Mice can permanently lose their innate fear of cats after they are infected with a microscopic parasite, find researchers.
The single-celled Toxoplasma gondii parasite is already known to inhibit their hard-wired fear of cats.
But even after they were cleared of the infection, mice no longer reacted with fear to a bobcat's urine, the BBC reported.
The team said that the infection could cause a permanent change to their brains.
Wendy Ingram and colleagues at the University of California, Berkeley, measured how mice reacted to a bobcat's urine.
Cats typically mark their territory with urine, which helps mice detect and avoid an area in which predators might lurk.
Those that remained uninfected with Toxoplasma gondii showed an aversion to the urine, whereas those that were infected walked freely around the test area.
The research is published in the journal Plos One.