Scientists have long known that animals engage in nonprocreative sex acts like oral sex. (Just look up the sex acts Bonobo chimps engage in and your sex life may look vanilla in comparison.) But they're trying to figure out if the fruit bats that are performing oral sex on each other might not also have sex for longer periods of time, which may have an evolutionary benefit.
Bats performing oral sex could be trying to increase the chances that sperm will fertilize the egg or attempting to kill bacteria on the penis, and in effect, keep both bat partners from getting STDs.