Suisun Shrew
Encyclopedia
Sorex ornatus sinuosus, the Suisun Shrew or Suisun ornate shrew, is a subspecies
of the Ornate Shrew
that occurs in the tidal marsh
es of the northern shores of San Pablo and Suisun bay
s (northern arms of the San Francisco Bay
, as far east as Grizzly Island and as far west as the mouth of Sonoma Creek
in the vicinity of Tubbs Island. Brown and Rudd redefined the western boundary of the range from a prior designation of the Petaluma 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.
of soricine shrew that is distinguished from other vicinity and sympatric shrew taxa by having darker pelage; its occurrence is strictly limited to tidal marshes near San Pablo and Suisun bays, a fact that makes identification and differentiation straightforward. The 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. Coloration is usually black, sometimes metallic. S. o. sinuosus has an elongated skull
shape, that is relatively narrow and fragile
es characterized in order of decreasing tolerance to inundation 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 small invertebrate
s are abundant. Structure of the plant community, not species diversity, is the greatest determinant in shrew occupancy. Driftwood
and other detritus
above the mean 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-19th century, the San Pablo and Suisun bays were completely perimetered by 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 the Napa Sonoma Marsh
are the most expansive, but S. o. sinuosus 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 marsh vegetation
, and even fewer border significant upland areas where marshland species can seek refuge from flood
ing. S. o. sinuosus inhabits a smaller range and is more limited in the habitats it occupies than are the Salt Marsh Harvest Mouse
, for example.
s. The normal birth season occurs during the spring and summer breeding season, with a typical gestation
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 of altricial
dependency occurs prior to weaning
. 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 the Dehnel 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. The skull
itself as well as kidney
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 winter home range
mosaic is thereby disrupted, frequently resulting in intraspecific aggression
. 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 suboptimal habitat
.
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 S. o. sinuosus as well as the California 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.
Subspecies
Subspecies in biological classification, is either a taxonomic rank subordinate to species, ora taxonomic unit in that rank . A subspecies cannot be recognized in isolation: a species will either be recognized as having no subspecies at all or two or more, never just one...
of the Ornate Shrew
Ornate Shrew
The Ornate Shrew, Sorex ornatus, is a species of mammal in the family Soricidae. It is endemic to Baja California in Mexico and California in the United States. The Tule Shrew is a likely extinct subspecies; it is only known by four specimens collected in 1905. Other subspecies include the "Suisun...
that occurs in the tidal marsh
Marsh
In geography, a marsh, or morass, is a type of wetland that is subject to frequent or continuous flood. Typically the water is shallow and features grasses, rushes, reeds, typhas, sedges, other herbaceous plants, and moss....
es of the northern shores of San Pablo and Suisun bay
Suisun Bay
Suisun Bay is a shallow tidal estuary at in northern California, USA. It lies at the confluence of the Sacramento and San Joaquin Rivers, forming the entrance to the Sacramento-San Joaquin River Delta, an inverted river delta...
s (northern arms of the San Francisco Bay
San Francisco Bay
San Francisco Bay is a shallow, productive estuary through which water draining from approximately forty percent of California, flowing in the Sacramento and San Joaquin rivers from the Sierra Nevada mountains, enters the Pacific Ocean...
, as far east as Grizzly Island and as far west as the mouth of Sonoma Creek
Sonoma Creek
Sonoma Creek is a stream in northern California. It is one of two principal drainages of southern Sonoma County, California, with headwaters rising in the rugged hills of Sugarloaf Ridge State Park and discharging to San Pablo Bay, the northern arm of San Francisco Bay. The watershed drained by...
in the vicinity of Tubbs Island. Brown and Rudd redefined the western boundary of the range from a prior designation of the Petaluma River
Petaluma River
The Petaluma River is a river in the California counties of Sonoma and Marin that becomes a tidal slough near its mouth. It springs from farmlands southwest of Cotati and flows generally southward through Petaluma's old town and of tidal marshes to end in northwest San Pablo Bay.-History:The word...
. 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 speciesRare species
A rare species is a group of organisms that are very uncommon or scarce. This designation may be applied to either a plant or animal taxon, and may be distinct from the term "endangered" or "threatened species" but not "extinct"....
of soricine shrew that is distinguished from other vicinity and sympatric shrew taxa by having darker pelage; its occurrence is strictly limited to tidal marshes near San Pablo and Suisun bays, a fact that makes identification and differentiation straightforward. The 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. Coloration is usually black, sometimes metallic. S. o. sinuosus has an elongated skull
Skull
The skull is a bony structure in the head of many animals that supports the structures of the face and forms a cavity for the brain.The skull is composed of two parts: the cranium and the mandible. A skull without a mandible is only a cranium. Animals that have skulls are called craniates...
shape, that is relatively narrow and fragile
Habitat
S. o. sinuosus occurs in tidal marshMarsh
In geography, a marsh, or morass, is a type of wetland that is subject to frequent or continuous flood. Typically the water is shallow and features grasses, rushes, reeds, typhas, sedges, other herbaceous plants, and moss....
es characterized in order of decreasing tolerance to inundation by California Cordgrass
Cordgrass
Spartina, commonly known as cordgrass or cord-grass, is a genus of 14 species of grasses in the family Poaceae. They are native to the coasts of the Atlantic Ocean in western and southern Europe, northwest and southern Africa, the Americas and the southern Atlantic Ocean islands; one or two species...
, Spartina foliosa
Spartina foliosa
Spartina foliosa is a species of grass known by the common name California cordgrass. It is native to the salt marshes and mudflats of coastal California and Baja California, especially San Francisco Bay. It is a perennial grass growing from short rhizomes. It produces single stems or clumps of...
; Glasswort
Glasswort
Salicornia is a genus of succulent, halophyte plants that grow in salt marshes, on beaches, and among mangroves. Salicornia species are native to North America, Europe, South Africa, and South Asia...
, Salicornia ambigua; and Hairy Gumweed, Grindelia
Grindelia
Grindelia is a genus of plants native to the Americas belonging to the family Asteraceae, . G. squarrosa, a plant with bright yellow flowers indigenous to much of the United States, is commonly called curlycup gumweed. G. robusta, found in the western states, is a coastal scrub bush that is...
cuneifolia, as well as brackish marshes dominated by California Bulrush, Scirpus
Scirpus
The plant genus Scirpus consists of a large number of aquatic, grass-like species in the family Cyperaceae , many with the common names club-rush or bulrush . Other common names are deergrass or grassweed.The genus has a cosmopolitan distribution, and grows in wetlands and moist soil...
californicus, and Common Cattail, Typha latifolia
Typha latifolia
Typha latifolia is a perennial herbaceous plant in the genus Typha. It is found as a native plant species in North and South America, Europe, Eurasia, and Africa...
. This animal needs dense, low-lying cover where small invertebrate
Invertebrate
An invertebrate is an animal without a backbone. The group includes 97% of all animal species – all animals except those in the chordate subphylum Vertebrata .Invertebrates form a paraphyletic group...
s are abundant. Structure of the plant community, not species diversity, is the greatest determinant in shrew occupancy. Driftwood
Driftwood
Driftwood is wood that has been washed onto a shore or beach of a sea or river by the action of winds, tides, waves or man. It is a form of marine debris or tidewrack....
and other detritus
Detritus
Detritus is a biological term used to describe dead or waste organic material.Detritus may also refer to:* Detritus , a geological term used to describe the particles of rock produced by weathering...
above the mean 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-19th century, the San Pablo and Suisun bays were completely perimetered by salt and brackish water marshes, but by the year 1990 these wetland
Wetland
A wetland is an area of land whose soil is saturated with water either permanently or seasonally. Wetlands are categorised by their characteristic vegetation, which is adapted to these unique soil conditions....
s are broken into a few small, isolated units. The marshes of Suisun Bay, chiefly consisting of the Napa Sonoma Marsh
Napa Sonoma Marsh
The Napa Sonoma Marsh is a wetland at the northern edge of San Pablo Bay, which is a northern arm of the San Francisco Bay in California, USA. This marsh has an area of 48,000 acres , of which 13,000 acres are abandoned salt evaporation ponds...
are the most expansive, but S. o. sinuosus populations there are threatened by human expansion
Overpopulation
Overpopulation is a condition where an organism's numbers exceed the carrying capacity of its habitat. The term often refers to the relationship between the human population and its environment, the Earth...
and by management of the marshes to favour Scirpus
Scirpus
The plant genus Scirpus consists of a large number of aquatic, grass-like species in the family Cyperaceae , many with the common names club-rush or bulrush . Other common names are deergrass or grassweed.The genus has a cosmopolitan distribution, and grows in wetlands and moist soil...
. Current habitat area is comparatively much less in the San Pablo Bay marshland. Very few local extant tidal marshes have true undisturbed marsh vegetation
Vegetation
Vegetation is a general term for the plant life of a region; it refers to the ground cover provided by plants. It is a general term, without specific reference to particular taxa, life forms, structure, spatial extent, or any other specific botanical or geographic characteristics. It is broader...
, and even fewer border significant upland areas where marshland species can seek refuge from flood
Flood
A flood is an overflow of an expanse of water that submerges land. The EU Floods directive defines a flood as a temporary covering by water of land not normally covered by water...
ing. S. o. sinuosus inhabits a smaller range and is more limited in the habitats it occupies than are the Salt Marsh Harvest Mouse
Salt Marsh Harvest Mouse
The Salt Marsh Harvest Mouse , also known as the Red-bellied Harvest Mouse and some times called by Saltmarsh Harvest Mouse, is an endangered rodent endemic to the San Francisco Bay Area salt marshes in California. There are two distinct subspecies, both endangered and listed together on federal...
, for example.
Behavior
A lifespan of 16 months is considered to apply to most shrew taxa, with females surviving slightly longer than males. Preferred food sources for this organism are small insects and other invertebrateInvertebrate
An invertebrate is an animal without a backbone. The group includes 97% of all animal species – all animals except those in the chordate subphylum Vertebrata .Invertebrates form a paraphyletic group...
s. The normal birth season occurs during the spring and summer breeding season, with a typical gestation
Gestation
Gestation is the carrying of an embryo or fetus inside a female viviparous animal. Mammals during pregnancy can have one or more gestations at the same time ....
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 of altricial
Altricial
Altricial, meaning "requiring nourishment", refers to a pattern of growth and development in organisms which are incapable of moving around on their own soon after hatching or being born...
dependency occurs prior to weaning
Weaning
Weaning is the process of gradually introducing a mammal infant, either human or animal, to what will be its adult diet and withdrawing the supply of its mother's milk.The process takes place only in mammals, as only mammals produce milk...
. 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 the Dehnel 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. The skull
Skull
The skull is a bony structure in the head of many animals that supports the structures of the face and forms a cavity for the brain.The skull is composed of two parts: the cranium and the mandible. A skull without a mandible is only a cranium. Animals that have skulls are called craniates...
itself as well as kidney
Kidney
The kidneys, organs with several functions, serve essential regulatory roles in most animals, including vertebrates and some invertebrates. They are essential in the urinary system and also serve homeostatic functions such as the regulation of electrolytes, maintenance of acid–base balance, and...
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 winter home range
Home range
Home range is the area where an animal lives and travels in. It is closely related to, but not identical with, the concept of "territory".The concept that can be traced back to a publication in 1943 by W. H. Burt, who constructed maps delineating the spatial extent or outside boundary of an...
mosaic is thereby disrupted, frequently resulting in intraspecific aggression
Aggression
In psychology, as well as other social and behavioral sciences, aggression refers to behavior between members of the same species that is intended to cause humiliation, pain, or harm. Ferguson and Beaver defined aggressive behavior as "Behavior which is intended to increase the social dominance of...
. 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 suboptimal habitat
Habitat
* Habitat , a place where a species lives and grows*Human habitat, a place where humans live, work or play** Space habitat, a space station intended as a permanent settlement...
.
Conservation
S. o. sinuosus is a rare speciesRare species
A rare species is a group of organisms that are very uncommon or scarce. This designation may be applied to either a plant or animal taxon, and may be distinct from the term "endangered" or "threatened species" but not "extinct"....
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 S. o. sinuosus as well as the California Clapper Rail
California Clapper Rail
The California Clapper Rail is an endangered subspecies of the Clapper Rail . It is found principally in California's San Francisco Bay, and also in Monterey Bay and Morro Bay...
, Salt Marsh Harvest Mouse
Salt Marsh Harvest Mouse
The Salt Marsh Harvest Mouse , also known as the Red-bellied Harvest Mouse and some times called by Saltmarsh Harvest Mouse, is an endangered rodent endemic to the San Francisco Bay Area salt marshes in California. There are two distinct subspecies, both endangered and listed together on federal...
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.
Specific occurrences
The following locations have been noted of wild occurrences of S. o. sinuosus:- 0.5 mile northeast of CordeliaCordeliaCordelia is a common first name in English. It is an elaboration of the word 'cor', which means 'heart' in Latin. In Celtic usages, the name is generally understood to mean 'daughter of the sea' or 'jewel of the sea' , due to its association with the mythological Welsh figure of...
Salt Marsh, Solano County - Gray Goose Duck Club, 1.5 mi Southwest of Suisun City
- Grizzly Island, Suisun BaySuisun BaySuisun Bay is a shallow tidal estuary at in northern California, USA. It lies at the confluence of the Sacramento and San Joaquin Rivers, forming the entrance to the Sacramento-San Joaquin River Delta, an inverted river delta...
- Honker Gun Club, near Dutton, Van Sickle Island
- 3.0 miles east of Mare Island Bridge, adjacent to White Slough and California Route 37
- 2.7 miles west junction of Napa Road and California Route 37 along Route 37)
- 8.0 miles north of Rio VistaRio VistaRio Vista may refer to:* Rio Vista, California* Rio Vista , a neighborhood in Fort Lauderdale, Florida* Rio Vista, a neighborhood in Alpine, New Jersey* Rio Vista, Texas* Rio Vista Park, a park in San Marcos, Texas...
- 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 Island