West LA Times

New research indicates that young griffon vultures frequently change sleeping sites and interact with many friends, but as they age, they tend to roost in the same spots with the same individuals. The study, published in Proceedings of the National Academy of Sciences, suggests that older vultures follow consistent paths and establish movement routines not observed in younger birds.

Eurasian griffon vultures (Gyps fulvus) are large birds found in the Mediterranean, Middle East, and India. They rely on locating animal carcasses for food, which can be unpredictable. Roosting sites serve as information hubs where vultures share knowledge about food sources.

Researchers used GPS data from 142 tagged vultures in Israel over 15 years to examine changes in movement patterns and social behavior throughout their lives. "What we found was as they age, their loyalty to certain roost sites increases," said Noa Pinter-Wollman, a UCLA professor of ecology and evolutionary biology.

The study showed that while young vultures often return to different roosts each night, older vultures become more sedentary. "When they are old, from the age of 10 onward, they no longer have the energy to be 'out and about' and return consistently to the same site," said Orr Spiegel of Tel Aviv University.

As vultures aged, their social bonds became stronger but fewer. Older vultures spent most of their time with close friends and followed predictable movement patterns. The research tracked individual vultures for up to 12 consecutive years over a 15-year period.

"We are able to show that the trends of individuals becoming more loyal to the same sites with age is not because the more exploratory individuals die earlier," said Marta Acácio of Tel Aviv University. "Individuals actually change their behavior with age."

The findings align with studies on other species showing increased site fidelity and selective social relationships with age. Understanding these behaviors could improve conservation efforts by protecting important roosting sites and mitigating risks such as poisoning.

"It looks like they just get set in their ways," Pinter-Wollman said. "They've gathered information over the years, and they might as well use it."