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The female of the chimpanzee species may be more deadly than we thought. Infanticide is known to occur in many species, but is predominantly a male trait. Now new field work by researchers in Uganda has revealed at least three instances of chimpanzee infanticide – by females.

Female chimpanzees are generally thought of as the less belligerent sex, but these new findings suggest that under certain socio-ecological conditions, lethal female aggression may form part of the behavioural repertoire in the species. Previous cases have been so isolated that scientists had disregarded them as pathological behaviour.

Now Simon Townsend and colleagues from St Andrews University have reported observing one infant killing and finding strong circumstantial evidence of two others, after hearing screams from their study groups in the Budongo Forest.  

What is driving this poorly understood behaviour is unclear, but may be related to a recent influx of females with dependant offspring, doubling the number of resident females. Competition for resources has become fierce, with few males available to increase the home range.

Although low levels of daily aggression between female chimps suggest that intra-sexual competition may be relatively unimportant, according to the researchers, these new findings indicate that in some circumstances female competition can have deadly consequences. It appears that lethal aggression in chimpanzees is not a gender-specific trait.
 
Source: Current Biology Volume 17 Issue 10, pp. R355-R356

 

Background

  • Infanticide, or killing of infants, is a common strategy used by males of many species to allow females to conceive again sooner. This allows a male to maximise the number of offspring he fathers.
  • Jane Goodall famously noted the “barbarous murder” of infant chimpanzees by a cooperating mother and daughter pair in 1976.
  • Bottlenose dolphins brutally kill the young not only of their own species, but of porpoises too. Infants are rammed and tossed high into the air, causing massive internal injuries. Once the young porpoise is dead the dolphins lose all interest.  Possible explanations range from rough play to sexual frustration.

 

Published in BBC Wildlife magazine, Summer 2007