This is comparable to other species with highly complex social structures and cooperative care, such as elephants and killer whales which spend 23 per cent and 35 per cent of their lives in a post-reproductive state respectively.
In these species, it has been demonstrated that the presence of post-menopausal females offers survival benefits for related offspring.
In mammals -- and including humans -- this is known as the 'grandmother hypothesis' which suggests that females live long past menopause so that they can help raise successive generations of offspring, thereby ensuring the preservation of their genes.
Researchers proposed that the presence of post-reproductive adult female giraffes could also function in the same way, and supported the author's assertion that giraffes are likely to engage in cooperative parenting, along matrilines, and contribute to the shared parental care of related kin.
Muller said, "It is baffling to me that such a large, iconic and charismatic African species has been understudied for so long. 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."
Muller added, "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."
For scientists to recognise giraffes as a socially complex species, Muller has suggested eight key areas for future research, including the need to understand the role that older, post-reproductive adults play in society and what fitness benefits they bring for group survival.