Cannibalism in Small Animals

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I am often asked by people 'Why has my animal eaten its litter?' I think this is so prominent in their mind because of the severity of the act, it shows the animal not as a fluffy pet but as the wild 'beast' it is.

It is unlikely that we will be able to give a certain diagnosis for the cannibalism but we can suggest reasons for it to better understand why they do it.

This article will only cover the cannibalism of litters and not of cage mates or in other circumstances.

The cannibalism of litters, is often given the names 'Brood Cannibalism; and 'Infantile Cannibalism' or simply 'Infanticide'. Whatever name you give it still mounts up to the same thing, the consumption of the litter, either wholly or partially.

This can be induced in many ways but I suspect the most common is environmental disturbances/changes when the litter is still very young (10 days or less), e.g. loud noises, disturbances of the nest, lack of food or water, litter mates being removed, sudden change in lighting etc.

Physical disturbances are probably the most destructive to litters: rustling around in the nest, banging the cage about, removing cage mates, moving the cage or cleaning them too early. As in the wild, if a burrow/nest is discovered the parents will abandon the litter if not eat them.

Moving and cleaning the cage also has biochemical and psychological effects on the parent/s as does lack of food and water.

Moving the cage may suddenly change temperature and/or lighting, and if not to the animals liking they may feel that the time of year has changed (winter is setting in perhaps) and therefore convincing then that their litter will not survive, so they cut their loses and consume the babies to gain valuable protein for the coming 'cold months'.

Cleaning the animals' cage will remove their scent which the animal will obviously dislike, causing them feel threatened, and again resulting in them cutting their loses.

Lack of food has a similar effect: The animals' instincts tells them that if food is not available then hard times are going to follow and they must look after number one, this will result in the reabsorbing of precious proteins to sustain themselves. This problem is more prominent if the father's paternity is suspect or if older littermates are present. In this scenario you may find that the litter will be culled slowly (weakest first) giving a chance for the situation to get better. If no food is given the whole litter will inevitably be consumed.

Animals sharing the cage will sometimes turn on the litter for no other reason than they have no maternal instinct (this sometimes includes the father, older male littermates, and to a lesser degree older females littermates).

All of the above problems are connected to variations of some factor or another: I suggest on the build up to (the gestation), during the birth of the litter, right up to when the babies are weaned, keep the conditions for the animals as stable as possible. Of course the boundaries of the variations will differ with each individual but it is better to be safe than litter-less.

On a more scientific level, it may be explained with genetics and more complex biochemistry.

The 'Mest' gene - also called PEG1 (Paternal Exp Gene) has an impression on the maternal behaviour. Defect genes result in non-feeding, non-cleaning, and non-retrieval of the young and also a lack of placentophagia.

Defective PEG3 genes are also aberrant to maternal behaviour. It has been shown that females with a defective PEG3 gene would only raise 8% of litters beyond weaning, while females with a normal gene raised 83% beyond.

This is such a significant find that scientist are investigating it as a cause for post-natal depression.

Ironically both the PEG1 and PEG3 genes are passed down by the father. Mothers do have some input with hereditary genes but little is known about it yet.

As a final idea, lack of oestrogen also has an adverse effect on the maternal behaviour, but short of HRT what is one to do?

Article by Matt Wright

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