Rough frog

Rough Frog was described by Tyler and Martin in 1997.[4] It is accepted under the genus' of Ranoidea, Litoria and Cyclorana [4][5]

Taxonomic studies of the Cyclorana family has described the Rough Frog as having evolved from ancestral Cyclorana Steindachner, from the Hylidae (tree frogs) family which formed in the Miocene (about 23 million years ago).[5][6][7] It is classified under the subfamily Pelodryadinae which describes the tree frogs of Australia and Papua New Guinea.[7]

While Litoria and Cyclorana are widely accepted, the classification of Ranoidea as a genus it not yet generally acknowledged, as species from this genus have until recently been placed in the paraphyletic genus Litoria.[8] Ranoidea is considered by some to be a subgenus.[9]

While taxonomic studies have linked its evolutionary past to that of Cyclorana Steindachner, it has more recently been accepted as Ranoidea verrucosa by Dubois and Frétey in 2016.[10]

Rough Frog displaying the tan and dark brown colour variation. [11]

R. Verrucosa is a medium-sized burrowing frog. Male frogs reach between 35-45mm in body length and females are slightly larger at 37-49mm in length.[2][3]

The stout frog is typically grey-brown to olive brown in colour.[1] Its back is irregularly marked with dark green spots on a tan background, or black/dark grey on a pale brown background.[2][1] Both colour variations have a thin pale cream coloured stripe that runs along the middle of the back from front to rear.[3] The belly is pale whitish colour, and the male has a grey throat.[3] The edge of the upper lip is brown with white flecks.[1] A broad dark band runs either side of the nose and continues behind the eye before merging with the patterns along the side body.[1]

As per its namesake, the Rough Frog’s skin has a rough, warty or ridged texture.[12] The throat of the male is finely granular, but the female's throat is smooth.[1] The rough skin of R. Verrucosa distinguishes it from all other frogs that live within its geographical area.[13]

Toes are one-third webbed.[1] The inner metatarsal tubercle is shovel-shaped to assist in burrowing.[1]

R. verrucosa can be found near seasonal ponds, creeks and claypans in open grassland and closed or open woodland on clay soils.[10][1][2][13] It is distributed across Northern NSW into south-eastern Queensland, but not along the coast or in the ranges.[1] It spends dry periods underground in dormancy and emerges following heavy rain. Roadside reserves are considered as significant habitat areas.[10]

Little is known regarding the behaviour of R. verrucosa. The Rough Frog is a burrowing frog that will burrow during dry periods, and emerge to breed and feed after extended periods of rain.[3]

Little is known about the Rough Frog’s lifespan. R. verrucosa breeds in flooded depressions during spring to summer, and sometimes in autumn, after heavy rains.[3][10][1] Males sound mating calls that resemble a long moaning growl.[13] Very little data exists regarding reproduction of the Rough Frog, however it is conserved to be similar to Litoria cultripes, in which eggs are laid in large clumps under the surface of water in temporary ponds, swamps or roadside ditches.[3] Larvae are free swimming, tadpoles can grow as long as 7.5cm being a dull gold/white in colour.[3][10] It is unknown how long they take to develop into frog, but they develop rapidly during warm months before water drys up.[3][14]

The Rough Frog is defined as Least Concern on IUCN’s Red List.[10] The population is stable. There are conservation sites throughout the habitat range of the frog, and it currently occurs in at least one protected area. Fragmentation of population is limited, but there is a continuing decline is area and quality of habitat.[10]

Agriculture and aquaculture including annual and perennial non-timber crops are identified as threats to R. Verrucosa. Future development in south-eastern Queensland may also pose a threat.[10] Direct human impact, urbanisation, tourism and inappropriate catchment management, including the degradation of water quality are also threats to the persistence of this species.[14]