Sri Lanka鈥檚 civil war lasted 26 years, coming to an end in 2009. But the country鈥檚 birds haven鈥檛 forgotten.
鈥淭here were many incidents reported, while growing up in Sri Lanka, of landmines causing injury or death to animals in war zones,鈥� says at Deakin University in Burwood, Australia.
He and his colleagues have found that in former war zones, wild birds are still wary of humans, while birds in areas that didn鈥檛 see armed conflict during the war let humans get closer before flying away.
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The civil war caused mass displacement of people, widespread poverty and the breakdown of normal levels of governance, and many thousands of people were killed or injured. This filtered down to Sri Lanka鈥檚 wildlife, as investment in nature conservation fell and civilians and combatants on both sides of the war engaged in hunting and poaching.
Gnanapragasam and his colleagues were studying fear responses in Sri Lankan birds for population management purposes when they wondered if there was any influence from the civil war in their data.
The researchers recorded the 鈥渇light initiation distance鈥� (FID) 鈥� how close a bird would let humans approach before flying away 鈥� for 157 species of birds in Sri Lanka. In all, they measured 1400 FIDs across varied habitats, in areas that saw armed conflict during the war and those that didn鈥檛.
The team found that birds in regions that experienced armed conflict had FIDs that were about 25 percent longer than those of birds in areas that didn鈥檛 see armed conflict, meaning that the war zone birds were more fearful of approaching humans and apt to flee.
Larger bird species showed a greater increase in FID in war zones than smaller birds. at the University of California, Los Angeles, who wasn鈥檛 involved in the study, thinks this pattern makes sense, because there would probably be higher hunting pressure on larger birds with more food value to people.
The findings reveal an echo of war in the behaviour of wild animals experiencing the conflict alongside humans. Previous research in other parts of the world has shown war鈥檚 indirect impact on wildlife populations or their physical evolution. But the new study is the first documentation of war changing behaviour across multiple species, the researchers say.
鈥淲e perhaps should not be surprised that human war victimises wildlife as well as people,鈥� says Gnanapragasam.
It鈥檚 not yet clear if the war zone birds鈥� fear comes from an evolved behaviour, as less cautious birds in the population were more likely to be killed off, or if it is learned. Both Gnanapragasam and Blumstein think it may be both, with the long-lived bird species recalling dangerous human encounters during the war.
鈥淭his could be a remnant of selection, or it could be a remnant of behavioral change that is still around,鈥� says Blumstein.
Join entomologist George McGavin in Sri Lanka:On a wildlife and conservation Discovery Tour
However it came about, the birds are experiencing an extended 鈥渓egacy of fear鈥� from the war, he says. Other scientists have studied the development of wildlife fear on the scale of single hunting seasons, but 鈥渢his [fear] is a number of years after the war ended鈥�, says Blumstein.
Gnanapragasam says management plans for threatened species in Sri Lanka should take into account the history of the civil war and its influence on animal behaviour. 鈥淐onservation should be a consideration in post-war recovery,鈥� he says. 鈥淎nd of course, avoiding any future wars would likely be appreciated by non-human species.鈥�
The American Naturalist
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