Like humans, vultures become trapped in their habits and have fewer friends as they get older

If you prefer watching TV on your couch to dancing at the club, you may have something in common with aging griffon vultures. New research shows that young griffon vultures frequently move between roosts in different locations and interact with many friends, but as they age they become entrenched in their habits and roost in the same spots with the same individuals. As moving between roosts becomes laborious, older vultures follow the same path and develop movement routines not seen in young vultures.

Younger vultures also tend to avoid the most popular roosting sites, suggesting that they feel intimidated by older ones or that there is a “hey kids, get off my lawn” mentality among vultures.

The study was published in Proceedings of the National Academy of Sciencesshows that older vultures, like many humans, form fewer, more selective friendships with stronger bonds. They may also have a better idea of ​​where to find food sources.

Griffon vultures (Gyps fulvus) are large vultures that live in the Mediterranean, the Middle East, and India. With a wingspan of up to 2.75 meters, they are much larger than North American turkey vultures and larger than bald eagles.

Foraging can be difficult for vultures because of their reliance on animal carcasses – an unpredictable and fleeting source. When griffon vultures find a carcass, they roost or rest nearby and feed on it for several days. Roosting sites can therefore be “information hubs” where vultures that have recently fed provide information about food sources to other animals. They then follow each other to the carcasses and form friendships that help them stay informed about food.

The researchers wanted to know whether the movement patterns and social behavior of individual griffon vultures change over their lifetime. They used GPS data from 142 individually tagged birds in Israel, collected over a 15-year period, to match the vultures’ age with their movements and social interactions at roosts.

“We found that their loyalty to particular roosting sites increases with age,” said co-author Noa Pinter-Wollman, a professor of ecology and evolutionary biology at UCLA. “Young vultures explore many different roosting sites, but in middle age they start to go to the same places over and over again.”

The study showed that young vultures sometimes returned to the same roost, but usually chose a different one and rarely spent two nights in the same place. From young adulthood, at around five years of age, to middle age, they spent about half their nights in the same “home” spot and the other half elsewhere. As they aged, they became real homebodies.

“When they are old, starting at age 10, they no longer have the energy to be ‘out there’ and keep returning to the same place,” said corresponding author Orr Spiegel of Tel Aviv University. “Those who were adventurous at age 5 became more sedentary at age 10.”

As the vultures grew older, the strength of their social bonds also declined, at least for part of the year. The number of individuals they interacted with did not change with age—if they had five friends when they were young, they still had five when they were older. But the amount of time they spent with vultures outside their close friend group dropped rapidly. Older vultures spent most of their time with these close friends and usually slept with them. Their movements also became more routine, eventually following a predictable pattern.

The study is unique because the researchers were able to track the movements and social behavior of the same vultures over a period of 15 years, up to 12 nearly consecutive years.

“We can show that the tendency for individuals to remain more loyal to the same locations as they age is not due to the more exploratory individuals dying earlier and living shorter lives, while the older, more sedentary individuals live longer,” said first author and postdoctoral researcher at Tel Aviv University Marta Acácio. “Individuals do indeed change their behavior as they age, and this has rarely been shown in nature in long-lived birds because it is difficult to track individuals over such a long period of time.”

The research supports the results of studies in other species that show that as animals age, they become more loyal to their familiar locations and routines – and may also become more selective in their social relationships. These behaviors are often attributed to the aging process in humans and may help us better understand how animal populations move around their environments and interact with other members of their species, and find better ways to protect them from threats.

For griffon vultures, this could mean better protecting important roosting sites and using knowledge of their social interactions to reduce the risk of poisoning.

“It seems they are simply set in their ways,” Pinter-Wollman said. “They have gathered information over the years and are able to use it. Carcasses are hard to come by and roosts are information hubs. Some roosts become popular for a reason; for example, they tend to be closer to reliable food sources and older vultures may monopolize these roosts.”