Bald Eagles

Scavengers, like raccoons, can be picky eaters

Scavengers, like raccoons, can be picky eaters

Birds and mammals preferred to feed on the carcasses of herbivores

When you picture a finicky eater, a raccoon usually doesn’t come to mind. But new research from the University of Georgia has found that scavengers, such as raccoons and vultures, can be selective about what they eat. The study provides insight into how nutrients can travel through food webs.

When multiple types of carcasses were available, bird and mammal scavengers chose those of herbivores, such as ducks and chickens, over carnivore carcasses.

A photo of a raccoon taken by the motion-triggered time-lapse cameras set up by the research team.

Miranda Butler-Valverde, principal investigator on the study, published in Food Webs, installed remote cameras at the heavily forested Savannah River site near Aiken, South Carolina. Then Butler-Valverde, a recent graduate of the Savannah River Ecology Laboratory and the Warnell School of Forestry and Natural Resources, placed bird carcasses of different trophic levels in the area.

Trophic levels refer to placement on the food chain. A food web begins at trophic level 1 with primary producers such as plants. Herbivores are at level 2 and carnivores at level 3 or higher.

A bobcat inspects the carcasses of two dead vultures, also believed to be scavengers.

A bobcat inspects two carcasses.

She placed 40 herbivore carcasses – 20 chickens and 20 mallards – along with the carcasses of 20 black vultures and 19 red-headed vultures in the landscape

Motion-triggered time-lapse photos taken every five minutes for more than a month revealed that scavengers, including coyotes, crows, bald eagles and feral pigs, had totally consumed the chicken carcasses and Ducks.

Cameras revealed that there was less feasting on vulture carcasses. Scavengers, including coyotes and Virginia opossums, consumed only 10 of 39 vulture carcasses, five of each species. A few scavengers tasted or partially salvaged vulture carcasses.

Scavenger behavior reveals animals may be avoiding disease

According to Butler-Valverde, now a wildlife technician at the Santa Fe National Forest in New Mexico, the fate of those carcasses provides insight into how nutrients can move through food webs.

A falcon, thought to be a scavenger, lands on a bird's carcass next to train tracks

Cameras captured a hawk eating one of the carcasses.

“The vulture carcasses, which were not recovered or were only partially recovered, remained in the landscape for a longer period of time,” Butler-Valverde said. “This means that the microbial and invertebrate communities were likely able to take advantage of the reduced competition and lack of disturbance from these carcasses. After the carcasses decayed, nutrients would most likely have been deposited in the soil and plant communities. located near the carcasses.

Insects and microbes often miss the opportunity to access carcass nutrients when scavengers arrive quickly and consume the bounty, the study found.

A bald eagle, also considered an occasional scavenger, sits on a bird carcass

A bald eagle inspects one of the carcasses used in the study.

In this case, the higher trophic level vertebrates arrived at the buffet early, obtaining nutrients from the lower level carcasses, but since the majority of the vulture carcasses remained in the landscape, an ecosystem balance occurred in the food web when everyone got something or someone to eat.

From a human perspective, you might expect scavengers to choose the tastiest meal, but researchers believe there’s more than the scavengers’ palate or taste buds at play.

James Beasley, a professor at SREL and Warnell and co-author of the study, said scavengers could avoid disease risks.

“Scavengers are most often predators and higher trophic level species, and by hunting similar species they may be more susceptible to exposure to pathogens to which they may be susceptible,” Beasley said. “Thus, carnivores might be less likely or unwilling to scavenge other carnivores to reduce their exposure to pathogens.”

The study reports that what these animals ate while alive could have influenced the scavengers’ decision to dine or not dine with them. Chickens and mallards are herbivores. Vultures are mainly fed on the carcasses of dead animals, so the nutritional value of carcass types differs.

Camera footage shows cannibalism has occurred. Red-headed vultures feasted on vulture carcasses, but the study notes that most of these scavengers were immature, like toddlers who haven’t yet learned what to eat.

Coyotes were the most frequent scavengers, followed by Virginia opossums. Coyotes scavenged all types of carcasses, but frequently visited vulture carcasses which they did not scavenge. Butler-Valverde acknowledges that this behavior may be the result of a scavenger not being hungry at the time, assessing the situation to return later, and being wary of predators that might be nearby.

The team’s research supports previous findings that fewer vertebrate species scavenge higher trophic level carrion, but Butler-Valverde pointed out that scavenging ecology is a relatively understudied area of ​​research. She said researchers should further investigate the ranges of both vulture species to identify scavenging patterns and their implications.

Travis L. DeVault, associate director and principal investigator at SREL and adjunct professor at the Warnell School, is also a co-author on the study.