Taxonomy

(Barker et al.,1995, Kraus and Allen, 2004,Tyler and Davies, 1978, Tyler and Davies, 1986)

The species name translates as two-coloured and possible refers to the difference between ventral and dorsal colouration.

Litoria bicolor did not achieve separate status from Litoria fallax until 1969. L. bicolor forms a species-group known as the Bicolor Group. Members include the Australian species Litoria cooloolensis (discovered in 1974) and Litoria fallax ; and New Guinea species. Litoria contrastens, Litoria longicrus,and Litoria mystax and perhaps Litoria bibonius from the Normandy Islands.

Description.

(Barker et al., 1995; Cameron and Cogger, 1992; Cogger, 1988; McDonald, 2000.)

L. bicolor is a slender, small green, arboreal frog with obvious finger and toe discs and a smooth skin. It has a narrow head area with a wide bronze-brown vertebral band that extend its entire length and is bordered on either side with green. Eyes are gold flecked. Through the eye area from the snout to the groin runs a dark stripe. The upper labial area is white striped. Vomerine teeth are absent and there is a strong pectoral fold. The tympanum is distinct. The groin and posterior of the thigh are a pale yellow and there may be a small amount of orange present.

The ventral area is a cream to very pale yellow with a granular stomach and femoral area. No outer metatarsal tubercle exists but there is a small inner one. The fingers are very slim and only exhibit a little webbing whilst the toes will be half to three quarters webbed. The second finger is longer than the first. Breeding males may appear mostly bronze above.

Note: Can be distinguished from Litoria Fallax (which it may closely resemble) by a head to width ratio of greater than 3 .5 whereas L. fallax will be less than 3 to 5 or by the call difference.

Size (snout-vent). Recorded average for species is 30mm. Females range between 25 and 29mm apx. with males smaller, from 23 to 27 mm. apx.

Adult male in breeding colours

Call

(Barker et al., 1995; Cogger 1988; Frith, 1987; McDonald, 2000, Sawyer and Morris, 2004; Tyler and Davies,1986)

The call is described as a complicated series of high pitched sounds as “wree –e-ech pip pip” with the first part of the call continuing after the second is started.it. It is known to call in the afternoon after rain (Darwin area) as well its usual calling, nocturnally.

Geographic range

(Barker et al., 1995; Cameron and Cogger, 1992; Cogger, 1988; McDonald, 2000, Tyler et al,. 1994; Tyler and Davies, 1986)

A tropical species that may extend to Indonesia it is generally found along the Coast and adjacent areas of north and northeast Australia. Its range covering all of Cape York and south to Bowen in QLD and west across the N.T. (around Lat. 17°, just south of Boroloola) to the W. A. coast at Yambi Peninsula north of Broome. It has limited distribution in the New Guinea lowlands. In areas where it overlaps with L. fallax it is said to inhabit lower elevations, however on Magnetic Island both species exist in lowland areas (pers com).

Biology/physiology

(Tyler and Davies, 1978; Young et al. 2005 )

Evaporative water loss has been measured in this species in the wet and dry seasons and there is thought to be little seasonal difference, excepting as relating to mass, indicating that it has a relatively high cutaneous resistance when compared with other species. L. bicolor, in common with its species group, has intercalary structures that are elongate and ossified with the hyoid plate bearing alary processes. The diploid chromosome number of 26 is shared with L. contrastens.

Typical breeding habitat for this species on Magnetic Island

Habitat, Ecology, Behaviour

(Barker et al., 1995; Cameron and Cogger, 1992; ;Cogger, 1988; Friend and Cellier, 1990; Lynch et al,. 2002)

Although usually found on vegetation beside standing water, Litoria bicolor is known to inhabit exposed leaves diurnally in temperatures of around 30°C. Observed to tolerate water temperatures of up to 35°C and to hide beneath bark in open forest trees the dry season.

L. bicolor can sometimes be found far from water. More usually they are found in most freshwater terrestrial habitats including mangrove fringed areas and suburbia, excepting vine thickets or rainforest although in Kakadu they have been found in closed monsoon forest. Preference is for reeds and low vegetation next to still waters such as in melaleuca swamps. May inhabit Pandanus species leaf axils during the dry season.

Litoria bicolor is only one of two terrestrial frog species in Australia, studied in the N.T., that is known to have a diet preference for adult aquatic insects (esp. dipterans & damselflies). The other, L. rothii is also a tropical species. Water, therefore would have to play a leading role in the feeding behaviour of this species at least in the area studied.

Reproduction

(Barker et al., 1995; Cameron and Cogger 1992; Cogger, 1988., McDonald, 2000, Tyler et al., 1994; Tyler, 1994)

Although calling begins with the first summer rains in November/December, this species may bet-hedge by also calling late in the wet season when other species are finished (pers. Obs) Clustered on the tips of exposed reeds and low overhanging vegetation in flooded paperbark woodlands, at night, is a common place for males who will also call intermittently on overcast days.

Clutches of about 10 - 20 tiny pigmented brown eggs in a clear mat of jelly, laid in water and usually attached to below surface vegetation are produced during amplexis.

Tadpoles may grow to 55mm and have an obvious, high, crested tail with blotched pigmentation which also appears on the body, similar to L. fallax. They are a bright, pale-brown with a white stripe appearing under the eye in the more advanced stages. There are 2 upper and 3 lower labial tooth rows in the larval mouth. Within 70 - 77 days, metamorphs usually emerge when water temperature are apx. 30 degrees.

References

Barker, J,Grigg, G. and Tyler, M.(1995) A Field Guide to Australian Frogs: Surrey, Beatty and Sons, NSW.

Cameron, E.E. and Cogger, H.G.,(1992) The Herpetofauna of the Weipa
Region, Cape York Peninsula;Technical Report Number 7, Australian Museum.

Cogger, H. G., 1988. "Reptiles and Amphibians of Australia ". Reed Books, N.S.W.

Frith, D. and Frith C., (1987), Australian Tropical Reptiles and Frogs, Tropical Australia Graphics, Paluma.

Friend, G.R. and Cellier,K.M. (1990) Wetland Herpetofauna of Kakadu National Park, Australia: Seasonal Richness Trends, Habitat Preferences and the Effects of Feral Ungulates, Journal of Tropical Ecology, 6(2):131-152

Kraus, F. and Allen, A.(2004) Two New Treefrogs from Normandy Island, Papua New Guinea,Journal of Herpetology 38 (2):197-207

Lynch, R.J., Bunn, S.E. and Catterall, C.P.,(2002), Adult aquatic insects: Potential contributors to riparian foodwebs in Australia’s wet–dry tropics, Austral Ecology, 27:515-526.

McDonald, K., 2000, in "Wildlife of Tropical North Queensland" Eds. Ryan, M. & Burwood,.C.Pp.170-195 :Queensland Museum.

Sawyer, G and Morris, I., (2004), Survey Report on Frog Fauna in the Darwin Wharf Precinct; Technical Report prepared for the Draft Environmental Impact Statement for the Darwin City Waterfront Redevelopment

Tyler M.J., (1994), Australian Frogs - A Natural History,Reed Books, Chatsworth, NSW.

Tyler, M.J., Smith, L.H. and Johnstone, R.E. (1994), Frogs of Western Australia, W.A. Museum, Perth.

Tyler M.J.and Davies, M. (1978)Species-groups within the Australopapuan Hylid Frog
Genus Eitovia Tschudi: Australian Journal of Zoology Supplementary Series No. 63 C.S.I.R.O

Tyler M.J.and Davies, M. (1986), Frogs of the Northern Territory, For the Conservation Commision of the Northern Territory by the University of Adelaide.

Young, J.E., Christian, K.A., Donnellan, S., Tracey, C.R.and Parry, D. Comparative analysis of Cutaneous Evaporative Water Loss in Frogs
Physiological and Biochemical Zoology 78(5):847-856 2005 University of Chicago

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All photos are by the author unless otherwise captioned