While young vultures gad about, older ones prefer to stay home – study
Tel Aviv University research shows that aging vultures become less sociable
Sue Surkes is The Times of Israel's environment reporter
While young vultures like to sleep over at friends’ houses and adolescents spend only half their nights at home, their aging parents prefer staying in, research from Tel Aviv University revealed, in a new study that also showed that older vultures are less sociable, particularly during the breeding season.
The study, led by Dr. Marta Acácio as part of her postdoctoral research in Dr. Orr Spiegel’s laboratory at Tel Aviv University’s Zoology School, used data accumulated from GPS devices attached to 142 endangered Eurasian griffon vultures for up to 12 years.
Published in the peer-reviewed journal PNAS last month, the research is one of few studies to shed light on behavioral changes in aging wild animals.
The birds play a critical ecological role as nature’s cleaners, consuming dead animals that could otherwise spread disease.
But they are exposed to a myriad of dangers, from eating carcasses poisoned by farmers to keep feral dogs away from flocks, to electrocution from high-voltage electricity wires.
The Israel Nature and Parks Authority has a captive breeding program for griffon vultures and invests immense efforts to protect the roughly 180 birds that still fly Israel’s skies.
GPS transmitters attached to birds bred in captivity and wild ones connect to a system that alerts the authorities, for example, if a vulture has not moved.
Spiegel was able to cross-reference the vultures’ ages with the GPS data on their cliff-side roosting sites.
“It turns out that aging vultures behave a bit like humans and are more inclined to stay home,” he explained.
“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.”
He continued, “When they reach adolescence at age five, this behavior stabilizes, and as adults, they spend 50 percent of their nights at the same site and the other 50 % at other sites.”
“When they are old, from age ten onwards, they no longer have the energy to be ‘out and about,’ and return consistently to the same site.”
“Furthermore, when adult vultures change sites, they do so in a predictable pattern–for example, one night in Ein Avdat, the next in the Small Crater, and the next at the Golhan stream (all relatively close sites in southern Israel), following a fixed order.”
Spiegel added, “It could be argued that older vultures move less not because they are old, but because they avoid taking risks in the first place, which is how they reached the age they did. But here we are talking about the same individual birds. Those who were adventurous at age five became more sedentary by age ten.”
He said findings about the vultures’ social circles could help better protect them from dangers such as poisoning as they tend to feed in groups.
The research was conducted with Prof. Noa Pinter-Wollman of the University of California, Los Angeles (UCLA), and several other researchers.
