Conservationists in Argentina are celebrating after the sighting last week of a wild giant otter, an animal that was last seen in the 1980s and believed to be extinct due to habitat loss and hunting. The otter was spotted swimming alone on the Bermejo River in Impenetrable national park, located in north-east Argentina.
Sebastián Di Martino, director of conservation at Fundación Rewilding Argentina, a conservation organization, captured the photo on his phone while kayaking on the river. He told The Guardian it was “a huge surprise” and that he was “incredulous,” wanting to “rush back” to tell the other members of the organization.
The giant otter (Pteronura brasiliensis) is the largest otter species in the world, measuring up to 1,8 meters and weighing about 33 kilos. It can be found in large rivers and swamps in northern and southern South America. They have been nearly wiped out, first because of their fur, and now because of extractive activities happening in their habitats.
It’s considered extinct in Argentina, with the last sighting reported in 1980 in the province of Misiones. In the Bermejo River, where it was now spotted, it hasn’t been seen for over 100 years. The closest registered populations live in the Paraguayan Pantanal, 1,000 kilometers away, so the otter could have arrived from there.
“Giant river otters, as top predators, exert a regulatory influence in the aquatic ecosystem,” Di Martino said. “It’s a regulator of fish populations, which contributes to the health of aquatic ecosystems. It’s a spectacular animal, and it’s enormous. They are trusting and curious. To share the environment with them is marvelous.”
Such is the importance of otters that the conservation organization has long been working on plans to reintroduce them. They first brough in a mating pair from Denmark and Hungary, named Coco and Alondra, soon to be released in Argentina’s massive Ibera wetland. Another otter, Nanay, recently arrived from Switzerland.
Rewilding Argentina has also been working to bring back top predators and other species to their native habitats. Six jaguars (Panthera onca), the largest predator in South America, were released earlier this year. The organization will continue working with the guanaco (Lama guanicoe) and the yaboti tortoise (Chelonoidis carbonaria).
The organization helped create the Impenetrable National Park in Argentina in 2014, where the otter was recently spotted, alongside Tompkins Conservation. The Park has 1280,000 hectares of native forests and waterways and is located in the Gran Chaco Forest, an area that has been subject to large levels of deforestation over the years.
“For us, the importance of this sighting is that we’re reminded that we have to protect more of this gem of biodiversity that is Impenetrable national park,” Di Martino said. “The Bermejo River, where this otter was found, is full of illegal hunting and fishing activity. There needs to be more supervision, but also the river has to open up to activities such as tourism.”
Kelp forests around the California coast have declined dramatically in recent years. Attacked by urchins, heat, and left without the defense of sea stars, kelp has fallen by up to 95% in some areas, leaving large swaths of “urchin barrens” behind. Even in these conditions, researchers have found, otters can help ensure that the remaining patches of kelp stay healthy.
It all starts with kelp. Kelp is an umbrella term for a group of large brown algae that grow in “underwater forests” (kelp forests) in shallow oceans. They harbor rich ecosystems and can grow quite fast and reach impressive heights. Up to a few years ago, this is exactly what was seen off the coast of California.
“I’ve been diving here in this ecosystem since 2012 and back then, things looked very different,” UC Santa Cruz graduate student Joshua Smith, lead author of the study, explains in an interview. “We had these kelp forests that were so dense that being underwater was like walking through a redwood forest. Back then, I remember some times when the kelp canopy — the top part of the kelp that’s made its way all the way to the surface of the ocean — was so dense, that we couldn’t even get a boat into the place where we needed to do our science. There were just hundreds of meters of kelp extending offshore.”
But then, in 2013, things started to change. Despite its ability to grow, kelp is vulnerable to overgrazing by sea urchins. Normally, sea urchins are themselves kept in check by sea stars, but around 2013, a mysterious disease called sea star wasting syndrome started to decimate the starfish population.
“Around 2013, I was diving in this area and I started to notice that the sea stars had these lesions,” Smith continues. “And before we even knew what was going on, these sea stars dissolved, they were being hit by this wasting syndrome.”
It didn’t take long for the sea urchins to figure out what was going on. Normally, they spend their time in crevices where they’re hiding from predators and eating drift kelp, kind of like leaves falling from a tree. But after the sea star wasting event, the urchins were emboldened. They started going out and actively grazing on the remaining kelp until they ate it all.
That’s when the otters came in.
“Sea otters haven’t been seen on the North Coast since the 1800s,” said Meredith McPherson, a graduate student in ocean science at UC Santa Cruz, and author of a separate study on California kelp forests. “From what we observed in the satellite data from the last 35 years, the kelp had been doing well without sea otters as long as we still had sunflower stars. Once they were gone, there were no urchin predators left in the system.”
Empty boxes of pizza
Climate dealt the finishing blow to kelp. The 2014 marine heatwave called “the blob” made the underwater forests more vulnerable and hampered their growth.
“And so as a diver, I remember seeing all of these events unfold,” Smith recalls. “Then finally, in 2017, when we spun up this study, the region had already kind of shifted from that really dense, lush kelp forests to this patchy mosaic of kelp forests interspersed with sea urchin barrens.”
“It happened so fast, before we knew it we had lost over 80 percent of the historic kelp forest cover in Northern California,” Smith said. “We also had an urchin outbreak on the Central Coast, but not to the same extent as in the areas north of San Francisco.”
By then, otters had already become very active in the area. Smith and colleagues had been keeping an eye on otters, who also like to munch on sea urchins. They found that after 2014, otters were eating three times more urchins than they had before — but not from the barrens. Otters were careful and focusing on urchins within remaining kelp forests, skipping those in the barrens.
Eager to understand why this is, divers surveyed those places not targeted by otters and collected urchins to examine in the lab. They found that urchins in the barrens have far fewer nutrients than those in healthy kelp forests. For the otter, the barren urchins are just not worth it.
“The sea otters prefer to eat those healthy, nutritionally valuable sea urchins that are in patches of kelp forests and they mostly ignore those that are in the barrens that are completely starved out,” says Smith.
It’s a bit like buying a pizza from a nearby shop, Smith explains, and getting an empty box. At first, you’d be confused, and perhaps get another pizza. But if the second one also comes up empty, you’d probably opt for a different pizza shop, even if it’s farther away — this is what’s happening to the otters. They quickly realized that barren urchins are no good for them and so they opt for the healthier urchins, even if it means traveling a greater distance.
This is good on one hand because it means that it’s helping remaining forests stay healthy and not become barrens. But on the other hand, this means that urchin barrens will continue to remain barren.
It’s different than in other ecosystems. If overgrazing were to happen on land, say if deer were to overgraze grasslands or shrublands, they would starve. But in the case of the urchins, that doesn’t really happen. Urchins can survive for years even being starved out. They can eat microorganisms living on the reef, or even scrape the reef itself for other types of algae. Even once all these food sources are depleted, they can still survive for a long time by slowing down their metabolism to a state of dormancy.
“Urchins can persist and survive and a starved state for a really long time. We’re talking several years. So when urchins overgraze kelp forests and transform for us to these underwater deserts that we call sea urchin barrens there’s no more food available for them or, or very little food,” Smith adds.
This is also why they’re so unappealing to otters: the urchins are starving themselves and have little that’s of interest to a predator.
That’s part of what makes these sea urchin barrens so tricky. They’re like environmental deserts, and the only way to change that is by bringing kelp back into the mix. But the moment kelp comes back in, the urchins will just devour it down to nothing — and predators like otters have little interest in these urchins.
But there are ways to get rid of an urchin barren.
While it hasn’t happened in the California area, urchins can contract devastating diseases that could quickly wipe out large parts of their population. Wind is another mechanism to dislodge urchins: large waves could physically swipe urchins off the reef. The third mechanism is predation.
“It’s clear that the otters are not foraging on urchins in the barrens, however, there could be other animals that would target urchin barrens. It’s possible that if and when the sunflower stars recover, they may be able to reduce the number of urchins in these barrens,” Smith adds.
In addition to those things, Smith notes, there are a number of pilot studies looking to see how effective urchin cleaning is. In some areas, especially in northern California, the state has approved divers to go out and remove the urchins themselves. There’s also one organization called California Reef Check which mobilizes members of the community to engage in science and survey these areas.
“The purpose of those pilot studies is twofold. Number one is to see if this is something that could actually be done by the local community. Can humans go in the water and remove enough urchins to make a difference? And then the second part of it is the science side, which is being charged by California Reef Check. And so they are going out and doing the monitoring of those locations where the urchins are being eliminated to see what happens once their numbers are reduced. Does that help the kelp come back? They’re the ones who are actually tracking all of those things.”
The study has been published in Proceedings of the National Academy of Sciences.
For all their cuteness, otters are voracious eating machines. They can easily devour 25% of their own body weight each day just to keep warm. However, relatively little is known about how they search for food — but now, a new study has been able to shed some light on this aspect of their lives.
Otters are perfectly adapted to the semi-aquatic environment they typically live in. They boast long, slim bodies, and relatively short limb with webbed feet which they use to swim. They also have sharp claws and can hold their breath for prolonged periods, which lets them hunt and look for food beneath the surface. They’re also quite nimble and skilled, often pounding clams and snails on rocks balanced on their chests as they float around.
However, otters are also pretty shy, which makes the difficult to study in both nature and captivity, says Sarah McKay Strobel from the University of California Santa Cruz (UCSC).
“Sea otters can sometimes be viewed as the “problem child” when it comes to training”, says Strobel, recalling the months of effort that went into preparing a wild sea otter named Selka at the Long Marine Laboratory at UCSC for her starring role.
Strobel had a hunch that since otters often hunt in murky or cloudy waters, they don’t only rely on their sight and sense of smell to navigate the waters. In a new study, she and her colleagues describe that their paws and whiskers are extremely sensitive, being able to distinguish between millimeter-sized grooves.
Helped by a large team of volunteers, Strobel trained Selka the otter to approach a cabinet perched on the side of her pool, in which they concealed a pair of side-by-side vertically ridged boards: one with 2 mm wide grooves and another with 5mm wide grooves. Whenever Selka would touch the 2 mm board, the board would produce a click, and Selka would be rewarded. They also trained the otter to identify the 2 mm with her whiskers while blindfolded — a particularly difficult task. After the training process was completed outside of the water, the team raised the water level in the pool, inundating the cabinet and repeating the same process submerged.
It took months of painstaking (and sometimes fun) training but ultimately, after several variations and tweaks, Selka was able to identify the 2 mm grooves. Then, researchers tested her ability to distinguish the 2 mm grooved board from boards with grooves ranging from 2.1 to 3 mm wide.
Selka was able to recognize the 2 mm grooves almost instantly if she encountered them first. If the grooves were the wrong width, she would quickly move on to search for the correct board. Not only was she very precise and accurate, but she was very decisive: it took less than 0.2 seconds to make a decision when testing with her paws, and 0.4 seconds when exploring with her whiskers. When human volunteers tried to do the same task, it took them 30 times longer.
It also made no difference if the boards were in the air or underwater — Selka seemed equally capable of distinguishing the grooves. Ultimately, she was able to distinguish grooves that were a meager 0.22 mm wider with her paw (0.48 mm wider with the whiskers).
Selka was also sneaky — whenever possible, she would memorize the correct solution so she wouldn’t have to work it out again.
“Selka used her memory to solve the trial as quickly as possible”, says Strobel, who suspects that sea otters’ ability to make rapid decisions based on touch is essential for their survival. “Their dives tend to be 1-2 minutes or shorter, which means they have to be very efficient,” she says, adding that results “suggest that sea otters are capable of using touch in this short amount of time to detect prey.”
The study was published in the Journal of Experimental Biology.
Journal Reference: Strobel, S. M., Sills, J. M., Tinker, M. T. and Reichmuth, C. J. (2018). Active touch in sea otters: in-air and underwater texture discrimination thresholds and behavioral strategies for paws and vibrissae. J. Exp. Biol. 220, jeb181347.
Up until the last Ice Age, the world was packed with over-sized mammals which scientists call megafauna. There were giant sloths, short-faced bears, several species of tapirs, mammoths, and saber-toothed cats like Smilodon, to name a few. Among them was also a recently identified wolf-sized otter that lived about six million years ago. Its massive jaws allowed the animal to bite with a huge force, likely making it a top predator of its time. This is one otter you wouldn’t want to mess with.
Artist’s rendering of Siamogale melilutra. Credit: Mauricio Anton
The Siamogale melilutra fossils, as the giant otter has been dubbed, were unearthed in southwest China. Judging from the remains, researchers led by Jack Tseng, assistant professor at University at Buffalo, believe the otter weighed about 50 kg (110 pounds), making it bigger than any other living otter. Its firm jaws suggested the otter likely had a hefty bite but the results of the 3D simulation exceeded expectations. Even for its size, S. melilutra packed a surprisingly strong bite.
“We don’t know for sure, but we think that this otter was more of a top predator than living species of otters are,” Tseng says. “Our findings imply that Siamogale could crush much harder and larger prey than any living otter can.”
Tseng and colleagues also made 3-D, computerized models of the jawbones of 10 of the 13 known species of living otters, not just S. melilutra. The comparison of all the otter jaws uncovered a linear relationship between jaw stiffness and the animal’s size. Namely, smaller otters have sturdier jaws. This makes S. melilutra an outlier since its jaws, at least according to the present model, were six times sturdier than expected. This ancient otter was likely a formidable hunter, according to the paper published in Scientific Reports.
“At the time that the otter lived, the area where its remains were found included a swamp or a shallow lake surrounded by evergreen forest or dense woodland,” said Denise F. Su, a paleoecologist at the Cleveland Museum of Natural History and one of the leaders of the Shuitangba Project that discovered the fossil otter.
3-D skull reconstructions of the 15-pound common otter Lutra lutra (left) and the 110-pound Siamogale melilutra (right). Credit: Z. Jack Tseng.
Today’s otters dine on a wide range of plants and animals from rodents to fish or crabs. We can’t tell what exactly S. melilutra used to eat but its powerful jaws suggest it could easily crush the shells of big mollusks or the bones of small mammals and birds.
“There was a diverse aquatic fauna at Shuitangba, including fish, crab, mollusks, turtles and frogs, as well as many different species of water birds, all of which could have been potential prey for S. melilutra,” Su said.
The powerful jaws likely made the ancient giant otter highly adapted to the wet and forested environment of South China where it had access to food other predators were barred from, such as big clams.
Beyond S. melilutra‘s diet, the study also paints a richer picture of the relationship between jaw strength and diet in animals in general. Scientists now learned that jaw strength correlated with size in living otters regardless of their meal choice whereas previously it was thought that more powerful jaws are found in creatures that eat harder foods. Tool use may explain this discrepancy — something which the primitive S. melilutra likely lacked. That’s strikingly similar to what happened to hominid skulls over the course of human evolution. By employing tools in their lives, our ancestors’ skulls transitioned from food munching units into a more ‘brainy’ role.
“Sea otters, for example, swim on their backs and use their chests as a platform for crushing their food with stones,” Tseng says.
“We think the anatomy means something because it doesn’t fall within the usual pattern that we see in other otters,” he says. “The strong jaws suggest that the primitive otter probably did not have the tool-using capability, and combined with the giant size, it was likely a top predator.”
It was adorable, but also terrifying. At110 lbs. (50 kilograms), it roamed the shallow, swampy waters of ancient China, likely spending its days swimming and looking for shellfish. But did it also hunt other things?
An artist’s rendition of the massive, prehistoric otters. (Mauricio Antón)
It’s the largest of all otters we’ve ever found.
“This extinct otter is larger than all living otters,” said study lead researcher Xiaoming Wang, a curator of vertebrate paleontology at the Natural History Museum of Los Angeles County in California.
The first fossil was discovered in 2010 but as it so often happens, it was too fragile for a serious reconstruction. It was also flattened, which brings extra problems. But the remains — which included an 8 inch (21 cm) skull and teeth — did give solid indications about the animal’s stature and lifestyle, hinting that they were on to something special. For instance, scientists found that the molars had actually evolved at least four separate times among other otter species, indicating that this species doesn’t share a common ancestor with other otters – it evolved on its own.
“The skull was unlike [that of] any other animals found so far, and that’s when we realized that this is something unique and important,” Wang told Live Science.
Still, reconstruction was not possible, so they had to attempt something else, something even more interesting: a virtual reconstruction.
“The bones are pretty fragile, so we couldn’t really reconstruct it physically,” Denise Su, the head of paleobotany and paleoecology at the Cleveland Museum of Natural History, told NPR. “So what we did is we took CT scans of the cranium, and then we digitally reconstructed it.”
It’s kind of like a 3D jigsaw puzzle done on a computer. You take the fossils you have and see how they might fit together; then, you start to think about what could fill in the holes.
Because the skull was flattened like a pancake, researchers did a computed tomography (CT) scan of the fossil. Each color in this digital scan represents an individual fragment. Image credits: Stuart C. White
While their virtual reconstruction does provide some answers, the study raises even more questions — particularly, why was the otter so big? Does its size reflect the size of its prey, or is there some other reason why it evolve to become so big? Usually, when carnivores grow so large, it’s because they want to eat other large animals, but the otter’s skull seems to indicate that it ate mollusks, so there would be no need for such a huge size. The reason for this might be that unlike modern otters, this ancient one wasn’t so smart.
Modern otters also like to crack mollusks, but they use tools to do so (sticks and stones). If the ancient species hadn’t figured out how to do so, then maybe it relied only on its raw strength and therefore needed to grow a big, strong skull.
The team also wants to figure out how the otter got on, both on land and in water and what its environment was generally like.
“We are working to answer questions regarding its paleobiology, like, ‘How did it swim? How did it move on the ground? Why is it so large?'”
Journal Reference: Xiaoming Wang, Camille Grohé, Denise F. Su, Stuart C. White, Xueping Ji, Jay Kelley, Nina G. Jablonski, Tao Deng, Youshan You & Xin Yang. A new otter of giant size, Siamogale melilutra sp. nov. (Lutrinae: Mustelidae: Carnivora), from the latest Miocene Shuitangba site in north-eastern Yunnan, south-western China, and a total-evidence phylogeny of lutrines. http://dx.doi.org/10.1080/14772019.2016.1267666
Sea otters, the cute creatures which hold hands while napping so they don’t drift away, have made a spectacular recovery. A new report from the US Geological Survey (USGS) has revealed that their population has reached the highest level since 1982, thanks to conservation efforts.
Sea otter in Morro Bay, California. Photo by Michael Baird.
The number of sea otters in California has grown to 3,272 this year, an 11 percent increase since 2013. If this trend is maintained for a couple more years then the species will move away from the “endangered” list, though they will still be considered “threatened.”
“The population is slowly but steadily recovering,” said Tim Tinker, a research biologist in Santa Cruz who leads the USGS’ otter program, in a report from Mercury Times. “And that’s good news because sea otters bring ecological benefits.”
Sea otters are among the smallest marine mammals. They have an exceptionally thick coat of fur, the densest in the animal kingdom with over 250,000 hairs per square inch (6.5 square centimeters), up to a million. Although they can still walk and manage themselves on ground, they spend most of the time in the water where they hunt marine invertebrates and fish. Their resurgence in number was owed in part to the abundance of sea urchins throughout northern and central California – something otters really like to chow on.
However, despite the general trend, some areas still report declining populations. The U.S. Geological Survey said Monday that the animals have a range that spans the coast from Monterey to Cambria and some areas are doing much better than others.
Historically, the number of sea otters has been around 16,000 but has dropped massively due to several factors – most notably fur traders. In the late 1700s and early 1800s Russian, British and American fur traders almost wiped them off. Another problem seems to be, surprisingly, great white sharks. No one is really sure why but in the past decades there has been an increase in the number of otters with shark bites. However, some biologists don’t believe sharks eat otters.
“We don’t think sharks eat otters; they just bite them and spit them out because sea otters don’t have blubber,” said Lilian Carswell, southern sea otter recovery and marine conservation coordinator for the U.S. Fish and Wildlife Service. “There’s not much there, just fur and bones. So they may be really targeting juvenile elephant seals and sea lions and biting otters instead.”
Sea otters have entered a select, but unfortunate club: they joined the ranks of ducks, chickens, pigs, whales, horses elephant seals and humans – all of which can contact the influenza. According to a new study conducted by the US Geological Survey and the CDC, sea otters living in a remote area in Washington state were found to carry the H1N1 virus, the strain of human flu that caused a pandemic back in 2009.
In 2009, the influenza strain spread to humans and caused worldwide panic; it sticked around ever since, and continues to hold potentially dark prospects for the future. However, only some animals can carry it, so it came as both a surprise and a shock when they found that 70 percent of the sea otters they were sampling along the Washington state coast were testing positive for the influenza.
USGS researchers don’t know how they caught the virus, though they do have a few ideas.
“Potential contact between northern elephant seals and sea otters is one possibility; elephant seals’ summer feeding ranges and breeding areas along the Northeast Pacific coast overlap with areas where the Washington sea otter population is distributed,” the researchers write in the paper.
Just a quick notice: while the disease may also spread to river otters, it hasn’t yet, and it’s worth noting that sea otters and river otters are not only from different species, but from a different genus. Studying and understanding how they contacted the virus in the first place may yield information as to how the influenza may spread to other species. But regardless of how it did spread, sea otters are indeed quite susceptible to it. Interestingly enough, even though 70% of all studied specimens had the virus, none of them appeared to be ill in any way. Still lots to be discovered, but that remains a subject for an otter study.