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Bats in my house!
July 20, 2009Posted by on
Last night, I was sleeping soundly. I don’t have AC, so the windows were open and my ceiling fan was on. I woke up rather suddenly, and it took me a minute to realize that there was something else in my room… something really flappy and kind of loud. A bat!
I’m doing some work with bats for my thesis, so even in my sleepy stupor, I was thrilled! A real live bat! In my house! I watched him for about 30 seconds to a minute, but then I realized that the little guy or gal was distressed. Here it was in a room with walls and a ceiling fan, when probably 5 minutes earlier it had been swooping around catching bugs in the meadow out front. It wasn’t having any luck with the lights off, so I turned them on and closed all of the doors upstairs. We made our way downstairs together, where I opened the door and waited for it to leave. It swooped around my living room for awhile, always on the diagonal. Just when I thought I was going to have to help it out somehow, it made a sharp 90 degree turn at the door and left.
In celebration of my little visitor, I’ll share with you some interesting sexual selection stuff related to bats. I’m sure you’ve heard about the paper about the Tiger Moths who respond to the sonar of bats by emitting their own clicks, jamming up the bat’s detection. Well, it turns out that some other species of moths are able to use these clicks to communicate with moths of the opposite sex. It’s a form of sensory bias in sexual selection. Sensory bias and exploitation is an hypothesis which explains the origins of some of the features which are sexually selected for in animals. In Wax moths, the females already have the equipment to sense the ultrasonic clicks because they are predated upon by bats. Natural selection has resulted in a moth which is able to detect the bat clicks, so males who are able to exploit that suite of sensory mechanisms are able to mate more successfully.
In one species of moth, the response to the clicks emitted by bats is to stop flying and fall out of the sky- a sort of self-paralyzing strategy. The males emit the clicks, the females fall out of the sky, and copulation begins!
We see sensory bias and exploitation in lots of other animals, too. Some populations of guppies in Trinidad like to eat bright orange fruit from the Cabrehash tree. Females have been shown to prefer orange objects to non-orange objects, so males who have a bright orange dot on their tails are able to successfully mate with females more often than other males. The interesting thing is that females prefer orange objects even in populations where the males don’t have the dot yet, suggesting that the preference for orange is a pre-existing bias which the males in the other population was able to exploit. Sensory bias and exploitation work has been done with frogs, fish, water mites, moths, and even cotton top tamarins. It’s an interesting field, and I will probably be writing about it more soon!
Ryan, M. (1998). Sexual Selection, Receiver Biases, and the Evolution of Sex Differences Science, 281 (5385), 1999-2003 DOI: 10.1126/science.281.5385.1999
Rodd, F., Hughes, K., Grether, G., & Baril, C. (2002). A possible non-sexual origin of mate preference: are male guppies mimicking fruit? Proceedings of the Royal Society B: Biological Sciences, 269 (1490), 475-481 DOI: 10.1098/rspb.2001.1891