In humans, the importance of social information is often taken for granted as we learn, from our parents, teachers and friends, how to get the most out of the world around us. The knowledge that we accumulate throughout our lifetimes is often superfluous to survival, and rarely dictates the outcome of life or death scenarios. In other social animals, however, the knowledge gained by older and more experienced individuals can drastically affect the survival of younger generations. The transmission of this vital information across generations is becoming evermore important as the habitats of many long-lived, social species are threatened by climate change and human activity.
This concept is perhaps best understood in African elephants (Loxodonta africana). Female and juvenile elephants live in what are known as matriarchal societies, where a dominant female – the matriarch – leads extended family groups of between four and 14 elephants. Ordinarily she is the oldest elephant in the group, living up to 65 years of age, and thus has a deep understanding of the environment in which she lives. Long-term research on how this translates to increased probability of survival for both her and the rest of her group has been carried out in elephant populations across Africa. Biologists have demonstrated the role of matriarchal experience in successful differentiation between friendly and unknown elephant calls1, as well as showing that older matriarchs are more able to distinguish between the calls of male lions and lionesses2 – a highly useful ability, as male lions hunt elephant calves more frequently than females due to the sheer size and strength needed to bring down such large prey.
These threats are not new to elephants, and matriarchs have been passing on their experience of how to deal with them over countless generations. However, a study in 2008, led by Charles Foley of the Tarangire Elephant Project, revealed for the first time that the experience level of matriarchs might affect how the species will cope with climate change3. They studied the behaviour of 21 family groups over an eight-month period of drought (June 1993 – February 1994). They discovered that groups with older matriarchs who had survived the last major drought, over 30 years earlier, were significantly more likely to leave the bounds of the national park and lead their groups to food and water resources further afield – it is thought they navigated from memory. Also, the survival rate of the calves in these groups was markedly higher than that of other groups with younger matriarchs. These results are of major importance because, as the earth warms with climate change, droughts in Africa are predicted to become much more frequent. And when you consider that the IUCN Red List already classifies the African elephant as vulnerable, the value of old, experienced matriarchs for the survival of the species as a whole becomes even clearer.
The threat of climate change is looming on the horizon, but scientists believe its full impact is yet to be felt in Africa. However, the lives of experienced matriarchs and their family groups are presently in danger from another anthropogenic threat: poaching. Although a global ban was put on the trade of ivory in 1989, which was relatively effective for many years, a huge black market has re-emerged recently which is thought to be fuelled largely by demand in China. As ivory is the desired product, poachers target individuals with large tusks that will sell for enormous prices to illegal traders. Sadly, the elephants with the largest tusks tend to be older individuals, such as the experienced matriarchs we know to be so important.
There have been a number of studies on the long-term effects of poaching on African elephants, made possible by the ivory trade ban of 1989. The results of these studies really put into perspective how much of a positive impact a knowledgeable matriarch can have on her family. In groups that had been subject to poaching 15 years previously and therefore lacked an experienced matriarch, the reproductive success of the females was significantly lower than in unpoached populations, despite many of them being in their reproductive prime. Females in poached populations were also less able to form stable bonds with each other, leading to disrupted groups with limited social cohesion4. But perhaps most strikingly, it seems that poaching had a lasting effect on the physiology of the elephants; the females in poached populations were shown to have significantly higher levels of the stress hormone glucocorticoid in their faeces5 – most likely a result of their more stressful social situation.
These results, combined with the studies of matriarchal knowledge and behaviours, leave no doubt that the leadership of an experienced matriarch in elephant family groups aids survival and fitness of all members of the group. If the poaching of older matriarchs can be controlled and their valuable knowledge safeguarded for future generations, there is evidence that elephants are well equipped to deal with the projected changes to their environment that may occur over the coming years as a result of climate change. Other anthropogenic changes, though, such as increasing habitat fragmentation as the human population of Africa skyrockets, pose a greater problem to the African elephant. Even the wealth of knowledge possessed by the oldest elephants is of no use if roads dissect their habitat and towns replace the landmarks they navigate by. So, if this iconic species is to survive the infrastructural and economic explosion coming its way, it is essential that strict anti-poaching laws are enforced and that all development is approached in a sustainable manner with conservation in mind.
- McComb, Karen, et al. “Matriarchs as repositories of social knowledge in African elephants.” Science 292.5516 (2001): 491-494.
- McComb, Karen, et al. “Leadership in elephants: the adaptive value of age.”Proceedings of the Royal Society B: Biological Sciences 278.1722 (2011): 3270-3276.
- Foley, Charles, Nathalie Pettorelli, and Lara Foley. “Severe drought and calf survival in elephants.” Biology Letters 4.5 (2008): 541-544.
- Gobush, Kathleen, B. E. N. Kerr, and Samuel Wasser. “Genetic relatedness and disrupted social structure in a poached population of African elephants.”Molecular ecology 18.4 (2009): 722-734.
- Gobush, Kathleen S., Benezeth M. Mutayoba, and Samuel K. Wasser. “Long‐Term Impacts of Poaching on Relatedness, Stress Physiology, and Reproductive Output of Adult Female African Elephants.” Conservation Biology22.6 (2008): 1590-1599.