Sunday, April 27, 2014

Why helping out is good for you

Some animals never reproduce, yet they use up their limited energy and resources caring for the young of others of their species. Why would they do that?

what some group members really do when not breeding...
photo: JamieMissy
We've talked about this altruistic behavior a little, in terms of "indirect" fitness - the genetic gain that sisters or cousins get by helping the pack's, herd's, or colony's dominant female – the one who breeds.

In some groups of animals, not all members are so closely related to the dominant female, yet they often help rear the young anyway.

Back to the initial question: Why would they do that?

Why do non-breeding lions, hyenas, wolves, meerkats, elephants, and various rodents and others, bother feeding, teaching, and defending the babies of other mothers, rather than better feeding themselves, finding a mate, or sleeping?

You might think of several reasons. Go on, take a shot at it.


In both lion prides and elephant herds, multiple females care for the young ones


1) Perhaps most obvious, by staying with the group, the helper maintains access to the group's territory, resources, and mutual protection, which may be critical for survival, particularly in harsh environments.

Namibia's Etosha National Park is tough country, so
elephant matriarchs teach their herds how to survive there
Meerkats, mole rats, prairie dogs, and many elephants all live in tough dry country, where a larger group may be more successful at escaping predators, staying warm at night, finding scarce water, and raising more young than a smaller one, so it pays to keep the clan large.

Some areas of the world are so harsh that animals living there cannot find enough food to raise healthy young without help.

In our modern society, teenagers that babysit their younger siblings contribute to the well-being of the household and receive praise and continued support from their parents, not to mention cash, but their help was much more critical to their siblings' survival a few thousand years ago.

2) Communal living also serves animals in regions, such as deserts, where nest sites or other critical resources are few and far between. By staying within their natal (birth) group, they don't need to risk harm trying to find their own new nest site, they stay warm even in cold temperatures, and some may get to inherit their home nest.

Similarly, joining and helping out an unrelated group might give the new member access to mates. In fact, some male birds help an unrelated pair with the hopes of some on-the-sly copulation with the female. If females mate with more than one male, several males presume they could be the father of chicks, so they all help raise them (but only one is the actual father -- oops).

Matabele ants work together to invade a termite nest
photo: Piotr Naskrecki
As a group survival strategy, communal living and raising young logically complements a team approach to self-defense and finding food – a platoon of thousands of carnivorous ants that take off together to raid a termite nest or widely scattered food resource are more successful than just a few, and their joint defense of their turf can dissuade much larger predators.

3) Through helping out, a sister or cousin may also learn how to raise her own young, and she may also receive help when it is her turn to have a baby. These benefits all help the animals survive and, if the helper eventually gets old or powerful enough, breed successfully.

I think most of us can relate to at least one of these benefits!


No free lunch(es)


high population density increases potential
competition for scarce resources
photo: MyOpenVoice
The costs to living in social groups might counter-balance those gains to their fitness.

More bees (or mole rats, or lions, or people) in a small space may increase the competition between individuals for sometimes scarce resources (food, water, space in the hive or burrow, iPhones).

High population densities in a hive, burrow, or tunnel might also allow parasites and diseases to transmit faster within the group, and more individuals buzzing about a hive or burrow entry can draw the attention of predators and parasites.

In the case of people, you could think about bubonic plague.

And, as you might guess, there are rules regulating proper behavior (fun monkey video!) within a large social group, even if most are related!

In some bee, mongoose, rat, and even primate species, the dominant female will kill the young of others if she discovers them. (But some non-dominant banded mongoose females can, apparently, time their births to that of the dominant, so she can't know whose is whose and won't kill them...).


Despite the costs, helping out as part of a social group may increase an animal's (or person's) indirect fitness AND direct fitness. This combination is his or her "inclusive fitness," and it helps to explain why worker bees feed their new siblings, why adult meerkats teach young ones who are not their offspring how to hunt, hide, and take care of the burrow, and why the aunt or cousin of a newborn elephant makes that deep, scary grumbling we hear if we get too close.

don't mess with the baby!


Have a look at:


This paper on Evolutionary routes to non-kin cooperative breeding in birds

This study sheet on how complex societies and eusociality may have evolved

This article on the complex societies of some animal species

No comments:

Post a Comment