July 15 (UPI) -- When the going gets especially tough, female mammals are sometimes compelled to commit infanticide.
While a dearth of resources is the driving factor, new research suggests specific circumstances can influence infanticide behavior.
Previous studies suggest males in search of a mate commit infanticide when they are spurned by females still caring for the offspring of another male.
"Across mammals, females are more likely to commit infanticide when conditions are harsh and when having offspring is particularly costly to females," Elise Huchard, a researcher with the Max Planck Society, said in a news release. "The potential triggers and likely benefits of infanticide however appear to differ according to the specific circumstances."
To better understand female infanticide, researchers surveyed the diversity of mammalian lineages, taking note of the conditions that drive different species to kill the offspring of their rivals. Scientists published their findings this week in the journal Philosophical Transactions of the Royal Society B: Biological Sciences.
"Our results show that female infanticide is widespread across mammals and varies in relation to social organization and life history, being more frequent where females breed in groups and have intense bouts of high reproductive output," researchers wrote in their paper.
Moms are more likely to become killers, scientists determined, when the offspring of their neighbor-turned-competitor threatens her access to food, shelter, care or social positioning.
For example, moms who commit infanticide increase the odds of their babies getting extra attention from females without their own infants. By committing infanticide, moms can also decrease the chances of her milk being stolen by the offspring of other females.
"All these circumstances have in common that infanticide occurs when the proximity of offspring born to other females directly threatens the killer's reproductive success by limiting access to the resources that are most critical for her own offspring: access to breeding space, milk, offspring care, or social status," said Huchard.
Researchers have previously theorized that life among close relatives diminishes the odds of infanticide. But the authors of the new paper determined group living increases the odds of infanticide regardless of the familial relations among a group.
"Among group-living species, females were equally likely to kill offspring when they lived with close relatives than with unrelated females," said researcher Dieter Lukas. "There are several instances of grandmothers killing their grandchildren or aunts killing their nieces. This observation indicates that the benefits gained by the killer and her offspring even outweigh the costs of harming a relative."