Giraffes are much more socially complex than once thought, and may depend upon their grandmothers as much as we do, according to a new study from the University of Bristol, UK.
Historically it was believed that giraffes lacked a social structure, interacting essentially at random. In a new paper in the journal Mammal Review, Zoe Muller, from the University of Bristol’s School of Biological Sciences, reviewed more than 400 studies on giraffe behaviour and social organisation.
Through this synthesis, Muller and study co-author Stephen Harris, also of Bristol, found that giraffes have a complex, cooperative social system, and that this system shows key features of matrilineal organisation – including the significance of ‘grandmothering’.
The grandmother hypothesis is an evolutionary theory that suggests human women have a long post-menopausal life because grandmothers – who provide additional care and teachings to their grandchildren – improve the group’s overall resilience and survival. By contrast, less socially complex mammals are often destined to die not long after their reproductive functions wane.
This hypothesis has since been theorised – and to some extent demonstrated – for other complex mammals, including killer whales and elephants, among whom the presence of grandmothers is shown to extend infant survival.
Muller and Harris’ study shows that female giraffes spend up to 30% of their lives in a post-reproductive state, and that s ‘grandmother’ provides crucial benefits for their offspring’s offspring. In essence, giraffes show key features of co-parenting with a grandmother.
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The study marks the first time such complex social organisation has been posited for these poorly understood creatures.
“It is baffling to me that such a large, iconic and charismatic African species has been under-studied for so long,” Muller says. “This paper collates all the evidence to suggest that giraffes are actually a highly complex social species, with intricate and high-functioning social systems, potentially comparable to elephants, cetaceans and chimpanzees.”
Beyond the grandmother hypothesis, the study showed other key features of life in a giraffe society that hint at a complex, female-driven social structure. For example, offspring stayed in their natal groups for much if not all of their lives, non-mothers helped mothers to rear their young, and males dispersed while females spent their lives in stable, cooperative groups.
Muller hopes this new research will revive an under-researched field, and offer hope for the conservation of these vulnerable giants that have lost 40% of their global population since 1985.
“Conservation measures will be more successful if we have an accurate understanding of the species’ behavioural ecology,” says Muller. Moreover, “if we view giraffes as a highly socially complex species, this also raises their ‘status’ towards being a more complex and intelligent mammal that is increasingly worthy of protection.
“I hope that this study draws a line in the sand, from which point forwards, giraffes will be regarded as intelligent, group-living mammals which have evolved highly successful and complex societies, which have facilitated their survival in tough, predator-filled ecosystems.”