Female mammals kill the offspring of their competitors when resources are scarce

JULY 15, 2019

by Max Planck Society

Dieter Lukas and Elise Huchard have now looked into infanticide by female mammals. In previous studies, males have been found to kill when females will not mate with them if they are still caring for an offspring sired by their previous partner. "Across mammals, females are more likely to commit infanticide when conditions are harsh and when having offspring is particularly costly to females," says Huchard. "The potential triggers and likely benefits of infanticide however appear to differ according to the specific circumstances."

Infanticide can remove potential competitors

The researchers found that when females are territorial and need access to breeding space or burrows, infanticide can cause neighbouring females to leave so that killers may expand their territory. When females come together on breeding grounds, females might commit infanticide to prevent other offspring from stealing their milk. When females live in groups with others who care for offspring that are not their own, infanticide increases the help that their own surviving offspring receive. And when females live in stable social groups, infanticide can remove potential competitors for access to status or resources. "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," says Huchard.

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Female snake living in captivity without a male companion gives birth – again

For the second time in two years, a female yellow-bellied water snake in Missouri reproduced on her own, a rare occurence called parthenogenesis

Associated Press in St Louis

Thursday 17 September 2015 18.57 BSTLast modified on Thursday 17 September 201519.10 BST

For the second time in two years, a captive snake in south-east Missouri has given birth without any interaction with a member of the opposite sex.

Officials at the Missouri department of conservation’s Cape Girardeau Conservation Nature Center say a female yellow-bellied water snake reproduced on her own in 2014 and again this summer. The snake has been living in captivity, without a male companion, for nearly eight years. An intern who cares for the snake found the freshly laid membranes in July.

This year’s offspring didn’t survive, but the two born last summer are on display at the nature center, about 100 miles south of St Louis.

Conservation Department herpetologist Jeff Briggler said virgin births are rare but can occur in some species through a process called parthenogenesis. It occurs in some insects, fish, amphibians, birds and reptiles, including some snakes, but not mammals.

Parthenogenesis is a type of asexual reproduction in which offspring develop from unfertilized eggs, meaning there is no genetic contribution by a male. It’s caused when cells known as polar bodies, which are produced with an animal’s egg and usually die, behave like sperm and fuse with the egg, triggering cell division.

Having and raising offspring is costly phase of life for baboon moms

Date:

May 19, 2014

Source:

Springer Science+Business Media

Summary:

Observations made over the past 29 years in Kenya as part of one of the world's longest-running studies of a wild primate show how having offspring influences the health of female baboons. These observations highlight that females are mostly injured on days when they are likely to conceive. In addition, injuries heal the slowest when they are suckling their young. Reproduction can be dangerous and energetically costly, exposing individuals to physical harm, infectious disease and reduced immunity.

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