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‘Horrified’ scientists watch killer whale infanticide for the first time

Infanticide is the act of killing an infant and can be carried out by either a parent or another adult.

It is common practise in many animal species and can be triggered by hunger, to eliminate competition or as a show of power.

In the majority of cases it is caused by either severe emotional disturbance of a mother or a new dominant figure in a social group stamping their authority.

Maternal infanticide 

Maternal infanticide describes mother killing their offspring.

Many examples have been recorded in nature, often when a mother’s mental state is diminished and she subsequently takes the life of her new-born child.

It has been observed in both pigs and rabbits.

Female infanticide  

The killing of young animals by other females is a phenomena that is often seen in large social groups.

In groups where there are many females to a few males, the sexual attention of the males can be limited.

In these cases, the females have been known to kill the offspring of other females to increase their chances of producing their own young.

This stems from a scientific term called ‘reproductive fitness’ where an individual’s success is measured by the amount of its genes that it passes to the next generation.

To be more successful and increase fitness, they prefer to have children of their own and killing another animal’s offspring allows this to happen. 

This is more common when food is scarce, and has been witnessed in chimpanzees.

Male infanticide

Male infanticide is the most common and well-documented form of the phenomena.

Often occurring in mammals and intelligent animals, the act is used as a show of power as well as bringing females into season earlier.

Prevalent in lion prides, there is normally one adult lion who is the alpha in a pride and controls several females. 

This alpha position can change hands when a younger, bigger and more virile male ousts the old male from the group.

In this event, there will likely be many young animals in the fold.

When the new male takes over, his first priority is asserting his authority and ensuring his own reproductive success. 

The most effective way this is done is by the culling of all youngsters. 

As well as removing any young that are not his, it brings the females into season earlier, ensuring he can sire his own offspring quicker. 

It has has been observed in mammal species ranging from dolphins to lions.

Researchers have also seen a  32-year-old male orca killing a newborn. 

The male orca was helped by his 46-year-old mother – who was instrumental in the attack, scientists say.

In doing so she effectively helped to pass on her lineage as long as her son was then successful in breeding with the animal that lost her calf, researchers believe.