Insectivora (Insectivores)

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Insectivora

Family: Gymnures and Hedgehogs
Family: Golden Moles
Family: Tenrecs
Family: Solenodons
Family: Extinct West Indian Shrews
I: Red-Toothed Shrews
II: White-Toothed Shrews
Family: Moles, Shrew Moles, and Desmans

(Insectivores)

Class Mammalia

Order Insectivora

Number of families 7

Number of genera, species 67 genera; 426 species

Introduction

In 1758, when Linnaeus published his taxonomy masterpiece, Systema Naturae—the bible for all past, present and undoubtedly future taxonomists—the organisms were classified according to their visible physical characteristics. The order Insectivora was reserved for organisms observed eating insects. Linnaeus listed three families in this category: Talpidae (Old World moles), Erinaceidae (hedgehogs), and Soricidae (long-tailed shrews).

Today, the order Insectivora consists of seven families: the Erinaceidae, with seven genera and 21 species of gymnures and hedgehogs; the Chrysochloridae includes seven genera and 18 species of golden moles; the Tenrecidae features ten genera and 24 species of tenrecs; the Solenodontidae consists of one genera and three species of solenodons; the Nesophontidae has one genus, Nesophontes, and six species of extinct West Indian shrews; the Soricidae includes 24 genera and 311 species of shrews; and the Talpidae features 17 genera and 41 species of moles, shrew moles, and desmans.

The order Insectivora has 426 species of small mammals, three-fourths of which are shrews, quite possibly the smallest of all mammals. The Insectivora is the third largest order of mammals. The Rodentia is the largest with over 2,000 species and the Chiroptera (bats) is the second with over 900 species.

Evolution and systematics

The timing of the origin of extant Insectivora species has been and continues to be a topic of great debate among scientists. It is widely accepted, however, that Insectivora are the most primitive of the true placental mammals existing today and the ones from which present day mammals evolved. Most of the primitive eutherian (placental) mammals were insectivores. To date, common classification practice has been to include some of the primitive eutherians with all recent Insectivora members based on their similar dentition. The earliest insectivore fossils are believed to be those of Batodon and Paranyctoides. These remains date from the mid to late Cretaceous period, approximately 100 million years ago (mya). Remains of small insect eaters from Asia, zalambdalestids, along with kennalestid remains from Central America, are believed to date back to the Late Cretaceous.

Erinaceidae fossils date back to the Paleocene to early Pliocene in North America. Other fossils discovered in Africa date from the early Miocene to Recent, from late Paleocene to Recent in Europe, and from Eocene to Recent in Asia. The Solenodontidae dates from the late Mesozoic and early Cenozoic in North America and the Caribbean to Recent in Cuba and Hispaniola. Eight species of Nesophontidae are believed to have survived the Pleistocene period on into the 1900s. Lack of physical evidence of their ongoing survival has led scientists to conclude that they are now extinct. Most of the Tenrecidae began to evolve in Madagascar from the Pleistocene to Recent. Other records show that they existed during the middle Eocene to middle Oligocene in North America and from the Miocene to Recent in Africa. Chrysochloridae fossils dating back to the Miocene (Kenya) and Pleistocene (South Africa) and resembling Recent species were discovered in Africa. There are varying opinions regarding the evolution

of the Soricidae. This is due to the rarity of soricid fossils. Some scientists believe that the Eocene period in Africa, Eurasia, northern South America, and North America marks the onset of this family's existence. Others believe that the Soricidae existed only in Europe and North America during this period and from Miocene to Recent in Africa and Asia, Pleistocene to Recent in northwest South America, and early Oligocene to Recent in Europe and Asia. We know of recent Talpidae fossils dating back to Miocene in Europe and recent protein studies show that they were present in North America during that period as well. Otherwise their geological range is also believed to be early Oligocene to Recent in North America, and late Miocene to Recent in Asia.

For a long time, Insectivora was the order into which scientists put species of questionable lineage or those mammals that were characterized by the lack of distinctive features possessed by other mammals. As phylogenetics (identifying and understanding relationships between life forms) and other scientific dating methods improve, and as additional fossils are discovered, Insectivora is becoming less of a catchall order but not necessarily less controversial.

There are many examples of the difficulties in classification surrounding Insectirora. Prior to 1972, for example, elephant shrews were part of Insectivora. Then one group of scientists decided that because these mammals possessed certain physical characteristics not typical of most other insectivores—moles, shrews, hedgehogs, and tenrecs—such as an auditory bulla, an entotympanic bone, a complete zygomatic arch and a large jugal bone, elephant shrews should be placed in a separate order, namely Macroscelidea. Other taxonomists believed that Insectivora should be divided into two suborders: Menotyphla consisting of Macroscelididae (elephant shrews), Tupaiidae (tree shrews), and Lipotyphla with the living families Erinaceidae (gymnures and hedgehogs), Chrysochloridae (golden moles), Tenrecidae (tenrecs), Solenodontidae (solenodons), Soricidae (shrews), and Talpidae (moles, shrew moles, and desmans). Other scientists felt that tree shrews belonged with the primates and yet others believed that they should be placed in a separate order altogether, Scandentia. There are also those who believe that they have molecular evidence for the origins of Insectivora and for a new order, Afrosoricida, of endemic African mammals to include the families Chrysochloridae (golden moles) and Tenrecidae (tenrecs). Reallotment of these two families would decrease the number of Insectivora species by 51. The elephant shrews (Macroscelididae) would be included in this new order as well. The Cynocephalidae (colugos) has been moved around over the years between Insectivora and Dermoptera, where they now reside. With Insectivora, it would appear that as scientific techniques evolve, so families and species fragment, multiply, and/or relocate.

Physical characteristics

The size of living insectivores ranges from a small mouse to a large house cat. Savi's pygmy shrew (Suncus etruscus), is believed by many scientists to be the world's smallest living mammal weighing 0.04–0.10 oz (1.2–2.7 g) and measuring 1.4–2.1 in (36–53 mm) without the tail. The 1998 discovery of a 65 million year old fossil jaw measuring 0.3 in (8 mm) and belonging to the extinct Batonodoides, suggests that some prehistoric insectivore mammals were even tinier than some Savi's pygmy shrew.

The moonrat, (Echinosorex gymnura) is the largest living insectivore, weighing as much as 4.4 lb (2 kg) with a body measuring up to 16 in (40.6 cm) and an 8 in (20.3 cm) long tail. Found on the Malay Peninsula, Sumatra, and Borneo this invertebrate and fruit-eating mammal keeps predators at bay by releasing a foul odor. The largest extinct member of Insectivora is thought to be Deinogalerix which means "terrible hedgehog." This 2-ft-long (61-cm-long) hairy mammal with elongated snout, sharp teeth, and short legs lived in Europe during the middle Miocene period about 15 mya.

Many members of Insectivora share the following characteristics: five-clawed digits on each limb (pentadactyly); short legs; annular (ring-shaped) tympanic bone; long, flat, small skull; flat cranium (brain case); a small, smooth brain with hemispheres that do not extend backward over the cerebellum; an incomplete zygomatic arch (cheek bone); largely interorbital, well developed and sharply demarcated olfactory bulbs; small ears (exterior ones nonexistent in Talpidae) often lacking ossified auditory bulla (the bony covering of the middle ear cavity); no intestinal caecum; pollex (thumbs) and hallux (big toes) are not opposable; tibia and fibula are often fused near the the ankle whereas the radius and ulna are separate. The otter shrew (Potamogale) is the only Insectivora genus that does not have clavicles. A cloaca, the common posterior chamber into which the digestive, urinary, and reproductive tracts all discharge, which is uncommon in most placental mammals, is frequently found in Insectivora species. Male testes are abdominal, inguinal, or borne in a sac in front of the penis; a baculum (os penis) is present in some species. All members of this order have a chorioallantoic placenta that allows the young to develop fully in the womb.

Tiny eyes and poor eyesight are typical of insectivores. Moles and desmans (talpids) are almost blind and in many mature species the eyes are entirely covered with fur. Most insectivores have small external ears, some concealed under fur. Moles have no external ears. Asiatic water shrews (Chimarrogale) have tiny ears featuring a valvular flap that seals the opening when they submerge themselves in water. The cone-shaped snouts characteristic of insectivores come in many different sizes and perform a wide variety of tasks. The ethmoturbinal bones (bony plates that support nasal membranes) are large. Coiled scrolls of bone make up the nasal chamber that is covered with olfactory epithelium, the receptors of which are stimulated by airborne chemical molecules. The insectivore olfactory sense is very keen. Some snouts are long and thin with flexible tips for prodding in muddy areas, others are short and stubby with leathery pads on the tip. Solenodons have a small round bone—os proboscis—located at the tip of their hairless nose that supports the snout cartilage.

Vibrissae—sensory hairs located on many insectivoran tails, snouts, behind ears, and even on feet—are large in diameter. They are relatively rigid so that they do not bend much, but instead act as levers, transmitting the applied force to their base. They are embedded in a fluid filled sack, which allows them to move about under the skin. Water shrews, like many other insectivores, have vibrissae on their snouts believed to help them locate prey. It is thought that unless these shrews actually touch their prey with their vibrissae, no matter how close they are, they cannot capture it. Long-tailed shrews (Sorex dispar) rotate their long, slender, vibrissaeadorned snouts constantly. Moles and desmans (Talpidae) depend primarily on their olfactory (smell) and tactile (touch) senses. The talpid snout is usually long, narrow, very mobile and extends beyond the end of the upper jaw. The tip is hairless, apart from a few vibrillae, and features Eimer's organs (minute sensory receptors). The star-nosed mole (Condylura cristata) has a snout tip featuring 22 fleshy pink appendages or tentacles consisting of 25,000 sensory receptors used to help it locate food. When the star-nosed mole eats, the tentacles curl up out of the way. The snout of the desman is such that it can be used as a snorkel or periscope that continously monitors the air for prey or predators.

Many variations on the dental formulae can be found among Insectivora but one of the most frequent is (I3/3 C1/1 P 4/4 M3-4/3-4) × 2 = 44, 46, or 48. All insectivores have rooted, primitive teeth. Deciduous teeth, the first set that develops in mammals, are shed early on and rarely serve a purpose. Insectivores have unspecialized sharp teeth and often a crown pattern typical of primitive placentals. Some have front teeth modified by specialized or at times enlarged incisors and canines with a varying morphology, sometimes shaped like incisors or premolars. Shrews and moles often have dilambdodont upper molars (W-shaped crest pattern). Tenrecs, golden moles, and solenodons have zalambdodont upper molars (V-shaped crest pattern). The upper molars in hedgehogs and gymnures are quadrate meaning they have four main cusps. The Haitian solenodon (solenodon means "grooved tooth") and European water shrews—both omnivorous but preferring an animal diet—have unusual dentition: a large upper incisor points slightly backward and a deeply grooved channel in the lower incisor at the base of which is a duct that transports venomous saliva.

The majority of insectivores have plantigrade feet meaning that, like humans, they place the full length of their foot on the ground during each stride. Fossorial insectivore limbs are specialized for digging tunnels and burrows. The fore-limbs are short, powerful, and shovel-like, rotated so that the elbows face upwards with strong large-clawed paws facing

backwards. Moles (Talpidae) have five claws and a falciform bone, which expands the palms and supports the digits. It is sometimes referred to as a "sixth digit." Tenrecs and golden moles have four claws. Talpids also have an elongated olecranon process (projection on the proximal, or elbow, end of the ulna). The aquatic desmans (Desmaninae) do not dig much and have small forelimbs with webbed feet. Moles, but not desmans, use their weaker, less developed posterior limbs for propulsion only. Shrew moles (Uropsilus) seldom dig as they spend most of their time under leaf litter. As a result, their forelimbs and claws are not as well adapted for digging. Several species of semi-aquatic insectivores have long stiff hairs (fibrillae) on their feet to help propel them in the water like paddles. Several aquatic forms of family Soricidae (shrews) have webbed feet with hairy fringes that increase the surface area of the foot. This allows air bubbles to be trapped making it possible for the shrew to run on the water's surface for up to several seconds at a time. No insectivore forelimbs are adapted for jumping or leaping.

Insectivore tail length and texture vary like most other physical characteristics belonging to this order. Most talpids and hedgehogs have relatively short tails, some covered with vibrissae. Several of the semi-aquatics, the desman for example, have stiff flat rudder-like tails. Golden moles (Chlrysochloridae) have no external sign of a tail. The star-nosed mole has a tail that is almost as long as its body. Mole tails brushing against tunnel walls and roofs are able to pick up a variety of information including ground vibrations. The tail of the Madagascar hedgehog (Microgale longicaudata) is 1.5 to 2.6 times longer than its body and has 47 vertebrae. It is one of the longest mammal tails, second only to the pangolin

(scaly anteater). Microgale also have a tail that is modified for prehension (grasping). The lesser hedgehog tenrec (Echinops telfairi), on the other hand, has no external tail whatsoever. Several shrew names denote the nature of their tails—shorttailed, pen-tailed—the other 300 plus have tails that range from short to long, thick to thin, hairy to sparse, and tubular to flat depending on the species. The giant otter shrew (Potamogale velox) has an eel-like, lateral tail that allows it to swim like a fish while its keeps its hind feet glued to its flanks.

One of the mammals' most unusual skeletal structures is found among Insectivora. The West African armored, or hero, shrew (Scutisorex somereni), is believed to possess amazing strength. It has vertebrae with many interlocking spines as well as dorsal and ventral spines. The spines appear to allow it to bend considerably as well as bear phenomenal amounts of weight. The way in which the muscles are attached is complex and it seems that the extra joints allow additional flexibility.

Insectivores have fur or, in the case of some tenrecs (Tenrecinae) and hedgehogs (Erinacidae), a spiny coat, or even a combination of hairs and blunt spines that serve as protection against predators. When threatened, these mammals activate a set of muscles that cause their spines to become erect. Hedgehogs can protect themselves further by rolling up into a tight ball by activating their panniculus carnosus (a powerful orbicular muscle). Most aquatic insectivores have water-repellent pelage. Fur colors go from light to black, covering all the earth tones in between. Insectivores can be mono-, bi-, or multi-colored. Many feature lighter shades on their undersides. Fur texture can be glossy on golden moles to short, dense and velvety in least shrews and thick and woolly in hero shrews. Water shrews have been reported to have iridescent fur when exiting the water. Other species with iridescent fur include the ground-dwelling Cape golden moles (Chrysochloris). Some of them are reported to display greenish, violet, or purplish tinges.

Distribution

Insectivores are found everywhere on Earth but Australia, Antarctica, and most of South America. The shrews (Soricidae) are the most widespread of all Insectivora families covering the entire planet except the poles, Australia, and the greater part of South America. Shrew mice (Soricidae) and moles (Talpidae) are the only families found in North America and a few wanderers have found their way from there to the northern edges of the South American continent. Hedgehogs and gymnures (Erinaceidae) are found in Africa, Eurasia, Southeast Asia, and Borneo. Hedgehogs were introduced to New Zealand where they are now flourishing. Solenodons, originally found in Hispaniola, Puerto Rico, Haiti, and Cuba are now Endangered and found only in Haiti and Cuba. The West Indian shrews (Nesophontidae) are believed to have existed in the West Indies until the Spaniards settled there at the beginning of the sixteenth century. The 1930 discovery of West Indies shrew remains in Haitian barn owl pellets ignited hopes that they still existed but no further evidence of their presence has come to light. Moles (Talpidae) are not found in Africa. Tenrecs (Tenrecidae) inhabit Madagascar and are found, to a lesser extent, on the Comoro Islands and in western central Africa. The golden moles (Chrysochloridae) exist on the southern half of the African continent. Recent discoveries of tiny placental mammal-like fossils in Australia, are leading scientists to believe that insectivores may have been on the Australian section of Gondwana when it separated 115 mya.

Habitat

The Insectivora are primarily terrestrial mammals, living either on or under the ground. Many insectivores are fossorial and a few are aquatic. Insectivores have been recorded to inhabit altitudes ranging from sea level up to 14,760 ft (4,500m) in the mountains of Nepal. Approximately 30 species of the Talpidae are fossorial (burrow diggers) to some extent. A number of tenrecs and soricids as well as all the chrysochlorids are fossorial as well. Golden moles dig burrows in sandy areas, plains, cultivated areas, and forests. Gymnures find shelter under brush piles, tree roots, deserted burrows, or even termite mounds. Solenondons prefer forests and rocky areas whereas tenrecs like rainforest and brushlands. Shrews, the most widespread members of the order, have been recorded living in a multitude of different habitats and altitudes ranging from the dry hot desert to high snowy mountains and everything in between.

Most shrew species prefer moist habitats. They live in shallow runways that they dig themselves or that are made by other animals, under decomposed leaves and twigs, and several species construct nests in hollowed out logs, under rocks, and in tunnels. Solenodons tend to build nests only during the mating season. The short-tailed shrews (Blarina brevicauda) build two types of leaf or grass nests in tunnels or

under logs and rocks: a small resting nest and a large mating nest.

The aquatic moles, desmans, shrews, and moonrats live right next to bogs, swamps, springs, rivers, and streams. Some, Eurasian water shrews (Neomys fodiens) for example, even dig tunnels that open into bodies of water. These mouse-sized mammals make sure the diameter of their tunnels is small enough to squeeze the water from their fur as they exit the water. Although most arboreal species appear in other orders, several insectivore species are known to seek refuge in trees when attacked or to forage (Sylvisorex, the forest musk shrews). Some shrews, such as the short-tailed shrew, are good climbers and have been observed scampering up several feet (meters) up trees to pilfer suet from a bird feeder.

Behavior

Insectivores are notoriously shy, secretive, and active mammals. Their vision is not highly developed, therefore they rely mostly on their other senses, hearing, touch, and smell. Some species of moles and shrews depend on echolocation, the use of sound to navigate. Insectivores have various means of protection, the most obvious being nocturnal, subterranean, or aquatic habitats. Most seek cover in deep forests, holes, and tunnels deserted by other animals, under leaves, branches, stems, and roots of plants. Hedgehogs and certain tenrecs have spiny armor for protection.

Insectivores communicate in a wide variety of ways. Insectivore communication can be both interspecific (between different

species) and intraspecific (among members of the same species). Adult hedgehogs make hissing snorts when threatened, and young make birdlike whistles and quacks while in the nest. Solenodons emit a high frequency clicking sound similar to that of many Soricidae, which may serve an echolocation function. White-toothed shrews (Crocidura leucodon) emit metallic squeaks. Suncus murinus chirps and buzzes. Among many tenrecs, communication is tactile, with a few audible signals. Some insectivores mark territory with bodily secretions. Scent glands are used for communication between golden moles, especially between mothers and their offspring and between sexes during the mating season. When marking their territory, moonrats (Echinosorex gymnura) produce a foul smell reminiscent of rotten onions or ammonia from small anal glands. Suncus murinus, the musk shrew, emits a pungent odor from a gland located between its last rib and hip bone. The Haitian solenodon (Solenodon paradoxus), has scent glands located in its groin and armpits that secrete a goatlike odor.

The Haitian solenodon produces a venom in a gland located in the mandible (lower jaw) then squirts it through a channeled bottom incisor. The southern short-tailed shrew (Blarina carolinensis), the short-tailed shrew, and Elliot's short-tailed shrew (Blarina hylophaga) have submaxillary glands that secrete venom as well. The toxicity of their saliva allows these tiny mammals to attack prey larger than themselves as their bites immobilize their victims. It is also thought that shrews use their venom to immobilize their prey for consumption at a later time.

Most of the species belonging to Insectivora are nocturnal (active between dusk and dawn). Sclater's golden moles, however, are among those who are active day and night. They must keep moving in order to maintain their body temperature and they do so by digging almost non-stop. When they do sleep, they keep their bodies warm with involuntary muscle twitches. Many shrew species are active day and night as well, because their metabolism requires them to eat continuously. Hedgehogs located in cooler climates hibernate during the winter and some desert-dwellers estivate (go into torpor by lowering their body temperature and slowing their metabolism) during very hot weather. In the months preceding their hibernation, hedgehogs build up substantial fat reserves to see them through their "down" time. Tenrecs and hedgehogs for example, are known to go into a state of torpor when food gets scarce. The tenrec's heartbeat can drop to one beat every three minutes accompanied by a drop in body temperature.

In the wild, insectivores are, for the most part, solitary animals whose social life is limited, for the most part, to mating and rearing of offspring. When hedgehogs gather during the breeding season; the animals establish a hierarchy. When solenodons meet, there may be some initial scuffling but they eventually tolerate each other. Solenodons are among the more social species with the young remaining for long periods with their mother. The nomadic shrew moles travel in groups of up to 11. Small-eared shrews (Cryptotis), are known to be sociable, with several adults sharing a nest at the same time. Outside of mating season, many Insectivora species do not tolerate each other in the wild and become extremely aggressive and violent. When in captivity however, these same animals initially avoid each other or exhibit aggressive behavior but eventually learn to live together quite peacefully.

Fossorial insectivores—moles, desmans, and a few species of tenrecs and shrews—spend much of their time digging burrows and tunnels for food and shelter. Eastern moles (Scalopus aquaticus) found in Central and North America, dig up to 102 ft (31 m) per day. The short-tailed shrew digs tunnels through leaves, plant debris and snow. The yellow golden mole (Calcochloris obtusirostris) is nicknamed "sand swimmer" because of the way it tunnels through the sand at an impressive speed.

Feeding ecology and diet

Insects are the mainstay of many insectivores. Others such as solenodons, hedgehogs, tenrecs, and some shrews prefer an animal-based diet that may include snails, reptiles, worms, and ground-nesting birds' eggs. The aquatic species subsist on crustaceans, mollusks, fish, and frogs. Plant matter and even fruits, vegetables, seeds, and nuts are other sources of insectivore nutrition.

Many moles and shrews have a very high metabolic rate and a voracious appetite causing some species to eat up to several times their own body weight in a 24-hour period. The long-tailed shrew (Sorex dispar) eats almost continuously, day and night. Insectivores forage for food in many different ways. Ground dwellers forage for insects under leaves, grasses, dirt, branches and among rocks. The fossorial insect eaters dig for food in sand or dirt or hunt in their own or borrowed burrows and tunnels. Desmans have flexible snouts that allow them to poke around in the dirt at the bottom of streams, lakes, and ponds for food. The aquatic moles, desmans, shrews, and moonrats or gymnures, are good swimmers and/or divers able to catch small fish and invertebrates in the water. Otter shrews are fond of freshwater crab. The life span of insectivores is relatively short and ranges from less than one year (shrews) to 11 years (solenodon in captivity).

Reproductive biology

Little is known about the reproductive biology of most members of Insectivora. Those with short life spans, the majority of the shrew species for example, produce several litters a year while longer living insectivores, such as tenrecs, mate only once a year. Insectivores produce as few as one offspring per litter but some tenrecs can have as many as 32 young at one time (the maximum offspring produced by mammals). Gestation periods vary from two weeks to two months. The same is true for the length of time the young nurse. The number of teats ranges from two to 24 and their location on the body depends on the species. Many male insectivores have testes in the abdominal cavity lying close to the opening of the perineum. Moles and tenrecs have a baculum (penis bone). Courtship and mating practices, which have seldom been observed but are probably polygynous, tend to be short and to the point lasting as little as a few seconds in some species, but lasting hours in other species. Some young, such as certain tenrecs, are born with hair, able to run around immediately following birth and are totally independent within weeks. On the other hand, moles are born completely naked save for a few vibrissae and guard hairs. The latter are helpless and highly dependent on the mother for several months.

There are some unusual reproductive and parenting habits among insectivorans. The female lesser hedgehog tenrec (Echinops telfairi), for example, emits odors during the mating season that cause males to secrete a milky white substance from glands near the eyes. Their mating ritual can last several hours, as it does among certain species of Erinaceinae (spiny hedgehogs). The male hedgehog tenrec stays with his mate up to a few hours before young are born, then he leaves and stays away as long as the young are dependent on their mother. The male spiny hedgehog must be persistent in his courtship as he often ends up chasing after his mate for several hours before she allows him to mount. The female spiny hedgehog flattens its spines during mating, if she is receptive. Because the spines are slippery, the male must hold on to his mate's shoulder with his teeth. Shrews are known for their antagonistic conduct towards one another, even during mating. Among many shrews, exposure to a conspecific (member of the same species) immediately triggers aggressive behavior. The sexual odors emitted by both parties during courtship eventually overpower the tendency towards violence, allowing copulation to take place.

The offspring of the white-toothed shrew (Crocidura leu-codon), and musk shrews (Suncus murinus) or pygmy shrews (Sorex hoyi)—anywhere from three to seven at a time—are led by their mother in line formation, also known as caravaning. The first young shrew grabs a mouthful of hair right above its mother's tail with its teeth. The siblings follow the example with each other down the line.

Conservation

The World Conservation Union (IUCN) carried out species status assessments in 1996. Over one third (39%) of Insectivora species were placed on the Red List. Of those, 21% were Critically Endangered; 26.5% were Endangered;40.5% were Vulnerable; 3% were Lower Risk/Near Threatened; 3.5% are Extinct; and 5% were Data Deficient. The majority of these Red-Listed species are from sub-Saharan Africa, south and Southeast Asia, and east Asia.

The reason why so many species worldwide are under threat is simple: human population growth. The major causes for the decline of whole species and genera, according to the IUCN and most conservation groups worldwide, are believed to be human-induced habitat loss, degradation, and fragmentation. Land clearing, logging, slash and burn, increased agriculture, and its widespread use of toxic fertilizers, pesticides and herbicides—all of these practices take a toll on the above ground and fossorial insectivores. Pollution of fresh water resources—springs, steams, rivers, ponds, and lakes—as well as clearing of banks, the construction of hydroelectric dams and canals, and the drainage of wetlands are greatly contributing to the reduction in numbers of aquatic species. Introduction of non-native plant and animal species are also a contributing factor to the decline of certain insectivores.

Because so little is known about the great majority of insectivores—their behavior, reproductive biology, social organization, migratory movements, and general ecology—it is difficult to identify strategies that could help predict potential threats, so as to design effective conservation plans. There are many specialist groups, however, the most active of which work under the auspices of the IUCN, dedicated to reversing the negative trend affecting the survival of mammals. The Internet allows the members of these groups to share information

easily with each other and with conservation groups that are in a position to apply the knowledge obtained to studies and projects underway worldwide.

Significance to humans

Insectivores are secretive, nocturnal, shy, and for most humans fall into neither the cute and cuddly nor the big and scary attention-generating categories. A few individual insectivore species, however, have been singled out for attention. The greater hedgehog tenrec (Setifer setosus), for example, is probably the most recognizable of the insectivores. This creature is easy to keep as a pet and has a large enthusiastic following. Hedgehogs are also important in research on diseases such as foot and mouth disease, yellow fever, and influenza. Old home remedies sometimes called for hedgehog blood, entrails or ashes. Mixed with pitch or resin, the burned hindquarters supposedly helped cure baldness. The hedgehog was used to predict the weather and if buried under a building was thought to bring good luck. The Romans kept hedgehogs as pets during the fourth century b.c. and they remain domesticated to this day. Other uses over the years for this spiny insectivore include: consumption of its meat, use of its spiny coat to card wool, deterring horses prone to leaning, and as a tool to help wean calves.

Shrews and moles are the next insectivores most familiar to humans. The armored shrew is important to some Africans who believe that any part of the animal will act as a talisman to save them from peril. Mummified shrews dating back to the twenty-seventh dynasty (ca. 400 b.c.) were discovered in a ceremonial animal tomb near Thebes, Egypt. According to archaelogists, shrews played an important part in the religion of ancient Egyptians as representatives of nocturnal creatures those who "came from the dark." In the West, the shrew's biggest contributions to culture are most likely linguistic and literary as in Shakespeare's The Taming of the Shrew. The term "shrew" is used to describe a quarrelsome, nagging, irritable woman because the little mammal was believed to have a poisonous bite. Beatrix Potter's The Tale of Mrs. Tiggy-Winkle and Kenneth Grahame's The Wind in the Willows have immortalized the hedgehog and the mole, respectively, in their children's stories. John Le Carre, among others, has made sure that moles remain infamous in the memory of all spy story buffs. In the East, shrews are called "chien shu" in Mandarin and "chin chih" in Taiwanese. Both terms mean "money" and "mouse" or "rat." The noise that shrews make sounds like the Chinese pronunciation of money. In Taiwan, a shrew in one's home is not killed as the presence of the small animal means money is coming. If the shrew is killed the source of the fortune is eliminated.

The economic benefits to humans offered by insectivores are few. Mole skin from the European mole (Talpa europaea) was a popular trim for women's cloaks during some time. The skin of the Russian desman (Desmana moschata) was also used for trimmings and perfume manufacturers used the strong musk from the glands located under the desman's tail. The common tenrec has been an important food source for the human inhabitants of Madagascar for thousands of years.

Very few insectivores are labeled as pests. Poultry farmers are not fond of hedgehogs that readily eat eggs and chickens. Ticks, mites, and fleas thrive on hedgehogs and these mammals are also known to carry and transmit ringworm, influenza, yellow fever, Salmonella eteritidis, leptospirosis, and foot and mouth disease. While some insectivores have rodent-like habits when it comes to humans, i.e., noisy, smelly, intrusive, and destructive, they make up for it by destroying insects and even the real rodent pests. Several mole species are not very popular with gardeners because of the damage they can cause with their tunnels.

Insectivores make meaningful contributions to the environment. A majority of the species help keep insects under control. The short-tailed shrew, for example, keeps a check on insect crop pests, especially the larch sawfly, with its voracious appetite. This shrew, along with other insectivores, including Sclater's golden mole (Chlorotalpa sclateri), destroy snails and mice that damage crops and are pests to humans. Fossorial insectivores do a good job aerating the soil. The burrowing and digging done by desert-dwelling fossorial insectivores in desert areas helps the vegetation in harsh sandy areas to flourish. The hedgehog controls vermin and is a helpful scavenger. And let us not forget the insectivores' invaluable contribution to the food chain.

Resources

Books

Butler, P. M. Studies in Vertebrate Evolution. Edinburgh: Oliver and Boyd, 1972.

Kingdon, Jonathan. East African Mammals: An Atlas of Evolution in Africa. Part A, Insectivores and Bats. Chicago: University of Chicago Press, 1984.

Nowak, R. Walker's Mammals of the World, 6th ed. Baltimore: Johns Hopkins University Press 1999.

Vaughan, T. A., J. M. Ryan, and N. J. Czaplewski. Mammalogy, 4th ed. Philadelphia: Saunders, 2000.

Yates, T. L. Order and Families of Recent Mammals. New York: John Wiley and Sons, 1984.

Periodicals

Anderson, I. "Uprooting our family tree—Ancient Australian teeth are upsetting cherished ideas about the evolution of mammals." New Scientist 156, 2110 (1997): 4.

Catania, K. C. "Epidermal sensory organs of moles, shrew-moles, and desmans: a study of the family Talpidae with comments on the function and evolution of Eimer's organ." Brain, Behavior and Evolution 56 (2000): 146–174.

Hecht, J. "Small bite makes big impression." New Scientist 160, 2155 (1998): 15.

Leszek, R., and E. Jancewicz. "Prey size, prey nutrition, and food handling by shrews of different body sizes." Behavioral Ecology 13, no. 2 (2000): 216–223.

Mouchaty, S. K., A. Gullberg, A. Janke, and U. Arnason. "The phylogenetic position of the Talpidae within Eutheria based on analysis of complete mitochondrial sequences." Molecular Biology and Evolution 17, no. 1 (2000): 60–67.

——. "Phylogenetic position of the tenrecs (Mammalia: Tenrecidae) of Madagascar based on analysis of the complete mitochondrial genome sequence of Echinops telfairi." Zoologica Scripta 29, no. 4 (2000): 307–317.