By David Braun
The large number of mature and experienced African elephants being killed illegally for their ivory is exposing younger surviving elephants to a higher risk of mortality from predation and other risks, wildlife conservationists said today.
Close monitoring of a thousand elephants in Samburu, northern Kenya, over the last 14 years has provided solid evidence of disruption of the social dynamics within families, according to Save the Elephants (STE), a Kenya-based conservation organization that conducted the research. “Over the last four years demand for their tusks has disrupted their close-knit society,” STE said in a news release about the study published today in the science journal PLOS One.
The STE research gives the first detailed analysis of the impacts of illegal killing on a well-studied population.
“Unfortunately, illegal killing and related population decline is increasingly common across Africa, therefore the results from this study are directly relevant to understanding the conservation status of this species,” writes George Wittemyer of Colorado State University and STE, who led the study.
The fate of 509 females and 425 males inside two adjacent national reserves, Samburu and Buffalo Springs, was studied between November 1997 and September 2011.
“Elephants roam far beyond the safety of the reserves and into danger zones where ivory poachers are active,” Save the Elephants writes in a news summary about the project. “At the start of the research the population was increasing, but in 2009 the poaching of these individually-known elephants began to take its toll. This change gave researchers an unprecedented opportunity to investigate the effects of the killing by comparing times of stability with times of strife.”
Older Animals Killed in Larger Number
The proportion of elephants that were illegally killed doubled in the last three years of the study. “Older animals—usually those with larger tusks—fared particularly badly. In 2000 there were 38 known males over 30 years old. By 2011 this number had dropped to 12, of whom 7 had grown into the older age class. Almost half of the known females over 30 years old were lost between 2006 and 2011, their number dropping from 59 to 32. While some of this mortality was due to a severe drought that hit the area in 2009-10, at least half is thought to be due to illegal killing,” the researchers write. More....