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Vampire bats and the golden rule

February 14, 2011

Today’s Monday, which means family home evening for many Mormon families and I have the lesson this week. As an atheist, I’m obviously not interested in teaching the usual lesson about the priesthood or prayer because, to the extent that morality can be taught in a lesson, these doctrines have little to do with being an ethical person.

No, my lesson will be on a version of the golden rule as illustrated by vampire bats vomiting blood. Awesome, right? I’ll cut out a cow and some bats from brown construction paper and use them to tell my boys a story based on the following fascinating information.

Michael Shermer writes in The Science of Good and Evil: Why people cheat, gossip, care, share, and follow the golden rule:

Examples of premoral sentiments among animals abound. It has been well documented that vampire bats, for example, exhibit food-sharing behavior and the principle of reciprocity. They go out at night in hordes seeking large sleeping mammals from which they can suck blood. Not all are successful, yet all need to eat regularly because of their excessively high metabolism. On average, older experienced bats fail one night in ten, younger inexperienced bats fail one night in three. Their solution: successful individuals regurgitate blood and share it with their less fortunate comrades, fully expecting reciprocity the next time they come home sans bacon. Gerald Wilkinson, in his extensive study of cooperation in vampire bats, has even identified a “buddy system” among bats, in which two individuals share and reciprocate from night to night, depending on their successes or failures. He found that the degree of affiliation between two bats—that is, the number of times they were observed together—predicted how often they would share food. Since bats live for upwards of eighteen years among the same community, they know who the cooperators are and who the defectors are. Of course, the bats are not aware of being cooperative in any conscious goodwill sense. All animals, including human animals, are just trying to survive, and it turns out that cooperation is a good strategy.

This account of food sharing among vampire bats was recently broadcast on my favorite podcast, WNYC’s Radiolab.

Wilkinson, who conducted this research, describes summer nights he spent on a cattle ranch in Costa Rica, lying down inside of hollow, four-story trees along a river, getting pooped on while observing the bats. Often one bat would snuggle up to another bat and begin licking at its mouth, almost like they were kissing, but really she was licking up blood that the second bat was regurgitating.

Wilkinson then controlled which bats ate and which didn’t, and kept track of who fed whom, and he found that there are friendship networks among bats. If hungry Sally feeds full Agnes on the first day, then hungry Agnes invariably feeds full Sally the second day. And this isn’t just among related bats; friendship ties are actually more predictive than kinship ties of who feeds whom.

Wilkinson also mentions that large mammals were abundant on the plains 40,000 years ago. But when the large mammals became scarce due to climate changes, vampire bats had to develop a way of working together. Being nice wasn’t an option; it was the only way for the species to survive.

Have a listen to the broadcast: It’s 14:45 minutes long.

The moral of the story? Be nice. I know being nice can’t be taught in a lesson; it’s modeled. But if I’m asked to teach a family home evening lesson, I might as well keep the boys interested with blood-sucking, -pooping, -vomiting bats.

But there’s a second unspoken lesson here—that the existence of altruism, compassion, generosity, kinship, and compassion can be explained very well by natural selection.

Dubious? Read the book.

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One Comment
  1. Interesting!

    Here are some words of scripture that impress me: “God granteth unto men according to their desire, whether it be unto death or unto life; yea, … He allotteth decrees which are unalterable, according to their wills, whether they be unto salvation or unto destruction. …Good and evil have come before all men; he that knoweth not good from evil is blameless; but he that knoweth good and evil, to him it is givem according to his desires, whether he desireth good or evil, life or death, joy or remorse of conscience.” (Nelson)

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