Watson's tree frog (''Litoria watsoni''), also known as the large brown tree frog or southern heath frog, is a species of tree frog

endemic Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found els ...

to south-eastern Australia.

Taxonomy

Following a taxonomic review using a

molecular genetics Molecular genetics is a sub-field of biology that addresses how differences in the structures or expression of DNA molecules manifests as variation among organisms. Molecular genetics often applies an "investigative approach" to determine the ...

approach, in 2020 Watson's tree frog was

split Split(s) or The Split may refer to: Places * Split, Croatia, the largest coastal city in Croatia * Split Island, Canada, an island in the Hudson Bay * Split Island, Falkland Islands * Split Island, Fiji, better known as Hạfliua Arts, entertain ...

from

Littlejohn's tree frog Littlejohn's tree frog (''Litoria littlejohni''), also called a heath frog or orange-bellied tree frog, is a species of tree frog native to eastern Australia from Wyong, New South Wales, to Buchan, Victoria. Taxonomy In 2020, following a taxonom ...

(''L. johnsoni''), with the southern populations assigned to the newly described species. The

species epithet Specific name may refer to: * in Database management systems, a system-assigned name that is unique within a particular database In taxonomy, either of these two meanings, each with its own set of rules: * Specific name (botany) A botanical name ...

''watsoni'' honours

zoologist Zoology ()The pronunciation of zoology as is usually regarded as nonstandard, though it is not uncommon. is the branch of biology that studies the animal kingdom, including the structure, embryology, evolution, classification, habits, and ...

Dr Graeme Watson, formerly of the

University of Melbourne The University of Melbourne is a public research university located in Melbourne, Australia. Founded in 1853, it is Australia's second oldest university and the oldest in Victoria. Its main campus is located in Parkville, an inner suburb n ...

, for his lifetime contributions to the study of frog biology.

Description

The species is a medium-sized frog. With a snout-vent length (SVL) of up to 64 mm, the females are larger than the males (SVL = 59 mm). The back and outer surfaces of the limbs are light brown, flecked and mottled with darker brown and yellow. The underparts are white. There are distinctive red-orange makings on the backs of the legs, the feet, sides and groin. The head has a rounded snout with yellow eyes, distinct circular tympanums and black stripes extending from the snout through the eyes to the sides of the body. The legs are long and the feet largely unwebbed, with terminal discs on the fingers and toes. The species is very similar to Littlejohn's tree frog; the main distinguishing characteristic is the breeding call of the males, with Watson's tree frog uttering fewer pulses in each note (with a mean of 22.8 per second as compared to 27.8) for a call length of 3–12 seconds. The call has been described as "''wriiik wriiik wriik wriik''".

Distribution and habitat

The ranges of the two split species appear to be separated at the southern border of the

Sydney Basin The Sydney Basin is an interim Australian bioregion and is both a structural entity and a depositional area, now preserved on the east coast of New South Wales, Australia and with some of its eastern side now subsided beneath the Tasman Sea. ...

bioregion A bioregion is an ecologically and geographically defined area that is smaller than a biogeographic realm, but larger than an ecoregion or an ecosystem, in the World Wide Fund for Nature classification scheme. There is also an attempt to use th ...

. The known range of ''L. watsoni'' extends from the

Budderoo National Park The Budderoo National Park is a national park that is located in the Illawarra region of New South Wales, Australia; situated approximately south southwest of Sydney. Location and features The National Parks & Wildlife Servicemanaged park ...

and

Barren Grounds Nature Reserve The Barren Grounds Nature Reserve is a protected nature park located in the Southern Highlands region of New South Wales, Australia. The reserve is situated east of Budderoo National Park, and west of the city of Kiama. The reserve can also ...

in the

Shoalhaven River The Shoalhaven River is a perennial river that rises from the Southern Tablelands and flows into an open mature wave dominated barrier estuary near Nowra on the South Coast of New South Wales, Australia. Location and features The Shoalh ...

catchment of south-eastern

New South Wales ) , nickname = , image_map = New South Wales in Australia.svg , map_caption = Location of New South Wales in AustraliaCoordinates: , subdivision_type = Country , subdivision_name = Australia , established_title = Before federation , es ...

southwards to the eastern side of the

Snowy River National Park The Snowy River National Park is a national park located in the alpine and East Gippsland regions of Victoria, Australia. The national park is situated approximately northeast of Melbourne and southwest of Canberra, south of the Black-A ...

East Gippsland East Gippsland is the eastern region of Gippsland, Victoria, Australia covering 31,740 square kilometres (14%) of Victoria. It has a population of 80,114. Australian Bureau of Statistics2006 Census Community Profile Series: East Gippsland (S ...

Victoria Victoria most commonly refers to: * Victoria (Australia), a state of the Commonwealth of Australia * Victoria, British Columbia, provincial capital of British Columbia, Canada * Victoria (mythology), Roman goddess of Victory * Victoria, Seychelle ...

, with an altitudinal range from near sea-level to 1,100 m. Distribution is very patchy, with few records from the southern part of the range. The topography of the northern end of the distribution range is characterised by steep cliffs and valleys, forming a

biogeographic barrier Allopatric speciation () – also referred to as geographic speciation, vicariant speciation, or its earlier name the dumbbell model – is a mode of speciation that occurs when biological populations become geographically isolated from ...

which marks the geographic separation between Littlejohn's and Watson's tree frogs. The species occurs in a variety of forest types, as well as woodland, bushland and heathland. It prefers moister sites, especially in or near tall moist forest. The most important habitat factor is the presence of pools that contain water long enough for tadpoles to complete metamorphosis. It has not been recorded from previously wooded land cleared for farming or plantation forestry.

Conservation

The species’ population is suspected to be in decline. Threatening factors include

habitat loss Habitat destruction (also termed habitat loss and habitat reduction) is the process by which a natural habitat becomes incapable of supporting its native species. The organisms that previously inhabited the site are displaced or dead, thereby ...

as well as

bushfire A wildfire, forest fire, bushfire, wildland fire or rural fire is an unplanned, uncontrolled and unpredictable fire in an area of combustible vegetation. Depending on the type of vegetation present, a wildfire may be more specifically identi ...

s, the incidence of which is likely to increase with

climate change In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to ...

. The 2019–20 bushfires overlapped with about 85% of the species’ known range.

References

{{Taxonbar, from=Q108991132 watsoni Amphibians of New South Wales Amphibians of Victoria (state) Amphibians described in 2020 Frogs of Australia