By Lesley Evans Ogden
When the two young elephants showed up unaccompanied, it was obvious they had lost their mother. Arriving at the park after a long absence, Chastity and her sister were from a family known to spend time in an area with security risks. Their mother's body was never recovered, so it was unclear whether they lost her at the hands of a gun, or from natural causes.
Surprisingly, as the orphaned sisters milled about, they didn't stay with the family group their mother had long been affiliated with. Normally, African elephant mother-calf groups are very cohesive, spending 50 to 60% of their time in multi-family "bond groups". But Chastity seemed to shun those previous relationships, and took great interest in a less familiar family, says George Wittemyer of Colorado State University in Fort Collins and scientific chair of Save the Elephants.
These young elephants provided Wittemyer's first close experience of watching an orphan, its social strategy, and its absorption into another group. They prompted him to investigate the behaviour of elephant orphans. There are plenty of them, thanks in no small part to poachers that kill adult elephants for their ivory. Can these parentless animals find their way, and create new families for themselves? There are a lot of unanswered questions, but so far they are proving impressively adaptable.
For 17 years, Wittemyer has been studying African elephants in the neighbouring Samburu and Buffalo Springs National Reserves in northern Kenya. In recent years, they have taken a battering. In 2009, Samburu was hit by a devastating drought, and this was followed by a surge in illegal killing.
Poaching has inflicted a severe toll on African elephants. Wittemyer has estimated that, in west and central Africa, numbers have fallen by at least 50% in the last four decades. In August this year, his team estimated that the level of continent-wide poaching was unsustainable between 2010 and 2012, with up to 8% of elephants being killed per year. This high level of poaching is driving a decline of the species.
As well as the simple impact on elephant numbers, Wittemyer noticed that poaching was causing a high level of social disruption, and that there were many orphaned elephants. That poses a particular problem for young elephants, because the species is so intensely social: the calves have to learn many key skills from their mothers.
Wittemyer, and his graduate student Shifra Goldenberg, want to find out how orphans reestablish relationships, and how losing their mother affects their survival. To do this, they are watching orphans' behaviour, analyzing tracking data from elephants fitted with GPS collars, examining who spends time with whom, and looking at which elephants initiate and receive friendly and aggressive behaviors.
An orphaned elephant needs the support of a group if it is to survive. But which group should an orphan join?
In general, elephants are more likely to form intimate ties with close genetic relatives, according to a study of the more protected Amboseli population by Elizabeth Archie of the University of Notre Dame in Indiana and her colleagues. This is usually true in Samburu as well, says Goldenberg, but in Samburu there are also groups made up entirely of unrelated individuals. Such groups are never seen in Amboseli, and probably reflect the higher level of disturbance in Samburu.
Accordingly, Wittemyer and Goldenberg have found that orphans cope with their situation in many ways. Some stay with their birth families. Others join distantly or unrelated groups. Still others form ties with one family for months at a time, then switch their loyalties to another.
So why would an orphaned elephant, like Chastity, attach herself to an unrelated, relatively unfamiliar family? "It wasn't clear," says Wittemyer.
One possible explanation is that there were two female elephants similar in age to Chastity in the new family. Conceivably she saw them as potential allies.
Alternatively, it could be because the matriarch had just given birth. It's not unusual for juvenile female African elephants to be fascinated with newborn calves, says Wittemyer.
In line with this idea, Chastity soon began pitching in, helping out her foster family by caring for the matriarch's baby, even suckling the calf. Such babysitting, technically called alloparenting, is quite common in young female elephants. More....