we were walking back from salt river this last week and came across a rat asleep right out in the open on the sidewalk. i thought it was a pretty strange sight, mainly because most of the rats i've seen living in cities are incredibly skittish and avoid confrontation at pretty much all cost.
i was wondering if there might be something wrong with the rat and decided to look into it a little—turns out there are a variety of parasites that rats can get that actually modify their behavior to optimize conditions for the survival of the parasite. one parasite in particular, toxoplasma gondii, prefers to live in cats, and so will form cysts in the rat's brain causing loss of inhibition and increased exploration of novel stimuli, resulting in higher chances of being eaten by a cat and passing the parasite on. more here:
not sure if that was what was happening to the little guy we saw on the street, but the whole parasite thing is fascinating—unbelievable how some organisms adapt to survive!