeze to death too. They found that smaller pikas were more prone to higher GC levels, which could be due to the higher metabolic rate of smaller pikas. The last thing they found that female pikas most likely exhibited higher chronic GC levels because of the physical stress of taking care of the young. With all of that being said they did acknowledge that the higher GC levels might just be because having a high metabolic rate in a constantly cold environment can be incredibly stressful.

Another GC levels study was done by Jennifer L. Wilkening et al. using fecal samples concerning micro-climates and rock glaciers and associated rock-ice features. This study found that pikas are less stressed in favorable microclimates that are created by the presence of ice. The ice allows for cooler micro-climates which resulted in lower GC levels in the fecal samples collected. Not only that, but they observed that the habitat that was created with the presence of rock-ice features was an ideal place for pikas to live. Rock-ice features created a more lush environment with wetlands that allowed for better diversity, quality, and quantity of vegetation. Since pikas are generalist herbivores (they’re not picky about what they eat), they will eat the most abundant vegetation. The ice also facilitated a cooler micro-climate which was correlated with lower stress levels. They acknowledged that GC levels could be influenced by diet. The evidence of the habitats being more diverse in vegetation had lower GC levels. It lends the question if that is another factor in GC production in climate-sensitive animals.


The Future of the Pika

In these mentioned studies and more, they observe GC levels in hair, fecal, and other samples. However, they fail to take other factors that are stress-inducing into account. One is the pika's social system; while pikas live in communities, they are highly territorial. In a behavioral study [2] by Harold E. Broadbooks, he notes how they maintain their territory boundaries by frequently calling and chasing neighbors a few times a day. Immediately that can relate to the article about GC levels in fecal samples. They mentioned that there could be immigration from the less ideal habitats (non-rock ice) to the more pika suitable habitats (with rock ice). This increases the competition for space along the already small niche area. The behaviors of O. princeps have been under study for over 30 years now. Behavioral changes could occur because of the increase of GC, and they could also help point to a perpetrator. Tracking the behavioral changes in tandem with the research done on GC would give a more specific indication of what climate change is doing to the pika and how it will handle the coming changes in their habitat. Through these next steps in research, we can help save our real-life Pikachu!


Key Words

glucocorticoids (GC) ~ corticosteroid hormone

basal metabolic rate ~ the rate at which the body uses energy while at rest to their vital working

torpor ~  a survival tactic used to conserve energy, but is only entered in short periods of time (usually just a night) and it’s not as deep of a sleep as hibernation

cold stress ~ when the pika's internal temperature declines to dangerous levels and causes the release of stress hormones



“Pika running on the snow” by Eivor Kuchta is a royalty-free stock photo downloaded under the shutter stock standard license. To view the terms, https://www.shutterstock.com/license

“American Pika in rocky habitat. A cool weather, high elevation species, Pika populations will suffer from global warming; alpine and mountain wildlife” by Tom Reichner is a royalty-free stock photo downloaded under the shutter stock standard license. To view the terms, https://www.shutterstock.com/license

The photo of Pikachu is from Wikipedia, Fair Use, https://en.wikipedia.org/wiki/Pikachu


Literature Cited

  1. “American Pika.” National Wildlife Federation, www.nwf.org/Educational-Resources/Wildlife-Guide/Mammals/American-Pika#:~:text=American%20pikas%20are%20believed%20to,west%20of%20the%20Rocky%20Mountains.
  2. H. E. Broadbooks, Ecology and Distribution of the Pikas of Washington and Alaska. American Midland Naturalist 73, 299 (1965)
  3. R. A. MacArthur, L. C. Wang, Physiology of Thermoregulation in the Pika, Ochotona Princeps. Canadian Journal of Zoology, 51, 11–16 (1973)
  4. M. D. Waterhouse, B. Sjodin, C. Ray, L. Erb, J. Wilkening, M. A. Russello, Individual-Based Analysis of Hair Corticosterone Reveals Factors Influencing Chronic Stress in the American Pika. Ecology and Evolution, 7, 4099–4108 (2017)
  5. J. L. Wilkening, C. Ray, J. Varner, Relating Sub-Surface Ice Features to Physiological Stress in a Climate Sensitive Mammal, the American Pika (Ochotona Princeps). PLOS ONE, 10, (2015)

If We Can Hear it, so Can Whales: How Much Noise is too Much Noise?

Author: Elizabeth Norton

Key words: beluga whale, hearing, noise pollution, communication

We all know and love the beluga whale for its unique white color and its interesting bulbous head, but what you may not know is how much our actions are hurting this distinctive species. The beluga whale, or scientifically known as Delphinapterus leucas, is a type of toothed whale that lives in icy cold Arctic waters. Beluga whales are an intelligent and very social species that rely on echolocation to communicate with one another. This social species is often seen vocalizing with other members of their pods and swim with one another. Not only are beluga whales very intelligent marine mammals that use a wide variety of communication levels, they are one of the most vocal cetaceans out there. The pods of beluga whales in the hundreds to thousands of whales, heavily relying and vocalizing with one another. They are also seen playing with things like wood, plants, or bubbles to entertain themselves. This communication is disrupted greatly due to extensive noise pollution from ships in their environment.

What’s happening to the whales?

Beluga whales have a very sensitive and large range hearing system that is used for navigation, foraging, and communication. This sensitive hearing system is easily disrupted by anthropogenic noise pollution from shipping vessels that often overlap the environment of beluga whale habitats. The high-level noise of these ships creates a very strong negative reaction, causing the whales to adjust and protect their hearing in order to counteract the noise. Noise pollution can make it hard for this species to function properly because of their reliance on acoustic cues to navigate and communicate with other belugas (1). This article goes more in depth on beluga hearing adjustment to loud anthropogenic noise.

Even though these loud ships force these whales to need to adjust their hearing to protect themselves, they are able to go back to normal hearing levels. After a long period of high-level noise, belugas can return to normal hearing levels over a small period of time.

These whales are very social and rely heavily on communication with each other through echolocation. Noise pollution plays a large role in disrupting the hearing and communication of beluga whales and can even have irreversible effects. Human disturbances like noise pollution from shipping vessels can cause high-level noises that is too loud for these whales. This noise can cause both temporary and permanent damage to the hearing of these whales which can affect how these whales echolocate with one another. More information on noise pollution on hearing of beluga whales can be found here (2).

Cook Inlet Whales

Not all anthropogenic noise in the ocean permanently damages the hearing of beluga whales, but it can mask their communication with others. Cook Inlet beluga whales are especially vulnerable to their communication being masked. These whales live in a critical habitat where they need to be protected, as this population of whales is marked as endangered by the National Marine Fisheries Service (NMFS) (2). The species that live in critical habitats need extensive protection from threats in order to prevent them from going extinct. One threat to this whale population is commercial ship noise masking their communication. Their communication and echolocation range can be reduced up to 85% when ship noise is at its peak. This range of communication masking can potentially expand to a large portion of their critical habitat. This disturbance can have huge negative impacts on this population as a whole, making it so they can’t properly communicate with each other. This puts the population in danger and could increase the risk of death and further pushing them towards extinction. (5). More information on the communication masking on Cook Inlet belugas can be found here.  

There needs to be action done to protect critical habitats of species around the world. Humans have been a large threat to beluga whales through hunting to near extinction and now through noise pollution.

Is there hope?

It may seem grim for whales nowadays with how much time humans spend out at sea and invade their environment, but there’s hope. Here’s some information from the National Park Service on managing underwater noise pollution. One of the main ways we can help whales from noise pollution is to reduce ship speed, how many there are out at sea, or adjusting ship schedule arrival times. Slowing the speed of ships may seem like it’s doing more harm than good with longer exposure in the environments of whales, but slower ship speed has a lower sound exposure level (CSEL) (3). Slower ship speed makes it much more quiet for the whales, so that they can communicate efficiently without their calls being masked by noise and to reduce damage done to their hearing. Having a system where ship arrival time is synchronized creates a period of increased quiet time for the whales to communicate with ease. There may some other lower level noises from other types of ships but is still greatly reduced from larger ships (3). I hope this information helps provide some insight to how much our actions can affect the world around us, even in the smallest of things. We should be more attentive to the things we do and make the active choice to try and protect out planet and life within it.


Image Credits

By Steve Snodgrass - Flickr:Beluga, CC BY 2.0, https://commons.wikimedia.org/w/index.php?curid=10006016

By Wmeinhart - Foto wurde mit einem Panoramaprogramm aus drei Fotos zusammengesetzt, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=124261



  1. Castellote, M., Thayre, B., Mahoney, M., Mondragon, J., Lammers, M. O., & Small, R. J. (2018). Anthropogenic Noise and the Endangered Cook Inlet Beluga Whale, Delphinapterus leucas: Acoustic Considerations for Management. Marine Fisheries Review, 80(3), 63–88. https://doi.org/10.7755/MFR.80.3.3
  1. Cook Inlet Beluga Whale. (n.d.). Marine Mammal Commission. Retrieved May 14, 2021, from https://www.mmc.gov/priority-topics/species-of-concern/cook-inlet-beluga-whale/
  1. Managing Underwater Noise Pollution (U.S. National Park Service). (n.d.). Retrieved May 14, 2021, from https://www.nps.gov/articles/canyouhearmenow.htm
  1. Nachtigall, P. E., Supin, A. Y., Estaban, J.-A., & Pacini, A. F. (2016). Learning and extinction of conditioned hearing sensation change in the beluga whale (Delphinapterus leucas). Journal of Comparative Physiology A, 202(2), 105–113. https://doi.org/10.1007/s00359-015-1056-x
  1. Popov, V. V., Supin, A. Y., Rozhnov, V. V., Nechaev, D. I., Sysuyeva, E. V., Klishin, V. O., Pletenko, M. G., & Tarakanov, M. B. (2013). Hearing threshold shifts and recovery after noise exposure in beluga whales, Delphinapterus leucas. Journal of Experimental Biology, 216(9), 1587–1596. https://doi.org/10.1242/jeb.078345

Are We Clogging the Ears of Humpback Whales?

Author: Madison Jacobs-Morris

Have you ever wondered how a huge animal that lives in such a vast habitat could be on the endangered species list? Well, humpback whales have a gruesome history and are still reaping the effects today. Hunters in the 20th century killed between 20,000 and 40,000 humpbacks during the whaling era (1). Anthropogenic, or human-caused, disturbances are inflicting harm to many species across the globe. Historic whaling increased stress levels greatly, and even nearly 50 years after the Marine Mammal Protection Act, stress levels are still higher than pre-whaling levels. 


Impact of Cortisol Levels

Baleen whales have a buildup of earwax layers within their ear canal called earplugs (2). The buildup in earwax actually aids in hearing, rather than disrupting it (3). The earwax forms layers, similar to the rings in a tree trunk, that show age, hormone levels (2), and pollutants (4) during their lives.  The increase of stress levels during and after the whaling era can be seen in the earplugs by measuring cortisol levels (2). Cortisol levels can be dated to see at what point spikes occurred and how long they were increased (2). A chronic increase in cortisol levels can have many adverse effects in animals including being more vulnerable to disease, changes in nervous system, reproductive, and metabolic functions, and stunts with growth and development (5). The effect of whaling caused heightened cortisol levels, not only during the whaling era, but was also passed down through generations (2). Therefore, we can still see the effects that whaling had on the species. 


Other Impacts

While humpback populations are making a steady recovery towards pre-whaling numbers, other factors could reverse this. Humpbacks feed in polar regions, and increasing sea surface temperatures are causing sea ice melt, decreasing prey populations (6) and increasing cortisol levels as seen in this paper. Humpbacks are also great indicators of other disturbances to the environment because they are considered sentinels, or animals that can accumulate pollutants in their tissues without serious effects (7). The accumulation of pollutants can be seen in their earplugs as well. The pollutants can have toxic and adverse effects to animals’ immune systems, nervous system, development, and can cause tumors, permanent changes in DNA, and issues with hormone production through the endocrine system (8). 


Modern Whaling

While the International Whaling Commission has banned whaling, Japan has left the commission and continued with hunting whales. To learn more about this, click here. Iceland also continued commercial whaling in 2006, but as of 2020 have decided to halt the hunting of whales as the whale watching industry is booming in the country. More information is available here. In addition, whale hunting is a significant part of many indigenous cultures and is mostly handled by the International Whaling Commission. To read a very informative article about the significance of whaling for indigenous communities in Alaska, Greenland, Russia, Grenadines, and Canada, click here.


Future Implications and How to Help

While they’re still on the endangered list, humpbacks have really rebounded from the brink of extinction. While we can’t reverse the impacts of historic whaling, we can work to protect humpbacks and ensure their populations keep growing. The Pacific Whale Foundation created a list of 40 ways to save the whales, including petitioning to keep them on the endangered species list,  reducing your CO2 emissions to help slow sea surface temperature rise and ocean acidification, sharing pictures of whale flukes to help build a database of population numbers, support Marine Mammal Protected Areas, use eco-friendly cleaning products, reduce the used of plastic grocery bags, and get involved in educational and volunteer programs. 


1. L. Nemo, (2019, November 18). From 440 To 25,000: One humpback Whale Population's Amazing recovery. Retrieved May 15, 2021, from  https://www.discovermagazine.com/planet-earth/from-440-to-25-000-one-humpback-whale-populations-amazing-recovery

2. S. J. Trumble, S. A. Norman, D. D. Crain, F. Mansouri, Z. C. Winfield, R. Sabin, S. Usenko, Baleen whale cortisol levels reveal a physiological response to 20th Century whaling. Nature Communications, 9, (2018). 

3. M. Chen, (2018, May 09). Whale earwax: What you can learn from strange collections. Retrieved May 15, 2021, from https://ocean.si.edu/ocean-life/marine-mammals/whale-earwax-what-you-can-learn-strange-collections

4. Z. C. Winfield, F. Mansouri, C. W. Potter, R. Sabin, S. J. Trumble, S. Usenko, Eighty years of chemical exposure profiles of persistent organic pollutants reconstructed through baleen whale earplugs. Science of The Total Environment. 737, 139564 (2020). 

5. J. F. Leatherland, M. M. Vijayan, N. Aluru, “Stress Response and the Role of Cortisol” in Fish diseases and disorders (Wallingford, UK, ed. 2, 2010), pp. 182-201.

6. M. P. Simmonds, W. J. Eliott, Climate change and cetaceans: concerns and recent developments. Journal of the Marine Biological Association of the United Kingdom. 89, 203–210 (2009). 

7. A. Beeby, What do sentinels stand for? Environmental Pollution. 112, 285-298 (2001). 

8. M. Nadal, M. Marquès, M. Mari, J. L. Domingo, Climate change and environmental concentrations of pops: A review. Environmental Research. 143, 177-185 (2015).


Photo Credit: 

Storck, A. (1690). Dutch whalers near Spitsbergen [Painting]. Stichting Rijksmuseum het Zuiderzeemuseum. Public Domain, retrieved from https://commons.wikimedia.org/wiki/File:Walvisvangst_bij_de_kust_van_Spitsbergen_-_Dutch_whalers_near_Spitsbergen_(Abraham_Storck,_1690).jpg

National Marine Sanctuaries (2013). A female Humpback whale with her calf [Photograph]. CC BY 2.0, retrieved from https://commons.wikimedia.org/wiki/File:Humpback_whale_with_her_calf.jpg. https://creativecommons.org/licenses/by/2.0/legalcode no changes were made.

Dolphin Communication: IT’S TOO LOUD! WHAT?! IT’S TOO LOUD! WHAT DID YOU SAY?!

Author: Virginia Chau

Hi! Can you hear me? No? Hold on a sec. Hello there! You’re probably wondering why I couldn’t hear you? Well, that’s because my neighbors were fighting and playing loud music. So, my housemates and I just told them to be quiet. Similar to my situation, Representative Cunningham honked an airhorn to demonstrate the effects of seismic blasting in the ocean. Now, imagine the loudest and most annoying sound possible, and then play that almost every minute. That is exactly what marine animals hear when there are many ships around, as they create extra noise in the ocean. This is extremely detrimental to the communication between species, especially those who use echolocation to talk. For example, Bottlenose dolphins, Tursiops truncatus, will naturally work together in a group. Dolphins would often work together to herd fish into a ball, creating a prey ball (1). While surrounding the prey ball, dolphins will typically pick fish from the sides, under or through the ball (1). However, without communication, they probably wouldn’t be able to effectively communicate to create this strategy.

Before we talk more about the effects of sound on dolphins, you may need some background information on them. Bottlenose dolphins can be seen in coastal temperate to tropical water (2). They have a spindle neck with a streamlined body form (4). These dolphins can grow to 3-4 m, and adults weigh about 150–650 kg (2). Their slightly stocky bodies are grey, have a domed melon, and a medium-sized beak (2). They typically eat fish and squid (3). Bottlenose dolphins can live to at least 40 years, with some females living to be 60 years old (3). Dolphins will reach sexual maturity and begin reproducing between 5 and 15 years old (3). Once pregnant, females will remain so for 12 months (3). After mothers have given birth, they will nurse their calf for 20 months, and the calf will stay with her for 3 to 6 years (3).

While dolphins are not considered a threatened species, their environment is being affected by the amount of sound pollution in the ocean. Dolphins use echolocation and a series of clicks in order to communicate and understand their surroundings. As a result, the amount of manmade noise in the oceans is affecting the dolphin’s communication. Mid-frequency sonar from these ships can cause temporary hearing loss in bottlenose dolphins (5). There needs to be repeated exposure to generate effects (5). So far, we only see a temporary effect with prolonged sonar. But, because there is always constant sonar coming from ships, Dolphins are experiencing long-term hearing loss. Sonar has reduced the hearing abilities of dolphins, reducing their ability to communicate when foraging. When a dolphin’s ability to hear is lost, they can miss important information or signals.

In order to talk to each other, dolphins need to communicate louder to overpower noise produced by ships, requiring a lot of energy. Many marine species are producing longer or more repetitive vocalizations to compensate for the extra noise in the ocean. However, this comes at the cost of energy, resulting in a shift in metabolic rate. Vocalization can increase their metabolic rate by 1.2 to 1.5 times from that of their resting metabolic rate (6). Due to the loss of hearing and energy costs of lengthened vocalizations, it has become increasingly difficult for dolphins to communicate. Remember, when I talked about how dolphins create balls of fish to forage? This strategy takes communication, but with their hearing loss, dolphins end up spending unnecessary time and energy on repetitive communication.

Another adaptation dolphins have used to compete against boats is to use shorter, less complex vocalizations to communicate with each other (7). The reduced clicking and vocalization means less information is being shared resulting in less effective communication. This is a clear example of the effects of sound pollution because the loss of information can affect parent-offspring proximity and group cohesion. The time calves stay with mothers is important to survival, as the young learn the pod’s communication and survival skills. 

Right now, there is not much being done to reduce the amount of noise in the ocean. However, we can reduce the amount of noise in the ocean by not supporting cruise ships or buying items internationally. I recognize that there are places like Japan and Hawaii that need their items shipped, but we should put a limit to the amount we are shipping. Dolphins are extremely majestic and intelligent creatures, so we should do our best to keep the environment the way it was intended. Otherwise, new generations won’t know what dolphins are. Their extinction can cause a horrible chain reaction in the marine ecosystem.


  1. Vaughn-Hirshorn, R. L., Muzi, E., Richardson, J. L., Fox, G. J., Hansen, L. N., Salley, A. M., Dudzinski, K. M. & Würsig, B. (2013). Dolphin underwater bait-balling behaviors in relation to group and prey ball sizes. Behavioural processes, 98, 1-8
  2. Cozzi, B., Huggenberger, S., Oelschläger, H., Demma, M., Gorter, U., & Oelschläger, J. (2016). Anatomy of dolphins : insights into body structure and function. Academic Press is an imprint of Elsevier.
  3. Fisheries, N. (n.d.) Common Bottlenose Dolphin. NOAA, www.fisheries.noaa.gov/species/common-bottlenose-dolphin.
  4. F.E. Fish, J.T. Beneski, D.R. Ketten. Examination of the three-dimensional geometry of cetacean flukes using computed tomography scans: hydrodynamic implications Anat. Rec. Adv. Integr. Anat. Evol. Biol., 290 (2007), pp. 614-623
  5. Mooney, T. A., Nachtigall, P. E., & Vlachos, S. (2009). Sonar-induced temporary hearing loss in dolphins. Biology letters, 5(4), 565-567.
  6. Holt, M. M., Noren, D. P., Dunkin, R. C., & Williams, T. M. (2015). Vocal performance affects metabolic rate in dolphins: implications for animals communicating in noisy environments. Journal of Experimental Biology, 218(11), 1647-1654.
  7. Fouda, L., Wingfield, J. E., Fandel, A. D., Garrod, A., Hodge, K. B., Rice, A. N., & Bailey, H. (2018). Dolphins simplify their vocal calls in response to increased ambient noise. Biology letters, 14(10), 20180484.

Image Credits

"Dolphins and Ships"  by Denni Schnapp is licensed with CC BY-NC-SA 2.0. To view a copy of this license, visit https://creativecommons.org/licenses/by-nc-sa/2.0/" data-sk="tooltip_parent">https://creativecommons.org/licenses/by-nc-sa/2.0/

airhorn via http://bigredbarrel.com and the blu show" by scottobear is licensed with CC BY-NC-SA 2.0. To view a copy of this license, visit https://creativecommons.org/licenses/by-nc-sa/2.0/


Even the Cheetah Cannot Outrun Climate Change

Author: Mauricio Cruz

When you think of “speed,” your mind might immediately go to a race car or a jet, or even Usain Bolt. But when you consider speedy animals, the cheetah (Acinonyx jubatus) is likely at the forefront of your thoughts. Thanks to its status as the fastest land animal in the world, the cheetah is one of the most widely known and easily recognizable large cats, up there with the lion and the tiger. Unfortunately, it is its specialization for speed that makes the cheetah particularly vulnerable to the effects of climate change--namely increasing global temperatures.

Built for Speed

The cheetah distinguishes itself from other large cats through its adaptations for speed. Externally, the cheetah is clearly built for speed. Like a formula 1 race car, its lightweight and aerodynamic head and body facilitate acceleration and reduce air resistance. Its long, skinny legs allow it to take longer strides while running. Moreover, its legs end in short, blunt claws that increase traction, like a sprinter’s cleats.

While these external traits are undoubtedly impressive, the cheetah’s internal sprinting adaptations are arguably even more important. The cheetah has evolved to move oxygen incredibly efficiently, allowing it to maximize energy output while running. For example, the cheetah increases its respiratory rate from 60 breaths per minute to 150 breaths per minute when it is at full sprint. It’s no surprise that similar traits are considered optimal for human athletes too!

However, the increased energy expenditure of sprinting means that the cheetah can only run for 300 to 400 meters before becoming exhausted. This post-hunt fatigue, coupled with its lightweight frame, results in the cheetah being particularly vulnerable to attacks from bigger predators. In fact, the cheetah experiences a remarkably high risk of attack from lions, leopards, and hyenas trying to steal their kills (1).

Daytime Cats

Another distinguishing feature of the cheetah is its daily activity pattern. The cheetah is mostly active during the day, while other large cats like lions and leopards are mostly active during the night. This activity pattern is partially due to the threat posed by the larger nocturnal predators (1). However, there is a tradeoff associated with the increased security of daytime activity: higher temperatures. Cheetahs are regulators; they use energy to maintain a core body temperature.

A study looking at body temperature and activity patterns in wild cheetahs found that the cheetahs maintained their body temperature within a small range (about 2 C) in a daily cycle. The researchers also found that in the hot-dry period cheetahs had a slightly higher maximum body temperature, despite the extreme heat the cheetahs can face in the day. However, to maintain this stable body temperature during the hottest period of the year, the cheetahs had to shift their activity pattern; instead of being most active during the day, they became most active during dawn and dusk. This change in activity pattern was also associated with an increase in nocturnal activity.

This shift away from daytime activity is due to the high energetic cost of sprinting for the cheetah. When the cheetah sprints, it produces a lot of heat as a byproduct of the biological processes that allows it to produce the muscle power necessary to accelerate to 120 kilometers per hour. This can amount to a 4 C swing in body temperature, from 36 C to 40 C. Because of this sprint-induced increase in body temperature, the cheetah cannot both hunt and regulate its body temperature effectively during the hottest period of the day in the hottest period of the year--it would overheat. This means that it must shift its activity pattern so that it is more active during cooler periods of the day, such as dawn, dusk, and even night. However, the issue of competition and attacks from large nocturnal predators remains (4).

The Effect of Climate Change

Due to anthropogenic climate change, global temperatures are increasing. This includes temperatures across the cheetah’s habitat, which likely means further shifts away from daytime activity for the cheetah (3). In addition to the noted increased competition and risk of attacks from nocturnal predators, the cheetah is also faced with the challenge of hunting in sub-optimal conditions. For example, the cheetah’s eyes are characterized by their visual streak: an adaptation specialized for locating prey against the horizon during the day, not for low light. We cannot be sure how well the cheetah will adapt to hunting in these new conditions, but we can predict how the cheetah will fare against the nocturnal predators thanks to previously recorded interactions between the species. In the same study mentioned above, the researchers found that two of the five cheetahs being observed died following leopard attacks (4).

Potential Solutions

A potential conservation strategy is to coordinate cheetah reintroductions so that cheetah populations are kept separated from predators such as lions, leopards, and hyenas (3). However, this solution affects only a symptom and not the disease itself. If climate change continues at its current rate, the daytime niche currently occupied by the cheetah will become unavailable to it, since it will be impossible for them to hunt and maintain their body temperature during the day. Therefore, it is important that we address the climate crisis as soon as possible. There are many things individuals can do to reduce personal emissions, but the vast majority of emissions are made by big corporations (4). Electing officials that will hold corporations accountable and that will support strict environmental regulations is the best way forward, not just for the cheetah, but for the whole world.


  1. L. Marker, “Aspects of cheetah (Acinonyx jubatus) biology, ecology and conservation strategies on Namibian farmlands,” thesis, University of Oxford, Oxford, United Kingdom (2002).
  2. K. G. Buk, V. C. van der Merwe, K. Marnewick, P. J. Funston, Conservation of severely fragmented populations: lessons from the transformation of uncoordinated reintroductions of cheetahs (Acinonyx jubatus) into a managed metapopulation with self-sustained growth. Biodiversity and conservation, 27, 3393-3423 (2018).
  3. R. S. Hetem, D. Mitchell, B. A. De Witt, L. G. Fick, S. K. Maloney, L. C. Meyer, A., A. Fuller, Body temperature, activity patterns and hunting in free‐living cheetah: biologging reveals new insights. Integrative Zoology, 14, 30-47 (2019).
  4. P. Griffin, CDP carbon majors report 2017. Carbon Majors Database (2017).

Image Credits

"File:Cheetah (Kruger National Park, South Africa, 2001).jpg" by Godot13 is licensed with CC BY-SA 3.0. To view a copy of this license, visit https://creativecommons.org/licenses/by-sa/3.0/deed.en

"File:Change in Average Temperature.svg" by NASA’s Scientific Visualization Studio, Key and Title by uploader (Eric Fisk) (2020) is licensed in the Public Domain.

It's Getting Hot in Here, Especially for Elephants

Author: Sarah Cain

KEY WORDS: Elephant, homeothermy, climate change, behavior, physiology.

There’s something in the air… Surprise! It’s greenhouse gases, and they contribute a lot to global warming. I think we’ve all noticed the changing climate and more extreme weather events, and trust me, animals are noticing it too. One animal in particular is Loxodonta africana, also known as the good ol’ African bush elephant. These gentle giants inhabit some of the hottest regions on the globe, and yes! You’ve guessed it! These regions are only projected to keep getting warmer. Visit the Animal Diversity Web to learn more about Loxodonta africana (1).

Homeothermy is a type of thermoregulation that maintains a stable internal body temperature regardless of external influence. Heat load is an indicator of the thermal stress that an animal experiences, and positive heat load occurs when environmental temperatures (and the associated weather conditions) exceed the internal body temperature of an animal.

African bush elephants are intense ecosystem engineers who help maintain and balance savanna, grassland, and forest habitats across central and southern Africa in the Ethiopian Region. Thanks to the environmental conditions of these inhabited regions, elephants are already capable of maintaining homeothermy under positive heat load and when dealing with large fluctuations between warm daytime and cool nighttime temperatures.

The coolest thing about elephants is they have an internal rhythm that manages their core body temperature in order to help them cope with changes in the environment. When environmental temperatures exceed internal body temperature, elephants experience positive heat load, and they are able to use their internal rhythms to maintain homeothermy with no more than 1.5º C internal body temperature fluctuation over 24 hours. Learn more about the internal rhythms of elephants in this article (2).

The not so cool thing about elephants is that we don’t really know how strong this internal rhythm is. In other words, if savanna daytime temperatures keep rising AND nighttime temperatures keep falling, we don’t know if the elephant’s internal rhythm will be able to keep up with increasing daytime positive heat load or the associated increase in daily temperature fluctuations. If their rhythms can shift and keep up with climate change, the elephants will be chilling! If not, they need to figure out a few more tricks to put up their trunks.

So far, the tricks they do have up their trunks are working. Along with their internal rhythm, elephants use a process called evaporative cooling to dissipate heat to their environment. Evaporative cooling occurs when heat is removed from a surface due to the evaporation of water. While homo sapiens are blessed with the lovely process of sweating, elephants lack sweat glands and instead are blessed with the lovely process of evaporative cooling. You can read more about evaporative cooling in this article (3).

Evaporative cooling works great for elephants because they have so much skin surface to use for evaporation! However, there always has to be at least one negative. Having a lot of skin surface unfortunately means having a lot of skin surface to cool down, which unfortunately also means needing a lot of water that can be used to cool down all of that skin surface. You get the point. Elephants need to have ample access to water in order to amply use evaporative cooling.

Additionally, elephants have an obligation to use evaporative cooling because of thermoregulatory consequences associated with their large body size. This obligation translates into patterns of habitat use because daily water requirements directly influence the foraging distance from a water source and the frequency of returning to that water source. Therefore, as the climate gets hotter and water becomes scarcer, we will most likely see elephants start to exploit other habitat types that better allow for evaporative cooling.

Internal processes cannot adapt as quickly as the environment is changing, and new habitat types filled with abundant water sources don’t show up overnight. The good thing is that elephants are intelligent creatures! Elephants have the largest brain out of any land mammal, and in addition, they have a large, intricate neocortex that allows for enhanced cognitive function and processing. Instead of constantly relying on internal mechanisms to keep themselves stable, elephants can display different behavioral adjustments in order to help out their internal rhythm and other physiological responses.

Elephants that seek shade reduce their surrounding environmental temperature (heat load) by avoiding solar radiation. Resting allows elephants to avoid extra internal heat that is generated via walking, as well as avoid the need to dissipate that extra heat. Ear flapping and/or walking enhances non-evaporative cooling by creating a forced convection, which is sort of like having your own personal wind gust. If water is available, elephants may participate in wetting of the skin in order to enhance evaporative cooling and lower the amount of body water depleted during evaporative cooling. More information about the behavioral responses of elephants can be found in this article (4).

As I brought up earlier, the tricks that elephants have up their trunks are working relatively well at this current time. More research needs to be done on their internal rhythms and how they adjust those rhythms, as well as other behavioral/physiological processes, in order to cope with different environmental variables. While animal conservation seems intimidating as an individual, you can help elephants by donating to elephant research and wildlife trusts, supporting elephant sanctuaries and ivory trade bans, and choosing elephant-friendly honey, coffees, and teas. Another way to help the elephants AND help the earth is by making a climate pledge to lower your carbon footprint. Learn more about how you can reduce your carbon footprint here. Support the Sheldrick Wildlife Trust by digitally adopting an elephant here.


  1. Howard, Loxodonta africana. Animal Diversity Web. (2017).
  2. A. Kinahan, R. Inge-moller, P. W. Bateman, A. Kotze, M. Scantlebury, Body temperature daily rhythm adaptations in African savanna elephants (Loxodonta africana). Physiology & Behavior. 92, 560–565 (2007).
  3. C. Dunkin, D. Wilson, N. Way, K. Johnson, T. M. Williams, Climate influences thermal balance and water use in African and Asian elephants: physiology can predict drivers of elephant distribution. Journal of Experimental Biology. 216, 2939–2952 (2013).
  4. A. Mole, S. Rodrigues DÁraujo, R. J. van Aarde, D. Mitchell, A. Fuller, Coping with heat: behavioural and physiological responses of savanna elephants in their natural habitat. Conserv Physiol. 4, cow044 (2016).



Both photographs were taken by Muhammad Mahdi Karim. Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 only as published by the Free Software Foundation.

  1. Photograph of African bush elephant was retrieved from https://commons.wikimedia.org/wiki/File:African_Bush_Elephant.jpg.
  2. Photograph of Mikumi National Park landscape was retrieved from https://commons.wikimedia.org/wiki/File:Mikumi_lanscape_alt.jpg.

Mermaids (I Mean Manatees) Get Cold Too …

Author: Juliette Wong

Would you mistake a grey, cow-like marine mammal weighing at around 1,000 kg and 3.5 m in length as a mystical mermaid (1)? No? Well the 15th century Columbus explorers, delusional from lack of nutrition and life on the sea, most definitely did. This is where the classified order of Sirenia (a term from greek mythology describing half woman/half fish sirens) for Manatees originated. Specifically the Florida Manatees, Trichechus manatus latirostris, are slow-moving herbivores that spend a lot of their time grazing seagrass and algae in shallow warm waters such as marshes and estuaries. They inhabit many tropical and subtropical regions but in this post we will be focusing on those along the Florida coast. If you want to learn more general background information on these gentle creatures check out this page!

As briefly mentioned, manatees are well adapted to warm waters. They require a minimum of 21°C temperatures to be able to properly function and overall survive (2). Considering their large size, they have a very low metabolic rate that can only operate in these warmer temperatures (3). When exposed to temperatures below this  21°C threshold, they experience cold-related health conditions and even mortality. As a result of cold temperature exposure and other environmental stressors such as algae toxin consumption and boat strikes, manatees have been an endangered species since 1967 (1). Most if not all of these environmental stressors can be linked to anthropogenic, or human-influenced, activities. Considering humans’ responsibility for their vulnerability, it’s important to be aware of the causes of their mortality in order to combat these consequences. For more overview on the multiple risks of anthropogenic climate change on Florida manatees you can read this journal article

Does global warming actually equate to warmer temperatures? 

As you may know, global warming is a vast phenomenon driven by the accumulation of greenhouse gases in our atmosphere giving rise to extreme weather events. A more appropriate term for global warming would be Global Climate Change (GCC) due to the name’s common misconception that global warming only leads to a world-wide increase in temperatures. Climate change events and recent research have debunked this belief as Florida has been experiencing, and is predicted to continue experiencing, cooler temperatures during the winter and spring seasons; models have suggested that cold spell outbreaks will surge, causing minimum winter water temperatures to drop even further (3).  As the Florida coast faces a higher frequency of abnormally cold winters associated with GCC events, the Florida manatees will need to find refuge to avoid cold-stress.

Being cold can be stressful -- Cold Stress Syndrome! 

No one likes to be uncomfortably cold, it can be miserable. But imagine if what feels like unbearably cold temperatures caused you to have unnatural weight loss, dehydration, skin lesions, indigestion, heart damage and even death; this is what the Florida manatees endure (3). These are just some of the described physiological impacts manatees may experience when unprotected from cold stress syndrome. Just from the years 2000 to 2003, The Florida Fish and Wildlife Conservation Commission revealed that around 11.3% of 961 manatee deaths were cold-related deaths (2). Another adverse effect from this sickness includes lymphocyte proliferation which in other words means that their immune system response to harmful substances entering their body is inadequate (2). To detail this finding further, a comparative study between rescue manatees and healthy manatees found that the rescue manatees’ white blood cell (or leukocytes) count was only a third of healthy manatees (2). White blood cells are cells of the immune system that are found in all animal species and protect us from foreign invaders and infectious diseases, so their abundance is very crucial! 

Now, let’s return back to discuss some of the other listed impacts of cold-stress on manatees. As previously mentioned, these creatures are slow-moving with an unpredictably low metabolic rate that performs best in warm water. This heavily influences their ability to consume food and easily digest. A dated study testing metabolism on captive Florida manatees discovered that in water temperatures between 18°C-20°C the manatees would feed irregularly and in 15°C-18°C they would refuse to feed entirely (4). Therefore, manatees exposed to cold water temperatures will experience extreme weight loss, indigestion, and in general starvation. As an attempt to avoid these various, and detrimental effects of cold-stress syndrome, Manatees will often migrate to warmer waters during colder seasons.

Taking refuge at the source of the issue…

Florida manatees are seasonal migratory marine mammals who will travel northward along the East coast during the spring and travel southward during the winter and fall (1). However, these migratory patterns have become more swayed by erratic climatic conditions and a spike in man made warm water sites such as power plants and other industrial refugia (1).  Back in 2010, when Florida experienced a year long cold spell, 63% of over 5,000 manatees counted inhabited an industrial source during winter (3). This trend has been apparent since the 1970s; Florida manatees have been notably located at these sites, revealing heavy reliance on human development in relation to expanded winter ranges as an attempt to avoid energetic maintenance (4). 

Even though man made refugia may appear to be beneficial for manatees’ health and wellbeing, it has caused manatees to become over dependent on artificial warm water sources that are not only threatened by sea level rise but serve as mass polluters. Most of the industrial warm water sites in Florida are along the coast which make them extremely vulnerable to the predicted 10% land loss from sea level rising (3). As this coastal degradation takes place, manatees will need to further migrate in order to seek other refugia such as natural springs. Considering the number of manatees that take refuge in copious industrial warm water sites, naturally warm and shallow waters may not be enough. Additionally, the possibility for them to rely on more extensive migratory paths becomes uncertain as Florida and the East coast are suspected to face temperature drops that may not be suitable for manatees’ physiological needs all year round. 

This topic is a tricky one since the implications of climate change act as the biggest threat to manatee survival and the sites that help protect manatees from this catastrophe are also the one’s contributing to it. Conservationists and researchers are still navigating this ironic and cyclical issue that will require innovative and vast efforts.

What can we do to protect these kind creatures?

As extensively bleak this matter may sound, there is so much that is being done and can continue to be done to save the Florida manatees. While further research on manatee behavior, physiology, and adaptability in relation to anthropogenic influence remains essential, there’s still sustainable and conservation practices that can take place from what we do know. For starters, being aware of your carbon footprint and taking measures to reduce your individual emissions that alter the climate that manatees are struggling to keep up with. To calculate your own carbon footprint and be provided with suggestions on how to reduce it, click this link! Also, if you want to learn more about ways you can help, here is a website with various resources on what you can do to take part in saving the manatees. Do your research, play your part, and save the mermaids!

Key words: cold stress, metabolic rate, refugia,


  1. West Indian Manatee Trichechus manatus. U.S. Fish & Wildlife Service.
  2. Walsh, C. J., Luer, C. A., & Noyes, D. R. (2005). Effects of environmental stressors on lymphocyte proliferation in Florida manatees, Trichechus manatus latirostris. Veterinary immunology and immunopathology, 103(3-4), 247-256.
  3. Edwards H.H. 2013. Potential impacts of climate change on warmwater megafauna: the Florida manatee example (Trichechus manatus latirostris). Climatic Change, 121(4): 727-738. DOI 10.1007/s10584-013-0921-2
  4. Irvine, A. B. (1983). Manatee metabolism and its influence on distribution in Florida. Biological Conservation, 25(4), 315-334.

Image Credits

“Mother manatee and calf” by Sam Farkas (NOAA Photo Library). Public Domain, https://commons.wikimedia.org/w/index.php?curid=87060123

"Lots of Manatees that turn up at the Power Plant in Apollo Beach" by amanderson2 is licensed with CC BY 2.0. To view a copy of this license,   visit https://creativecommons.org/licenses/by/2.0/

Does Human Interaction Stress Out Chimpanzees?

Author: Austin Anderson

Chimpanzees, also known as Pan troglodytes, are fascinating animals that display human-like behaviors and have been facet of biological and anthropological concern. These primates provide a glimpse into the evolutionary processes that may have acted upon our most recent common ancestor. Regrettably, chimpanzees are facing unnaturally heightened levels of stress, and humans might be at the core of the problem. While humans might be stressed out on a daily basis from school, work, and finances, researchers believe chimpanzees may be stressed for something totally different: human interaction as a result of deforestation. Human induced deforestation is no secret; It is a topic discussed frequently among news outlets and environmental conservation advocates online. The most obvious consequence of deforestation is habitat loss resulting in diminished resources and space for a species to persist. However, a less apparent physiological manifestation of anthropogenic deforestation is a heightened level of chronic stress among chimpanzees.

Naturally and optimally, chimpanzees reside in undisturbed areas of sub-Saharan Africa, specifically in habitats such as lowland forests, dry forests, savanna woodlands, and human-dominated farmland (1). While chimpanzees are found throughout these locations, their distribution is clumped due to a community-based living strategy. Chimpanzees live in small communities averaging 35 members and are reliant on fission-fusion dynamics (1). The average lifespan for a chimpanzee is thought to be roughly 35 years, though this is often debated (2). Fission-fusion is a strategy of social organization that involves the animals moving between and throughout groups, giving the chimpanzee community a consistently changing individual composition. Chimpanzees are currently designated as endangered according to the IUCN, and more information and examples of threats contributing to their dwindling population can be found at this link. Unfortunately, rising rates of human population growth in chimpanzee habitat areas creates an environment more likely to cause increased stress for these primates.

How to Determine Chimpanzee Stress Levels

With the question of physiological chimpanzee stress in mind, scientists are posed with an important question; What is the best way to measure stress among chimpanzees? The most recognized indicator of physiological stress is commonly accepted to be glucocorticoids, which are a class of steroid hormones that aid in the release and production of energy during the “fight or flight” response (3). Several methods of measuring these hormones exist, including blood, urine, hair, and more. However, researchers have opted for fecal and hair sample collection, as these are the most convenient and realistic given the difficulty presented by some of the other methods (4). The next notable criteria for measuring stress is to determine to what degree different aspects play a role in increased or decreased stress. This can be estimated by choosing specific populations to study that either have human disturbed habitat or live in a protected, undisturbed area. For example, the most prominent studies on this topic have often chosen two representative communities; one in the undisturbed Budongo Forest of Uganda, and another in the Bulundi region of Uganda, which does not benefit from protection of human interference.

How do Humans Cause Increased Stress in Chimpanzees?

Increased Contact

Hypothesized by McLennan et. al., increased interactions with humans is thought to correlate with higher glucocorticoid levels. Studying the two communities mentioned previously, the Budongo and the Bulundi, McLennan et. al. found that there is indeed higher glucocorticoid levels in the human-coinhabited Bulundi region (5). In fact, the mean level is over three times higher than their chimpanzee counterparts in the Budongo forest!

Agriculturally Purposed Destruction

Interestingly, the destruction of chimpanzee habitat for agriculture has both pros and cons. Surely, chimpanzee habitat loss and increased human contact will stress them out, yet the high quality food made available via human agriculture supposedly acts as buffer for the stress. Traditionally, chimpanzees have a diet consisting of small-medium sized mammals, insects, seeds, flowers, honey mushrooms, and bark (1). However, many of these resources are severely limited with increased human development, and chimpanzees instead resort to feeding on agriculture near the forest edge. At first, researchers hypothesized that a higher finding of agricultural fruit in fecal remains would equate to higher glucocorticoids since this would mean more instances of human interaction. They were proven wrong though, and found that within non-protected chimpanzee community of Bulundi, chimpanzees had lower stress levels (5).


Although it might sound tempting, visiting unprotected chimpanzee habitat to observe our close great ape friends is probably another contributing factor to their heightened stress. Carlitz et. al. found that tourists are commonly told to follow the “7-meter rule,” where 7 meters is the closest they are allowed to be to the chimpanzees (6). To a chimpanzee, having constant visitors may be a stressful experience. The animals do not always know the intentions of humans and this could trigger unnecessary fight or flight responses. While the researchers did find heightened glucocorticoid levels in hair samples here, they also mentioned that more research should be done to determine if ecotourism is the culprit.


The evidence that human contact as a result of deforestation causes heightened stress hormones in chimpanzees is convincing, yet limited. To date, very few complete studies focusing on chimpanzee stress from human impact have been carried out. This is likely partially due to the difficult habituation process for chimpanzees, or also the remoteness and time consumption of such studies. Nevertheless, one thing all researchers in this field agree on is that more communities should be studied for their physiological responses to increased human activity. Beyond the release of more stress hormones, what other physiological problems are at play? In addition, what are the implications of long-term stress on chimpanzees and what can we do to mitigate this? These are both questions to address for the future of this topic. While the exact consequences are not yet known, McLennan et. al. suggest educational outreach to diminish negative villager-chimpanzee interactions in Uganda and beyond. Viable alternatives to deforestation are a start to the potential resolution of this complicated issue.


Photo Credit

Photograph of chimpanzee Credit: Public Domain, Pixabay License, https://pixabay.com/photos/chimpanzee-monkey-ape-mammal-zoo-3703230/

Photograph example of deforestation in Uganda Credit: Rod Waddington, CC BY-SA 2.0, https://commons.wikimedia.org/wiki/File:Habitat_Destruction,_Uganda_(21429887344).jpg


References Cited

1. T. Humle, Pan troglodytes (errata version published in 2018). The IUCN Red List of Threatened Species (2016).

2. J. B., How long do chimpanzees live? Chimpanzee Sanctuary Northwest (2013).

3. S. Whirledge, Glucocorticoids, Stress, and Fertility. Minerva Endocrinology 35, 109-125 (2013).

4. B. Dantzer, Measures of physiological stress: a transparent or opaque window into the status, management and conservation of species? Conservation Physiology 2, 1-18 (2014).

5. M.R. McLennan, Are human-dominated landscapes stressful for wild chimpanzees (Pan troglodytes)? Biological Conservation 233, 73-82 (2019). 6. E.H.D. Carlitz, Measuring hair cortisol concentrations to access the affect of anthropogenic impacts on wild chimpanzees (Pan troglodytes). PLOS One 11, 1-13 (2016).

Sea Unicorns May Be on the Verge of Becoming a Fairytale: The Arctic Narwhal

Author: Haley Valdez

Sea Unicorns May Be on the Verge of Becoming a Fairytale: The Arctic Narwhal 

Unfortunately, the mythical creature we all loved as children, the unicorn, does not exist. Thankfully to fill the void we’ve all had since finding out they aren’t real, we have Monodon monoceros, otherwise known as narwhals. It is likely you haven’t seen these amazing creatures in real life as they are native to colder waters in the arctic mainly staying in waters around Canada, Greenland, and Norway. During the winter the majority of the species population migrates to Baffin Bay, an area between Canada and Greenland, where they spend up to five months under ice-covered waters. This article goes more in depth about the habitats of the species (1). Narwhals are highly specialized animals that have very specific migratory patterns and diets consisting mainly of cod, halibut, squid, and shrimp. Because of their limitations to the food they can eat and habitat they can live in, many scientists are worried about the negative impacts rising sea temperatures / climate change will have on these animals. More about the specialization of these animals can be found here (2). As for mating, little is known about the breeding habitat for narwhals; however, it is known that they breed seasonally between March and May and usually give birth about fifteen months later.   

But are these amazing animals going to soon become non-existent like the fairytale creature they’re compared to? 

Much like all the other wildlife on our planet, climate change has been seen negatively impacting narwhals over the last few years. Due to the increased water temperatures, ice in the arctic has been less available, more unreliable, and has started to break off into large floating sheets called ice floe. Because of these factors, breathing holes in ice have become more unpredictable leading to entrapments and death for narwhals. This journal talks more about these findings (5). Not only are entrapments a big threat, but these animals have been recorded exceeding their dive limits causing major energy loss while foraging for food. One study documented a subgroup and reported that the narwhals consistently surpassed depths of 800 m with about 13% exceeding the approximate dive limit. Added information on this study can be found in this article (6)

It’s not just exhaustion that narwhals have to worry about…

Due to the water temperatures warming all over the ocean, one of the oceans top predators, the orca, has appeared more frequently in narwhal’s habitats. Sadly, it’s not so they can visit their sea unicorn buddies. Killer whales have been known to prey on narwhals, which may further affect their behavior and distribution across the arctic. In an attempt to avoid free Willy, narwhals have been seen moving to areas with denser packed ice, which can again lead to more energy loss from longer required dives (5).       

One might ask, ‘well what's so bad about warmer water? Who doesn't like a jacuzzi?!’   

To better understand why rising water temperatures and the presence of orcas affect narwhals, let's learn a little about how their bodies work! Living in such extremely cold waters, narwhals are able to keep warm through a couple of methods. One of these methods includes lacking a dorsal fin which allows them to retain more warmth since a dorsal fin serves as a way to dissipate excess heat. The second method narwhals use to stay toasty is blubber. The large amounts of blubber these animals carry help to act as insulation, this is a lot like having a good winter coat except you can’t take it off when you start getting hot, or in the narwhal’s instance, when the water temperatures are rising (1). Along with the ability to endure some of the coldest water in the ocean, narwhals have also physically adapted to be able to dive to depths as deep as 800 m for as long as eighteen minutes. They are able to do this through having predominantly slow twitch muscles in order to slowly ascend to depths while saving energy, being able to store large amounts of oxygen in the muscles and blood stream, and having high levels of myoglobin (5). Adding all that up equates to one of the best equipped mammals for deep water marathons. Unfortunately though having predominantly slow twitch muscles means that they won't be racing Michael Phelps anytime soon. This also makes it extremely hard for narwhals to quickly get away from orcas, which is why they have been documented moving to densely ice packed regions because they are able to dive deeper and longer than killer whales.          

All hope is not lost!

Because narwhals live in such a remote region of the world there are not a lot of direct steps that we can take to help the efforts in protecting them, but we can help by raising more awareness and educating others on the topic, signing petitions to get more funding for their protection, and donating when we can to organizations that dedicate themselves to helping threatened species. If you would like to donate or ‘adopt a narwhal’ visit The World Wildlife Fund.  Just because there may not be a lot of ways to directly help narwhals, there are still ways we can help our oceans! This includes conserving our water at home, being more conscious of choosing nontoxic products, buying sustainable seafood, practicing safe boating, reducing vehicle pollution when possible, and volunteering. To learn more about these steps visit the NOAA.  


  1. Chambault, P., O. M. Tervo, E. Garde, R. G. Hansen, S. B. Blackwell, T. M. Williams, R. Dietz, et al. “The Impact of Rising Sea Temperatures on an Arctic Top Predator, the Narwhal.” Scientific Reports 10, no. 1 (December 2020)
  2. Laidre, Kristin L., Ian Stirling, Lloyd F. Lowry, Øystein Wiig, Mads Peter Heide-Jørgensen, and Steven H. Ferguson. “QUANTIFYING THE SENSITIVITY OF ARCTIC MARINE MAMMALS TO CLIMATE-INDUCED HABITAT CHANGE.” Ecological Applications 18, no. sp2 (March 2008)
  3. Nicklen, Paul. HIGH-TECH AND INDIGENOUS KNOWLEDGE JOIN FORCES TO PROTECT THE MELTING ARCTIC’S MOST AT-RISK ANIMALS, National Geographic , 9 July 2019, wwf.ca/stories/arctic-species-conservation-fund-2019/. 
  4. Nicklen, Paul. UNICORN OF THE SEA: NARWHAL FACTS, National Geographic , www.worldwildlife.org/stories/unicorn-of-the-sea-narwhal-facts. 
  5. Pagano, Anthony M., and Terrie M. Williams. “Physiological Consequences of Arctic Sea Ice Loss on Large Marine Carnivores: Unique Responses by Polar Bears and Narwhals.” The Journal of Experimental Biology 224, no. Suppl 1 (February 15, 2021)
  6. Williams, Terrie M., Shawn R. Noren, and Mike Glenn. “Extreme Physiological Adaptations as Predictors of Climate-Change Sensitivity in the Narwhal, Monodon Monoceros.” Marine Mammal Science 27, no. 2 (April 2011)

Image Credit

"File:Monodon monoceros pod.jpg" by Dr. Kristin Laidre, Polar Science Center, UW NOAA/OAR/OER (2006), accessed via Wikimedia Commons and licensed under Public Domain.

"File:Pod Monodon monoceros.jpg" Dr. Kristin Laidre, Polar Science Center, UW NOAA/OAR/OER (2006), accessed via Wikimedia Commons and licensed under Public Domain.

Copyright © 2023 UCSC Biology 136 Environmental Physiology. All Rights Reserved.
Website By: Tree Top Web Design