Most parents would hotly deny favouring one child over another but new research suggests they may have little choice in the matter.
Biologists studying a unique species of beetle that raises and cares for its young have found that parents instinctively favour the oldest offspring.
The University of Manchester research published in Ecology this month supports the findings of studies carried out on human families but is significant in that it suggests a wholly natural tendency towards older siblings.
The burying beetle Nicrophorus vespilloides has a similar family structure to that of a human family unit in that there are two parents, a number of offspring and interactions between parents and their young, said Dr Per Smiseth, who led the research in the Universitys Faculty of Life Sciences.
Of course human families are more complex and parent-child relationships are much more sophisticated. However, studying this beetle can help us understand the basic biological principles of how family relationships work.
Our study looked at how the parent beetles mediate competition between different aged offspring compared to what happens when the young were left to fend for themselves and indicates that parental decisions are important in determining the outcome of competition between offspring.
The beetles, which are native to Britain, give birth to a batch of about 20 young in the carcass of a dead animal over a period of 30 hours. The parents feed the young grubs on regurgitated flesh from the carcass.
The young beetles are able to feed themselves but they grow more quickly and become larger when fed by their parents. By generating experimental broods comprising two sets of offspring, one set of older grubs and one younger set, the scientists were able to study their development, first with the parents present and then when left to fend for themselves.
When both sets of grubs were left to fend
|Contact: Aeron Haworth|
University of Manchester