Rats Return Favors: A First in Animal Kingdom Karma

"What goes around comes around," may be a common adage used by people, but new research has revealed that it's not a belief exclusive to humans. Rats, or at least ones in Norway, it seems, believe in doing favors when they are due as well, returning kindness shown to them by other rats in the past.

That's according to an animal behavioral study recently published in the journal Biology Letters, which details how individual Norwegian rats were most helpful to rats that had previously helped them.

It's easy enough to show that communal animals, rats and mice included, help one another moment-to-moment. It's a bit harder to show that one party can remember a favor done and return it in kind in the future. If fact, this behavior, called direct reciprocation, has never before been recorded among non-humans.

So how did researchers manage to get a bunch of rats to show favors at their finest? Bananas and carrots of course!

A funny, but well-known fact is that Norwegian rats absolutely love bananas; carrots... not so much. This may have a lot to do with the fact that bananas have more of the nutrients rats need. It could also simply be that the rats like sweet foods. It's likely that, as with most unexplained phenomena, it's a little of both.

A series of experiments were set up so that two rats could deliver one of these two foods to another rat pair in an adjacent enclosure by pulling on a stick. Eventually, the receiving rats would learn to recognize each neighbor as a good helper (providing bananas) or a low-quality helper  (handing out carrots).

Then the pairs were swapped, giving the once-receiving pair an opportunity to hand out cereal flakes to one of the neighbors. As was expected, the banana sender received the great majority of these tasty gifts, suggesting that the other rats appreciated his work.

Still, there is some skepticism. Thomas Zentall, an animal behaviorist who was not involved in the study, recently told National Geographic that the flake-senders could simply be associating the banana-sender with bananas. They may have thought that if they pulled a lever while he was around, they would get more bananas.

That leaves the issue of rat karma really still up in the air, but it may be nice to think that the giant NYC subway rats who chew on our crumbs appreciate these small offerings, all the same. Perhaps when the next biblical plague comes, swarming rats will overlook my humble city, returning a favor long due. A man can dream right?

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