Proximity to humans affects local social structure in a giraffe metapopulation

• Published in: The Journal of animal ecology 2021-01, Vol.90 (1), p.212-221
• Main Authors: Bond, Monica L., König, Barbara, Lee, Derek E., Ozgul, Arpat, Farine, Damien R., Vander Wal, Eric
• Format: Article
• Language: English
• Subjects: Animals; anthropogenic disruption; Anthropogenic factors; Capture-recapture studies; community detection; Environmental factors; Female; Food resources; Giraffa camelopardalis; Giraffe; Giraffes; Giraffidae; Human influences; Humans; Livestock; Metapopulations; Questions; Social conditions; social network analysis; Social networks; Social organization; Social structure; Tanzania
• ISSN: 0021-8790; 1365-2656
• DOI: 10.1111/1365-2656.13247

Experimental laboratory evidence suggests that animals with disrupted social systems express weakened relationship strengths and have more exclusive social associations, and that these changes have functional consequences. A key question is whether anthropogenic pressures have a similar impact on the social structure of wild animal communities. We addressed this question by constructing a social network from 6 years of systematically collected photographic capture–recapture data spanning 1,139 individual adult female Masai giraffes inhabiting a large, unfenced, heterogeneous landscape in northern Tanzania. We then used the social network to identify distinct social communities, and tested whether social or anthropogenic and other environmental factors predicted differences in social structure among these communities. We reveal that giraffes have a multilevel social structure. Local preferences in associations among individuals scale up to a number of distinct, but spatially overlapping, social communities, that can be viewed as a large interconnected metapopulation. We then find that communities that are closer to traditional compounds of Indigenous Masai people express weaker relationship strengths and the giraffes in these communities are more exclusive in their associations. The patterns we characterize in response to proximity to humans reflect the predictions of disrupted social systems. Near bomas, fuelwood cutting can reduce food resources, and groups of giraffes are more likely to encounter livestock and humans on foot, thus disrupting the social associations among group members. Our results suggest that human presence could potentially be playing an important role in determining the conservation future of this megaherbivore. Using one of the largest‐scale metapopulation networks ever studied in a wild mammal, the authors reveal that social communities of giraffes living closer to human settlements exhibit weaker relationship strengths and more exclusive social associations—a signature of a disrupted social environment based upon previous experimental research.