271.
Tusked frog
(Adelotus brevis)
NT
Overview
The tusked frog is from an ancient lineage with around 100 million years worth of independent evolution, and has large bony tusks protruding from its lower jaw which the males use to fight each other.  It is the only Australian frog species in which the males are larger than the females, and has an unusual marbled belly in black, white and red.  This species is native to the East Coast of Australia and the mountains of the Great Dividing Range, but has disappeared from a significant portion of its range, especially in upland areas. These local extinctions are thought to have been caused by the chytrid fungus, which has caused amphibian declines worldwide. This deadly pathogen is now widespread throughout eastern Australia, so the race is on to prevent its spread to as yet unaffected frog populations.
Urgent Conservation Actions
Distribution
Eastern Australia.

 
Media from ARKive
ARKive image - Male tusked frog
ARKive image - Male tusked frog
ARKive image - Male tusked frog, dorsal view
ARKive image - Male tusked frog in leaf litter
ARKive image - Male tusked frog with tusks clearly visible
ARKive image - Ventral surface of tusked frog
ARKive image - Male tusked frog calling for a mate
ARKive image - Male tusked frog calling from water filled burrow in the bank of a pond
ARKive image - Tusked frog with eggs
Evolutionary Distinctiveness
Order: Anura
Family: Limnodynastidae
Adelotus brevis is one of the oldest species of the Limnodynastidae family, which began diverging around 100 million years ago.  They may be as old as the birds, as recent studies have placed bird divergence from crocodiles, their closest living relatives, around this time.  The tusked frog is so called because of its large pair of tusks or fangs, which it uses in territorial battles.  Technically, these are known as odontids, as they are tooth-like but are made of bone.  Males have been observed ‘locking jaws’ with each other, in a similar way to male deer locking antlers in the struggle to exert dominance over each other.
Description
This frog is distinguishable from all others because of its tusks and the unusual markings on its underside.  The pair of bony tusks protrude from the middle of the lower jaw and fit into special grooves on the upper jaw when the mouth is closed.  They are slightly curved and sharply pointed, and are present in both males and females, although they are larger in males.

Adelotus brevis also displays the unusual trait of the male being slightly larger than the female (often the reverse in frog species), with females between 3 and 4cm, and males ranging from 3.5 to 4.5 cm.  Males also have a broader head, often being as large as the rest of the body.  Fingers and toes are cylindrical and are not webbed, and the back is covered in a scattering of small warts.  Viewed from above they are olive green to brown in colour with dark flecks and markings.  The underside is more striking, being marbled black and white with flashes of red on the groin and hind legs.  Males and females have different belly patterns.

Tadpoles are dark from above, some with a small cream patch on the snout, and grey underneath with fine golden flecks.  The tail is whitish with light brown spots, dorsal and ventral fins also have fine spots.
Ecology
Males call throughout the year from clumps of vegetation or cover objects in the water.  This advertisement call is in two parts, and has been described as a slowly repeated, soft “chuluk” or “b’look”.

In the breeding season (October - December), males build nests out of foam hidden from direct sunlight in ponds and swamps.  Over 600 eggs may be laid in each floating mass of foam, and are guarded by the male until they hatch into tadpoles.  The tadpoles grow over a period of two to three months to around 3 to 3.5 cm, when they undergo metamorphosis into ‘mini adult’ froglets.
Habitat
Adelotus brevis occurs in a range of habitats from open grassland to dry forest and rainforest.  Streams and ponds are required for breeding.  They hide underneath rocks or logs or in crevices, usually not too far from water.
Distribution
This species is native to eastern Australia, and is found in the Great Diving Range or Eastern Highlands and on the coast from central Queensland down to southern New South Wales.  It is currently found at altitudes of less than 400 metres above sea level, but used to have a wider altitudinal range.

There is a disjunct population in the Clarke Range (Queensland).  The distribution then goes from Shoalwater Bay ( Queensland) south along the coast to Moss Vale (New South Wales) and inland to Blackdown Tableland and Carnarvon Gorge. 
Population Estimate
There is no data on the overall population size of this species, but local population declines have been noted.
Population Trend
Decreasing.  Upland populations have declined, and recent surveys have not found it along the Great Diving Range.
Status
The IUCN has listed the tusked frog in the Near Threatened category of the Red List of Threatened Species, and notes that it is probably in significant decline due to chytridiomycosis.
Threats
Urban and agricultural development are thought to be the primary threats to this species, causing the degradation and loss of its habitat.  Introduced species are causing further decline, such as the predatory Eastern mosquitofish Gambusia holbrooki, and weed species which outcompete the tusked frog’s natural vegetation.  Dead frogs testing positive for chytridiomycosis have been found in south-eastern Queensland and north-eastern New South Wales, and the spread of this fungus to the rest of the population represents another significant threat to the species.
Conservation Underway
The range of the tusked frog includes several protected areas, where the species is safe from habitat loss.  The southern Tablelands population has been listed as an Endangered Population under the Threatened Species Conservation Act, following the disappearance of the species from the rest of its former Tablelands range.
Conservation Proposed
The IUCN calls for research into the spread of the chytrid fungus, and education on minimising and preventing the further spread of this pathogen.  Local experts suggest that efforts should be put forth to work with landowners whose property encompasses Adelotus populations.
Links
AmphibiaWeb           http://amphibiaweb.org/

Global Amphibian Assessment       http://www.iucnredlist.org/amphibians

Tree of Life Web Project      http://tolweb.org/tree/
References
Amphibiaweb: Information on amphibian biology and conservation [web application]. 2009. Berkeley, California: AmphibiaWeb. Available: http://amphibiaweb.org/. (Accessed: Feb 27, 2009.)

Barker, J., Grigg, G., Tyler, M. 1995. A Field Guide to Australian Frogs. Surrey Beatty and Sons, New South Wales.

Cannatella, D. 1995. Limnodynastinae. Version 01 January 1995 (under construction). http://tolweb.org/Limnodynastinae/16944/1995.01.01 in The Tree of Life Web Project, http://tolweb.org/.

Frost, D. R. 2009. Amphibian Species of the World: an Online Reference. Version 5.3 (12 February 2009). Electronic Database accessible at: http://research.amnh.org/herpetology/amphibia/. American Museum of Natural History, New York, USA.

Hines, H., Meyer, E., Hero, J., Newell, D., Clarke, J. 2004. Adelotus brevis. In: IUCN 2008. 2008 IUCN Red List of Threatened Species. www.iucnredlist.org. Downloaded on 17 February 2009.

Lynch, D. 1971. Evolutionary relationships, osteology, & zoogeography of leptodactyloid frogs. Miscellaneous Publication Museum of Natural History 53: 1-238.

Roelants, K., Gower, D. J., Wilkinson, M., Loader, S. P., Biju, S. D., Guillaume, K., Moriau, L. and Bossuyt, F. 2007. Global patterns of diversification in the history of modern amphibians. PNAS 104(3): 887-892.

Turner, J. R. 2004. Frogs of Australia. Pensoft Publishers, Bulgaria.

Tyler, M. J. Australian Frogs: A Natural History. Cornell University Press, New York.

Distribution dataset:  IUCN 2008. 2008 IUCN Red List of Threatened Species. http://www.iucnredlist.org

if you can provide new information to update this species account or to correct any errors, please email us at info@edgeofexistence.org


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