THE ORDER INSECTIVORA
Insectivora – Insect Eating Mammals (About 350 species.)
Shrews, hedgehogs, moles, and a number of other small animals native to Madagascar known as tenrecs, make up the order called Insectivora, Insect Eaters. These creatures have in common a diet of insects. Actually, other small invertebrates such as worms and crustaceans are eaten too, while aquatic species may add small fish and even amphibians to their meals (see the Shrew above).
Six or seven families of Insectivora are recognized comprising between about 360 up to 430 species, depending on who is doing the sorting. They are widely distributed, found throughout most of the world except in the polar, Australian, and most of the South American regions. Only five species of shrews inhabit the South American continent, and there they are limited to the northwestern corner.
One entire family, consisting of only two species, is confined to the Caribbean islands of Cuba and Hispaniola (Santo Domingo). These rare, endangered species are the solenodons – relict forms that are apparently unable to survive agricultural cultivation of the ground and the introduction of dogs, cats, house rats, and the mongoose. Together with the European water shrew and the North American short-tailed shrew, solenodons are among the only venomous mammals known (the male platypus has a poisonous spur on its hind feet).
Insectivores are the most primitive of the true placental mammals (Eutheria) living today, and many, in fact, are probably fairly close facsimiles of the earliest ancestral forms. It is assumed that from this kind of true mammal all present-day mammals evolved. There is little that unites all of these animals into one order, since the fact that they eat insects is not unique to this group, nor do the members of this group restrict themselves to insects. As biologists study these animals more and more, it is to be assumed that other Insectivores will break away into new orders, just as the orders of Scandentia (Tree Shrews) and Macroscelididae (Elephant Shrews) have recently been formed.
Generally, Insectivores have a small brain and unspecialized teeth. Most insectivores have poorly developed eyes, small ears, and a long, pointed snout. They are small four-footed plantigrade animals, which vary in size from among the very smallest of living mammals to about the size of a house cat.
A certain degree of specialization does exist among certain animals of this rather generalized order, however. Hedgehogs and some tenrecs have developed a spiny coat, underlying which is a set of special muscles to control the erection of the spines when danger approaches. They may further protect themselves by then rolling into a tight, sharp spiny ball. Some species of hedgehogs hibernate in winter, and desert-dwelling species may estivate (that is, reduce their body temperature and metabolic rate, thereby entering a state of torpor) during extremely hot weather.
The pectoral girdle and front limbs of moles are modified for burrowing, and they have developed large, spadelike front feet with broad, heavy claws enabling them to nearly “swim” through moist topsoil. And several Insectivores have “converged” into semi-aquatic animals. The European desman, an aquatic mole, has webbed feet and a laterally flattened tail to aid in swimming as well as a waterproof coat and a specialized breathing apparatus. These same characteristics are also present in at least two other Insectivores: the Nimba Otter Shrew and the Madagascan Tenrec. Perhaps this is one order best studied by reading about each of the individual animals, and then making your own comparisons.
Check out the following specific insectivores:
Moon rat (Gymnure)
Pygmy (Etruscan) shrew