Scientists have recently discovered that female Masai giraffes live in distinct social communities of up to 90 other friends, and although areas used by these ‘girl gangs’ often overlap, they have very different rates of reproduction and calf survival. This means the girl gang social units may be important to giraffe evolution.
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Study overview
The team calculated the survival rates of more than 1,400 adult females and calves, and the annual number of calves per female, and examined if there were differences among the social communities. They then investigated if the differences were explained by social factors like the strength of relationships, or by features of the environment, such as how close to people the giraffes roamed, the fertility of the soils, or the kind of vegetation in their ranges.
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Study Findings
“Gang membership was pretty tight, and even though members of different girl gangs often spent time in the same areas, members of different communities rarely interacted with each other.”
-Dr. Derek Lee, associate research professor, Penn State and senior author of the study
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The scientists also discovered that calf survival and reproductive rates were different among these social communities, even when communities’ home ranges overlapped in space and therefore shared similar environmental conditions. Additionally, each giraffe social community exhibited different social characteristics, like how strong the relationships were among the community members.
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“This shows that population structure can arise from social behavior rather than discrete space use. These social subpopulations have different survival and reproductive rates, so some might have greater competitive abilities than others, like being able to dominate the better-quality food, or there might be cultural differences such as having better strategies for protecting their calves from predators.”
-Dr. Monica Bond, lead author and research associate, University of Zurich
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The study findings can help humans help giraffes
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“The good news for conservation is that giraffes can survive and raise their offspring in areas close to people. We can help giraffes to thrive by giving them enough living space in the savanna—both inside and outside of national parks—and by taking care not to disturb them and disrupt their social relationships.”
-Dr. Derek Lee, associate research professor, Penn State and senior author of the study
Journal reference: Bond, M.L., König, B., Ozgul, A., Farine, D.R. and Lee, D.E. (2021), Socially Defined Subpopulations Reveal Demographic Variation in a Giraffe Metapopulation. Journal of Wildlife Management. https://doi.org/10.1002/jwmg.22044 Summary
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