Introducing Dr. Shawn Larson:
Last Friday, Dr. Shawn Larson, a Senior Conservation Research Manager at the Seattle Aquarium, gave a talk as part of the Friday Biology Seminar Series about the population, history, and recovery of sea otters (Enhydra lutris). Having studied sea otters for over two decades, Dr. Larson started her academic journey studying biology at UC Berkeley before going on to study big cats at Cal Poly SLO. After volunteering at a zoo and working as a vet tech in Seattle, she finally started as an animal health and research coordinator at the Seattle Aquarium in 1995. Her study of sea otters inspired her Ph.D. at the University of Washington’s School of Aquatic and Fishery Sciences, where she gave a dissertation focused on sea otter genetics and endocrinology. In this research, she used non-invasive endocrinology. In other words, she examined sea otter feces to explore their reproductive hormones. She currently oversees 20 conservation research projects and is the Sea Otter Species Coordinator for the International Union for Conservation of Nature’s Otter Specialist Group.
Sea otters, – not to be confused with river otters (Lontra canadensis) – are unique in that they are “true marine mammals.” They sleep, eat, and live in the water, and although they sometimes do for fun, they never need to come to shore. Dr. Larson spoke of the confusion between the two, that when she’s told “I have a sea otter living on my boat,” in reality, it is almost always a river otter. Sea otters also have the densest fur in the animal kingdom (up to 1 million hairs per square inch), in order to stay warm in the chilly northern waters of the pacific. They are often seen blowing air into their fur in order to create an insulating bubble around their body. Also importantly, they’re super cute! In fact, it is estimated that each otter creates three jobs due to the tourism that they create. I mean, look at that face!
Human otter history and human impact:
Humans and sea otters have a long history of interaction. Before colonization, indigenous people hunted them for food, used their fur, and the otters held important cultural value. After the involvement of European colonizers however, the fur trade quickly led to a steep decline in sea otter populations. By the 19th century, fur trade had fallen out of practice simply because it became too difficult to find the otters with so few individuals left. It is predicted that before the fur trade, the sea otter population off the west coast was 600,000 to 1,000,000 individuals. Following the extensive overhunting of the sea otters, the estimated population dipped as low as 100-1,000 individuals. Another casualty of the fur trade was the stellar sea cow (Hydrodamalis gigas), a large manatee the size of a whale at 8-9 meters long. This beautiful creature was discovered in 1741, but because of overhunting, became extinct only 27 years later!
Otters’ role in the ecosystem:
With the extensive overhunting of sea otters came extreme impacts on their aquatic ecosystems. Sea otters are known in the ecological world as a keystone species. That essentially boils down to the importance of the animals at the top of the food chain. The effect of removing key predators from an ecological pyramid (read sea otter massacre) is felt all the way down to the lowest levels of the ecosystem. In the giant kelp forests (Macrocystis pyrifera), the absence of sea otters has caused the occurrence of urchin barrens. These large stretches of ocean that once housed a bustling community of sea life are now rocky and abandoned. Urchins – specifically purple urchins (Strongylocentrotus purpuratus) – graze along the seabeds in the shallow waters of the kelp forests. When the sea otter populations are healthy, urchins are a natural part of the ecosystem. However, after the hunting done for sea otter pelts, urchins lost their main predator. Sea urchins graze on the holdfasts of kelp, the part that anchors the algae to the rocks. With the kelp constantly being ‘uprooted’ and the inability of young kelp to establish themselves – where there was once an abundant kelp forest – there is left only an ocean wasteland devoid of life. There was a similar occurrence with the eelgrass beds, where crabs – another favorite food of the sea otters – were left to decimate the local eelgrass population. Both eelgrass and kelp perform important ecosystem services as primary producers, meaning that without them, the health of the rest of the ecosystem dwindles.
Current restoration and pushback:
Today, after restoration efforts, the population sits at around 120,000 individuals, a steep climb from the post-fur trade numbers in the 100s. A large part of this population growth – roughly 30%! – can be attributed to the translocation efforts made in the second half of the 20th century. Small portions of sea otters off the waters of Alaska were relocated throughout the pacific coast. Sea otters were then reintroduced to areas where otter populations had previously been hunted to extinction, enabling the beginning of the long ecosystem restoration process.
However, despite the host of goods that sea otters bring to destabilized environments, the impact that their reintroduction has had on commercial fishing has led to conflicts with fishermen. This is because, although reintroduction increases the number and size of fish in an ecosystem, otters also eat some organisms that humans eat like crabs and oysters. When asked about her approach to dealing with those who resent the restoration of the sea otters, Dr. Larson advised that simply explaining the concepts of ecological balance has gone a long way. She mentioned how discussing the stabilizing effect sea otters have on kelp forests and seagrass communities, and how the sea otters’ appetite for competing sea food will increase harvests in the long term often alleviated much anger. “Dr. Larson emphasizes that these topics are important, and that environmentalists need to “have those conversations early and often”.
The Biology Department Seminar series is free and open to the public and takes place weekly on Fridays in Psych 105. Snacks are available at 3:50 pm and talks begin at 4:15 pm. Join to learn about cool research from the guest speakers!