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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 forage¹ 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 dominant² bullies³.

"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 strictly⁴ 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 amorous⁵ male, but it does up his odds⁶. 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.

这里是科学美国人——60秒科学。我是凯伦·霍普金。

分享食物是许多哺乳动物交配仪式的标准第一步。但埃及果蝠将“分享主菜”的做法带到了另一个水平。因为允许雌性直接从其口中取食的雄性，会得到繁殖权作为回报——而且更有可能与它们最喜欢的雌性“水果骗子”繁衍后代。这是《当代生物学》期刊上发表的一篇研究得出的结论。

几年前，研究人员注意到，在果蝠群体中，有些果蝠自已觅食，而其它果蝠则直接从觅食者嘴里抢食物。

“有不同的假设来解释这种情况。”

特拉维夫大学的约西·尤维尔多年来一直在研究这些果蝠。他表示，也许“行乞者”是亲属关系。或者它们可能只是社交上占主导地位的恃强凌弱者。

“我们观察到，大多数‘行乞者’是雌性。”

这让研究人员想到了对大多数动物来说非常重要的事情：繁殖。

“我们尤其想知道的是，雌性果蝠后来是否与给它们提供食物的雄性进行了交配。因此，这就是我们测试的假设——以性换食物的假设。”

尤维尔和同事对果蝠在群体内的互动情况进行了长达一年多的监测，他们检查了新生果蝠的父亲身份。他们发现，雌性果蝠更可能与给它们提供免费食物的雄性生孩子。

但是尤维尔说，这个过程并非严格意义上的交易：“有时，它们从一个特定个体处拿走很多食物，但并不会与它交配。我们认为，重要的是这两者之间的关系。如果雄性个体是雌性的主要供养者，那它们之后进行交配的可能性就会增加。”

这就意味着，对一个多情的雄性来说，提供免费午餐并不一定能保证交配成功，但确实会增加他的胜算。与人类男性不同，雄性果蝠很清楚地知道，张大嘴巴咀嚼食物，有助于发展它们的浪漫关系。

谢谢大家收听科学美国人——60秒科学。我是凯伦·霍普金。