Colours of Wildlife - The Heroic Giant Rat
Created | Updated Oct 13, 2013
The Heroic Giant Rat
Willem is a wildlife artist based in South Africa. He says "My aim is simply to express the beauty and wonder that is in Nature, and to heighten people's appreciation of plants, animals and the wilderness. Not everything I paint is African! Though I've never been there, I'm also fascinated by Asia and I've done paintings of Asian rhinos and birds as well. I may in future do some of European, Australian and American species too. I'm fascinated by wild things from all over the world! I mainly paint in watercolours. . . but actually many media including 'digital' paintings with the computer!"
Another critter that deserves far more love! This is Cricetomys gambianus, the Giant Rat, also known as the Giant Pouched Rat. It is indeed a seriously-sized rat, reaching a total length of 90 cm/3', and a weight of 2.8 kg/6 lbs. There are two to four recognized species, depending on how they're classified. Only one occurs in Southern Africa. Over here they're rarely seen, only inhabiting the far northeast of the country, in densely wooded country where they are quite reclusive. They're widely distributed in the rest of Africa, replaced in the rainforest belt by the similar species Cricetomys emini. Sometimes two more species are split from it, Cricetomys ansorgei and Cricetomys kivuensis.
This is the largest rat/mouse species in Africa. There's not really any biologically-significant distinction between rats and mice; this species is classified in the Nesomyidae, an African and Madagascan family of rat- and mouse-like rodents. It has cheek pouches, like hamsters, in which it can stuff quite large food items to carry back to its burrow. Despite its size it is strangely sensitive. In spite of living in tropical regions, it cannot tolerate much heat. Its large ears, short fur and long tail help it to radiate and shed excess heat. Also it is active mostly at night, spending the day in its burrow, which it will construct in a cool place such as the shade of trees and shrubs. It cannot tolerate much cold either. Furthermore it is restricted to fairly moist regions, with year-round availability of soft, living plants. It seems to be quite timid in its foraging behaviour, keeping under or close to cover and rarely venturing more than 150m/yards from its burrow. The burrow itself consists of several sections: one for eating and storing food, one for sleeping, one as a latrine, and for the female, a chamber lined with leaves for giving birth and caring for her babies. Each burrow will have several emergency exits; also rats may move regularly from one burrow to another.
This rat's large size does confer some advantages to it. It is not an easy prey for hawks, owls or many snakes. It isn't even targeted by mammalian predators as far as we know – except for humans. Its large size also means that it can carry larger items of food to its burrow, using its sharp teeth or cheek pouches, and there eat in safety. Also its large intestines can process larger quantities of food, and it can derive nutrition even from fairly poor quality food. Similar to rabbits – to which they are not at all closely related, rabbits being lagomorphs rather than rodents – these rats have a system of re-ingesting their own droppings to take them through a second round of nutrient absorption.
This is a quite omnivorous species. It mostly eats plant material like fruit, seeds and nuts, roots and leaves, but also snails and insects like termites. It will accumulate hoards of edibles that don't perish quickly, like nuts. It will line its burrow with the inedible bits. One burrow has been found with over 8 kg/18 lbs of macadamia nut shells! Strangely it hoards not only food, but burrows have also been found containing collections of a great variety of objects: pebbles, bones, iron nails, bottle caps, pieces of rope and wire, and a small key! They're almost like the rodent versions of magpies, in their zeal for collecting fancy trinkets.
Like most rodents these are prolific breeders. Females can have nine litters each year, each containing 2 to 4 pups. While normally living solitarily, male and female rats come together and form pair-bonds for the breeding season. Courtship consists of the two standing upright and shoving each other with their front feet, the male sometimes shoving her backward for several metres/yards. If the female tries to leave the male grabs her with his teeth and pulls her back. He will groom her over the face, ears and neck, and will also hug her around the middle, and then rapidly jiggle his 'hands' forward and backward to calm her. If she accepts him she will let him sniff and lick her rear parts, and then mount her.
After giving birth in the nest chamber, the female will clean the pups and eat the afterbirth. She stays with them a full week, only then exiting again to find food for herself. At the age of about seventeen to eighteen days the pups start eating solid food; their eyes open at 20 to 24 days. At this point they start leaving the nest.
Although these rats are secretive, they move slowly and can be caught easily. They're also very gentle. They might bluff by puffing up their cheek pouches and making hissing sounds, but if handled gently will soon calm down and may eat out of their captor's hands! Only females with youngsters are aggressive and may bite.
The Hero Rats
Most impressively, these rats can honestly be called heroes for the way they serve humanity! In Africa there are, aside from many other problems, two that are quite nasty. The first is tuberculosis, still one of the big killer diseases in Africa. Another one, totally man-made, is the landmine. The various wars in Africa have left huge regions that are still full of mines, leaving vast areas unsuitable for farming and a hazard to anyone venturing in them. Many people including many children are still losing lives and limbs to these.
It might seem incredible that a rodent is our best ally in dealing with both these scourges, but so it is! These giant rats have excellent noses and can actually be trained to smell the tuberculosis infection in people at an early stage, merely needing a sputum sample to do so. A single rat can sniff hundreds of samples each day, contrasting with 30 or so using mainstream medical methods, and costing only a small ration of daily nibbles! Once a rat has identified an infection it can be confirmed by more regular methods, and overall this early detection can help people get treatment more quickly and also can help with containing this infectious disease.
In the case of the landmines, the rats again use their excellent sense of smell to detect them, despite their being buried (the mines, not the rats). What is more, the rats can explore the areas where the mines are planted with no danger of setting them off … even being big for rats, they are much smaller than the people the mines are intended to be triggered by. The rats are guided on LONG leashes, or along spanned ropes, to methodically cover the mine-infested territory. Here is a video showing their training: http://www.youtube.com/watch?v=3IxU-MZ12VE
Isn't that just heartwarming? They let the rats work in the morning because they can't stand the heat later in the day. I hope after this you have some new appreciation for our rodent friends of the Earth! Many people do love them and keep them as pets worldwide, but this has to be done responsibly: escaped or released pets have recently been found in Florida, and such escaped populations in areas that they are not native to can end up causing serious ecological problems.
