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Some primate mums 'carry out infanticide to eliminate female competitors'

June 9, 2011 - Washington

A new study has found that some primate mothers, who cannot raise their infants without the help from male group members, carried out infanticide to prevent the subsequent death of their offspring if they are stressed and in competition with other females.

An international team of scientists, with Spanish participation, has shed light on cannibalism and infanticide carried out by primates, documenting these acts for the first time in the moustached tamarin (Saguinus mystax).

"Infanticide is an extreme behaviour, and in most species is used by males to eliminate competitors and make females become sexually receptive more quickly," said Yvan Lledo-Ferrer, one of the authors and a researcher in the Psychobiology Department at the Autonomous University of Madrid (UAM) and at the German Primate Centre.

However, in callithrix primates (the primate family that Saguinus mystax belongs to), it is the females that perpetrate infanticide.

"Genetic analysis enabled us to show that the mothers themselves take the lives of their own offspring," said Lledo-Ferrer.

The study observed three different groups of moustached tamarins in the Peruvian forest from 1999 to 2008 to determine how help from male members of the group and the absence of competition between females helped to ensure the survival of infants.

The results showed that 75 percent of infants survive when at least three males are helping, but only 41.7 percent survive if the group has one or two male helpers.

With regard to competition with other females, 80 percent of infants die at less than three months of age if there are two gestating females in the group. This figure falls to 20 percent if there is only one reproductive female.

The scientists were surprised when four infants died within the space of a year and the autopsies carried out did not reveal any pathology that would have compromised their survival.

The researchers say that reproductive dominance is not well established in cases where infanticide takes place, and there is competition between females to occupy the dominant position.

"This competition leads to high levels of prenatal stress, which can affect the Foetus and therefore the viability of the offspring and the mother's milk production," said Lledo-Ferrer.

The study has been published in the journal Primates.


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