A new study is attempting to answer one of mankind’s oldest questions: why does love exist?
A pair of zebra finches (Taeniopygia guttata) at Bird Kingdom, Niagara Falls, Ontario, Canada. Image credit: Keith Gerstung / CC BY 2.0.
A bird known as the zebra finch (Taeniopygia guttata) shares many characteristics with humans, mating monogamously for life, and sharing the burden of parental care.
Using a population of 160 zebra finches, authors of the new study set up a speed-dating session, leaving groups of 20 females to choose freely between 20 males.
Once the birds had paired off, half of the couples were allowed to go off into a life of wedded bliss.
For the other half, however, the scientists intervened like overbearing Victorian parents, splitting up the happy pair, and forcibly pairing them with other broken-hearted individuals.
The pairs, whether happy or somewhat disgruntled, were then left to breed in aviaries, and the team assessed couples’ behavior and the number and paternity of dead embryos, dead chicks and surviving offspring.
Strikingly, the number of surviving chicks was 37 percent higher for individuals in ‘free-choice’ pairs than those in ‘forced’ pairs.
The nests of ‘forced’ pairs had almost 3 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.
Watching the pairs’ courtship showed some noticeable differences – although ‘forced’ males paid the same amount of attention to their mates as the chosen ones did, the ‘forced’ females were far less receptive to their advances, and tended to copulate less often.
An analysis of harmonious behavior revealed that ‘forced’ pairs were generally significantly less lovey-dovey than the chosen ones.
There was also a higher level of infidelity in birds from ‘forced’ pairs – interestingly the straying of male birds increased as time went by while females roamed less.
Overall the scientists conclude that birds vary rather 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.
This experiment ‘turns on’ the females to increase the likelihood of successful copulation and encourages paternal commitment for the time needed to raise young; together these maximize the pair’s likelihood of perpetuating their genes through their thriving offspring.
The results were published online this week in the open-access journal PLoS Biology.