Monday, 9 September 2013

New species of Hero Shrew from Équateur Province, Democratic Republic of the Congo.

Shrews (Soricidae) are small insectivorous or omnivorous Mammals found across much of the world, the only major landmasses from which they are absent being Australia, New Zealand and New Guinea, though they are restricted to the northwest of South America, suggesting they are recent arrivals in that continent. They are small animals, superficially resembling Mice, though they are not closely related to Rodents, with the largest species reaching only about 15 cm. Shrews are notoriously verocious eaters, consuming around 80-90% of their bodyweight each day. They also reproduce extremely rapidly, with females of many species able to produce up to ten litters of young a year, though they seldom live more than 30 months. The White-toothed Shrews (there are also Red-toothed Shrews) are found across Eurasia and Africa. They are the most diverse group of Shrews, and contain both the largest and smallest species in the group. Hero Shrews, Scutisorex, are White Toothed Shrews from Central Africa, with an exceptionally enlarged and fortified spine, which enables them to bear exceptionally heavy loads, though the exact use of such an adaptation to a small insectivorous Mammal is unclear.

In a paper published in the journal Biology Letters on 24 July 2013, a team of scientists led by William Stanley of the Field Museum of Natural History in Chicago describe a new species of Hero Shrew from Équateur Province in the Democratic Republic of the Congo.

The new species is named Scutisorex thori, the Thor's Hero Shrew, after Thorvald ‘Thor’ Holmes of the Humboldt State University Vertebrate Museum, though the authors admit that they are also alluding to the Norse god of the same name. Scutisorex thori is a large (~48 g) grey Shrew with a short tail and a stout skull and reinforced spine. It is slightly less robust than the previously described Armored Hero Shrew (Scutisorex somereni).

The Thor's Hero Shrew, Scutisorex thori. William Stanley.

Stanley et al. theorize that the exceptional spine of Hero Shrews might be use to leverage its way between the trunk and leaf bases of mature palm trees, in order to gain access to invertebrate prey that would be otherwise unaccessible, noting that the animals are often found between the dead leaf bases and living palm trunks in the swampy palm forests near Tandala in Équateur Province, where the local population regularly find them while hunting for nutritious Beetle grubs. They further suggest that the Shrews could also potentially more logs or other heavy objects in order to gain access to Worms and other invertebrates.

The spines and rib cages of (i) the African Giant Shrew, Crocidura olivieri, (ii) the Armored Hero Shrew, Scutisorex somereni, and (iii) the Thor's Hero Shrew Scutisorex thori. Stanley et al. (2013).

Scutisorex thori is known only from a single location in seasonally flooded lowland forestfrom the area of Baleko near the Tshuapa River in Équateur Province, Democratic Republic of Congo. This is outside of the range of the Scutisorex somereni, which is known from Équateur Province, but but north of the Congo River and is more abundant in the northeastern part of the country, as well as in Uganda, Rwanda and Burundi.


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