ScienceDaily (Mar. 20, 2011) - A puzzling example of altruism in nature has
been debunked with researchers showing that purple-crowned fairy wrens are
in reality cunningly planning for their own future when they assist in
raising other birds' young by balancing the amount of assistance they give
with the benefits they expect to receive in the future.
Dr Anne Peters, of the Monash University School of Biological Sciences,
together with co-authors Sjouke Kingma from the Max Planck Institute for
Ornithology and Michelle L. Hall of the Australian National University, have
conducted a long term study of the cooperative breeding behaviour of
fairy-wrens in tropical Australia.
The results, published in the journal The American Naturalist, show that
helpers are not motivated by kindness.
"The study showed that the seemingly selfless little helpers are in fact
carefully calculating accountants" said Dr Peters, senior author of the
study.
Cooperative breeding, where birds apparently selflessly raise others'
offspring, has long perplexed biologists as this behaviour runs counter to
Darwin's theory of natural selection, which predicts that individuals invest
only in their own reproduction.
Fairy-wrens are habitual cooperative breeders. The helpers are generally
older silblings or half-siblings of the current nestlings, and their
behaviour is likely explained by an instinctive desire to see more of their
shared genes entering the gene pool.
Purple-crowned fairy-wrens extend this assistance to unrelated nestlings.
Dr Peters' study shows that these apparently altruistic helpers are actually
playing a selfish game: they help when their chances of inheriting the
current breeding territory are greater, and they are thus helping to raise
their own future assistants.
"Ours is the first study to show that helpers at the nest adjust their
behaviour precisely according to multiple potential rewards: they provide
food to kin, and to unrelated nestlings to produce future helpers of their
own," Dr Peters said.
"However, we suspect once more researchers look at their study species in
this dual light, more cases will be found of helpers that can do their sums
so precisely."
--------------------------------------------------------------------------------
Story Source:
The above story is reprinted (with editorial adaptations by ScienceDaily
staff) from materials provided by Monash University.
--------------------------------------------------------------------------------
Journal Reference:
1.. Sjouke A. Kingma, Michelle L. Hall and Anne Peters. Multiple Benefits
Drive Helping Behavior in a Cooperatively Breeding Bird: An Integrated
Analysis. The American Naturalist, March 10, 2011 DOI: 10.5061/dryad.8210
http://www.sciencedaily.com/releases/2011/03/110318102252.htm
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