According to a recent study conducted in South Africa, the human species is not the only one to depend on societal dynamics for social health and growth. The study is the first to explore the relationships between culling (selective killing of animals as a method of population control) and the social health of the animals spared. A research team observed an elephant population whose members had been relocated following a culling event that depleted the original population. While the study focuses specifically on elephants, researchers suggest its findings could apply to all large-brained mammals living in sizeable family groups.
In South Africa, culling has long been employed as a management technique, intending to balance the ecosystem by shielding the food web’s producers from the strain of supporting a growing group of large consumers. The main concern stemming from this method is that it focuses on a population’s size rather than its societal dynamics, when both factors play significant roles in the group’s effects on the ecosystem.
The study found that the social effects of losing members of the herd echoed through the remainder of the group for decades. Several elephants were relocated from Kruger National Park in South Africa to Pilanesberg National Park in the country’s North West province after a cull eliminated their older kin. The extent of psychosocial consequences observed in the animals — even two to three decades following the event — “shows unequivocally that elephants are psychologically damaged by culling,” according to Lori Marino, a neuroscientist at Emory University.
Social instruction is of vital importance in elephant herds, whose young learn appropriate behaviors and reactions from the group’s oldest female. In the absence of the older generation’s guidance, elephants have been shown to exhibit markedly aggressive behavior — sometimes closely resembling the symptoms of post-traumatic stress disorder. Some of the male elephants relocated to Pilanesberg, after attracting media attention for killing rhinoceroses in their new home, were flagged as socially inept. The problem was remedied with the introduction of older male elephants to the herd, but newer research suggests that a deeper underlying issue continues to plague the group.
Scientists set out to gauge the Pilanesberg herd’s responses to various social threats and compare them to the expected reaction, as exhibited by the relatively undisturbed population of Amboseli National Park in Kenya. For each of the observed groups, the researchers broadcast unfamiliar elephant calls into the midst of the herd. They found the Amboseli elephants’ responses demonstrated the appropriate reaction of bunching defensively together and following the matriarch’s lead in anticipation of confronting a threat. The stimuli elicited a starkly contrasting response from the Pilanesberg group, which consistently failed to react as a cohesive whole. Karen McComb, a behavioral ecologist and co-author of the study, noted: “the pattern there was no pattern at all — their reactions were completely random.”
The lack of social finesse and societal aptitude may continue to influence the population into the future: other studies suggest that reproductive success in the herd is linked to the skills its members lose to culling.
