Scientists have found that human interaction reduces the threat of predators to animals that are kept in captivity or live in urban environments. Thanks to people, they get used to safe life and lose the ability to defend themselves or hide from enemies.
An international team of scientists analyzed the results of 173 peer-reviewed studies examining the ability to resist predators in 102 species of animals that are constantly in contact with humans. The team divided them into three categories – domesticated, captive, and urban – and studied how the disappearance of defense mechanisms occurs in each group. The results showed that due to frequent contact with humans, animals begin to feel safe and stop fearing or fleeing predators, as in the wild. Details of the study are published in the journal PLOS Biology.
Scientists have found that human influence reduces the risks of predators. For domesticated and captive animals, the threat is significantly reduced or disappears altogether, and even just living in an urban environment eases the pressure on some species, although it is assumed that in this case, human exposure is minimal. In response to new, safer conditions, animals change their behavior patterns. At the same time, the loss of the ability to escape from predators in animals living in an urban environment occurs three times slower than in domestic animals, and keeping in captivity leads to the slowest changes. In addition, herbivorous and omnivorous domesticated animals got used to the new environment much faster than carnivores, and loners faster than herd ones.
Scientists noted that such behavior can cause problems when species that have been in contact with humans for a long time fall into the wild. Many of them stop responding correctly to the threat from other species and wait for humans to intervene, and this ultimately leads to their death.
In addition, it turned out that simultaneously with the loss of protective mechanisms in individuals, the rate of hereditary changes increased – with generations it gradually decreased. As the authors suggested, this is because the influence of natural selection in a safe environment was decreasing, but along with it, rapid artificial selection began – this especially affected the evolution of domesticated species.
Biologists believe understanding how human intervention is changing animal behavior is essential to the conservation of species – especially those that breed in captivity but then return to their natural habitat – as well as livestock and urban planning. Dr. Benjamin Geffroy, head of the study, added that scientists need more data to figure out how human contact affects each individual and whether the mere presence of tourists matters to them.