Researchers have long wondered why and how people fall in love. And a related topic of interest in recent years has been the effects that monogamy has on the quality of a relationship. Does it make it better or worse?
A new study conducted on Zebra Finches may have found answers to some of these questions. First thing to know is that these birds are similar to humans in many ways. They generally have monogamous relationships that are similar to human marriages and center on raising their children.
But, as is the case with humans, not all Zebra Finch relationships are sexually monogamous. Field experts have documented examples of both male and female subjects who went looking for sex outside of their “marriages”.
Another remarkable similarity between Zebra Finches and humans is that Zebra Finch females aren’t all drawn to the same Zebra Finch male that seems to have superior genes. Each female member of the species has their own taste and preferences that she uses to choose a partner.
Malika Ihle, field expert with the Max Planck Institute for Ornithology, explained in the study she conducted with her colleagues that “Zebra Finches choose mates on the basis of behavioral compatibility”.
To assess the quality of the relationships that these birds have, the research team took some Zebra Finches and put them in a room where they could socialize and form couples.
After the Zebra Finch females chose their partners, Ihle and her colleagues divided the couples in two (2) separate groups. The birds in the first group were allowed to stay with the partner that they selected, whereas the birds in the second group were split from the mate that they selected and paired up with a random suitor in an arranged marriage.
As the research team expected, the Zebra Finch specimens that were allowed to stay with the partner that they chose, had better reproductive success and the chance that their babies had of surviving was 37 percent (37%) higher, compared to the chance of surviving that the babies of birds in arranged marriages had.
And the Zebra Finches forced to be in a relationship that they didn’t choose were not very fertile to begin with. They had around three (3) times more unfertilized eggs, compared to the Zebra Finches who got to choose their partner, and once their babies hatched, they didn’t pay enough attention to them. This resulted in many of them dying not long after they came into the world.
Ihle and her colleagues also concluded that Zebra Finches made to “marry” someone they didn’t love usually practiced infidelity. Female birds were generally the first to cheat on their partners, and the male birds followed soon after.
This happened despite the fact that the males in arranged marriages still showed just as much affection towards their partners as the ones in marriages where the birds chose each other.
One possible explanation is that males and females in these arranged marriages may have behavioral incompatibility, rather than genetic incompatibility. Female Zebra Finches find it hard to show the same affection that their “husbands” do if they don’t love said “husbands”, or if they suffer the trauma of being separated from a male that they actually cared about.
The study was published earlier this week, on September 14, 2015, in the journal PLOS Biology.
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