科学美国人60秒:雄性果蝠用嘴里的食物增加交配几率

This is Scientific American — 60-Second Science. I'm Karen Hopkin.
Sharing a meal is a standard first step in the mating rituals of many mammals. But Egyptian fruit bats take "splitting an entrée" to a whole other level. Because males that allow females to take the food right out of their mouths are repaid with reproductive rights—and are more likely to sire offspring with their favorite female fruit finaglers. That's according to a study in the journal Current Biology.
A couple years back, researchers noticed that in fruit bat colonies some bats forage for food while others simply snatch it from the foragers' mouths.
"And there are different hypotheses for explaining this."
Yossi Yovel of Tel-Aviv University has studied these bats for years. Maybe the scroungers were relatives, he says. Or maybe they were just socially dominant bullies.
"What we observed is that mostly scroungers are females."
That got the researchers thinking about something of great importance to most animals: reproduction.

"And specifically we were wondering whether females might then mate with males that provide them with food. So this was the hypothesis, the sex-for-food hypothesis, that we tested."
Yovel and his colleagues monitored the interactions among bats in their colony for more than a year, and they checked the paternity of the baby bats that were born. What they found is that females were more likely to make babies with those males that provided free meals.
But Yovel says that the process is not strictly transactional: "So sometimes they took a lot of food from a specific individual but did not mate with him. What's important is, what we think, is the bond between the two. So if this individual is the main provider of the female then the probability that they will later mate increases."
That means that offering free lunch is no guarantee for an amorous male, but it does up his odds. And unlike human males, batboys clearly learn that it's in their romantic interest to chew with their mouths open.
Thanks for listening for Scientific American — 60-Second Science. I'm Karen Hopkin.