A new study has found that vultures, much like humans, experience changes in movement habits and social relationships as they age. Young vultures frequently move between roosting sites and hang out a lot with their friends. During adolescence, they spend about half their nights at a permanent site at home and the other half at other sites.
In old age, however, vultures scale back on socializing, preferring to “stay home.”
The study followed 142 Eurasian Griffon Vultures (Gyps fulvus) and is among the first to shed light on the behavioral changes in aging animals in the wild.
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The researchers utilized a database accumulated over 15 years from GPS devices attached to 142 vultures that tracked them for periods of up to 12 years. The vulture, a social bird, sleeps in roosts on cliffs. By cross-referencing the vultures’ ages with the GPS data on their roosting sites, the researchers discovered that as the vultures aged, they increasingly preferred to stay at the same roosting site.
The study was led by Marta Acácio at Tel Aviv University and Prof. Noa Pinter-Wollman of the University of California, Los Angeles (UCLA). The findings were published in the prestigious journal PNAS.
“Vultures are a locally endangered species in Israel, with only about 200 individual vultures remaining. They are closely monitored to determine the best possible conservation methods. We thought about what else could be gleaned from the extensive database we have accumulated over the years and agreed it would be interesting to explore how vultures age,” says Spiegel.
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“Tracking the same individuals in the wild over many years is often very challenging, but the transmitters we use to monitor the population provided us with a rare opportunity to observe the aging process in vultures specifically and in animals generally.
It turns out that aging vultures behave a bit like humans and are more inclined to stay at home. When they are young, vultures like to explore new sites and frequently move between places; the likelihood that a young vulture will sleep at the same site two nights in a row is low.
When they reach adolescence at the age of five, this behavior stabilizes, and as adults they spend 50 percent of their nights at the same site and the other 50 percent at other sites. When they are old, from the age of 10 onwards, they no longer have the energy to be “out and about,” and return consistently to the same site.
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According to Spiegel, these fascinating findings on the aging of birds also have very practical implications for conservation efforts. “This new study can help us better protect vultures’ roosting sites in the wild. Additionally, we have now seen that older vultures have fewer social connections, which can help us to prevent poisoning. The transmitters are connected to a system that sends an alert to the Israel Nature and Parks Authority, and to us by phone, if the vulture is not moving or has landed in a dangerous place, indicating that it may have been poisoned. Unfortunately, this happens frequently.
The danger arises when a vulture descends on a poisoned goat carcass, not knowing that a farmer has poisoned the carcass in order to kill stray dogs. Being social birds, vultures do not come down alone, leading to the risk of dozens of vultures dying at once. Understanding how wide the poisoned vulture’s social circle is will significantly help in mitigating the damage.”
It is important to note that vultures play an important ecological role in the disposing of carcasses. Studies have shown that the extinction of vultures ultimately leads to the loss of human lives, due to the rise of diseases such as rabies. In India, for example, a recently published study revealed that the extinction of vultures due to poisoning resulted in the deaths of half a million people over the course of five years.
