How does smell influence rat behaviour?
Having seen a normally docile buck aggressively bite the pet judge at a show I began thinking about his behaviour and (from a rat's point of view) what might explain it. There are a number of physical occurences that might explain his behaviour, but I was interested in the possible influences of smell in that context.
Examples of the rat’s reliance on smell
From the moment a rat is born it begins to interpret its world through its sense of smell, and throughout its life this is its primary sense, in much the same way as vision is ours. Newborns locate their mother’s nipples by smell. During the birthing process the mother transfers the smell of amniotic fluid to her own nipples - by cleaning the babies and then grooming her underbelly. Without this transfer of familiar smell the babies will not feed. Within a few days, it is the smell of their own saliva that attracts them. Rat kittens have been shown to show preferences (by smell) towards those things that offered positive touching/nurturing experiences in their first few days, which is one of the benefits of gentle, early human handling.
From a droplet of urine left by another rat, an exploring rat can determine the gender, sexual maturity, reproductive status, familiarity, social status, and stress levels of the other. Individuals can also be recognised.
Rats have instinctive responses (fear and flight) to predator smells such as feline smells.
Food choices are made from cues received by smell from the mother’s milk (determined by what she has eaten), and later in life by the smells picked up from the coat, whiskers and breath of other rats.
Situations where the sense of smell might be impaired
Research suggests that albino rats have greatly reduced ability to either perceive or interpret smells.
Rats with upper respiratory infections are likely to have a reduced sense of smell.
Strong and unfamiliar smells may overwhelm and confuse a rat.
Back to smell and aggression
I have heard of a few situations where a rat made a gross error of judgement and bitten aggressively as a one off event, and completely out of character. These ‘mistakes’ seem just as likely to involve the owner as a stranger. Having investigated a little further the humans involved seemed often to have just come out of the bath, just washed their hands or (in the case of our pet judge, above) used an antiseptic hand-rub. In view of our human obsession with strong perfumes, many soaps and scrubs have smells that are noticeably overpowering (even to us). Could it be that when their olfactory organs are drenched in these overwhelming and unfamiliar scents, rats (given a certain set of circumstances) are simply startled and confused… and bite from fear rather than aggression. Or, since rat aggression is itself fuelled by their sense of smell, perhaps we are unwittingly pushing the wrong buttons as far as the messages given to them by these scents are concerned. Ideally, a rat’s environment (and us, when we handle them) should smell neutral, to allow them to easily and accurately interpret the scents that flood their worlds.
Author: Alison Campbell
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