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Who ate the leftovers? Puma kills are enjoyed by a who's who of scavengers
A female puma known as F61, who was followed by Panthera's Teton Cougar Project, stands over her elk kill in northwest Wyoming. Image: Mark Elbroch/Panthera
Do chickadees, chipmunks and woodrats thank their lucky stars for sharing real estate with pumas?
The answer may well be "yes" (in whatever way songbirds and rodents might recognise and express gratitude for a 70-kilogram cat).
Those little creatures, plus a whole gaggle of others, are among an impressively diverse guild of scavengers that nibbles and gnaws on puma leftovers in the US Rockies, according to new research by Panthera's Teton Cougar Project.
The study – published in the November edition of Biological Conservation – shows not only how bountiful puma kills can be as a food source for other animals, but suggests that other ecologically similar felids around the world may provide significant ecosystem services of a similar nature.
The fieldwork took place in the Greater Yellowstone Ecosystem, specifically in and around Grand Teton National Park. Tracking GPS-collared pumas allowed the researchers to locate nearly 250 active kills they deemed still "meaty" enough to draw in scavengers, then place motion-sensor cameras near the carcasses to record the dining parties
.The cameras documented a whopping 39 different species of mammals and birds scavenging this puma-delivered meat: all told, nearly 15 percent of the local mammalian and avian roster, and a diversity "higher than any other scavenger study to date from around the world", as lead author Mark Elbroch wrote in aPanthera blog post announcing the results.
The most common scavengers were red foxes and black-billed magpies, but a veritable who's who of neighbourhood meat-eaters (omnivores very much included) partook: everything from flying squirrels, deer mice and sparrows to grey wolves, black bears and grizzlies.
Obviously a lot of this pilfering goes down when the puma is finished with its kill, or in between mealtime visits – though some scavengers slip in with the big cat sleeping nearby, hang out until it is through eating, or even share the carcass with it.
On the Panthera blog, Elbroch suggested that across their vast North and South American range – greater than any other large land mammal in the Western Hemisphere – pumas may supply better than 1.5 million kilograms (3.3 million pounds) of meat to other critters on a daily basis.
(A previous study by Elbroch and Heiko U. Wittmer showed puma kills in central Patagonia fed at least a dozen kinds of vertebrate scavengers, including Andean condors.)
Spot the fox! A red fox bides its time while F61 stands over her kill. Image: Mark Elbroch/Panthera
The new research suggests pumas may supply more than three times the amount of carrion to local scavengers that wolves in the Greater Yellowstone do. This highlights a key difference between the two carnivores, which historically overlapped in most of their North American domains and which target roughly similar prey. Wolf packs may polish off a carcass in a day, leaving few scraps behind for scavengers; furthermore, wolves will aggressively defend their kills from pilferers, from ravens to grizzlies. (It doesn't always work with grizzlies.)
Because they're solitary hunters targeting large animals (deer, elk, bighorn sheep, etc.), pumas don't burn through their kills as quickly as their canine counterparts. As Toni Ruth and Kerry Murphy note in Cougar: Ecology and Conservation, it may take a puma three to six days to finish a carcass. That means significantly more opportunities for scavenging by other animals, though pumas do make efforts to discourage this. For example, they cache their kills in thickets or woods and under heaps of grass or leaf litter to try to prevent magpies, ravens and other noisy carrion birds from finding the prize and alerting other scavengers.
Finally, the fox's turn at the table. Image: Mark Elbroch/Panthera
Though pumas sometimes kill smaller carnivores such as bobcats and foxes that get too close to their dinner table, the big cats generally shy away from confrontations with larger rivals. Previous research has showngrizzly and black bears as well as grey wolves to be significant "kleptoparasites" of pumas in North America, actively displacing the cats from their feasts. (Not that the tables never turn: pumas have been recorded killing lone wolves on occasion, and some evidence suggests a male wolf of the erstwhile Druid Peak Pack in Yellowstone National Park, No. 163, may have been taken out by a puma in a face-off over a dead bighorn sheep.) With their better-than-a-bloodhound's sense of smell, bears may zero in on a carcass within hours of a puma's kill.
Elbroch suggests that, because their ambush-style hunting tactics often expend less energy than the distance-running strategies employed by many wild canines (as well as spotted hyenas), pumas may be better able to deal with a certain level of pirated kills without necessarily having to hunt extra to compensate. “Pumas lose or abandon on average 39% of their prey to competitors and scavengers,” the researchers write, "and, like cheetahs, are likely tolerant of some level of kleptoparasitism of their kills."
As part of their study, Elbroch and his colleagues also identified six other large (20kg-plus) felids that, like pumas, are both solitary apex predators and subordinate to other big carnivores in direct competition:cheetahs, for one, as well as clouded leopards and Sunda clouded leopards, Eurasian lynx, snow leopards and common leopards.
"[These species] may also disproportionately provision carrion to their ecological communities," the authors write. That inadvertent bounty is potentially all the more significant, they note, when the huge collective range of all these felids – pumas included – is considered.
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