It’s a classic David and Goliath story, except there are 90,000 Davids and they all have stings. On the African plains, the whistling-thorn acacia tree protects itself against the mightiest of savannah animals – elephants – by recruiting some of the tiniest – ants.
Elephants are strong enough to bulldoze entire trees and you might think that there can be no defence against such brute strength. But an elephant’s large size and tough hide afford little protection from a mass attack by tiny ants. These defenders can bite and sting the thinnest layers of skin, the eyes, and even the inside of the sensitive trunk. Jacob Goheen and Todd Palmer from Kenya’s Mpala Research Centre have found that ants are such a potent deterrent that their presence on a tree is enough to put off an elephant.
Moving to a new area can be a daunting experience, especially if you don’t know anyone. At first, you might cling to any friends who do live nearby but eventually, you meet new people and start to integrate. As it is with humans, so it is with elephants.
Noa Pinter-Wollman and colleagues from the University of California, Davis wanted to study how African elephants behave when they move to new environments. This happens quite naturally as elephants live in dynamic societies where small family groups continuously merge with, and separate from, each other. But they also face new territories with increasing regularity as human activity encroaches on their home ranges and forces them further afield, and as increasing conservation efforts lead to individuals being deliberately moved, or exchanged between zoos and wildlife parks.
Pinter-Wollman took advantage of just one such forced relocation to see how the animals would react. In September 2005, in an effort to reduce conflicts between humans and elephants, Kenya’s Wildlife Service moved 150 individuals from the Shimba Hills National Reserve to the Tsavo East National Park, some 160km away. They consisted of 20 groups of around 7 individuals each – mainly adult females and calves – and 20 independent males. Their new home was very different to their old one and Pinter-Wollman wanted to see how they reacted to it.