Why do animals fight with members of other species? A nine-year study by UCLA biologists says the reason often has to do with "obtaining priority access to females" in the area.The scientists observed and analyzed the behavior of several species of Hetaerina damselflies, also known as rubyspot damselflies. For the study, published this month in the print edition of the journal Proceedings of the Royal Society B, researchers observed more than 100 damselflies a day in their natural habitat along rivers and streams in Texas, Arizona and Mexico.