Young griffon vultures frequently change their sleeping locations and socialize with various companions. However, as they grow older, they tend to stick to familiar spots and associate mainly with the same group of friends. Older vultures establish consistent routes for their travels, which younger vultures do not have. These resting places serve as crucial information centers; older vultures often possess extensive knowledge about food sources and typically require less input from other vultures.
If you prefer cuddling on your couch to hitting the dance floor, you might relate to aging griffon vultures. Recent studies indicate that young griffon vultures often shift between various sleeping locations and form numerous friendships, but as they grow older, they become more habitual, choosing to roost in familiar areas alongside the same peers. As the routine of moving becomes tedious, older vultures establish set paths that younger ones typically do not follow.
Young vultures tend to avoid the most crowded roosts, possibly due to intimidation from older vultures or because of a certain “stay off my lawn” attitude exhibited by the older birds.
This research, featured in Proceedings of the National Academy of Sciences, reveals that like many humans, older vultures prefer fewer but deeper friendships. They also develop a better understanding of where to locate food.
Eurasian griffon vultures, known scientifically as Gyps fulvus, are sizable birds residing in the Mediterranean, the Middle East, and India. With wingspans that can reach up to 9 feet, they are significantly larger than turkey vultures found in North America and even exceed the size of bald eagles.
Finding food is quite challenging for vultures as it involves locating animal carcasses, which can be unpredictable. When griffon vultures spot a carcass, they typically roost nearby and feast on it over several days. Roosting locations can serve as ‘information hubs,’ where vultures that have recently eaten signal others about available food sources, allowing them to follow each other to carcasses and build friendships that enhance their knowledge about food availability.
The researchers aimed to explore how the movement patterns and social behaviors of individual griffon vultures evolved throughout their lifetime. They analyzed GPS data from 142 tagged birds in Israel collected over 15 years to link the vultures’ ages with their movement and social behaviors at roost sites.
“Our findings indicate that as vultures age, their loyalty to specific roost sites increases,” stated co-author Noa Pinter-Wollman, a UCLA ecology and evolutionary biology professor. “Young vultures often explore various roosts but as they enter middle age, they start returning consistently to the same areas.”
The study found that young vultures occasionally revisited the same roost but primarily opted for different locations, rarely spending two consecutive nights in the same place. From around 5 years old into middle age, they roughly split their nights between their primary “home” site and other locations. In their old age, however, they become true homebodies.
“By the time they reach around 10 years old, they lack the energy to be adventurous and routinely return to the same site,” mentioned corresponding author Orr Spiegel from Tel Aviv University. “Those adventurous at 5 tend to become less active by age 10.”
As vultures grow older, the strength of their social connections also diminishes for part of the year. Though the number of individuals they engage with remains consistent with age — if they had five friends when young, they still have five as they age — the time spent with other vultures outside of their close friend group drastically decreases. Older vultures primarily associate with their close friends, leading to more predictable and routine movements.
This study is unique as it tracked the movements and social behaviors of the same vultures for up to 12 nearly consecutive years across a 15-year span.
“We’ve demonstrated that the trend of individuals growing more loyal to the same roosts with age isn’t merely a result of the more exploratory ones dying out sooner, while the sedentary ones live longer,” explained first author and Tel Aviv University postdoctoral researcher Marta Acácio. “Instead, the individuals genuinely change their behaviors as they age, which is rare to observe in nature among long-lived birds due to tracking difficulties over extended periods.”
This research reinforces findings from studies on other species that reveal older animals tend to become more attached to locations and routines, potentially becoming more selective in their social relationships. These behaviors are often associated with aging in humans and can enhance our understanding of how animal populations navigate their environments and interact with peers, leading to better protection strategies against threats. For griffon vultures, this could involve safeguarding crucial roosting sites or leveraging knowledge of their social dynamics to mitigate poisoning risks.
“It appears they become set in their routines,” noted Pinter-Wollman. “Over the years, they gather information and decide to use it since food sources can be scarce and roosts serve as information hubs. Some roosts gain popularity for particular reasons; for example, they might be closer to reliable food sources, with older vultures tending to dominate these spots.”
