Thursday, April 26, 2012

Darwin vs Wordsworth: Is Nature cruel or beneficent?

In what looks an awful lot like cooperative behavior, groups of birds often get together to 'mob' a predator.  That is, they swarm predators together, in an attempt to chase them away from nests or from a food source, and so on.  Birds often make mobbing calls, that alert nearby birds to danger, and solicit their aid.

A new paper in Biology Letters suggests that "long-term familiarity" is a factor in whether or not birds choose to help each other when faced with threat from a predator.  A.M. Grabowska-Zhang et al. show that "neighbours that shared a territory boundary the previous year are more likely to join their neighbours' nest defence than neighbours that did not share a boundary before."

Predation is a major cause of death in nestlings, so driving predators from an area in defense of the nest is crucial.  And, the more birds that can mob a threatening predator, the more likely they'll drive it away, so soliciting the help of neighboring birds is also crucial.

Grabowska-Zhang et al. "tested the hypothesis that long-term familiarity between territorial neighbours is positively related to joining behaviour in predator mobbing."  They did this in a population of great tits breeding in next-boxes in Oxfordshire, in the UK. These birds have been tagged and followed in previous years, so that their ages and familiarity are already known.  The researchers served as predators, by approaching a nest and making noise, and then assessed the birds' response.
For pairs of nests where each contained at least one familiar individual, in 12 out of 16 trials (seven out of eight nest pairs), at least one neighbour joined the mob. Individuals from the unfamiliar group joined the mob in just two out of 16 trials (one out of eight nest pairs). No neighbours joined the mob in first-years' nest.
That is, they report that they've demonstrated a significant influence of familiarity on taking part in solicited mobbing behavior.  The idea that birds decide who to cooperate with is interesting one -- apparently, they don't help just anyone.  But, what interests us more is that the authors conclude that they can't tease out from this study whether the birds cooperate because they are good neighbors (altruistically), or because they figure they'll get help from their neighbors when they need it themselves (selfishly).  The same behavior can be interpreted in two very different ways.

This is not new to this study, of course -- altruism has long been explained away as selfish.  And similarly, cooperation as competition.  There is a danger in reading ourselves into what we see in Nature.  It's a problem of subjectivity intruding where we hope and strive to be objective to the extent possible.  The issue first of all can affect study design itself, and then the interpretation of results.  Thus, if competition is the lens of your view of Nature, you can design studies to find competition or evaluate organisms' success in comparative terms.  If cooperation is your bent, you can study what happens when organisms work together for whatever reason.   The truth, as this study shows, is typically a mix.

The danger extends to reading other work, in science but even in other areas.  One can mine important thinkers for statements supporting one's bias, just as can be done with Biblical exegesis.  For example, at about the same time, and totally unbeknownst to each other, two famously brilliant authors wrote about the awesome splendor of Nature.  Darwin looked upon Nature's 'grandeur' (his word) and saw beneath it a relentless, impersonal, and savage 'struggle for survival' against limiting resources.  In an 1838 notebook, he denigrated philosophers who were trying to understand life by saying that one would learn "more towards methaphysics than Locke" by understanding baboons.  But last night Ken was writing on something for Evolutionary Anthropology that referred to Darwin's quote.  He has also been reading the famous pastoral poems written at almost the same time by the poet laureate William Wordsworth.  Like Darwin, Wordsworth denigrated stuffy academics, remarking that one who wished to understand life should turn not to the work of philosophers but to Nature's magnificent panoply reflecting God's beneficent intent.

Birds may not think about competition vs cooperation in ways that we do, but in their own way they show us the nuances of Nature.

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