Northwestern Salamander
Encyclopedia
The Northwestern Salamander (Ambystoma gracile) inhabits the northwest Pacific coast of North America
. These fairly large salamanders grow to 8.7 in (220 mm) in length. It is found from southeastern Alaska
on May Island, through Washington and Oregon
south to the mouth of the Gulala River, Sonoma County, California
. It occurs from sea level to timberline, but not east of the Cascade Divide
. Its range includes Vancouver Island
in British Columbia
and Cypress, Whidbey, Bainbridge, and Vashon Islands in Washington (Snyder 1963).
The spotted forms occur in the northern portion of A. graciles range (Petranka 1998; Snyder 1963). A dividing line of 51 degrees north
latitude has been recognized between the two subspecies, with A. g. decorticatum occurring north of the line and A. g. gracile living to the south (Snyder 1963).
Populations with neotenic adults are widespread; the frequency of gill
ed adults increases with altitude such that adults at low and intermediate altitudes are almost all terrestrial, while adults at very high elevations are mostly neotenic (Eagleson 1976).
An example of a paedomorphic population of the Northwestern Salamander occurs at Crater Lake
, Oregon
, which population is syntopic with Taricha granulosa.
Terrestrial adults live in mesic
habitats ranging from grasslands to mesophytic forests. Terrestrial adults are mostly fossorial
, and are usually active on the surface only during fall rains and spring migrations to their aquatic breeding sites. However, they can sometimes be found under logs and other surface debris outside of the breeding season
(Petranka 1998; Efford and Mathias 1969).
(Weller and Green 1997). In the Cascade Mountains of Washington, Aubry and Hall (1991) found A. gracile to be far less abundant in young forests than in old-growth forests. However, Corn and Bury (1991) surveyed Western Oregon and found little correlation between salamander abundance and stand age, so it remains unclear whether A. gracile requires old growth forest
to thrive. Clear-cutting, however, seems to render the habitat unsuitable; Corn and Bury found no salamanders on recent clear-cuts. Petranka (1998) suggests leaving a forest buffer of 200-250 m surrounding breeding sites used by terrestrial adults to preserve optimal environmental conditions for local populations.
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
. These fairly large salamanders grow to 8.7 in (220 mm) in length. It is found from southeastern Alaska
Alaska
Alaska is the largest state in the United States by area. It is situated in the northwest extremity of the North American continent, with Canada to the east, the Arctic Ocean to the north, and the Pacific Ocean to the west and south, with Russia further west across the Bering Strait...
on May Island, through Washington and Oregon
Oregon
Oregon is a state in the Pacific Northwest region of the United States. It is located on the Pacific coast, with Washington to the north, California to the south, Nevada on the southeast and Idaho to the east. The Columbia and Snake rivers delineate much of Oregon's northern and eastern...
south to the mouth of the Gulala River, Sonoma County, California
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
. It occurs from sea level to timberline, but not east of the Cascade Divide
Cascade Range
The Cascade Range is a major mountain range of western North America, extending from southern British Columbia through Washington and Oregon to Northern California. It includes both non-volcanic mountains, such as the North Cascades, and the notable volcanoes known as the High Cascades...
. Its range includes Vancouver Island
Vancouver Island
Vancouver Island is a large island in British Columbia, Canada. It is one of several North American locations named after George Vancouver, the British Royal Navy officer who explored the Pacific Northwest coast of North America between 1791 and 1794...
in British Columbia
British Columbia
British Columbia is the westernmost of Canada's provinces and is known for its natural beauty, as reflected in its Latin motto, Splendor sine occasu . Its name was chosen by Queen Victoria in 1858...
and Cypress, Whidbey, Bainbridge, and Vashon Islands in Washington (Snyder 1963).
Occurrence
51st parallel north
The 51st parallel north is a circle of latitude that is 51 degrees north of the Earth's equatorial plane. It crosses Europe, Asia, the Pacific Ocean, North America, and the Atlantic Ocean....
latitude has been recognized between the two subspecies, with A. g. decorticatum occurring north of the line and A. g. gracile living to the south (Snyder 1963).
Populations with neotenic adults are widespread; the frequency of gill
Gill
A gill is a respiratory organ found in many aquatic organisms that extracts dissolved oxygen from water, afterward excreting carbon dioxide. The gills of some species such as hermit crabs have adapted to allow respiration on land provided they are kept moist...
ed adults increases with altitude such that adults at low and intermediate altitudes are almost all terrestrial, while adults at very high elevations are mostly neotenic (Eagleson 1976).
An example of a paedomorphic population of the Northwestern Salamander occurs at Crater Lake
Crater Lake
Crater Lake is a caldera lake located in the south-central region of the U.S. state of Oregon. It is the main feature of Crater Lake National Park and famous for its deep blue color and water clarity. The lake partly fills a nearly deep caldera that was formed around 7,700 years agoby the...
, Oregon
Oregon
Oregon is a state in the Pacific Northwest region of the United States. It is located on the Pacific coast, with Washington to the north, California to the south, Nevada on the southeast and Idaho to the east. The Columbia and Snake rivers delineate much of Oregon's northern and eastern...
, which population is syntopic with Taricha granulosa.
Terrestrial adults live in mesic
Mesic
Mesic may refer to:* Mesic, North Carolina, a town in the United States* Mesic habitat, a type of habitat...
habitats ranging from grasslands to mesophytic forests. Terrestrial adults are mostly fossorial
Fossorial
A fossorial organism is one that is adapted to digging and life underground such as the badger, the naked mole rat, and the mole salamanders Ambystomatidae...
, and are usually active on the surface only during fall rains and spring migrations to their aquatic breeding sites. However, they can sometimes be found under logs and other surface debris outside of the breeding season
Breeding season
The breeding season is the most suitable season, usually with favourable conditions and abundant food and water, for breeding among some wild animals and birds . Species with a breeding season have naturally evolved to have sexual intercourse during a certain time of year in order to achieve the...
(Petranka 1998; Efford and Mathias 1969).
Conservation
The status of Ambystoma gracile populations is unknown (Blaustein et al. 1994). No declines are apparent in CanadaCanada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
(Weller and Green 1997). In the Cascade Mountains of Washington, Aubry and Hall (1991) found A. gracile to be far less abundant in young forests than in old-growth forests. However, Corn and Bury (1991) surveyed Western Oregon and found little correlation between salamander abundance and stand age, so it remains unclear whether A. gracile requires old growth forest
Old growth forest
An old-growth forest is a forest that has attained great age , and thereby exhibits unique ecological features. An old growth forest has also usually reached a climax community...
to thrive. Clear-cutting, however, seems to render the habitat unsuitable; Corn and Bury found no salamanders on recent clear-cuts. Petranka (1998) suggests leaving a forest buffer of 200-250 m surrounding breeding sites used by terrestrial adults to preserve optimal environmental conditions for local populations.
Sources
Database entry includes a range map- C. Michael Hogan (2008) Newt (Taricha granulosa), Globaltwitcher, ed. Nicklas Stromberg