- Suisun Shrew
Taxobox
name = Suisun Shrew
status = VU
regnum =Animal ia
phylum = Chordata
classis =Mammal ia
ordo =Soricomorpha
familia =Soricidae
genus = "Sorex "
species = "S. ornatus"
subspecies = "S. o. sinuosus"
trinomial = "Sorex ornatus sinuosus"The Suisun Shrew ("Sorex ornatus sinuosus)", is a
subspecies of theOrnate Shrew that occurs in the tidalmarsh es of the northern shores of San Pablo andSuisun Bay s (northern arms of theSan Francisco Bay , as far east asGrizzly Island and as far west as the mouth ofSonoma Creek in the vicinity ofTubbs Island . ["Sorex ornatus sinuosus", Williams, Ann. Carnegie Mus., 48:426 (1986)] [ "Environmental Assessment of the Columbus Parkway Widening between Ascot Parkway and the Northgate Development, Vallejo", Earth Metrics Inc. Report 7853, California State Clearinghouse, Sept, 1989] ["Sorex sinuosus": Type Locality: Grizzly Island, Suisun Bay, Solano Co., California", Grinnell, Univ. California Publ. Zool., 10:181 (1913) ] Brown and Rudd redefined the western boundary of the range from a prior designation of thePetaluma River . The Suisun Shrew has been designated as a "Species of Concern" by the U.S. Government and a "Mammalian Species of Special Concern" by the State of California.Morphology
"S. o. sinuosus" is a smallish
rare species of soricine shrew that is distinguished from other vicinity andsympatric shrew taxa by having darkerpelage ; its occurrence is strictly limited to tidal marshes near San Pablo and Suisun Bays, a fact that makes identification and differentiation straightforward. [Jesus E. Maldonado, Carles VilÀ, Robert K. Wayne, "Tripartite genetic subdivisions in the ornate shrew ("Sorex ornatus")", Molecular Ecology 10 (1), 127–147 (2001)] The Suisun Shrew body mass ranges from 4.5 to 6.8 grams, with a total length (including tail) of 98 to 106 millimeters; The tail structure itself is between 35 and 44 millimeters in length [Jameson, E.W., and Hans J. Peeters. "California Mammals" Berkeley (1988)University of California Press.] . Coloration is usually black, sometimes metallic. "S. o. sinuosus" has an elongatedskull shape, that is relatively narrow and fragileHabitat
The Suisun Shrew occurs in tidal
marsh es characterized in order of decreasing tolerance toinundation by California Cordgrass, "Spartina foliosa ";Glasswort , "Salicornia ambigua"; and Hairy gumweed, "Grindelia cuneifolia", as well as brackish marshes dominated by California Bulrush, "Scirpus californicus", and Common Cattail, "Typha latifolia ". This animal needs dense, low-lying cover where smallinvertebrate s are abundant. Structure of the plant community, not species diversity, is the greatest determinant in shrew occupancy.Driftwood and otherdetritus above themean high-tide line is required for nesting and foraging sites. Upland habitats, contiguous to the marshes, offering sufficient cover and sources of food to sustain shrews during prolonged flooding of marshes and dikes are also essential.As recently as the mid 1800s the San Pablo and Suisun bays were completely perimetered by with salt and brackish water marshes, but by the year 1990 these
wetland s are broken into a few small, isolated units. The marshes of Suisun Bay, chiefly consisting of theNapa Sonoma Marsh are the most expansive, but Suisun Shrew populations there are threatened by human expansion and by management of the marshes to favour "Scirpus ". Current habitat area is comparatively much less in the San Pablo Bay marshland. Very few local extant tidal marshes have true undisturbed marshvegetation , and even fewer border significant upland areas where marshland species can seek refuge fromflood ing. The Suisun Shrew inhabits a smaller range and is more limited in the habitats it occupies than are theSalt Marsh Harvest Mouse , for example.Behavior
A lifespan of 16 months is considered to apply to most shrew taxa, with females surviving slightly longer than males. [Richard F. Johnston, Robert L. Rudd, "Breeding of the Salt Marsh Shrew", Journal of Mammalogy, Vol. 38, No. 2 (May, 1957)] Preferred food sources for this organism are small insects and other
invertebrate s. [David C. Zeiner et al., "California Wildlife: Volume III, Mammals", State of California Department of Fish and Game (1990)] The normal birth season occurs during the spring and summer breeding season, with a typicalgestation period of 21 days. The litter size may vary between two and nine individuals While females are capable of producing two litters within a year, one litter per annum is the norm. Another 21 days ofaltricial dependency occurs prior toweaning . It known that some individuals under 12 months in age breed in late summer. During winter, most shrews undergo a dramatic decrease in body mass, and second year individuals typically die at this time. This wintertime body mass decrease is known as theDehnel phenomenon , an adaptation to survive winter with lower food intake. In most species, winter body mass is 70 percent of first year body mass and 50 percent of second year body mass. Body length is correspondingly reduced due to the reduction of invertebral discs. Theskull itself as well askidney s and some other internal organs are actually reduced in size so as to require less nutrition intake for survival. In the spring, shrews increase body mass and equilibrate to a slightly higher body mass than that of the previous summer. A large influx of mostly adult male shrews to the population locus occurs. Areal extent of the population can double. The once stable winterhome range mosaic is thereby disrupted, frequently resulting in intraspecificaggression . Breeding then begins anew, occurring in dense, harem-structured population foci within a narrow band of preferred habitat, from April through October. Young females will often continue to live near their birthplace, while young males often disperse, due to the presence of other dominant males. The young males will remain near their original colony, probably in suboptimalhabitat .Conservation
The Suisun Shrew is a
rare species afforded protection by the U.S. Federal Government and by the State of California. Besides designation as a "Species of Special Concern", California has enacted the "Suisun Marsh Preservation Act" to establish specific protection measures for this habitat of the Suisun Shrew as well as theCalifornia Clapper Rail ,Salt Marsh Harvest Mouse and other sensitive species. [http://www.bcdc.ca.gov/index.php?p=80&more=1&page=3] Many marsh protection items serve to protect a variety of organisms, some of which are threatened and some of which are relatively more common.pecific occurrences
The following locations have been noted of wild occurrences of the Suisun Shrew: ["Profile for the Suisun Shrew", California department of Fish and Game (1986)]
*0.5 mile northeast ofCordelia Salt Marsh, Solano County
*Gray Goose Duck Club, 1.5 mi Southwest ofSuisun City
*Grizzly Island,Suisun Bay
*Honker Gun Club, near Dutton,Van Sickle Island
*3.0 miles east ofMare Island Bridge , adjacent toWhite Slough andCalifornia Route 37
*2.7 miles west junction of Napa Road and California Route 37 along Route 37)
*8.0 miles north ofRio Vista
*Sears Point Road, 6 miles northwest of Vallejo
*Sears Point Road, 8 mi northwest of Vallejo
*Sears Point Road, San Pablo Bay
*Southhampton Bay , near the Solano County Landfill
*Southhampton Bay
*Suisun City, salt marsh adjacent to Cordelia Street
*Suisun marshes, periphery of Grizzly Island
*3.0 miles northwest of Vallejo
*1.0 miles south of Dutton, Van Sickle IslandReferences
External links
* [http://zipcodezoo.com/Animals/S/Sorex_ornatus_sinuosus.asp "Sorex ornatus sinuosus" Literature]
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