Wildlife

Wildlife Wednesday: “milestone achievement” — Bhutan records a nearly 40 per cent increase in snow leopard numbers

Plus: city lights make bird eyes smaller, killer whales play “pass the porpoise,” Atlantic walrus more at risk than ever, and grizzly bears besieged by forestry roads

Photo caption: Well adapted to cold environments, snow leopard's wide, fur-covered paws act as natural snowshoes, helping to distribute their weight over soft snow. (Photo: Frida Lannerström/Unsplash)
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There’s no leopard like the snow leopard. One of the world’s most elusive cats, the snow leopard is native to the mountain ranges of Central and South Asia, where it lurks at elevations between 3,000 and 4,500 metres. Adapted to hunt and thrive in places like the Himalayas thanks to their thick white-grey fur and black spots, snow leopards are historically threatened by poachers and a climate change-induced shink in habitat. Simultaneously, loss of prey, human-wildlife conflict and habitat destruction are also causing this ethereal species to decline. 

But in a joyous and unexpected turn of events, Bhutan has announced a nearly 40 per cent increase in snow leopards since 2016, bringing their population in the area to 134. According to Snow Leopard Trust, there are only between 3,620 and 6,390 snow leopards left in the wild globally, so this increase comes as a sigh of relief to conservationists. 

With the numbers confirmed by the National Snow Leopard Survey 2022-2023, Country Director for WWF-Bhutan Chimi Rinzin describes the increase as a “milestone achievement for Bhutan’s conservation journey.” The survey, which covered more than 9,000 square kilometres of snow leopard habitat across the northern alpine landscape of Bhutan, included 310 camera trap stations to capture the species. Not only did the survey record snow leopards in new locations, it also found an overall density of 1.34 snow leopards per square kilometres. 

Beady-eyed

City lights might be causing an evolutionary adaptation that sees some birds develop smaller eyes. (Photo: World Wildlife)
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Bright lights, beady eyes? Looks like city lights might be causing an evolutionary adaptation that sees some birds develop smaller eyes to deal with the constant light in urban environments. A new study published in Global Change Biology found that two common songbirds, northern cardinals and Carolina wrens, that lived year-round in the urban core of San Antonio, Texas, had eyes that were five per cent smaller than their country cousins’. 

Interestingly, migratory birds that lived in the city only part of the year did not show any difference in eye size, suggesting that while resident birds may be adapting to life in the city, migratory birds are not, which could put them at a disadvantage during the part of the year when they’re in the city. (It’s theorized that birds with bigger eyes can be somewhat blinded by the glare of city lights or less likely to sleep well.)

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Pass the porpoise

Over the last six decades, scientists have recorded 78 instances of resident orcas harassing porpoises in the Salish Sea. (Photo: Cristopher Michel/Wikimedia Commons)
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If you thought a cat with a mouse was nasty, wait till you hear about the orca and the porpoise. Just like cats, Southern Resident killer whales are highly picky eaters, basically accepting nothing but Chinook salmon for dinner. In other words, these predators don’t often chow down on porpoise, so have no reason to attack them. But if a porpoise crosses their paths, it’s playtime.

Over the last six decades, scientists have recorded 78 instances of resident orcas harassing porpoises in the Salish Sea between B.C. and Washington State. They might push the porpoise along with their nose, hold it in their mouth, bounce it up and down, allow it to escape briefly before grabbing it again, and sometimes even play “pass the porpoise” with others in the pod. The one thing they don’t do is actually eat the porpoise.

Researchers, who published their findings in Marine Mammal Science, have three theories. Could it be a cruel form of play? Is it hunting practise? In a few cases, are the orcas attempting to care for the porpoises, treating the smaller, weaker porpoises as though they were the orca’s own young? Whatever the truth is, meeting up with the orcas is bad news for a porpoise.

Waning walrus

Atlantic walrus are more at risk than ever, say researchers from Lund University, Sweden. (Photo: USFWS/Joel Garlich-Miller)
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The last remaining stocks of Atlantic walrus are more at risk than ever, say researchers from Lund University, Sweden. The combination of Arctic warming and historic human exploitation has made them more vulnerable to pressures such as ice loss, Arctic shipping, resource extraction and mass tourism.

The researchers examined how walrus coped with past cycles of climate change by sequencing and analyzing ancient genetic information contained in teeth and bones frozen in Arctic archaeological sites. “We found that Arctic warming has led to a surprisingly high genetic separation of local walrus stocks,” says Peter Jordan, professor of archaeology at Lund University. Very specific habitat requirements meant the last Ice Age and the subsequent warming period that followed caused spreading, isolation and extinction in many walrus stocks as they migrated with the ice edge. 

And in the last thousand years, human hunting — from the expansion of Norse settlers to the modern industrial scale culling of walrus — has led to numerous local extinction events.

As a result, genetic diversity has reduced to a fraction of what previously existed, and species is therefore less prepared for the current period of climate change that’s causing Arctic sea ice to retreat; walrus will likely disperse further into smaller, more isolated pockets, further endangering their survival. 

A road to nowhere

Forestry built roads brought about a pincer-like interplay between top-down and bottom-up influences on grizzly bears. (Photo: Pexels)
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While construction of forestry roads has been found to increase wolf populations in Canada, the same can’t be said for grizzly bears in British Columbia, according to recent research published in WIldlife Monographs.

The researchers, including lead author Michael Proctor of Birchdale Ecological, found that forestry built roads brought about a pincer-like interplay between top-down and bottom-up influences on grizzly bears. Forestry roads both caused direct bear deaths through conflict and illegal killings, thereby reducing female grizzly fitness and density, and limited the bears’ access to food from vital huckleberry patches — in essence having a similar effect as habitat loss.

“Our results suggest that benefits of critical bear foods are not satisfactorily realized unless human access to nearby roads is reduced,” says Proctor.

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