When it comes to finding a potential mate, humans are notoriously picky, carefully screening a number of potential candidates through dates and online match-making websites, seeking someone we could start a family with.
As it turns out, we are not alone when it comes to our desire to find true love, and new research published Monday in the journal PLOS Biology indicates that there may be an evolutionary advantage to the practice of selecting a mate that meets rigorous standards.
In their study, Drs. Malika Ihle, Bart Kempenaers, and Wolfgang Forstmeier of the Max Planck Institute for Ornithology in Germany did a sort of cost/benefit analysis of love versus the simple act of going out and procreating in terms of evolutionary benefits. However, they studied zebra finches instead of people, as like humans they tend to mate monogamously for life and typically evenly share the burden of raising their offspring with their partners.
They studied a population of 160 birds and set-up a speed-dating session involving groups of 20 female finches and 20 males. After the birds selected their desired mates, half of the new couples were allowed to live together, while the authors intervened with the remaining birds and forced them into pairs with other birds away from their partners of choice.
Mate preferences have fitness consequences, study found
Each of the couples were left to breed, and the research team assessed their behavior, as well as the number and paternity of dead embryos, deceased chicks, and surviving offspring. The number of surviving chicks were 37 percent higher for individuals in chosen pairs than non-chosen ones, while the nests of non-chose pairs had nearly three times more unfertilized eggs.
While non-chosen males paid the same amount of attention to their partners as the chosen ones, the non-chosen females were found to be far less receptive to the advances of those males and tended to copulate less frequently. The non-chosen males were also more likely to be unfaithful to their partners as time went on, while females roamed less later on in the relationship.
Dr. Ihle, who called studying mate choice in these birds “a passion… because of their similarities to humans,” told redOrbit that the study shows that they “vary in their preferences and that these idiosyncratic preferences do lead to fitness consequences. Our results also show that this came about behavioral compatibility advantages but had nothing to do with genetic compatibility.”
“Our exploratory analyses… suggest that birds were not necessarily more coordinated in their activities but were more committed to their relationships,” the behavioral ecologist explained via email.
“We observed higher female within-pair responsiveness, lower male extra-pair courtship rate, and higher male nest attendance. Therefore it seems that chosen pairs… invested more into reproduction, were more committed, more faithful, and more motivated to raise their family.”
Why do fools fall in love? Sensory stimulation, apparently
Dr. Ihle also said that the experiments found that those birds that agreed to breed with a partner assigned to them did not invest as much in the reproductive process as those who selected their own mate, and were less committed to one another despite forming a pair bond (albeit by force) with their partner. They simply were not as stimulated by their assigned partner.
The researchers reported that female finches selected their mates in a way that is specific to each one of them, and there appeared to be little consensus as to what made a male appealing. So what is it that causes one bird to, for lack of a better term, fall in love with another?
Dr. Ihle believes it may be a “stimulation” such as a song that meets “the specific sensory biases” of a partner which in turn “activates a physiological mechanism” that makes them invest more into reproduction.
“Our results could raise awareness of behavioral and phenotypic compatibility aspects in many species. In monogamous bi-parental care species,” the biologist added, “behavioral compatibility could play a role both in terms of personality matching/coordination of activities and in terms of ‘idiosyncratic stimulation.’ Since partners stay a long time together to raise their family, it gives many opportunities for this phenomenon to take place.”
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Feature Image: Thinkstock
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