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To others, it illustrates the problem of wild animals becoming habituated to interacting with humans.

Taking care to not stress the animals or get too close, the researchers followed the monkeys, which are habituated to human presence, until they urinated.

In other words, the immune cells responsible for recognizing cancer may get somehow habituated to the presence of a cancer cell -- the immune cell gets used to the stimulus and no longer responds to it.

The authors said the urban experiences of P41, P22 and others in the study illustrate how, when faced with increased human activity, mountain lions actively seek to avoid people rather than becoming habituated to them.

Sierra Madre has a mix of no harm, no foul bears and habituated bears, Wilson said.