New research from The University of Queensland reinforces the value of network analysis and long-term studies for examining the social systems of wild animals.
Lead researcher, Dr Kerryn Carter, from UQ's School of Biological Sciences, analysed the social groupings of 625 individually identified wild giraffes in Etosha National Park, Namibia from studies spanning six years.
“Long-term studies of sociality in wild animals are quite rare, despite being critical for determining the benefits of social relationships and testing how long such relationships last and whether they change as individual’s age,” said Dr Carter.
Knowledge about social relationships in animal species that exhibit fission-fusion dynamics can enhance our understanding of the evolution of close social bonds in humans, who also have a fission-fusion social system.
“We found that giraffes, which exhibit fission-fusion sociality, formed a cohesive society in which on average any two giraffes could be connected in the population’s social network via 1 to 3 other giraffes.
This reflects the ‘six degrees of separation’ described for people in U.S.A. in which there were on average only five acquaintances in the shortest path between any two Americans.
“Such cohesive giraffe societies may facilitate passive information sharing about food resources that have recently started to flower or bear fruit, or other relevant ecological information. Such information sharing is more likely to benefit the most well connected individuals in the network,” she said.
The results of the study have been published in the scientific journal Animal Behaviour.
Despite the daily changes in giraffes’ group compositions that are typical of fission-fusion taxa, the study also found that long-term relationships spanning six years were evident among female giraffes, but not males.
This may be explained by sex differences in ranging patterns and reproductive priorities.
Long-term friendships among females may help individuals to find food and detect predators by learning from others, which may enhance their own survival and that of their offspring.
In contrast, long-term relationships among males who may be direct reproductive competitors would not bring reproductive benefits and injuries from fighting could reduce, rather than enhance, survival.
The study also discovered that as immature female giraffes matured to young adults they appeared to increase their gregariousness by forming weaker relationships with a greater number of females, perhaps as they moved around to different groups prior to settling into a home range.
In contrast, older females showed greater stability over time in the strengths of their friendships and the numbers of females they associated with, probably because they had settled into stable home ranges and frequently encountered known females at food patches and waterholes.
Media: UQ School of Biological Sciences Communications Manager Tracey Franchi, 07 3365 4831 or t.franchi@uq.ed.au; Dr Kerryn Carter, +260 96991598, kerryn.carter@uqconnect.edu.au.
Images for Publication: Images of male and female giraffes are taken at Etosha National Park, Namibia by Dr Kerryn Carter. More images available by emailing t.franchi@uq.edu.au
About the School of Biological Sciences: Through research undertaken in the School, UQ has been ranked by the 2012 National Taiwan University Rankings in the top five universities globally for research in ecology and environmental biology and in the top 18 universities globally for plant and animal biology. The UQ School of Biological Sciences attracts researchers of world standing in a range of disciplines, with international leaders in many diverse fields. Our work spans the scales of biological organisation, from molecules and cells to organisms, populations, species and communities. With more than 150 researchers working in the fields of evolution, global change biology, ecology, aquaculture, animal behaviour, physiology, entomology, zoology, botany, genomics, developmental biology and conservation biology, our researchers and graduate scientists are well-equipped to make a real difference in contributing to solving global problems.
