What You Otter Know About Sea Otters - Part 1
The last week in September is known as Sea Otter Awareness Week throughout California. To bring more attention to the issues surrounding the sea otter and its ongoing recovery from near extinction, we interviewed Tim Tinker, USGS lead sea-otter researcher. Video also provided in the Transcript/Links section.
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Paul Laustsen: Hello and welcome to the USGS CoreCast, I’m Paul Laustsen. And today I’d like to welcome and introduce you to our guest, Dr. Tim Tinker, a research biologist with the USGS Western Ecological Research Center. Tim is here to talk to us about the California Sea Otter, a little aquatic animal with an incredible comeback story. Welcome, Tim!
Tim Tinker: Well, thank you very much for having me on.
Paul Laustsen: I was wondering if you could tell us why the USGS is studying the sea otter.
Tim Tinker: Well, the USGS has been interested in sea otters and the environment that sea otters live in for a long time. Sea otters are one of the more important members of the nearshore marine communities we find in the western coast of North America. And also right up around the North Pacific Rim over to the Russian Commander Islands and Kamchatka Peninsula.
Sea otters are what we refer to as a keystone species. And by that we mean that they have a very strong impact on the ecosystem that they live in. In the case of sea otters, when sea otters are absent from a system, from the nearshore communities, you tend to find an environment that is dominated by large benthic grazing invertebrates such as sea urchins. And a lot of these benthic grazers are able to limit the abundance of kelp. So the nearshore marine ecosystem without otters is one that’s dominated by these grazers. There is kelp but it is not particularly abundant.
As sea otters move back into a system, the characteristics of their biology including their incredibly voracious diet, their high metabolic rate, means that they consume a lot of shellfish. And by doing that they’re actually able to limit these grazing invertebrates and that leads to a great increase in the abundance of kelp. And so, you see the entire nearshore marine environment change to one dominated by urchins to one dominated by kelps. This whole ecosystem shift occurs simply by the presence or absence of sea otters. And so we refer to them as a keystone species.
Understanding sea otters and their relationships to the other members of that ecosystem has been one of the more interesting stories that we’ve tried to understand over the last 20 or 30 years.
Paul Laustsen: You mentioned that there’s different colonies, some up in Alaska, some off the coast of Washington and down in California. What’s the difference between these sea otters?
Tim Tinker: Well, the southern sea otter is a separate subspecies from the northern sea otters. It’s genetically distinct, both the geographical distinctness but also the genetic differences lead to it being designated as a separate subspecies.
As far as their sort of overall appearance, their behavior and life history patterns, you wouldn’t really notice any great difference between the northern sea otters and the southern sea otters. They look pretty much the same. The southern sea otters are a little bit smaller than their northern cousins, both males and females. Male sea otters are larger than females in all populations. But the way they spend their lives, what they eat and all aspect of their behavior are pretty similar between the northern populations and the southern populations. So, you might not notice any difference at all.
Paul Laustsen: So I’m curious and perhaps for our CoreCast listeners you could describe the way that a sea otter moves and sounds.
Tim Tinker: Boy, that’s a tricky one. Well, sea otters are a little bit different from other marine mammals in that they spend most of their time on their backs, well, at least while they’re on the surface. They also spend more time at the surface in general than most other marine mammals.
When they’re feeding they bring their prey up to the surface and then they float on their backs and hold their prey which are generally benthic marine invertebrates such as crabs or urchins or abalone or clams. They hold them on their chest. They actually can form a little pocket between a fold of skin in their underarms. And by holding their arms up they create a little tray or a little pocket so they can actually hold quite a few invertebrates in that little tray. I’ve seen them eat as many as 20 or 25 sea urchins at a time for instance can fit into those little pockets. So they process that prey on their chest, often using tools, rocks or shells for instance and then sort of discard the empty shells back into the ocean.
So you’ll often see them floating around, eating on their backs. They’re also – even when they’re swimming from place to place, they generally swim on their backs except territorial males which tend to swim on their front. So if you see a large sea otter swimming on its front, sort of plowing through the water, that’s probably a male. Females when they’re swimming, they have a dependant pup; will often carry the pups on their belly. So, if you see an otter that seems to have a big furry pup on its chest or on its tummy as it’s swimming along that’s a female sea otter with her pup.
How they sound? Boy, that’s a tough one. Well, if you happen to be standing on Cannery Row or somewhere along the coast of California and you hear what sounds like a small child screaming, assuming it’s not a small child screaming it may very well be a sea otter. It sounds sort of like a two year old screaming at a very high-pitched voice. That’s a sea otter pup. The mothers will often reply with another scream that tends to be a little bit lower. And mothers are able to recognize their own pups’ vocalization. So if they surface and the pup has got separated from them due to current or wind, the pup will often scream with this high-pitched scream and that allows the mother to identify them.
Paul Laustsen: Can you tell me how the sea otter got onto the endangered species list?
Tim Tinker: Well, the California Sea Otter, like other sea otter populations, ended up in the endangered species list, again, because of an interesting biological trait. And that is their incredibly thick and warm fur coats. Sea otters, unlike other marine mammals, do not have a blubber layer so they’re reliant to thermal regulate to maintain their body temperature. In a cold marine environment, they rely on their high metabolic rate, thus their tendency to eat a lot of sea urchins, and also on this incredibly thick fur coat. It’s the thickest fur of any mammal. It’s very good for sea otters but it turns out to be bad for sea otters when people begin to like to wear fur coats themselves. And that happened in the mid 1700’s, when the Europeans discovered these mammals living close along the coastline with these thick fur coats that were very easy to hunt.
And so within the period of about from 1750 up to about 1900, they hunted sea otters and also for seals to near extinction. And by 1900 there were only a few, tiny remnant colonies of sea otters left and they were protected by international treaty in 1911. And at that time it was actually thought that sea otters were extinct in California. But around 1930 they discovered a little remnant colony, about 50 animals, down in the central part of the Big Sur coastline, a very remote and difficult to reach place.
And that was the source of today’s sea otters in California. They recovered from those 50 animals up to about 2,700 animals that are here in California now.
Paul Laustsen: Well thank you, Tim. I really appreciate the time you took to speak to us about sea otters today.
Tim Tinker: Thank you very much for talking to me.
Paul Laustsen: CoreCast is a product of the US Geological Survey, Department of the Interior.
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Resources related to this episode
- Sea otters in action
- Sea Otter Studies at the USGS Western Ecological Research Center
- A Day in the Life of a Marine Biologist: Tracking Sea Otters off the California Coast