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TOM WHEELER:

Welcome to the EcoNews Report. I'm your host this week, Tom Wheeler, Executive Director of EPIC, the Environmental Protection Information Center. We are talking about river otters this week. I have two special guests here. Join me in the studio, Charlotte Norman and Gina Culver, master's students or formerly master's students. Congratulations to you both from Cal Poly Humboldt, who studied river otters locally. Welcome to the show.

All right, so let's get to know river otters generally. River otters are distinct and separate from sea otters. Let's start there because I think that a lot of people might be confused when they look out at Humboldt Bay and they see something swimming in the waters and the waters are pretty salty and so then they assume that that must be a sea otter. So what is the kind of range or normal habitat types of a river otter?

CHARLOTTE NORMAN:

Yeah, so river otters, they're across the entire United States and they have been for a long time. They were extirpated from most of their range at one point, but they've been recovering and coming back. And in California, they're doing quite well and increasing in numbers and they're not threatened or endangered anymore. And here in Humboldt, we only have river otters. We actually don't have sea otters here at all, but river otters, they do use freshwater and they can also be out in the ocean in saltwater. However, they can't live in saltwater as sea otters can. So they do need to come back to freshwater regularly to drink for drinking water and also to clean themselves because saltwater from the ocean, it'll clog up the insulative capacity of their fur. So they need to get all that salt out of their fur to keep warm. So we'll see them here. They do go back and forth from the rivers to the ocean, but you know, yeah, you probably have something to add.

GINA CULVER:

Yeah, and I think a lot of people when they look at sea otters and river otters, they kind of mistake the two. Some key differences between the two are that sea otters are only seen in marine habitats and they're also about double the size of a river otter. So it's pretty, pretty big distinction there. They also have different diets. So sea otters are typically you see a sea otter on its back and it's kind of opening the clam or that typical photo that we all see. But river otters actually, they use their hands to hold their prey items, but they don't actually open up. They don't use their hands as a tool to open up their prey like sea otters do.

WHEELER:

And I am obsessed with mustelids. I think it's like my favorite, I don't even know if it's, what is it, class? Species? Genus? Family. Family. My favorite family of life, I think, are mustelids. So, humble martins, and fishers, and weasels, and otters. So, that also kind of gives us maybe a little bit of a clue about their diets. And we'll get into more diet specifics, but generally, you started on the diet of river otters. Are they carnivores? What sort of food do they eat?

CULVER:

Yeah, so river otters are exclusively carnivores. In the literature, when you get into it, a lot of the times they highlight fish as a primary prey item, but it kind of depends where they're living. So based on the habitat that they're occupying, sometimes we see different species of birds. We also see crustaceans like crab and occasionally some aquatic insects.

WHEELER:

Charlotte, you said that they were extirpated for most of their range in the United States. What's the history behind that extirpation? I'm familiar with sea otters and hunting of sea otters. Were river otters hunted in the same way for their pelts?

NORMAN:

Yeah, exactly. They have very dense fur, so I think it's quite desirable, those pelts. And it was over-harvesting, over-hunting that led to them, their numbers having huge declines and then starting in the 1950s or so, there was a lot of reintroduction efforts and there was new hunting laws, I think, that were put into place to protect them a little more. So they have been making comebacks across the United States, but there's 14 otter species globally too, and we have one of the few otter species that's doing okay, but I think 12 out of the 14 otter species globally are threatened or endangered, so around the world they're not doing too well, but here they've been doing okay.

WHEELER:

Are there other conservation issues impacting river otters besides over-extraction or over-hunting?

CULVER:

Yeah, so I know historically, like, so additionally, with the introduction of the Clean Water Act, that was seen as a key factor in otters, otter numbers increasing again, they're seen as sensitive to pollution. So with these new regulations and less pollutants in the water, that was another factor that influenced conservation.

WHEELER:

So otters are carnivores and when they are missing from ecosystems, I imagine there's going to be an impact on those ecosystems as carnivores often have a role in regulating prey species. Can you talk about what the absence or presence might mean for ecosystem health?

CULVER:

Yeah, so otters are seen as apex predators, so, and they're a keystone species, which means they do have a big impact on the habitats that they occupy. And when we see a good example is kind of like the, the key, you know, the, the classic wolves in Yellowstone example of the wolves are gone and now these prey species populations are exploding. So that's kind of how we think about it. So if otters were not present, then you would probably see prey species, the numbers are going up and perhaps the vegetation or kind of like that top-down, the top-down effects. And then with otters being present, they, they regulate the species populations that they're consuming to an.

WHEELER:

And does anyone, besides humans, prey on otters?

NORMAN:

There are a lot of examples from some older literature. I think it's largely the pups, so the young otters that are most vulnerable to predation. But it could be, you know, it could be large avian predators, like eagles could potentially even take a...

or scavenger, but then there's like coyotes, bobcats, mountain lions are all considered potential predators. How much that really actually happens, I don't think it's too common. I think humans, dogs, cars are probably the most.

CULVER:

Yeah, yeah, because they're also, they're constantly in and out of the water. So when you think about them occupying spaces where they're in waterways and rivers and lakes and et cetera, you're not going to see that coyote chase an otter into the water.

NORMAN:

I did see something similar happen. So in my study, which took place at the Little River, which is here in Humboldt, Little River comes out to Moonstone Beach, so many of us are probably familiar with it. But one day I saw a coyote up high in the dunes and an otter got out on its latrine site on the banks of the river and the coyote ran down from the dunes right towards the otter and the otter had to back out and it swam away and left. There's a lot of, I don't know if the, I doubt the coyote was going to attack the otter, but it was pushing it away it seemed. And then there's a lot of examples from Marin County of otters getting some big prey item, like pelicans actually, they can get this huge prey item, and then a coyote can push the otters off and come in and scavenge on their find and on their kill. So yeah, there's interesting relationships probably at play.

CULVER:

And did you guys hear about that coyote that was swimming in San Francisco Bay recently? So you never know, I mean, coyotes could chase them.

NORMAN:

Yeah, yeah, and then there's studies from up in Alaska, too, where they suspect that marine mammals could potentially be a predator of river otters, too, where the river otters are going out in groups to prey on marine prey items.

WHEELER:

Yeah. So you mentioned the role of dogs and cars. I'm most familiar with our otters at the marsh here in Arcata, just down the block from where we're recording right now, and I imagine it must be difficult to be a river otter there given the amount of humans and the way that we have a road network that goes through their habitat. Can you talk about how, in particular, humans are impacting local river otters? Yeah.

CULVER:

So actually, throughout both of our studies, and specifically at the marsh, we have seen a few otters get hit by vehicles. And we try to spread the word with slow down, follow the speed limit signs. And I believe they recently also put in some speed bumps to help with this. But typically, there are culverts that go underneath the roads. So sometimes we're seeing otters just use those culverts under the road. And that way they can avoid this from happening, but for the most part they do cross the road and that is a big issue locally. We also see some otters that have been hit on the 101 coming out of the marsh area. So it's definitely a threat.

NORMAN:

Yeah at the marsh too you'll see these otter crossing signs that have been put up and they're put up in specific spots because the otters tend to use the same paths to cross over from pond to pond or from pond into the bay and so where those signs are where otters have been hit before and it's where you're likely to encounter them so especially in those places I guess it's best to keep to the speed limit.

WHEELER:

All right. Well, when you're visiting the marsh, be on the lookout for otters, especially when you're maybe driving your car or if you have your dog, be sure to keep it leashed as is required at the marsh. How are river otters doing their populations locally? Are we confident that they are stable? Are they increasing? Are they decreasing?

NORMAN:

I don't think we have quite enough information to say that, but one of our fellow grad students in our lab, Whitney Vickers, did a study a couple years ago. She did a genetic study where she collected DNA from their scat all across the Humboldt Bay. And I think, oh gosh, I'm forgetting the number now, but I think it was 80, I think?

CULVER:

82 otters were genotyped from Trinidad to Ferndale, and it was 16 at the Arcata Marsh.

NORMAN:

There were 16 otters found to use the Arcata Marsh during her study, which was I think one calendar year, maybe nine, ten months of a year, yeah.

WHEELER:

All right. Let's get into each of your individual research areas. So I'm going to start with you, Charlotte. So tell us about what you studied broadly, and then we can start to dive into specifics.

NORMAN:

Great. So we'll be starting off talking about family mustelidae, like the otters, or sorry, the fishers, the martens, et cetera. Otters are pretty unique within family mustelidae in that they're quite social creatures. A lot of these weasel-type mustelids, they're very solitary. They live on their own. They come together for mating and breeding, perhaps, but they largely live on their own. Otters are not so, especially our coastal living otters. So we do see a difference in the social dynamics and social systems of otters on the coast versus inland, whereas inland river systems, they tend to be more solitary. But here on the coast, it seems to be a benefit to be part of a larger group, can work together to forage, and you probably have better success finding food that way. So my study was looking at some of those social dynamics that come into play. So I looked specifically at two behaviors in river otter groups at the Little River Estuary, and I was looking at their play behavior, their social play, and at their allo-grooming behavior. And allo-grooming is when two individuals groom each other. So I focused on these two behaviors to hopefully shed some light on what social dynamics might look like within a family group and also within adult groups.

WHEELER:

So what does the kind of research process look like there? Did you just plant a chair in the dunes and just sit with binoculars for hours, hoping to?

NORMAN:

That is pretty close. Yeah. That is very close. Yeah. Yeah. So I went out five mornings a week for five months. So I was out there at the Little River quite a bit. And I, yeah, I had a spotting scope that I would attach an iPhone to. I had a special adapter. So rather than just recording in the moment, I recorded it on video so I could play the video back to get data from. But it was sitting up in the dunes for hours at a time, watching otters whenever they moved through the river.

WHEELER:

And I imagine that this has allowed you to form a relationship of sorts with the otters. Maybe they don't recognize you, but you've been able to recognize them and come to understand individuals. Do you want to talk about that?

NORMAN:

Yeah, I felt very lucky and very grateful to get to have that time there watching them. Individuals I could tell individuals apart within the family group and so the family group that I saw at the Little River that held that territory was a breeding female. So the mom, she had two young female pups and then she had a younger female helper come and join her. So that was my family group that I could tell apart. I could tell the helper from the mom from the two pups. We did have adults also moving through the estuary, but I wasn't actually able to tell individuals in that case. I think I was still just too far away and didn't get quite enough definition of their features. What I've heard too is that, I've heard this from Jeff, our advisor, our professor who started this project, that he's been to the Sequoia Park Zoo and he's seen the otters up close there and he says, ah, now I can tell them apart. They look like dogs almost. You know, you can really see their, you know, you possibly can't tell two labs apart from each other, but then when you're up close, maybe you can see those individual differences. So I think it's similar with otters. Once you're close enough, I'm sure you could notice those differences, but yeah, for me, I couldn't quite tell individuals except for based on behavior, such as in the family group.

WHEELER:

You are listening to the Econews Report, and we're talking about river otters this week. And Gina, you were at the Arcata Marsh. Tell us about what you studied.

CULVER:

Yeah, so my study was more focused on river otter diet and also how they were selecting different bird species and perhaps what types of behaviors these bird species displayed that made them more vulnerable to predation. So I spent a lot of time at the marsh watching the otters hunting, basically, and then also watching the bird's behaviors as well to see would they fly off the water, did they stay in the water when the otters were present. And then we also collected, I think, 1,000 scat samples of otter scat. So like Charlotte mentioned earlier, the otters use the same trails. And I think we have documentation of about 30 years of the same latrines being used. They use these latrines to communicate with other otters and they deposit scat there. And it's really easy to tell what they're eating just by looking at their scat. So we collected a lot and we took it back to the lab at the university and dissected it and washed it by hand. And basically, we picked out all of the bird feathers and then we utilized specimens at the university of taxidermied birds to compare the feathers. And identify exactly what species of birds they were eating.

WHEELER:

So based on the scat, were you able to determine the relative importance of various bird species to the diet of these otters? Or what are the otters eating most, I guess is what I'm trying to get at.

CULVER:

So the nice thing was that my study was a year long, so we were able to get a really nice composition of what are they eating throughout the year. And so we found that in the winter, the fall and the winter, when we see a huge influx of birds flying into the Arcata Marsh and Humboldt Bay, that we're seeing almost birds in their diet exclusively. And we were seeing specific species of birds more so than others. And then we also saw crabs. I always laugh because the season when everybody here around Humboldt Bay is looking forward to eating crab, that's when otters have crab in their scat as well. So yeah, and then we saw that they were really favoring ruddy ducks and buffalo head. Those were kind of the top two. We saw American coot and mallards, wigeon. The wigeons come in in thousands at the marsh. I think our highest count of wigeon there was like 5,000 once. So that wintertime when all the birds are here, they're just essentially feasting on birds.

WHEELER:

And how does an otter go about hunting a duck? I think about a mallard duck and I think about an otter and that's a nice sized prize for an otter. It seems like a pretty impressive hunting feat. So what is the hunting process?

CULVER:

Yeah, so initially we thought that they would probably go for larger ducks as well and that body size would be something more relevant in the study, but we found that they actually, that was not their primary focus.

WHEELER:

How do they go about hunting? Uh, yeah. So, so what does that, what does an otter hunt even look like?

CULVER:

Oh yes, so the otters will actually conceal themselves within the vegetation, within those ponds, and they, they dive underwater, they hide within the vegetation and they essentially sneak up on the birds. We've seen an otter actually scoop a bird up from, from under the water. So the bird was sleeping on the water and then they just grabbed them. We've also seen otters working together from different angles of the pond and kind of just, the ducks are just flying frantically throughout these ponds. So they, we've seen them working together and then also hunting ducks on their own.

WHEELER:

So your advisor published a paper, Wolves in the Watershed, I think is the title of it, or part of the title. Wolves of the Wetland. Wolves of the Wetland. And here, it really sounds like wolf behavior, right? Hunting in packs, that's kind of incredible, especially to your point about other mustelids being largely solitary creatures. Here, we have not only this social behavior that Charlotte studied of grooming and play between otters, but we also have group hunting activities. That's pretty exciting.

CULVER:

Yeah, yeah. It was, it was really, really cool to see. And in that particular instance, they were hunting a huge group of ruddy ducks that like to hang out on the oxidation palms at the Arcata Marsh. And I think we saw it several times. So it's really unique there because we have, essentially you have a wastewater facility and then you have a recreational space, but then there's people from the university that have been doing studies at the marsh for years and years and years. So it's really unique.

NORMAN:

Yeah, that's one of your tips too, I think, for otter spotters or otter watchers at the marshes to look for ducks flying off the pond and perhaps you'll find an otter there. Maybe it's that that chased them off the pond.

WHEELER:

Well, so let's talk about kind of citizen science or the ability for individuals to help participate in the accumulation of knowledge about otters. I believe that Jeff has some portal by which folks can submit information. Do either of you want to tell me about this?

NORMAN:

Yes, I don't remember the exact name of it, but you can Google River otter demography study and it'll pop up. But it's been going on for about 25 years where Jeff's been getting sightings from the public for Humboldt, Del Norte County, Southern Oregon. You can put in what time, what date you saw an otter, how many you saw, whether they had pups with them. We love getting pictures or videos you have to send in. Yeah, I mean, now he now has this huge database that's been going on for 25 years.

CULVER:

Yeah, and it's great because we have a lot of people who love watching otters and they know where to go and they are essentially helping us with providing data. So what we get from citizen science is not only community contribution, but we're figuring out where the otters are, how many, when people provide photos. It helps us look at perhaps if there's a female with a pup, that size difference. So it really helps us with data just to understand where are people seeing otters in this area, especially for a species we were talking about earlier where at one point we didn't really see them that much. So this kind of helps an ongoing study of local populations.

WHEELER:

Let's give some tips for folks who want to go out and see river otters. Where should they go? Obviously the marsh has some. What should they look for and other things that would help enhance the river otter experience.

CULVER:

Okay, so at the Arcata Marsh, to enhance your river otter experience, the Clop Lake is a really good one. You'll very frequently see otters fishing in there, so that's where they primarily go fishing. So...

WHEELER:

And what would we look for for fishing?

CULVER:

You'll see the otters coming in and out of the water. So they're diving into the water, then coming up and then diving again. And then often you'll see their face coming up and they'll be holding a fish and then eating it. You can also look for the latrines that are the trails along pretty much all of the walking trails at the marsh. At some point, you'll see a latrine. And what I tell people is when you smell something really fishy all of a sudden, if you look to the side, there's probably an otter latrine. And a lot of dogs like to smell it. I was always like, hey, don't eat this cat. Yeah, and then for bird, I always tell people look at the birds. When you see the birds that are alarm calling and frantically flying off the pond in large groups, there's probably an otter there.

NORMAN:

Earlier in the morning tends to be a better time to see them, but they're so variable they don't keep to specific timelines during the day. So you can kind of see them any time, but typically earlier in the morning you'll have better luck.

WHEELER:

On, on this social aspect of otters, have you, this might be kind of dumb, but like, have you learned something about like what it means to be a mammal by, by studying another mammal? Like what it means to be a human by studying otters?

NORMAN:

I just gave my defense for my thesis and had a lot of people come up to me afterwards and say, oh, it made me think of some humans I know that I heard after hearing about it. One thing that I loved learning more about with the otters is that they do something called cooperative breeding, which is where the breeding female gets help from another individual to raise the pups. So in this case, the breeding female had two pups here at the little river and she had a female come and join her and help her in the raising of the pups. I mentioned before I was looking at their grooming behavior and their play behavior and one of the things I found was that the helper, the younger helper, she was playing with the pups a lot more than the mom was. However, they both groomed the pups equally, so it's possible that these behaviors have some different social function within the groups too, where maybe this helper, kind of like this older cousin sort of feeling, she's playing with the pups more, potentially a non-related individual, and perhaps that's serving as a function to help the pups integrate into these new social systems as they get older.

WHEELER:

So before we started recording, we were talking a little bit about how to differentiate otters. And I think you were saying that you could tell different otters from their palates.

NORMAN:

Oh, yeah. So we have a lot of otter spotters that help the Citizen Science Project. So a lot of people at the marsh with their cameras taking pictures of otters and what we found from getting their submissions of their photos was that when the otters are up with their heads out of the water munching on their fish or you know, eating their crab, their mouths are wide open. And so we got a number of photos of the palates of their mouth and it really some of them had birthmarks, some of them had teeth that were worn down in specific places. So that when we got these images of the otters with their mouths wide open, we could tell individuals apart. So we had inky and pinky for a while.

CULVER:

It was two females that one of them was the helper and the other one was the breeding female and one had a black spot on the palate of her mouth and the other one didn't and they were always together so we gave them nicknames. And then we also see some that have scars or broken teeth, things like that. And then we would also see groups of males and they're a lot more blocky, larger versus when we saw perhaps a group of two females and a pup, they were a lot smaller. So that's kind of how we would differentiate individuals.

NORMAN:

Yeah and then in my study too, another way I was determining the sex of an individual was waiting for them to get out on land and watching them urinate because they're quite like dogs so you could tell male or female based on where you saw a stream of urine coming from on their body and so I did a lot of zooming into them.

WHEELER:

It's kind of being a weird animal per zoo.

CULVER:

I mean our jobs, our jobs were...

WHEELER:

Speaking of the-

CULVER:

My wife always says, it's a dirty job, but somebody's gotta do it.

WHEELER:

Absolutely. Well, this is, this is a good advertisement for folks to go to grad school, right? You get to stare at animal genitals and handle their feces. Wonderful. Well, and on that, congratulations. You both, Charlotte, you recently completed your, your master's defense and you completed yours last year. I hope to have you on in the future as you continue your wonderful careers in wildlife.

NORMAN:

Thank you for having us.

CULVER:

Yeah, thank you.

WHEELER:

Thank you. All right. Join us again next week on this time and channel for more environmental news from the North Coast of California.