Human presence weakens social relationships of giraffes

Date:
June 9, 2020
Source:
University of Zurich
Summary:
Living close to human settlements disturbs the social networks
of giraffes. They have weaker bonds with other giraffes and fewer
interactions with other members of the species, an international
study has shown.



FULL STORY ==========================================================================
The effects of human presence on the social relationships of wild
animals have rarely been studied. Even if the animals are not hunted
or killed, increasing contact with humans could have profound indirect
impacts. This is because proximity to humans could disturb the animals'
ability to perform at tasks that are important for survival -- such as
feeding together or rearing young.


========================================================================== Researchers from the Department of Evolutionary Biology and Environmental Studies at the University of Zurich (UZH) have now taken a closer look
at this topic by studying Masai giraffes in Tanzania. The study, carried
out with researchers from the Max Planck Institute of Animal Behavior,
the University of Konstanz and Pennsylvania State University, provides
the first robust evidence that human presence affects the social structure
in this iconic herbivore.

Mapping the social networks of giraffes For their study, the
scientists first needed to obtain large amounts of data from field
research. "Detecting signals of natural versus human-caused influences on social relationships among wild animals is challenging," says Monica Bond,
PhD candidate at the University of Zurich and first author of the study.

Over a period of six years, Bond and her research collaborators collected photographic data spanning 540 adult female Masai giraffes that live in
a large, unfenced landscape in the Tarangire Ecosystem of Tanzania -- an environment that features varying levels of anthropogenic (human-caused) disturbance. The researchers were able to identify individual giraffes
by their unique and unchanging spot patterns. This resulted in one of
the largest-scale social networks ever studied in a wild mammal.

Females live in groups The field research sheds new light on the social relationships of giraffes: The female giraffes in Tarangire 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 groups, even when these share the
same general area. "The study reveals that social structuring is clearly
an important feature of female giraffe populations," says Barbara Ko"nig,
UZH professor and co-author of the study.



========================================================================== Humans disturb social groups The data analysis also revealed that the
social networks exhibit signs of disturbance when groups of giraffes
are exposed to humans: Giraffes living closer to traditional compounds
of indigenous Masai people have weaker relationship strengths and more exclusive social associations.

The researchers suspect that giraffes living near traditional human
settlements are more likely to encounter livestock and humans. This
potentially causes groups of giraffes to split up, even though they are tolerated by the Masai people. This disruption to the giraffes' social
system -- in addition to poaching, loss of habitat and changes in food
supply -- could be a reason why Masai giraffe populations have declined
50% in recent years.

Better protection for calves In other research, the team found that
groups of female giraffes with calves were more likely to occur closer
to human settlements -- possibly because this provides better protection
from lions and hyenas. "It seems that female giraffes face a trade-off
between maintaining important social bonds and reducing risk to their
calves near these traditional settlements," explains Bond.

Overall, the study's results suggest that human presence could play an important role in determining the conservation future of this species
of giraffe. Moreover, the study's leading-edge methodology highlights
the importance of using the social network approach to reveal otherwise
hidden potential causes of population declines.


========================================================================== Story Source: Materials provided by University_of_Zurich. Note: Content
may be edited for style and length.


========================================================================== Journal Reference:
1. Monica L. Bond, Barbara Ko"nig, Derek E. Lee, Arpat Ozgul, Damien R.

Farine. Proximity to humans affects local social structure in
a giraffe metapopulation. Journal of Animal Ecology, 2020; DOI:
10.1111/1365- 2656.13247 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/06/200609095016.htm

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