Animals

Native to the Brazilian Amazon, pied tamarins have always used vocal calls to communicate. But noise pollution from car traffic and other human activity are forcing some tamarins to complement those voice calls with smell markings to alert others to dangers, researchers report September 20 in Ethology Ecology & Evolution.

Most pied tamarins (Saguinus bicolor) live in Manaus, Brazil, inhabiting fragmented patches of forest scattered around urban environments. According to the International Union for Conservation of Nature, this small, black and whitish-yellow primate is critically endangered.

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Vocal communication is crucial for pied tamarins’ survival; they use it to alert other individuals to danger — an important feat considering the urban environment surrounding them. “Pied tamarins have 12 different types of vocalization with several uses, from pointing to food and cuddling each other to calling out for some danger,” says Tainara Sobroza, a biologist at the Federal University of Amazonas in Manaus.

The “danger” vocalization is particularly important for these animals, Sobroza says, as many are hit by cars and killed when they cross streets to move between forest patches. “We wanted to understand if this type of vocalization is being affected by the noise of urban environments,” she says.

Sobroza and colleagues spent about a year observing pied tamarins, which normally wander in groups of less than 10 individuals. Using radio collars, the team tracked nine groups in Manaus for 10 days each from November 2018 to December 2019. While physically following the groups, the researchers measured the loudness of the alpha female’s alert call and visually counted how often individuals rubbed their chest and lower parts on the ground and trees, spreading an odorous, waxy substance to signal which direction they were heading.

The team thought the tamarins would use fewer vocal callings and more smell-spreading to communicate effectively between groups — but that is not what happened. Estimates of the behaviors suggest tamarins complemented one with the other: They maintained the loudness and quantity of their vocal calls while also marking the terrain with their scents.

“It is just like being at a noisy party, and you want to call a friend that can’t hear you from the other side of the room,” Sobroza says. “Added to calling him or her, you also usually wave and do arm gestures to call the attention of that person.”

The new observations bring extra knowledge about the ecology and behavior of this species, says Luciane Lopes de Souza, a biologist at the University of the State of Amazonas in Manaus who did not take part in the study. “It is very interesting to see that pied tamarins can adapt to use [a scent-marking] form of communication, which we see much more frequently in other species such as the squirrel monkey.”

Human activity is changing the behavior of several species such as birds, spiders and crabs (SN: 6/26/16, SN: 7/16/03). Understanding these changes is crucial if humans want to mitigate their impacts through conservation.

“I do hope this study goes on, as it is of extreme importance we have research like this running for longer periods,” Souza says. “This way, we can understand annual or seasonal changes in animal behavior and think of evolutionary changes they might be facing.” More

Luis Melecio-Zambrano is the summer 2023 science writing intern at Science News. They are finishing their master’s degree in science communication from the University of California, Santa Cruz, where they have reported on issues of environmental justice and agriculture. More

Pet owners may have a new reason to reach for the kibble.

Dry cat and dog food tends to be better for the environment than wet food, veterinary nutritionist Vivian Pedrinelli of the University of São Paulo in Brazil and colleagues report. Their analysis of more than 900 hundred pet diets shows that nearly 90 percent of calories in wet chow comes from animal sources. That’s roughly double the share of calories from animal ingredients in dry food.

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The team factored in the cost of different pet food ingredients across several environmental measures. The findings, described November 17 in Scientific Reports, suggest that wet food production uses more land and water and emits more greenhouse gases than dry food.  

Scientists already knew that meat-heavy human diets drive greenhouse gas emissions (SN: 5/5/22). But when it comes to environmental sustainability, “we shouldn’t ignore pet food,” says Peter Alexander, an economist at the University of Edinburgh who was not involved in the work.

Just how much various pet foods impact the environment isn’t clear, Alexander says. Commercial cat and canine fares aren’t typically made from prime cuts of meat. Instead, the ingredient lists often include animal byproducts — the gristle and bits people aren’t likely to eat anyway.

How to calculate the carbon cost of these leftovers is an ongoing debate, says Gregory Okin, an environmental scientist at the University of California, Los Angeles who was not involved with study.

Some argue that the byproducts in pet food are essentially free, since they come from animals already raised for human consumption. Others note that any calories require energy and therefore incur an environmental cost. Plus, animal ingredients in pet food might not be just scraps. If they contain even a small amount of human-edible meat, that could add up to a big impact.

Knowing that there’s an environmental difference between moist morsels and crunchier cuisines could be helpful for eco-conscious pet owners, Okin says. Having that info handy at the grocery store is “super important when people are making decisions,” he adds. “There are consumers who want to pay attention.” More

A new gadget takes advantage of sharks’ sixth sense to send the fish scurrying away from deadly hooks.

Sharks, rays and their relatives can detect tiny electric fields, thanks to bulbous organs concentrated near their heads called ampullae of Lorenzini. So researchers developed SharkGuard, a cylindrical device that attaches to fishing lines just above the hook and emits a pulsing, short-range electric field. The device successfully deters sharks and rays, probably by temporarily overwhelming their sensory system, the scientists report November 21 in Current Biology.

While many people are afraid of sharks, the fear makes more sense the other way around; numerous shark species are at risk of extinction, largely due to human activities (SN: 11/10/22).

One major problem facing sharks and rays is bycatch, where the creatures get accidentally snagged by fishermen targeting other fish like tuna, says David Shiffman, a marine biologist and faculty research associate at Arizona State University in Tempe.

Whether sharks and rays would be repelled or attracted by the electric fields generated by SharkGuard devices was an open question. The animals use their extra sense when hunting to detect the small electrical fields given off by prey. So marine biologist Rob Enever of Fishtek Marine, a conservation engineering company in Dartington, England, and his colleagues sent out two fishing vessels in the summer of 2021 — both outfitted with some normal hooks and some hooks with SharkGuard — and had them fish for tuna.

In short, the sharks wanted nothing to do with the SharkGuard gadgets. Video reveals blue sharks approaching a hook with SharkGuard and veering away with no apparent harm. When encountering an unadorned hook, sharks took the bait, becoming bycatch.

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Sharks and their relatives can detect electric fields using organs in the skin called ampullae of Lorenzini. So researchers tested whether attaching a SharkGuard device, which emits a pulse of electricity every two seconds, to a fishing line just above the hook could deter a shark. The results, showing a shark taking the bait of a normal hook but other sharks veering away from hooks with the device, could hold promise for preventing millions of sharks from becoming bycatch.

Hooks with the electric repellant reduced catch rates of blue sharks (Prionace glauca) by 91 percent compared with standard hooks, dropping from an average of 6.1 blue sharks caught per 1,000 hooks to 0.5 sharks. And 71 percent fewer pelagic stingrays (Pteroplatytrygon violacea) were caught using SharkGuard hooks, going from seven captured rays per 1,000 hooks on average to two rays.

A typical fishing boat like those used in the study has approximately 10,000 hooks. So a boat whose entire set of hooks were outfitted with SharkGuard would go from catching about 61 blue sharks to 5, and 70 pelagic rays to 20.

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When you scale those numbers up to the millions of sharks and rays that are accidentally caught in longline fisheries every year, Enever says, “you’re going to have massive recovery of these pelagic shark populations.”

“It’s definitely a notable and significant effect,” says Shiffman, who was not involved with the study. “If [the devices] went into effect across the fishing fleet that interacts with blue sharks, it would certainly be good news for [them].”

But that doesn’t mean that SharkGuard is ready to be rolled out. Tuna catch rates were unseasonably low across the board in this study, which made it impossible to determine yet whether tuna are also bothered by the device. If they are, it wouldn’t make sense for fishermen to use the device in its current form.

The team is also working to make SharkGuard smaller, cheaper and as easy to manage as possible, so that fishermen can “fit and forget” it. For example, the current battery, which needs to be changed every couple of weeks, will be swapped for one that can be induction charged while the fishing line is not in use, “like a toothbrush, basically,” Enever says.

Shiffman would like to see SharkGuard tested in different environments and on other types of sharks. “There are a lot of shark species that are caught as bycatch on these longlines,” he says.

And while this invention seems effective so far, no technology will serve as a silver bullet for shark conservation. “Fixing this problem of bycatch is going to require a lot of different solutions working in concert,” Shiffman says.

The need for solutions is urgent. “We’re at a situation now where many of our pelagic species are either critically endangered, endangered or vulnerable,” Enever says. But the new findings are “a real story of ocean optimism,” he says. They show that “there’s people out there … trying to resolve these things. There’s hope for the future.” More

Holding an antenna above his head, Jeff Lewis crept through an evergreen forest in the Cascade mountains, southeast of Seattle. As he navigated fallen fir logs and dripping ferns, he heard it: a faint “beep” from a radio transmitter implanted in an animal code-named F023.

F023 is a fisher (Pekania pennanti), an elusive member of the weasel family that Lewis fondly describes as a “tree wolverine.” Resembling a cross between a cat and an otter, these sleek carnivores hunt in forests in Canada and parts of the northern United States. But fur trapping and habitat loss had wiped out Washington’s population by the mid-1900s.

Back in 2017 when Lewis was keeping tabs on F023, he tracked her radio signal from a plane two or three times a month, along with dozens of other recently released fishers. Come spring, he noticed that F023’s behavior was different from the others.

Her locations had been clustered close together for a few weeks, a sign that she might be “busy with babies,” says Lewis, a conservation biologist with the Washington Department of Fish and Wildlife. He and colleagues trekked into the woods to see if she had indeed given birth. If so, it would be the first wild-born fisher documented in the Cascades in at least half a century.

As the faint beeps grew louder, the biologists found a clump of fur snagged on a branch, scratch marks in the bark and — the best clue of all — fisher scat. The team rigged motion-detecting cameras to surrounding trees. A few days later, after sifting through hundreds of images of squirrels and deer, the team hit the jackpot: a grainy photo of F023 ferrying a kit down from her den high in a hemlock tree. The scientists were ecstatic.

“We’re all a bunch of little kids when it comes to getting photos like that,” Lewis says.

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Chasing babies

This notable birth came during the second phase of a 14-year fisher reintroduction effort. After 90 fishers were released in Olympic National Park from 2008 to 2010, the project turned its focus east of Seattle, relocating 81 fishers in the South Cascades (home to Mount Rainier National Park) from 2015 to 2020, and then 89 fishers in the North Cascades from 2018 to 2020. The animals were brought in from British Columbia and Alberta. The project concluded last year, when researchers let loose the final batch of fishers.

Baby animals are the key measure of success for a wildlife reintroduction project. As part of Washington’s Fisher Recovery Plan, biologists set out to document newborn kits as an indicator of how fishers were faring in the three relocation regions.

Before F023’s kit was caught on camera in May 2017, biologists had already confirmed births by seven relocated females on the Olympic Peninsula, where the whole project began. Two of the seven females had four kits, “the largest litter size ever documented on the West Coast,” says Patti Happe, wildlife branch chief at Olympic National Park. Most females have one to three kits.

Lewis is often asked, why put all of this effort into restoring a critter many people have never heard of? His answer: A full array of carnivores makes the ecosystem more resilient.

Happe admits to another motive: “They’re freaking adorable — that’s partly why we’re saving them.”

This agile member of the weasel family is a fearsome predator. Fishers are one of the few carnivores that can hunt and kill quill-covered porcupines.EMILY BROUWER/NPS (CC BY 2.0)

The missing piece

Contrary to their name, fishers don’t hunt fish, though they’ll happily munch on a dead one if it’s handy. They mainly prey on small mammals, but they also eat reptiles, amphibians, insects, fruit and carrion. About a meter long, males weigh up to six kilograms, about twice as much as females. Fun facts: Females raise young high above the forest floor in hollowed-out spaces in tree trunks. Fishers can travel face-first down tree trunks by turning their hind feet 180 degrees. They have wickedly sharp teeth and partially retractable claws. And they’re incredibly agile, leaping up to two meters between branches and traveling as much as 30 kilometers in a day.

Fishers’ stubby legs and unique climbing skills make them a threat to tree-climbing porcupines. It isn’t pretty: A fisher will force the quill-covered animal down a tree and attack its face until it dies from blood loss or shock. Then the fisher neatly skins the prickly prey, eating most everything except the quills and bones.

These camera trap photos, taken in April 2021, show female fisher F105 carrying one of her four kits down from her tree den near Lake Wenatchee in the North Cascades.NPS

But these fearsome predators were no match for humans. In the 1800s, trappers began targeting fishers for their fur. Soft and luxuriant, the glossy brown-gold pelts were coveted fashion accessories, selling for as much as $345 each in the 1920s. This demand meant fishers disappeared not only from Washington, but from more than a dozen states across the northern United States. Once fisher populations plummeted, porcupines ran rampant across the Great Lakes region and New England. This wreaked havoc on forests because the porcupines gobbled up tree seedlings.

Hoping to keep porcupine populations in check, private timber companies partnered with state agencies to bring fishers back to several states in the 1950s and 1960s. Thanks to these efforts and stricter trapping regulations, fishers are once again abundant in Michigan, Wisconsin, New York and Massachusetts.

But in Washington, like most of the West, fisher numbers were still slim. By the turn of the 21st century, no fisher had been sighted in the state for over three decades.

As in the Midwest and New England, private timber companies in Washington supported bringing back fishers. Although porcupines are uncommon in Washington, mountain beavers — a large, primitive rodent endemic to the Pacific Northwest — fill a similar role in Washington’s evergreen forests: They eat tree seedlings. And fishers eat them.

By 2006, the state hatched a plan to bring the animals in from Canada. “It was a big opportunity to restore a species,” Lewis says. “We can fix this.”

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This 2009 camera trap vídeo from Olympic Peninsula shows fisher F007 scaling a cedar tree and carrying her four kits to the forest floor, one at a time

A new home

Like the other Canadian fishers moved to Washington, F023’s relocation story began when she walked into a box trap in British Columbia, lured by a tasty morsel of meat. The bait had been set by local trappers hired by Conservation Northwest, a nonprofit that is one of the recovery project’s three main partners, along with Washington Fish and Wildlife and the National Park Service. After veterinarians checked her health and administered vaccines and antiparasitics to help her survive in her new home, F023 received a surgically implanted radio transmitter and was driven across the border.

She was met by members of the fisher recovery team, who released her just south of Mount Rainier National Park. The forest’s towering Douglas fir, western red cedar and western hemlock trees were full of cubby holes and cavities to hide in, and the undergrowth held plenty of small mammals to eat. At the release, upward of 150 people gathered around F023’s box, part of the team’s effort to engage the public in championing fisher recovery. Everyone cheered as a child opened the door and the furry female bounded into the snowy woods, out of sight in a flash.

The team monitored each relocated fisher for up to two years to see if the project met key benchmarks of success in each of the three regions: more than 50 percent of the fishers surviving their first year, at least half establishing a home range near the release site, and a confirmed kit born to at least one female.

“We met those marks,” says Dave Werntz, science and conservation director at Conservation Northwest.

The effort may have been aided by a series of bypasses built over and under a roughly 25-kilometer stretch of Interstate 90 east of Seattle. One of these structures is the largest wildlife bridge in North America, an overpass “paved” with forest. In 2020, a remote camera caught an image of what looks like a fisher moving through one of the underpasses.

Speeding vehicles on busy highways pose a threat to fishers and other migrating wildlife. This new bridge east of Seattle is “paved” with trees and plants to let animals safely cross I-90 to find habitat, food or mates on the other side.WASHINGTON STATE DEPT. OF TRANSPORTATION

“Male fishers go on these huge walkabouts to find females,” Werntz says. While biologists assumed fishers would cross the freeway to search for mates, having photographic proof “is pretty wonderful,” he says.

Happe and others hope to also see wildlife crossings along Interstate 5 one day. The freeway, which runs north-south near the coast, is the main obstacle keeping the Olympic and Cascade populations apart, she says. “We’re all working on wildlife travel corridors and connectivity in hopes the two populations hook up.”

Learning curve

The majority of the initial 90 fishers relocated to the Olympic Peninsula settled nicely into their new homes, according to radio tracking. In the year following release in that location, the fisher survival rate averaged 73 percent, but varied based on the year and season they were released, as well as sex and age of the fishers.

Males fared better than females: Seventy-four percent of recorded deaths were of females, partly because they are smaller and more vulnerable to predators, such as bobcats and coyotes. Of 24 recovered carcasses where cause of death could be determined, 14 were killed by predators, seven were struck by vehicles, two drowned and one died in a leg-hold trap, Lewis, Happe and colleagues reported in the April 2022 Journal of Wildlife Management.

Because the first fishers relocated to the Olympic Peninsula were released in several locations, the animals had trouble finding mates. As a result, only a few parents sired the subsequent generations.

The researchers became concerned when they looked at the genetic diversity of fishers on the Olympic Peninsula six years post-relocation. Happe and colleagues set up 788 remote cameras and hair-snare stations: triangular cubbies open on either end with a chicken leg as bait in the middle and wire brushes protruding from either side to grab strands of fur. DNA analysis of the fur raised red flags about inbreeding, Happe and Lewis say.

“Models showed we were going to lose up to 50 percent of genetic diversity, and the population would wink out in something like 100 years,” Happe says. To expand the gene pool, the team brought 20 more fishers to the Olympic Peninsula in 2021. These animals came from Alberta whereas the founding population had hailed from British Columbia.

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Two fishers from Canada are released from wooden crates, quickly disappearing into Olympic National Park in November 2021. Both wear radio tracking devices so that researchers can monitor their well-being.

As the reintroduction effort moved into the Cascades, the team adapted, based on lessons learned from the Olympic Peninsula. For instance, to increase the likelihood of fishers finding each other more quickly, the animals were released at fewer sites that were closer together. The team also released the animals before January, giving females ample time to settle into a home range before the spring mating and birthing season.

Finding their food

As the experiment went on, more unanticipated findings popped up. Fishers released in the southern part of the Cascades were more likely to survive the first year (76 percent) than those relocated north of I-90 (40 percent), according to the final project report, released in June. Remote-camera data suggest that’s because there are less prey and slightly more predators in the North Cascades, says Tanner Humphries, community wildlife monitoring program lead for Conservation Northwest.

And in both the Cascades and the Olympic Peninsula, fishers are using different types of habitat than biologists had predicted, Happe says. The mammals — once assumed to be old-growth specialists — are using a mosaic of young and old forests. Fishers require large, old trees with cavities for denning and resting. But in younger managed forests where trees are thinned or cut, prey may be easier to come by.

Live traps in the South Cascades support that idea. Fishers’ preferred prey — snowshoe hares and mountain beavers — were most abundant in young regenerating forests. In older forests, traps detected mainly mice, voles and chipmunks, which are not substantial meals for fishers, Mitchell Parsons, a wildlife ecologist at Utah State University in Logan, reported with Lewis, Werntz and others in 2020 in Forest Ecology and Management.

North America’s fisher populations are blossoming, helping to rebalance forest ecosystems.Emily Brouwer/NPS (CC BY 2.0)

The future is re-wild

After F023’s baby was caught on camera five years ago, the mother’s tracking chip degraded as designed — the hardware lasts less than two years. Since then, many more fisher kits have been born in Washington.

In fact, these furry carnivores are one of the most successfully translocated mammals in North America. According to Lewis, 41 different translocation efforts across the continent have helped fisher populations blossom. The animals now occupy 68 percent of their historical range, up from 43 percent in the mid-1900s.

With the last batch of fishers delivered to Washington in 2021, the relocation phase of the project has ended. Lewis, Happe and their partners plan to continue monitoring how these sleek tree-climbing carnivores are faring — and how the ecosystem is responding. For instance, fishers are indeed feasting on seedling-eating mountain beavers, according to research reported by Happe, Lewis and others in 2021 in Northwestern Naturalist.

Given climate change, species loss and ecosystem degradation, animals worldwide face difficult challenges. The fact that fishers are thriving once again in Washington offers hope, Lewis says.

“It’s a hard time, it’s a hard world, and this feels like something we’re doing right,” he says. “Instead of losing something, we’re getting it back.” More