Myosorex varius
forest shrew

Myosorex varius is a forest shrew that is native to the Ethiopian region of the world. The shrew is endemic to the southern portion of Africa. Of all the 15 different species of South African forest shrews, M. varius is one of the most widely distributed species. It can be found in Limopopo Province, Gauteng, Mpumalanga, the north-eastern Free State, throughout KwaZulu-Natal, Eastern and Western Cape, where M. varius is found inland to Murraysberg and Beaufort West, as well as coastally from Western Cape to the northwestern parts of North Cape. They are found as far north as Pot Nolloth. This species is also found in Lesotho and the Highveld and Middleveld regions of Swaziland. The areas encompass much of the southern region of Africa. Myosorex varius is sympatric throughout much of its geographic range with Myosorex cafer. (Apps, 2000; Rowe-Rowe and Meester, 1982; Skinner and Chimimba, 2005)

Myosorex varius is a terrestrial mammal that can be found at elevations ranging from sea level to 1,740 m of elevation. It is called the forest shrew because it is most often found in forest habitats. Myosorex varius can be found in moist, densely vegetated areas, ranging from primary forest to montane grassland to the Highveld, which is a high plateau region of inland South Africa. It is often the first small animal to appear after a burn. (Apps, 2000; Rowe-Rowe and Meester, 1982; Skinner and Chimimba, 2005)

Myosorex varius ranges from dark grey to a brown. Venter hair tends to be grey with white tips and its feet are an off-white color. Its tail is dark-brown dorsally and pale underneath. Total body length averages 12.6 cm, with an average tail length of 4.3 cm, which is about 46% of its entire body length. Mysorex varius is sexually dimorphic in the KwaZulu-Natal/Drankensberg region, with males being significantly larger than females in regards to total mass as well as head and body size; however, populations in other regions, such as Eastern Cape, exhibit little to no sexual dimorphism. Body-size is correlated to habitat altitude, as higher altitude individuals tend to be much smaller than those resident to lower altitudes. Myosorex varius is endothermic and bilaterally symmetric. It has a basal metabolic rate of 38.9 J/g hr. The forest shrew’s body temperature is highly variable, ranging from 33.2 to 38.3 degrees C. It can withstand temperatures as low as 6 degrees C by increasing heat production. (Apps, 2000; Brown, et al., 1997; Skinner and Chimimba, 2005)

The mating system of Myosorex varius has not been documented. Single breeding pairs are often found in nests. Many species of shrew (e.g., least shrews) are promiscuous. Myosorex varius has never been successfully bred in captivity. (Apps, 2000; Bedford, et al., 1998; Bedford, et al., 2004)

Myosorex varius breeds seasonally from September to March, which correlates to the wet seasons of spring and summer. Although it is known to be a seasonal breeder, pregnant females are found year round, with the exception of December. At higher altitudes, breeding season may be delayed for a month due to lower ambient temperatures. Males court female by chasing and grabbing potential mates by the loose skin surrounding the neck. Litters range in size from 2 to 5 pups, with an average of 3. Neonates weigh about 1g at birth. For the first 5 days after parturition, offspring nipple cling. Then, they begin caravanning, which initially consists of the offspring grabbing the mother’s fur with their teeth in a cluster. At about 10 to 13 days old, young form a chain by grabbing ahold of one another, while the lead pup grabs ahold of the mother. Weaning is complete by 20 to 25 days after birth. Females exhibit post-partum estrus and often comes into heat within hours after giving birth. (Apps, 2000; Bedford, et al., 1998; Bedford, et al., 2004)

Prior to weaning, Myosorex varius females provide food and protection for their offspring. Once pups are fully weaned, they become independent of their mother's care. (Apps, 2000)

This African forest shrew has a lifespan ranging from 12-16 months in the wild. (Apps, 2000; Rowe-Rowe and Meester, 1982)

African forest shrews are predominantly nocturnal, showing a sharp rise in activity at dusk and sharp decline at dawn. However, diurnal activities have also been documented occasionally active during the daytime. Evidence suggests that African forest shrews are nocturnal during the summer months but becomes diurnal during mid-winter. This allows the shrew to be in its warm nest during the coldest hours of the night. During the day, they stay in their nests for only a couple hours at a time, leaving for brief periods to find food and defecate. The feces of the forest shrews is highly pungent. When the shrew does leave its nest, it is extremely cautious and remarkably aggressive. African forest shrews are active burrowers, using their front claws and their long pointed snout. The insides of their burrows and nests are spherical. Forest shrews often modify abandoned burrows of mole rats, rather than excavate their own. If they do create their own nest, it is typically a shallow nest. Nests are constructed from grass, and contain two to four entrances. Typically, nests contain a single breeding pair of shrews. In general, shrews sleep on their bellies with their head tucked under their chest and their feet and tail tucked in under the body. Forest shrews, like most soricids is territorial and aggressive. (Apps, 2000)

There is no information available regarding the average home range size of African forest shrews. (Apps, 2000; Wirminghaus and Perrin, 1992)

Communication in African Forest shrews is limited. Nesting pairs chatter to each other, and when alarmed or fighting, they may produce a sharp squeak. Forest shrews rely on acoustic, visual, tactile, and chemical cues to perceive their environment. Courting behavior between potential mates consists of a males chasing and catching mates by the nape. Males rely on their sense of smell to determine whether a female is in estrus or not. (Apps, 2000; Skinner and Chimimba, 2005)

Myosorex varius is insectivorous. It is considered an opportunistic feeders and eats most invertebrates it encounters. Evidence suggests that it feeds on at least 7 different types of arthropods including crustaceans, millipedes and centipedes, and arachnids. It frequently drinks small amounts of water. When eating small prey, it first beheads the arthropod and then rapidly bites the insect down the abdomen before beginning to actually eat the animal. When consuming large prey, M. varius throws the insect into the air and breaks off any legs or hind limbs by jerking or twisting them off and then beheads and bites the insect. Cannibalism has been documented in M varius and occasionally consumes carrion of conspecifics or rodents. In captivity, it has been known to eat plants, however, this has never been observed in wild populations. (Apps, 2000; Bedford, et al., 2004; Wirminghaus and Perrin, 1992)

The main predator of forest shrews is barn owls. However, water mongooses, striped weasels and striped polecats are also significant predators as well. To avoid predation, they only leave their nest to obtain food and to defecate. When they do leave their nest, it only leaves for small amounts of time to avoid contact with predators. When in danger, they let out a sharp squeak to alert their nest mate of the potential threat. (Apps, 2000)

Myosorex varius acts as prey to numerous larger mammals. It also serves as a predator to insects and other invertebrates, and as a result, may help control insect pest species. It also acts as a scavenger and eats carrion from dead rodents and conspecifics. It creates creates habitat via shallow burrows in the soil and under rocks. Disturbing soil helps to release nitrogen contents to the surface of the soil, allowing for a diversity of plants to grow. Parasites of this species have not been documented. (Apps, 2000; Wirminghaus and Perrin, 1992)

As an insectivore, Myosorex varius likely helps control insect pest species throughout its geographic range. (Apps, 2000)

There are no known adverse effects of Myosorex varius on humans.

Myosorex varius is categorized as a species of least concern by the IUCN's Red List of Threatened Species and all other known conservation organizations. Population trends are stable, and there are no major threats to the long-term persistence of this species.