Wild Animals Lose Fear of Predators Quickly After They Start Encountering Humans
Most wild animals show a suite of predator avoidance behaviors such as vigilance, freezing, and fleeing. But these are quickly reduced after the animals come into contact with humans through captivity, domestication, or urbanization, according to a study led by Benjamin Geffroy from MARBEC (Institute of Marine Biodiversity, Exploitation and Conservation), published on September 22, 2020, in the open-access journal PLOS Biology.
The international team of researchers analyzed the results of 173 peer-reviewed studies investigating antipredator traits (behavioral and physiological) in 102 species of domesticated, captive, and urbanized mammals, birds, reptiles, fish and molluscs, while taking into account their position in the Tree of Life.
The scientists found that contact with humans led to a rapid loss of animals antipredator traits, but simultaneously the variability between individuals initially increases and then gradually decreases over the generations in contact with human. The authors suppose that this two-step process is caused by reduced pressure from natural selection as a result of living in a safer environment, followed by artificial selection by humans for docility in the case of domestication.
Animals showed immediate changes in antipredator responses in the first generation after contact with humans, suggesting that the initial response is a result of behavioral flexibility, which may later be accompanied by genetic changes if contact continues over many generations. The researchers also found that domestication altered animal antipredator responses three times faster than urbanization, while captivity resulted in the slowest changes. The results also showed that herbivores changed behavior more rapidly than carnivores and that solitary species tended to change quicker that group-living animals.