African white-backed vultures (Gyps africanus) are a species that has experienced a rapid decline in population over the last several decades. This concerning trend has led conservationists to rethink vultures’ status and study their behavior. Research from our GAIA Initiative has shown how social foraging strategies benefit vultures. Collaborating on food helps them reap far more benefits than they incur harms. This makes this current study all the more important. The species has experienced an incredible 90% decrease in its population in less than three generations.
The African white-backed vulture has undergone a population decline of an alarming 4% per year over the last three decades. This abrupt drop-off has caused major alarm bells to go off for conservationists. In 2007, the International Union for Conservation of Nature (IUCN) took an important step. They downlisted some species from “least concern” to “near threatened.” Later, in 2012, this status was raised even higher to “endangered,” and by October of 2015 it was elevated to “critically endangered.” That steady drop-off is even deeper than we first realized. We are in desperate need of research to identify what factors allow these species to persist.
Understanding Vulture Behavior
To investigate the benefits of information exchange among African white-backed vultures, scientists utilized agent-based models focused on three different foraging strategies: non-social foraging, local enhancement, and a coordinated “chain of vultures.” These models were carefully constructed and validated, using data gathered from 30 satellite-tagged vultures in Etosha National Park, Namibia. This data set included more than 26 million GPS traces in addition to matching acceleration data.
Te. Curk, a PhD researcher on the study, described why they compared these three strategies, with rigorous empirical data collected in Namibia. This ultimately enabled them to consistently compute critical parameters, most notably search efficiency. When comparing social strategies to nonsocial strategies, the results showed that social strategies were significantly more effective at finding food sources.
“Working together when searching for food has more benefits than trade-offs for vultures.” – Jan Zwilling
The study revealed that when vultures time their search with one another, they can more quickly find carcasses. This technique is a particularly effective strategy in areas that are home to large vulture populations. It even permits information to flow over long distances, increasing their overall foraging success.
Social Strategies Prove Superior
An unmistakable winner emerged from the study’s findings. Both the social strategy, local enhancement and the chain of vultures performed better than the non-social strategy. Curk expanded on these discoveries. He explained, “We discovered that, of the two social strategies, both were more efficient in searching than the non-social strategy. People found carcasses faster than the non-social model.”
The advantages of these social approaches become apparent, especially in regions where vultures are highly concentrated. As more vultures converge, these benefits further multiply. Curk also mentioned how the “chain of vultures” is especially beneficial. It’s what enables thousands of vultures in an area to collaborate, systematically combing the landscape and communicating from miles apart to efficiently search and share resources. This type of coordination enables vultures to better capitalize on ephemeral food resources.
There are limitations to these strategies. The research indicated that “only at very high vulture densities did the scavenging efficiency of the ‘chain of vultures’ fall short of local enhancement.” In these scenarios, large vulture trains often overcrowd feeding sites. Consequently, some vultures feed only on a few carcasses, and others have nothing to eat.
Implications for Conservation Efforts
The results from this research are extremely important for conservationists trying to save African white-backed vultures. Understanding their behavior and the benefits of social foraging strategies can inform management practices aimed at stabilizing and eventually increasing their populations.
Those numbers are frighteningly dropping, and these species have all reached a state of critically endangered. First, we have to get serious about protecting their habitats and addressing other threats such as poisoning and habitat destruction. This new research is a great start. Conservationists will now be able to use these fascinating findings to inform strategies that promote social behaviors in vultures, allowing them to rebound.