The mammals are the most important group of animals from human point of view. They are economically important to human beings for many reasons as they have served or harmed man from earliest times.
Beneficial Mammals:
1. Domesticated Mammals:
Since the beginning of civilization, man has been domesticating various mammals for work, food and clothing. Man would probably not be able to survive without mammals, particularly the domesticated species. The useful information about the principal domesticated mammals the world over is given in the table 33.1. All the domesticated mammals provide meat and hides, some provide milk, wool and hair; others serve for transport, draft or hunting.
2. As Food:
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Mammals have been serving as food for man since very ancient time.
Various mammals are useful in the following way:
(i) Meat:
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The domesticated mammals provide enormous quantities of various kinds of meat and meat products. Large even-toed ungulates, such as cattle, buffaloes, pigs, goats, sheep, reindeer, etc., provide the bulk of meat supply of the world. The big game mammals, such as deer’s, provide the necessary proteins for many people. Seals, whales, rabbits and even dogs, rats and bears are also used as food in many parts of the world.
(ii) Milk:
Cows, buffaloes, goats, sheep, llamas, camels, reindeers, etc., provide milk which forms an important product for human food. Ghee, butter, cheese and curd are prepared from milk.
3. Commercial Products:
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Countless items of commercial value are produced by different products of mammals.
These are as follows:
(i) Hides:
The hides of various domesticated as well as wild mammals provide leather and fur for the manufacture of clothing and for a variety of other purposes. Animal pelts have been used as clothing for many centuries. Eskimos in the Arctic use reindeer and bear skins for clothing, seal hides for footwear and skin of other species for boats.
Much of the early explorations of North America were made by trappers in search of furs. Various mammals such as otter, mink, weasel, marten, ermine, beaver, fur seal, muskrat, skunk, fox, reacoon, lynx, bear, rabbit, kangaroo, house cat and innumerable other mammals provide natural furs of soft texture and pleasing colours.
Leather and fur are also used for the manufacture of suitcases, bags, shoes, harness, saddles, belts, purses, garments, etc., and support big industries. Muskrat is the most important and leading fur-producing mammal in U.S.A. Many mink and fox farms running have proved quite profitable.
Most of the fur-bearing mammals are fast becoming scarce so that man-made acrylic fibres, designed to look-like fur, now compete with and replacing the natural furs.
(ii) Hair and Wool:
The wool of sheep is the most important animal fibre. It is extensively used for weaving into cloth for winter. Goats, alpaca, camels, etc., also produce wool. Hairs of camels, pigs, sabbles and a host of others are made into brushes, etc.
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(iii) Perfume:
Ambergris, used as a base in fine perfume, is a product of intestinal canal of sperm whales. Musk, another substance used in perfumes, is obtained from the glands of musk deer of Central and Eastern Asia.
(iv) Oil and Fat:
Blubber of baleen whale and seal are the source of edible fat or oil. Eskimos use seal blubber as fuel oil. Oil of sperm whale is not edible. It is used as a base for cosmetics and in manufacture of candles and lubricants. Pigs provide cooking fat.
(v) Ivory and Baleen:
Ivory is obtained mainly from the tusks of elephants and walrus. It is used for making toys and in decorations. Baleen or whalebone is obtained from toothless whales. It was formerly an important commercial article.
(vi) Glue and Gelatin:
These are obtained from the skin, horns, hoofs and bones of cattle.
4. Beasts of Burden:
Various mammals have been domesticated by man to serve as beasts of burden for transport and draft of heavy loads. In the more progressive countries, they have been greatly replaced by automotive vehicles.
However, in the underdeveloped countries, cattle, horses, mules, sheep and goats are still being used for work in plains and mountains, elephants in jungles, camels and llamas in deserts, and reindeers and dogs on ice in cold countries. Of all the beasts of burden, perhaps the horse has played the greatest role in the development of human civilisation.
5. In agriculture:
Bullocks, buffaloes, yak, horses and camels are employed for ploughing fields. They provide manure in the form of dung and urine. The manure nitrifies soil and yield fuel biogas. Bone meal is prepared by crushing bones of cattle, sheep and goats, etc., is a good fertilizer.
Some carnivorous predators, such as mongooses, prey upon rats and mice which are serious pests of crops. Ant-eaters feed upon harmful insects. Skunks destroy grubs and cutworms, while moles and shrews consume enormous number of insect larvae.
6. As Pollinators:
Arboreal mammals such as bats, squirrels, monkeys, etc., visit one tree after another in search of fruits may incidentally help in the pollination of flowers. In East Indies, bats are said to pollinate bananas.
7. As Scavengers:
Hyaenas and jackals are of great utility as scavengers in nature. The common pig also clears away the refuge in the Indian villages and towns.
8. In Recreation:
In amusement no animal is safe.
(i) Pets:
Since time immemorial, man has tried to tame a large number of mammals as pets such as monkeys, bears, mongooses, rabbits, etc. But only dogs and cats have become popular and of general interest.
(ii) Zoos:
Lions, tigers, horses, elephants and monkeys are generally employed in sports and circuses. Bull fights are by no means confined to Spain only. Larger and rarer varieties of mammals are exhibited in zoological gardens and national parks.
(iii) Hunting:
Hunting is generally done by civilised man. It is actually for pleasure and recreation. Dogs, leopards, elephants and horses are used in the hunting. Important game animals are deer, elk, moose, mountain sheep, bear, lion, tiger, rabbit, raccoon, opossum, tree squirrel, etc. They are sought for their heads, hides and meat. Various countries now protect their game animals to prevent their extermination.
(iv) Decoration:
Antlers heads, and pelts of various mammals are displayed as trophies or mementos and for decoration of houses.
(v) Laboratory Animals:
Common mammals such as rats, guinea pigs, rabbits, cats, pigs, monkeys, apes, dogs, etc., are extensively used in laboratories for research and scientific studies.
Harmful Mammals:
There are some mammals which are decidedly harmful or injurious to man.
These are as follows:
1. Pests:
Many mammals act as pests. Most dangerous mammals to crops are the rodents. They destroy crops in fields. They are harmful in houses and buildings also. They consume all kinds of food stuffs and destroy property.
Rabbits, mice, wood chucks and some others forage in vegetable fields and gardens and gnaw at bark to trees. Pocket gophers eats roots of plants, while squirrels damage grain and other crops. Besides, bigger herbivorous ungulates such as deer, bear, boar, hippopotamus, elephant, kangaroo, etc., also damage and eat up crops. Cats in kitchen forage on food besides rats.
2. Predators:
Several wild carnivorous or predatory mammals are constant menace to the lives of people and livestock. Lions, tigers, wolves and bears prey at times on domestic cattle, sheep, hogs, poultry, etc. Wolves and hyaenas sometimes attack sleeping persons. In tropical Africa, the sanguivorous vampire bats feed on blood of various mammals, including man.
3. Disease Carriers:
Rodents are the worst carriers and distributors of the germs of certain diseases. Rats, mice, pigs, cats, dogs, etc., transmit many diseases to humans such as bubonic plague, typhus, relapsing fever, spotted fever, tularemia, trichinia, hydrophobia, etc.
4. Economic Importance of Rats:
Rats occur in almost all the terrestrial habitats that support life. They multiply rapidly and soon establish their colony. Rats are omnivorous, feeding on seeds, fruits, grains, roots, insects, snails and invertebrate and vertebrate bodies. They are mainly fossorial, nesting and living much of the time in burrows. They live freely in competition with humans.
Damage caused by rats includes grazing of young trees, root destruction and seed eating. Generally rats prefer very young plants having a high nutritional value than mature ones. These injured plants remain weak and small. Various species of rats are distributed in different parts and cause damage to different crops.
The short tailed bandicoot rat Nesokia indica is found across Egypt and India. It is mainly a subterranean feeder. The lesser bandicoot, Bandicota bengalensis is found alongwith Nesokia indica in Bangladesh and Myanmar. It causes 20-40% losses in cereals. The soft furred rat, Millardia meltada, a pest of cereals, is found in India and Pakistan.
Bandicota bengalensis and Millardia meltada cause 10% or more losses to various crops and wheat. Rattus losea and Bandicota indicata are principal pests of crops in China. In Australia, various crops including seedling fruits are damaged by bark stripping. In Australia, the number of rats increases tremendously reaching nearly 3000 holes in about 0.5 in one hectare.
When the food is exhausted, a large number of rats die and enormous external parasites grow on their dead bodies. Rice field rat, Rattus agriventor and other species of rat are serious pests of rice. They gnaw the small plants and eat grain in fields.
The population of rat damaging rice has one or two peaks correlated with single or double crops per year. Bandicota bengalensis causes 7-22% loss of rice in North India and 5-18% in South India and at some places the loss is up to 60%.
In sugarcane fields, the populations of rats are established. They find suitable shelter and food in sugarcane fields. Rats cause direct loss of cane by eating into internodes. This permits entry of harmful microorganisms and cause physiological stress, which can reduce weight of sugar content. Rats also damage the oil palm crop by eating upon their ripe oil bearing fruit lets and carrying them with them.
Unripe fruit lets are also gnawed by the rats Rattus rattus diandi, which is the commonest oil palm pest in Malaysia. Rat species like Rattus praetor, Rattus exulans attack coconuts. Rats climb the palms of all ages to feed on developing nuts when then fall prematurely. In some regions the loss due to coconut fall is up to 50%.
Rats also damage the crops of potato, groundnut, sweet potato, maize, casava and others to large extent. Up to 16% of ripening pine apples are damaged by Bandicota bengalensis and Rattus rattus.
Rats as Carriers of Disease:
Some rodent species are reservoirs of a large number of infectious organisms of man. If these infectious organisms are transmitted to human and domestic animal populations may cause outbreak of diseases often leading to high mortality.
Some of the diseases for which rats are the reservoirs are given in the following table:
Control of Rats:
For the control of rat population various methods are employed which are given below:
1. Repellants and Attractants:
In this method chemicals like cyclohexamide and tributylin acetate are used as repellants. The repellants may be incorporated in the packing material to keep the rats away from the packed food stuffs. Various types of attractants such as sugar, archis oil are used to attract the rats to the traps laid for them in the fields.
Sometimes the poisons are also mixed into baits used which are placed in rat burrows. Selective rodenticides like Norborne carboximide, Quintos and Brodifacoum are also used.
2. Fumigation:
In this method fumes of chemicals like Fomafog, are introduced into the rat burrows by suitable apparatus.
Rats as Food:
In India and Central Asian, African and some European countries some species of rats are used as food. The rats, Ondalria zibethica is served as a delicacy in restaurants in Holland and Belgium. The cane rat, Jhryononys swinderianus forms an important constituent of the food of majority of the population in West Africa.
Use of Rat Skin:
Skin of larger species of rats is tanned. It can be used in preparation of gloves, purses and other small items. This helps in providing jobs to people and also controls the rat population.