UNIVERSITY PARK, Pa. — Living in close proximity to human settlements disturbs giraffe social networks, with animals having weaker bonds and fewer interactions with other giraffes, according to a new study by a team including a Penn State biologist. The researchers believe this could impact the giraffes' ability to perform social behaviors, like foraging for food, which has important implications for how endangered Masai giraffes are managed.
The research team, which also includes researchers from the University of Zürich, the Max Planck Institute of Animal Behavior, and the University of Konstanz, monitored more than 500 giraffes over six years and used a state-of-the art social network analysis to provide new insight into the social relationships of wild giraffes and how they are affected by humans. A paper describing the results appears June 9 in the Journal of Animal Ecology.
“In Tanzania, giraffes are generally tolerated by humans because they do not cause conflicts with farmers or livestock,” said Derek Lee, associate research professor of biology at Penn State and principal investigator of the long-term giraffe research project. “But even if animals are not hunted and killed by humans, increased interactions with humans could have indirect but profound effects, including on their social structure. For example, proximity to humans could disturb an animal’s ability to perform tasks that are important for survival, such as feeding together or rearing young. In this study, we have found the first robust evidence that humans modify the social structure of this iconic megaherbivore.”
Over a period of six years, the researchers collected photographic data on 540 adult female Masai giraffes inhabiting a large, unfenced area in Tanzania with varying levels of human disturbances. The researchers were able to identify individual giraffes by their unique and unchanging spot patterns.
“Detecting signals of natural versus human-caused influences on social relationships among wild animals is challenging,” said Monica Bond, research associate at the University of Zürich and first author of the study. “It requires large-scale studies of individually identified animals across numerous social groups living under different environmental conditions. Our study was one of the first to do this and, to our knowledge, is one of the largest-scale social networks ever studied in a wild mammal.”
The research team first characterized the social relationships of giraffes, and then explored the impact of humans. They found that female giraffes live in a complex multilevel society, with individuals preferring to associate with some females while avoiding others. These preferences result in discrete social communities of 60 to 90 females with little mixing among the communities, even when they share the same general area.