Based on studies in: England: Oxfordshire, Wytham Wood (Forest) USA: Illinois (Forest) USA: Montana (Tundra)
This list may not be complete but is based on published studies.
A. C. Twomey, The bird population of an elm-maple forest with special reference to aspection, territorialism, and coactions, Ecol. Monogr. 15(2):175-205, from p. 202 (1945).
G. C. Varley, The concept of energy flow applied to a woodland community. In: Animal Populations in Relation to Their Food Resources, A. Watson, Ed. (Blackwell Scientific, Oxford, England, 1970), pp. 389-401, from p. 389.
D. L. Pattie and N. A. M. Verbeek, Alpine birds of the Beartooth Mountains, Condor 68:167-176 (1966); Alpine mammals of the Beartooth Mountains, Northwest Sci. 41(3):110-117 (1967).
Myers, P., R. Espinosa, C. S. Parr, T. Jones, G. S. Hammond, and T. A. Dewey. 2006. The Animal Diversity Web (online). Accessed February 16, 2011 at http://animaldiversity.org. http://www.animaldiversity.org
Barcode of Life Data Systems (BOLD) Stats Specimen Records:2957 Specimens with Sequences:2387 Specimens with Barcodes:2245 Species:130 Species With Barcodes:113 Public Records:1353 Public Species:58 Public BINs:77
Although its external appearance is generally that of a long-nosed mouse, a shrew is not a rodent, as mice are, and is in fact more closely related to moles. Shrews have sharp, spike-like teeth, not the familiar gnawing front incisor teeth of rodents.
All shrews are comparatively small, most no larger than a mouse. The largest species is the Asian house shrew (Suncus murinus) of tropical Asia, which is about 15 cm long and weighs around 100 grams; several are very small, notably the Etruscan shrew (Suncus etruscus), which at about 3.5 cm and 2 grams is the smallest living terrestrial mammal.
Water shrew skeleton
In general, shrews are terrestrial creatures that forage for seeds, insects, nuts, worms and a variety of other foods in leaf litter and dense vegetation, but some specialise in climbing trees, living underground, living under snow or even hunting in water. They have small eyes, and generally poor vision, but have excellent senses of hearing and smell. They are very active animals, with voracious appetites. Shrews have an unusually high metabolic rate, above that expected in comparable small mammals. Shrews typically eat 80–90% of their own body weight in food daily.
They do not hibernate, but are capable of entering torpor. In winter, many species undergo morphological changes that drastically reduce their body weight. Shrews can lose between 30% and 50% of their body weight, shrinking the size of bones, skull and internal organs.
Whereas rodents have gnawing incisors that grow throughout life, the teeth of shrews wear down throughout life, a problem made more extreme because they lose their milk teeth before birth, and therefore have only one set of teeth throughout their lifetimes. Apart from the first pair of incisors, which are long and sharp, and the chewing molars at the back of the mouth, the teeth of shrews are small and peg-like, and may be reduced in number. The dental formula of shrews is:3.1.1-3.31-2.0-1.1.3
Shrews are fiercely territorial, driving off rivals, and only coming together to mate. Many species dig burrows for caching food and hiding from predators, although this is not universal.
Female shrews can have up to 10 litters a year; in the tropics, they breed all year round; in temperate zones, they only stop breeding in the winter. Shrews have gestation periods of 17–32 days. The female often becomes pregnant within a day or so of giving birth, and lactates during her pregnancy, weaning one litter as the next is born. Shrews live 12 to 30 months.
Shrews are unusual among mammals in a number of respects. Unlike most mammals, some species of shrew are venomous. Shrew venom is not conducted into the wound by fangs, but by grooves in the teeth. The venom contains various compounds, and the contents of the venom glands of the American short-tailed shrew are sufficient to kill 200 mice by intravenous injection. One chemical extracted from shrew venom may be potentially useful in the treatment of high blood pressure, while another compound may be useful in the treatment of some neuromuscular diseases and migraines. The saliva of the northern short-tailed shrew (Blarina brevicauda) contains the peptidesoricidin, which has been studied for use in treating ovarian cancer. Also, along with the bats and toothed whales, some species of shrews use echolocation. Unlike most other mammals, shrews lack zygomatic bones (also called the jugals), so have incomplete zygomatic arches.
The only terrestrial mammals known to echolocate are two genera (Sorex and Blarina) of shrews and the tenrecs of Madagascar. These include the vagrant shrew (Sorex vagrans), the common or Eurasian shrew (Sorex araneus), and the northern short-tailed shrew (Blarina brevicauda). The shrews emit series of ultrasonic squeaks. The nature of shrew sounds, unlike those of bats, are low amplitude, broadband, multiharmonic and frequency modulated. They contain no "echolocation clicks" with reverberations and would seem to be used for simple, close-range spatial orientation. In contrast to bats, shrews use echolocation only to investigate their habitats rather than additionally to pinpoint food.
Except for large and thus strongly reflecting objects, such as a big stone or tree trunk, they will probably not be able to disentangle echo scenes, but rather derive information on habitat type from the overall call reverberations. This might be comparable to human hearing whether one calls into a beech forest or into a reverberant wine cellar.
Hutterer, Rainer (1976). Deskriptive und vergleichende Verhaltensstudien an der Zwergspitzmaus, Sorex minutus L., und der Waldspitzmaus, Sorex araneus L. (Soricidae - Insectivora - Mammalia) (Ph.D. Thesis) (in German). Univ. Wien. OCLC716064334.
Hutterer, R.; Vogel, P.; Frey, H.; Genoud, M. (1979). "Vocalization of the shrews Suncus etruscus and Crocidura russula during normothermia and torpor". Acta Theriologica 24 (21): 267–71.
Irwin, D.V., Baxter, R.M. 1980. Evidence against the use of echolocation by Crocidura f. flavescens (Soricidae). Säugetierk. Mitt. 28(4): 323.
Kahmann, H.; Ostermann, K. (1951). "Wahrnehmen und Hervorbringen hoher Töne bei kleinen Säugetieren" [Perception of production of high tones by small mammals]. Experientia (in German) 7 (7): 268–269. doi:10.1007/BF02154548. PMID14860152.
Köhler, D.; Wallschläger, D. (1987). "Über die Lautäußerungen der Wasserspitzmaus, Neomys fodiens (Insectivora: Soricidae)" [On vocalization of the european water shrew Neomys fodiens (Insectivora: Soricidae)]. Zoologische Jahrbücher (in German) 91 (1): 89–99.
Sales, G., Pye, D. 1974. Ultrasonic communication by animals. London.