Birds and humans are often remarkably similar when it comes to mate choice and falling in love, finds a new study that suggests nature maybe have a romantic side after all.
Successful relationships among birds, as well as humans, are not just about the strongest, fittest and best-looking among us, but instead rely upon pairings based on compatibility and attraction to others.
Malika Ihle of the Max Planck Institute for Ornithology and colleagues wrote that "zebra finches choose mates on the basis of behavioral compatibility" and can't stand being in a relationship that is "forced," a/la an arranged marriage between a man and a woman.
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For the study, Ihle and co-authors Bart Kempenaers and Wolfgang Forstmeier set up a speed-dating session for the little birds, allowing 20 females to choose freely between 20 males.
When the birds paired off, half were allowed "to go off into a life of wedded bliss," the researchers said in a press release, while the other half experienced an intervention. Like overbearing Victorian parents, the scientists split up this second group of happy couples, and forcibly paired them with other "broken-hearted individuals."
Bird couples, whether satisfied or somewhat disgruntled, were then left to breed in aviaries. The authors monitored what happened next.
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The researchers were surprised to find that "zebra finch pairs that resulted from free mate choice achieved a 37 percent higher reproductive success than pairs that were forced to mate," Ihle and her team wrote.
What's more, the nests of non-chosen pairs had almost three times as many unfertilized eggs as the chosen ones, a greater number of eggs were either buried or lost, and markedly more chicks died after hatching.
In terms of the parents, non-chosen males paid the same amount of attention to their mates as the chosen ones did, but the non-chosen females were far less receptive to their partner's advances, and tended to copulate less often.
The males in these relationships then frequently strayed and had affairs, which further annoyed the already perturbed females.
As for the birds that paired off with their own choice of mate, the researchers could find no patterns explaining those partner selections. Like humans, birds seem to vary idiosyncratically in their tastes, and choose mates on the basis that they find them stimulating in some way that isn't necessarily obvious to an outside observer.
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This stimulation then "turns on" the females to increase the likelihood of successful copulation, and encourages paternal commitment for the time needed to raise young. In short, what we think of as love and attraction maximize a couple's likelihood of perpetuating their genes through their thriving offspring.
The whims of attraction and love therefore factor into the evolution of lineages, and are likely fueled by the extended phase of dependence during which our, and zebra finch's, offspring need parental support.
The authors' results concerning zebra finches are consistent with some studies on the differences between love-based and arranged marriages in human societies.
The study is published in the latest issue of the journal PLOS Biology.