Table Scraps: Inter-Trophic Food Provisioning by Pumas

1. What they did

Large carnivores shape natural communities by hunting, and also by leaving food for scavengers. Little is known about how solitary big cats such as pumas feed other animals, even as managers increasingly call for pumas to be controlled to protect prey species, people and livestock. Pumas often hide large prey and return to feed several times, but sometimes they leave a kill early, either because competitors push them off or for other reasons.

In Chile’s Aysén District in Patagonia, the researchers:

• Captured pumas. Between March 2008 and September 2009, hounds pushed 11 pumas into a tree or onto rocks so they could be safely anaesthetized. Nine were fitted with Argos-Global Positioning System (GPS) collars that took a location every 2 hours.
• Found kills. Any two or more locations within 150 m of each other counted as a cluster. Certified observers visited every cluster that included at least one night-time location, on average 11 ± 12 days after the kill. They identified the prey from the remains, and used the state of the remains to judge whether the puma had killed the animal or was scavenging.
• Estimated how much meat was left. They estimated each prey animal’s weight and edible portion from published figures. They then estimated how much the puma ate from the number of days they spent at the carcass and the feeding rates of captive pumas. For mothers with kittens over three months old, they added the kittens’ share. What remained was the meat abandoned to other animals.
• Recorded scavengers. Scavengers at puma kills were recorded from sightings, remote cameras and signs such as droppings and footprints.

2. What they found

Kills

• They visited 694 GPS clusters and found 433 sites with prey remains (350 ungulates and 83 smaller vertebrates), plus 6 sites where pumas were scavenging animals that were already dead.
• Eight pumas (three males and five females) could be monitored continuously for long enough to measure kill rates. On average, each killed 6.5 ± 1.8 animals per month.

Meat left behind

• Each puma abandoned on average 171.9 ± 72.8 kg of edible meat per month to scavengers and decomposers. This ranged from 32 kg (a female who gave birth to three kittens during monitoring) to 292 kg (a female with two kittens) per month.
• Males and females did not differ in kill rates or in the amount of meat they left.
• Using their earlier estimate of 1.35 resident adult pumas per 100 km², pumas provided about 232 kg of meat per month per 100 km², or 2553 kg per month over the 1100 km² study area.

Scavengers

• Andean condors were recorded at 43% of the ungulate kills where the researchers could confidently tell whether condors had been there (n = 126).
• Eleven other vertebrate scavengers were recorded: black vulture, culpeo fox, Patagonia hog-nosed skunk, southern, chimango and white-throated caracaras, black-chested buzzard eagle, great shrike tyrant, Austral blackbird, thorn-tailed rayadito and a lizard.

3. What they concluded

• Pumas in Patagonia provided up to 3.1 times more food to their communities than wolves do in Yellowstone National Park (84.5 to 155.9 kg per month per 100 km²).
• This is probably an underestimate, because transient pumas, which also leave meat, were not counted. Pumas also live at lower densities than wolves, so each puma provides even more than each wolf.
• The difference is partly because pumas are solitary. Wolf packs eat carcasses more quickly and defend them, while solitary cats tend to retreat to cover to avoid conflict, which makes them more likely to lose kills to other animals.
• Pumas’ direct effects on their communities include positive ones as well as predation. Food they provide may be vital for scavengers and decomposers in Patagonia and elsewhere.

4. How tracking was or was not used

GPS collars showed where pumas spent time, and the field teams then read the tracks and signs at each cluster. They identified prey species from the remains and judged from the state of the remains whether the puma had made the kill or was scavenging. The number of kittens with collared mothers was found from captures, direct sightings, tracks in snow and cameras at kill sites. Scavengers at kills were recorded partly from their signs, such as droppings and footprints. No trailing was reported.

5. Tracker or observer certification

The paper says cluster investigations were carried out by “certified observers”, citing Elbroch et al. (2011), the paper on employing local experts that describes CyberTracker tracker evaluation. The type or level of certification, and who held it, is not stated. Four people are thanked for help with kill site investigations.

6. Other technologies, skills or innovations

• Argos-GPS collars that sent data by satellite every 2 to 5 days, so kills could be found without recapturing the pumas.
• Distances between locations calculated in ArcGIS (Geographic Information System, GIS) software.
• Remote cameras at kill sites, which recorded scavengers and kittens.
• Hounds used to bring pumas to bay for capture.
• Estimates of meat eaten built from captive feeding rates and kitten growth equations, since actual consumption could not be measured.

7. Implications for conservation (from the paper)

• Managers should weigh the benefits of culling pumas against the possible negative effects of removing them on the wider ecological community.
• Pumas are persecuted because of perceived threats to people and livestock, and are increasingly controlled to help rare prey species recover. Removing them could reduce food for scavengers such as the near-threatened Andean condor, a species that depends on carrion.
• The role of large, solitary cats in feeding other species should be considered in future management and conservation of all large felids.