Rat
Rescue :: Rat
Article
Paws for Thought
Some years ago there was a TV commercial where a white cat advertises
a brand of cat food by dipping his paw into the tin, scooping
out chunks and eating them off his paw. This cat had been trained
to do something rats do naturally, namely eating using his front
paws. Even with training a cat can only balance the food on
his paw rather than hold it.
I became fascinated by the way rats use their paws to feed
when I was investigating diseases where rats lose this ability.
Whilst it’s possible for rats to eat some foods without their
paws, they far prefer to use them. Many times I’ve witnessed
my rats trying to pick up porridge instead of lapping it. Elderly,
weak or sick rats will resort to holding the food in one paw
whilst keeping the other on the ground for balance. Towards
the end of her life, my doe Froth (Photo 1) lost the ability
to sit up on her hind legs due to spinal degeneration, but still
persisted in eating her food with her front paws by leaning
on her elbows. Furthermore plastic collars that are sometimes
put on rats after operations to prevent them taking out their
stitches, can be highly stressful because the collars stop rats
getting their paws to their mouths. Fortunately with better
stitching techniques these collars are becoming less necessary,
as some rats will even give up trying to eat with one on even
when the food is held for them.
Photo 1
Many species of animal feed very successfully without using
their front paws. Herbivores such as horses, cows and rabbits
don’t use them nor do carnivores like the cat. We and our relatives
the apes and monkeys do use them as do rats and many other rodents
so what is it that makes using your front paws necessary? To
answer this we need to look at four questions all animals consider
when feeding.
What’s on the menu?
Herbivores and carnivores are specialists. Their teeth, their
digestive system, their anatomy and their behaviour equips them
to feast on one particular type of food. Grass and plants in
the case of a herbivore like the horse, meat for a carnivore
like the cat. The rat is far more versatile, not only will it
tackle meat and veg it will also eat nuts, grains, fruit plus
anything else it considers edible. To take advantage of all
these possible meals means having the ‘tools’, such as teeth
and paws to deal with them.
How is the meal served?
Horses often don’t need to hold their food as it is rooted
(quite literally) to the spot. For a hunter like the cat their
food is mobile and it will probably run for it’s life. Rat’s
food can come into both these categories, but even if their
food is neither alive nor anchored, trying to eat it without
securing it with their front paws must be like us trying apple
bobbing, it keeps rolling out of reach. As well as using the
front paws to secure their food, they also use them to position
it so the front teeth can take bites or husk a seed or grain.
Eating with your mouth full
Another reason rats hold their food in their paws is they
can’t take bites with the front teeth and chew with the back
teeth at the same time. Many grazing animals can do this and
can even bypass biting with the front teeth altogether. If you’ve
ever watched a rabbit eating a long dandelion leaf you’ve picked
for it, you’ll see the leaf gradually disappearing into the
rabbit’s mouth a bit like us sucking up spaghetti. The rabbit
just keeps drawing it past the front teeth and chewing it up
with the back ones. If it’s startled it can bite through the
remaining leaf and drop it as it runs off.
The rat takes bites with it’s incisor teeth. The incisors in
the lower jaw slot behind the ones in the upper jaw. This perhaps
partly explains the myth that rats must have something to gnaw
on or their teeth will overgrow, because the teeth don’t look
like they meet. In fact when the rat wants to bite something
(or grind the incisors against each other) the lower jaw is
pushed forward so the teeth do meet. When it chews it’s food
with the back teeth it has to bring the lower jaw back, so the
back teeth can grind against each other. It is therefore useful
for the rat to keep hold of it’s food in it’s paws between bites.
For herbivores like the horse the next concern is very important:
Am I on someone else’s menu?
To avoid ending up as someone else’s dinner a horse has long
legs so it can run away whenever necessary. Their eyes are positioned
so they have close to 360 vision all round them even with their
heads down grazing. The only blind spot being directly behind
their bodies. A rat’s vision is poor by comparison but it can
stay alert to predators by sitting up on it’s hind legs whilst
eating. This also puts the rat in a position from which it can
dart off in any direction if threatened.
Cats are less concerned with being preyed upon and more concerned
about losing their meal to someone else. Their main worry is
the last question:
Is there enough to go round?
Apart from in times of famine, herbivores like the horse are
surrounded by their food so they aren’t competitive with each
other for it. Even if they have to run to safety and leave their
food it will be there when they get back or they can find some
elsewhere.
For carnivores their food is often not visible, they have to
hunt for it and most hunting attempts are unsuccessful so when
they do catch their prey they aren’t keen to share it. Carnivores
that do share their prey often have a strict pecking order as
to who eats first, such as in packs of wolves.
Being able to take advantage of many different kinds of food
means rats don’t have to defend it as fiercely as carnivores.
Nevertheless keeping hold of their food in their paws whilst
they eat can stop another rat pinching it. I’ve also been amused
to see rats hold each other off the food in their bowl by grabbing
fistfuls of each other’s fur like children squabbling in a playground.
Something else rats can do which solves these last two questions
is to store their food so they can eat it in safety.
Takeaway meals
If you hold out a banana to a chimpanzee he’ll take it with
his ‘hand’. Hold out a piece of banana to a rat and he’ll most
likely take it in his mouth. We can walk off on two feet carrying
our food, as can the chimp who can also clutch the food to his
chest with one paw and run off on three legs. Unlike us rats
can’t carry their food in their front paws, although they will
use their paws to help cram as much food as possible into their
mouths, before making for their store. Kwee Choo, my dumbo doe’s
current record for how much she can haul off in her mouth in
one go is 4 peas and a piece of potato.
Photo 2
My buck Ravel in Photo 2 looks like he might be reaching for
the food with his paw. However if the photo had been taken a
moment later, you’d have seen him placing his paw on my hand
to balance so he could lean forward and grab the food in his
mouth.
How to eat like a rat
So what sort of front legs do you need to eat like a rodent?
First you need digits. Hooves, trotters or even digits with
webbing in between, as sported by dogs and cats just wont do
the job. The rat has four digits on each front paw and an unusable
stump of a thumb. If you try turning the pages of this magazine
without using your thumbs you’ll get an idea of how essential
they are for true dexterity. Also unlike us the rat’s digits
can’t move independently, rats can’t ‘point’ with one finger.
All the digits on one paw either flex together or extend together.
Nonetheless by holding and manipulating it’s food between both
front paws it can achieve very delicate movements.
The second requirement is the ability to rotate the lower front
limb. Most of our rotation comes from just below the elbow joint
and we can manage both a palms up and a palms down position.
The rat walks around with the paws palms down and can get them
palms sideways to hold it’s food though not palms up. A mammal
like the horse has virtually no rotation in the front limb at
all, it’s hooves always point forwards.
Finally you need to be able to balance with your front feet
off the ground. We achieve this by standing on only two feet,
the rat has a flexible spine so it can sit up on it’s haunches.
Sitting up like this to eat is not only possible for the rat,
it’s also far more efficient than eating with all four feet
on the ground. Whilst the rat has a long head he also has short
legs and a short neck meaning his body and head are already
very close to the floor. Bending his neck to pick up food when
standing on all fours is awkward, if he doesn’t arch his back
slightly he’s likely to bang his nose on the floor, but once
sitting up he can move his head more freely.
You might say I’ve become somewhat obsessed with the way rats
feed and my rats might appreciate not having an audience every
time they tuck into their meals, but I’ve come to realise it’s
a very clever and complex process getting food into your mouth
before you even start to chew or digest it. So when you serve
up your rats’ next meal just take a moment to paws for thought!
Author: Sally Clark 2005
