Animals

PITTSBURGH — Salmon may now have their own version of human air conditioning.  

This past summer, hundreds of fish in the Wrights River in Nova Scotia, Canada, found reprieve from the heat in human-generated plumes of cold water, civil engineer Kathryn Smith reported October 17 at the Geological Society of America meeting. The work, though only proof of concept, could aid efforts to conserve cold-water species amid the widespread warming of rivers due to climate change (SN: 10/20/22).

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When water temperatures get too hot, fish can become stressed or even die. In rivers, Atlantic salmon and other cold-water species sometimes escape the heat by flocking to cooler areas, which often arise near groundwater springs or relatively cool tributaries.

Lots of work has been done to preserve and augment these naturally occurring refuges, said Smith, of Dalhousie University in Halifax, Canada, “but there hasn’t really been an emphasis or focus on if we can create cold-water habitat.”

So she and her colleagues pumped groundwater that was about 9° Celsius (or about 48° Fahrenheit) from a nearby well into the river, manifesting an artificial plume of water that could be as much as 20 degrees Celsius cooler than the surrounding water.

Researchers pumped groundwater into the Wrights River during the summer to create a plume of cooler water that fish could shelter in (image on the left). A thermal image (right) shows the effect: Cooler water appears darker purple while warmer water and sun-baked rocks are orange and yellow.Kathryn Smith

The plume attracted several hundred fish of varying life stages and species, including Atlantic salmon and brown trout. Most were alevins — juvenile fish still attached to yolk sacs — that occupied the plume throughout the tests. But when a heat wave brought on maximum water temperatures of about 30° C, more mature fish also took shelter in the plume.

For a pump-free approach, the team also rerouted some water from the river into an underground trench, where it cooled before reentering the river. Though this method lowered the water temperature by only a few degrees Celsius, fish were observed frequenting the passively cooled flow throughout the summer.

More work lies ahead to determine how many of these sites would need to be constructed and sustained to significantly benefit fish populations, and how to do so while keeping energy costs low, says John Ackerman, a consulting engineer based in Hazleton, Pa., who was not involved in the research. But the researchers are demonstrating that these solutions can work, he says. “The concept is solid.” More

Nearly 20 years ago, the first global assessment of amphibians found the animals facing widespread declines. Now, a second, updated report shows that many amphibians are still in trouble, but with some silver linings, researchers report October 4 in Nature.

“We are realistic and hopeful at the same time,” says Jennifer Luedtke, a conservationist at the International Union for Conservation of Nature, which tracks extinction risk trends for species around the world.

In particular, the wealth of data in the new report, which includes about 8,000 amphibian species, could help focus conservation efforts for years to come, says Luedtke, who also works from Washington, D.C., for Re:wild, a conservation organization based in Austin, Texas. That’s what happened after the first Global Amphibian Assessment in 2004, which brought awareness to the amphibian crisis and galvanized researchers to coordinate efforts.

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Having two assessments that can be compared is a big deal, experts say. “It’s important not just to have a picture, but actually to have a sequence of pictures … where you can see what’s happening over time,” says conservation ecologist Ana Rodrigues of CNRS in Montpelier, France, who worked on the first assessment but was not involved in the second. “I’m really happy to see this done.”

Here are five big takeaways from the new report.

1. Amphibians remain more threatened with extinction than any other vertebrate group.

About 41 percent of amphibian species, which include frogs, toads and salamanders, are threatened with extinction, Luedtke and her colleagues found. That’s more than any other group of vertebrates, beating out sharks and rays (37 percent), mammals (27 percent), reptiles (21 percent) and birds (13 percent).

Amphibians held this title in 2004 too, when 39 percent of species were threatened. As part of the 2022 update, researchers also used data to reconstruct the situation in 1980. They found that even in 1980, that number was already high, at 38 percent. Basically, amphibians have been really threatened for a really long time, Luedtke says.

The most common threat that affects amphibians is habitat loss and degradation, with agriculture affecting as many as 77 percent of the studied species. Other threats include climate change and disease, each affecting 29 percent of species. Of course, “these things are never completely isolated,” says Rodrigues, and each threat may increase the likelihood of other threats.

2. Many of the worst amphibian declines are being caused by climate change now, instead of disease.

Luedtke and colleagues also wanted to know which threats were most responsible for driving the worst declines. So they looked at a subset of 788 species that, between 1980 and 2022, moved down an IUCN Red List status level — for instance, from vulnerable to endangered. They found that, in 2004, disease was the primary driver behind the drop in conservation status for 58 percent of that species subset. At the time, the fungal pathogen chytrid was devastating frog populations around the world (SN: 8/23/02). Climate change, on the other hand, was a significant contributor to declines in only 1 percent of species.

Now, less than 20 years later, climate change is behind a status drop for 39 percent of species. That makes it the most common primary driver of declines across the amphibian group, the researchers found. And still the finding is probably an underestimate, Luedtke says, as studies continue to emerge detailing how climate change–related temperature increases, changes in precipitation, extreme weather events and wildfires impact amphibians.

“It’s very worrying,” Rodrigues says. “We’re at the beginning of climate change.… What’s ahead of us?”

Amphibian species in the tepuis, or tabletop mountains, of Venezuela, like this Chimantá poison frog (Anomaloglossus rufulus), are particularly vulnerable to climate change, as they are unable to shift much higher in altitude to escape warming temperatures.F.J.M. ROJAS-RUNJAIC

3. It’s bad around the world. But amphibians are doing worse in some regions than others.

Each region faces its own set of threats. The chytrid outbreak, for example, has affected much of the world, but it hit Central and South America especially hard from the 1970s to the 2000s. That likely explains why that region contains the largest proportion of species in the IUCN Red List categories of highest concern, the researchers say. New Guinea and Africa were spared much of the devastation, though the pathogen has recently started to emerge in sub-Saharan Africa.

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Across Europe and East Asia, habitat loss is the leading cause of decline, followed by a newly emerging fungal pathogen in Europe called Batrachochytrium salamandrivorans, this time that affects salamanders (SN: 9/3/13). It hasn’t yet spread to North America, which would be disastrous, Rodrigues says. The continent is home to more than 200 types of salamanders, over a quarter of the world’s salamander species.

For now, North America’s amphibian declines are most associated with climate change, the report found. South and Southeast Asia are seeing an improving trend among their species’ extinction risk, probably due to better management of protected areas.

4. Scientists know a lot more about amphibians now than they did in 2004.

One of the assessment’s few bright spots is its sheer amount of data. The update includes more than 2,000 additional species — all newly described since 2004. There was also a decrease in species labeled as “data deficient” by the IUCN, from 23 percent in 2004 to only 11 percent in 2022. By comparison, though, less than 1 percent of bird species are listed as data deficient.

While there’s still a long way to go for amphibians, researchers are thrilled by the new amount of information. “It’s like, wow, all the knowledge!” Rodrigues says. “So that’s absolutely good news.” With more data, she says, conservation efforts can be better focused.

This indigo bush frog (Raorchestes indigo) has moved from critically endangered to vulnerable thanks to habitat protection efforts in the Kudremukh Massif mountain range of India.Saurabh Sawant

5. Some amphibian species have improved since 2004.

The new report didn’t just find declines — 120 species saw their IUCN conservation status improve.

About half of those species recovered unaided. Many of those had suffered declines due to chytrid and are now bouncing back, possibly as frogs become resistant to the pathogen (SN: 3/29/18). It’s a source of hope that “we have these little frogs evolving, in front of our eyes, resistance to chytridiomycosis,” Luedtke says.

The other half improved thanks to conservation efforts, the report found. One of those species is India’s indigo bush frog (Raorchestes indigo), which was classified as critically endangered in 2004. A couple years later, a legal battle led to the end of all mining in the Kudremukh Massif mountain range, and the species’ IUCN status has since improved to vulnerable.

Stories like that are evidence that effective habitat protection can make a noticeable difference, the researchers say, and yet, with most amphibians still facing declines, it’s clear that current efforts are not enough. The assessment’s accompanying State of the World’s Amphibians Report focuses on action steps based on the new findings. Among other things, it identifies 50 target conservation areas around the world — including Jamaica, Brazil’s Atlantic Forest and the Central Annamite Highlands in Vietnam — that feature a high density of threatened species.

“Yes, the number of threatened amphibians continues to increase, but our understanding is improving,” Luedtke says. “And because we understand them better, we can act in a more accurate and effective way.” More

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