動物行動：人間によるかく乱は動物の移動に影響を与えてその生存を脅かす

Human activities alter the way that animals move around their environments, according to a paper published in Nature Ecology & Evolution. This poses a potential risk to animals’ lives, and contributes to threats of extinction around the world.

Most human activities can affect animal movement. Our direct presence — through hunting, tourism or recreation — can cause animals to avoid certain areas. More indirectly, roads and cities, logging and agriculture all lead to disturbed habitats, causing animals to travel further or to less-suited locations looking for food, homes or mates. Birds, for example, often have to fly further in response to logging, whereas reptile home ranges shrink in response to urbanization.

Tim Doherty and colleagues compiled data from 208 studies on 167 species of land and water animals across six continents. They found that human disturbance has restructured animal movement across the world. More than two-thirds of the 719 cases assessed showed that animals altered their movement by 20% or more. They also found that animals were more likely to increase than decrease how far they travelled in response to human disturbance, and that direct human disturbance had the greatest impacts.

Finding food and mates is already an all-consuming task for most animals, and many will struggle if they have to move further or if their movement is impaired. This change in movement also has cascading effects, such as changed dispersal of seeds by birds, or the number of rodents killed by carnivores.