Couples bonded in love
partnerships prove to be more effective parents than couples in arranged
marriages. That’s the results of a study on birds – zebra finches to be precise
(New Scientist, September 14, 2015).
Birds that are allowed
to choose their own partners become more diligent parents, according to a study
in which arranged marriages were tested for zebra finches.
Why study zebra
finches? Zebra finches are birds that mate for life and both birds look after
their young – they share parental duties. Hence it was easier for the research
team to study their parenting techniques.
Researchers from the
Max Planck Institute for Ornithology (MPIO) in Seewiesen, Germany, were
interested in how animals select their mates – presumably matching genes that
were compatible with their own or choosing mates with ‘good’ behaviour.
The MPIO researchers
deliberately arranged marriages for a group of zebra finches and let others
have free choice in selecting their partners.
The research involved
organising a ‘speed-dating’ event for 160 aviary zebra finches (80 males and 80
females), allowing them to choose their own mate. Then they paired half of the
females with a male that they had not chosen – that is, they broke up the chosen
partnership and arranged the ‘marriage’ for 40 females and 40 males.
The new couples (arranged
and freely chosen) were put in individual cages for a few months to enable them
to bond, after which time three pairs were transferred to aviaries for five
months to allow them to breed.
The result was that
there were 37% more surviving chicks (baby zebra finches) for the pairs who
chose their own mate. For the arranged couples, three times more eggs were
unfertilised, more eggs were buried or lost, and more chicks died after
hatching than for freely chosen couples. Males in arranged marriages attended
to the nest less diligently while the eggs were hatching than males in love partnerships.
The death rate for
embryos was the same in both groups, suggesting that the lower egg survival
rate was due to the quality of parenting, not genetic incompatibility in the
arranged marriages. If the birds were choosing mates for genetic compatibility
there would be more embryo deaths for the arranged couples’ eggs and more live
hatchings for the love couples.
In addition, females
were less willing to mate with males that they had not chosen and the males
were more likely to leave their mate to look for a new partner.
Researchers suggest
that reproductive success was lower for the arranged couples because
‘psychological constraints’ prevented them from parenting to the best of their
ability. They think attractiveness is a relative, not absolute, concept in
dating and mating, bonding and breeding.
Journal reference: PLOS Biology,
DOI:
10.1371/journal.pbio.1002248
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