Expert Article
WOAH! What’s that?!
A guide to some amazing mammals you might come across in Southern California
Introduction
What comes to mind when I say the word “mammal?” You might think of elephants, whales, tigers, or even us! Mammals are a diverse group of animals located all over the world. People are often drawn to the cuteness of panda bears or the stunning stature of a giraffe and forget that incredible mammalian species live in our backyard.
As a pre-veterinary student, I have worked with several species, including polar bears, howler monkeys, and sea lions. I explored my interest in animals by taking the mammalogy class at USC. I learned about different mammalian groups and their ecological niches, or "the role an organism plays in a community" (National Geographic Society). I found the course so captivating that I became a teaching assistant for the class and have taught for the past two semesters.
In this blog, I will review some species you can encounter in Southern California, from marine mammals to terrestrial megafauna and desert rodents. There may be some scary words in this post, such as "megafauna," but do not be worried! I will explain the bolded terms so you can learn to speak like a true mammalogist. For example, megafauna means large animals.
THE CLOSEST MAMMALS TO MERMAIDS
Figure 1. Zalophus californianus. Left to Right: female, pup, male.
Zalophus californianus, California Sea Lion
Order Carnivora (carnivores)
Suborder Caniformia (dog-like)
Superfamily Pinnipedimorpha
Family Otariidae (sea lions)
Taxonomy, or as I like to call it, Animal Ancestry
Since this might be your first encounter with taxonomy, I will break it down for you. Taxonomy is a field where scientists group animals based on common ancestors.
Sea Lions are part of Carnivora, which means they have the features of a carnivore or meat-eater, and Caniformia, means they evolved from a "dog-like" ancestor (Dines et al., 2022). Sea lions are in the superfamily Pinnipedimorpha, which also includes seals and walruses. Animals in this group evolved from a bear-like ancestor and became aquatic!
Defining Characteristics
Adult females and juveniles are tan
Adult males are larger and dark brown to black (NOAA Fisheries, 2022)
Broad front flippers
Long rostrum or snouts
Small ear flaps (NOAA Fisheries, 2022)
Nothing better than a summer in Southern California
California sea lions can be found along the California Coast (Gearin, et al., 2017). During the summer, they gather in Southern California for breeding season. In late August, males migrate North, while females remain in Southern California and care for their pups.
Figure 2. Eumetopias jubatus. Left to Right: female, pup, male.
Eumetopias jubatus, Steller Sea Lion
Order Carnivora (carnivores)
Suborder Caniformia (dog-like)
Superfamily Pinnipedimorpha
Family: Otariidae (sea lions)
Defining Characteristics
Largest species in the family Otariidae, with males reaching 11 feet in length and 2,500 lbs in weight (NOAA Fisheries, 2023; The Marine Mammal Center, 2024).
Light tan to reddish-brown color
Short rostrum (The Marine Mammal Center, 2024)
Where to Spot
This species is less common on the California coast than the California Sea Lion (Jameson & Peeters, 2004). If you want to catch a glimpse, I recommend visiting the Channel Islands or Año Nuevo Island in late spring/early summer, as these are locations of breeding colonies.
Figure 3. Comparison of the California Sea Lion (left) and Steller Sea Lion (right)
Who’s who? (Fig 3.)
There are several differences between the two sea lions, the main difference being that Steller Sea Lions are much larger and have a shorter rostrum (Los Padres Forest Watch, 2018).
LAND-LOCKED MEGAFAUNA
Figure 4. Antilocapra americana.
Antilocapra americana, Pronghorn
Order Artiodactyla
Suborder Ruminantia
Family Antilocapridae
Astonishing Ancestry of Antiocapridae
Artiodactyla is one of the two major clades, or groups, of primarily hoofed mammals (Dines et al., 2022). Surprisingly, whales are also in this clade! Suborder Ruminantia refers to the four-chambered stomach these animals have that allows for enhanced nutritional intake. Other animals in this group are giraffes, deer, and cows.
Defining Characteristics
Both males and females have black, branched horns (Dines et al., 2022)
Horns are a bony core covered in a fused hair sheath
Black stripe along nose; white cheek patch
Two toes on each foot (Pronghorn (Antilocapra americana))
Figure 5. Extinct American cheetah hunting a pronghorn.
Outrunning Extinction
Pronghorns are cursorial animals, meaning they are adapted for running. In fact, they are the second-fastest land mammal (Higgins, et al., 2023). They acquired this enhanced ability because they were hunted by the extinct American cheetah and American lion, Fig 5.
Figure 6. Puma concolor. A mother cougar and her cub.
Puma concolor, North American Cougar
Order Carnivora (carnivores)
Suborder Feliformia (cat-like)
Family Felidae (cats)
Cat-Like Carnivores
Similar to sea lions, cougars belong to Carnivora. However, cougars are in the suborder Feliformia, meaning "cat-like," and the family Felidae, whose members include wild and domestic cats (Dines et al., 2022).
Defining Characteristics
Yellowish- brown color
"The sides of the muzzle, the backs of the ears, and the tip of the tail are black or dark brown"
Long Tail (U.S. National Park Service, Puma Profiles)
Secodont cheeckteeth, means teeth with sharp cutting edges (Dines et al., 2022).
Close Encounters
Cougars have a vast habitat, with some populations existing within city limits (Jameson & Peeters, 2004). One of the most famous cougars was a resident of Griffith Park named P22. Although he passed away, he made a lasting mark on the community (U.S. National Park Service, Puma Profiles).
Since these apex predators are endemic, or native, to Los Angeles, here is what to do if you should encounter one (Biodiversity Atlas of LA):
Do not run
Maintain eye contact
Try to Appear Larger
Back Away Slowly
If it attacks, fight back!
Figure 7. Didelphis virginiana
Didelphis virginiana, Virginia Opossum
Infraclass Metatherians (marsupials)
Superorder Ameridelphia
Order Didelphimorpha (opossums)
Family Didelphidae
America's Marsupial
Although most marsupials like koalas and kangaroos live in Australia, one species, the Virginia opossum, made it to North America. (Hanlon, 2013). Metatherian is the clade of marsupials. Metatherians give birth to babies that must finish their development in a marsupium or pouch. The superorder Ameridelphia refers to South American Metatherians, which include other opossum species (Dines et al., 2022).
Defining Characteristics
"Face is white with a dark V-shaped marking"
Body has "dense, gray underfur and long, gray or black guard hairs"
Black, hairless ears
Prehensile tail, meaning capable of grasping
Opposable thumb (like us!) (Smith & Marable, 2022)
50 total teeth! (we only have 32) (Dines et al., 2022)
Misunderstood Mammals
Many people view opossums as disease-ridden, dangerous species, but this is not the case. Opossums act as nature's "trash can" by consuming dead animals (Jameson & Peeters, 2004).
When opossums are startled, they "play dead," which is similar to fainting (San Diego Zoo, 2024). “Playing dead” can make people think the opossum is sick; however, studies have shown that opossums are resistant to rabies due to their low body temperature (Elzinga, 2020; Hanlon, 2013). Opossums are also immune to snake bites, and some researchers are using opossum proteins to develop antivenom drugs (Komives et al., 2016). I have seen opossums on campus before, so if you see one, try not to startle them and thank them for keeping our ecosystems clean!
RODENTS: MORE THAN JUST LAB RATS
Figure 8. Dipodomys agilis
Figure 9. Dipodomys merriami
Dipodomys agilis, Agile Kangaroo Rat and Dipodomys merriami, Merriam's Kangaroo Rat
Order Rodentia (rodents)
Zygomasseteric Morphology Clade Myomorphous (mouse-like)
Suborder Castorimorpha
Family Heteromyidae (kangaroo rats)
Kangaroos or Rats?
Kangaroo rats are rodents, which make up 42% of all mammal species. Rodents have large incisors and jaws designed for chewing. Since they have specialized chewing adaptations, they are grouped based on their zygomasseteric morphology or chewing muscle structure (Helmer, et al., 2005). In the case of kangaroo rats, they belong to Myomorphous or the "mouse-like" clade, which includes rats, hamsters, and gerbils (Dines et al., 2022).
Defining Characteristics
Fur is tan with a white belly (U.S. National Park Service, Kangaroo Rats)
Tail longer than body with fur tufts
Large auditory bullae, that allow for enhanced hearing of predators, Fig 10. (Dines et al., 2022)
Dipodomys merriami has 4 toes on each hind foot; Dipodomys agilis has 5 (Wilson & Ruff, 2000)
Can I buy you a drink?
Kangaroo rats live in desert environments, including the San Gabriel Mountains (Dipodomys agilis) and Mojave Desert (Dipodomys merriami) (Jameson & Peeters, 2004). Despite their arid environment, kangaroo rats can live without EVER drinking water (Dines et al., 2022). These animals dig burrows that allow stored seeds to gain moisture (U.S. National Park Service, Kangaroo Rats). In addition, kangaroo rats have specialized kidneys that produce highly concentrated urine (Schmidt‐Nielsen, 1952).
Figure 11. Video of kangaroo rat defensively kicking snake (Ninja Rat, 2019)
Leaping Away from Your Problems
Kangaroo rats get the name "kangaroo" from their incredible leaping ability, Fig 11 (Biewener & Blickhan, 1988). Kangaroo rats can jump 9ft into the air and change direction mid-leap using their tail (U.S. National Park Service, Kangaroo Rats).
Congratulations Mammalogists!
I hope you enjoyed learning about some of the fantastic mammalian species in Southern California. Mammals can be found all over the globe and help hold ecosystems together. Next time you are on campus, I challenge you to observe all the incredible animals around you. Although we live in an urban community, we are connected to surrounding ecosystems and the animals that inhabit them. Learning about these species can help us appreciate the diversity of life and the importance of natural environments.
References
Biewener, A. A., & Blickhan, R. (1988). Kangaroo RAT locomotion: design for elastic energy storage or acceleration ? The Journal of Experimental Biology, 140(1), 243–255. https://doi.org/10.1242/jeb.140.1.243
Biodiversity Atlas of LA. (n.d.). Mountain lion, Puma concolor. https://biodiversityla.org/species/iconic/mountain-lion/
Dines, Jim; Dean, Matthew; Lough-Stevens, Michael. (2022). BISC 363 Mammalogy [PowerPoint slides]. University of Southern California.
Elzinga, C. (2020, June 2) Why should I care about Virginia Opossums? - Veterinary Medicine at Illinois. Veterinary Medicine at Illinois. https://vetmed.illinois.edu/hospital/wildlife-medical-clinic/wmc-blog/why-should-i-care-about-virginia-opossums/
Gearin, P. J., Melin, S. R., DeLong, R. L., Gosho, M., & Jeffries, S. J. (2017). Migration patterns of adult male California sea lions (Zalophus californianus). NOAA Technical Memorandum. https://doi.org/10.7289/v5/tm-afsc-346
Hanlon, C. A. (2013). Rabies in terrestrial animals. In Elsevier eBooks (pp. 179–213). https://doi.org/10.1016/b978-0-12-396547-9.00005-5
Helmer, P., Whiteside, D.P., Lewington, J.H. (2005) Introduction to small mammals. In Elsevier eBooks (pp. 165–171). https://doi.org/10.1016/b978-070202782-6.50010-7
Higgins, P., Meachen, J., & Lovelace, D. M. (2023). Were pronghorns (Antilocapra) primary prey for North American cheetahs (Miracinonyx)? Quaternary International, 647–648, 81–87. https://doi.org/10.1016/j.quaint.2022.08.003
Jameson, E. W., & Peeters, H. J. (2004). Mammals of California. Univ of California Press.
Komives, C., Sánchez, E. E., Rathore, A. S., White, B., Balderrama, M., Suntravat, M., Cifelli, A., & Joshi, V. (2016). Opossum peptide that can neutralize rattlesnake venom is expressed in Escherichia coli. Biotechnology Progress, 33(1), 81–86. https://doi.org/10.1002/btpr.2386
Los Padres Forest Watch. (2018, February 2). Steller Sea Lion | Los Padres ForestWatch. https://lpfw.org/our-region/wildlife/steller-sea-lion/#:~:text=As%20strange%20as%20it%20might,southern%20rocky%20Big%20Sur%20coastline
National Geographic Society. (n.d.). Niche. https://education.nationalgeographic.org/resource/niche/
Ninja Rat. (2019, March 27). Kangaroo rat defensive kicking of rattlesnake while jumping [Video]. YouTube. https://www.youtube.com/watch?v=HTjX8YilcJg
NOAA Fisheries. (2022, April 21). California Sea Lion. NOAA. https://www.fisheries.noaa.gov/species/california-sea-lion
NOAA Fisheries. (2023, September 18). Steller Sea Lion. NOAA. https://www.fisheries.noaa.gov/species/steller-sea-lion
Pronghorn (Antilocapra americana). (n.d.). https://tpwd.texas.gov/huntwild/wild/species/prong/#:~:text=The%20antelope%20is%20a%20small,and%20a%20white%20cheek%20patch
San Diego Zoo. (2024). Opossum. https://animals.sandiegozoo.org/animals/opossum
Schmidt‐Nielsen, B. (1952). Renal tubular excretion of urea in kangaroo rats. American Journal of Physiology, 170(1), 45–56. https://doi.org/10.1152/ajplegacy.1952.170.1.45
Smith, M.D. & Marable, A.D. (2022, July 18). Virginia Opossum: our only native marsupial - Alabama Cooperative Extension System. https://www.aces.edu/blog/topics/forestry-wildlife/virginia-opossum-our-only-native-marsupial/#:~:text=The%20female%27s%20pouch%20is%20perhaps,Only%20females%20have%20marsupia
The Marine Mammal Center. (2024) Steller Sea Lion | The Marine Mammal Center. https://www.marinemammalcenter.org/animal-care/learn-about-marine-mammals/pinnipeds/steller-sea-lion#:~:text=Steller%20sea%20lions%20are%20similar,length%20and%20weigh%201%2C000%20pounds.
U.S. National Park Service (n.d.).Kangaroo Rat - Organ Pipe Cactus National Monument. https://www.nps.gov/orpi/learn/nature/kangaroo-rat.htm
U.S. National Park Service. (n.d.) Puma Profiles: P-22 (U.S. National Park Service). https://www.nps.gov/articles/000/puma-profiles-p-22.htm
Wilson, D. E., & Ruff, S. (2000). The Smithsonian Book of North American Mammals. Journal of Mammalogy, 81(2), 521–523. https://auburn.edu/cosam/faculty/biology/best/research/PDFs/1999BestDipodomysAgilis.pdf
Image Links
Figure 1. https://thewhaletrail.org/wt-species/california-sea-lion/
Figure 2. https://www.sciencedirect.com/science/article/pii/B9780124095427500056
Figure 4. https://www.danitadelimontprints.com/pronghorn-antilocapra-americana-13971718.html
Figure 6. https://www.smithsonianmag.com/smart-news/cougars-are-returning-midwest-180957263/
Figure 7. https://www.reconnectwithnature.org/news-events/the-buzz/things-we-love-those-precious-possums/
Figure 8. https://www.inaturalist.org/taxa/44115-Dipodomys-agilis
Figure 10. https://www.youtube.com/watch?v=fzILRx2QiQY and https://animaldiversity.org/accounts/Heteromyidae/specimens/collections/contributors/skulls/microdipodops/m._pallidus/78759.ventral/?start=15
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