Limnodynastes ornatus (Grey 1842)
Ornate Burrowing Frog, Ornate Frog
C. Lane 2007
 






Taxonomy:

(Barker et al.,1995, Burton, 2001; Martin and Davies, 1979; Shauble et al.,2000, Tyler and Davies 1986; Tyler et al,. 1979; Tyler et al., 1994 )

Ornatus translates directly from the Latin for ornate.

Mitochondrical DNA studies show a highly distinctive clade is formed by the the Ornatus Species Group that consists of Limnodynastes ornatus and its closest relative L spenceri (distinguished by webbing differences and call). It is a sister clade or group to the other Limnodynastes groups and perhaps should include Adelotis brevis. There is speculation that with more phylogenetic study it could be removed from the genus Limnodynastes altogether. There is also a digging muscle associated with all other Limnodynastes groups that is not present in this species group, who have a different burrowing style (backwards-sliding). The study on this indicated that this style may have evolved independently. It is further postulated that the 'split' may have been as long ago as 60 million years. Other Immunilogical studies have suggested that the Ornatus Group and the Dorsalis group be moved to a new genus, again with A. brevis.


Description

(Cameron and Cogger 1992. Barker et al., 1995, Cogger,1988 , Clyne, 1969; Littlejohn et al., 1991; McDonald, 2000, Swan, 2001; Tyler and Davies1986 ; Tyler et al 1994.)

Limnodynastes ornatus is a robust, medium size burrowing frog that has a short blunted snout and (as in members of the Myobatrachidae) has no discs on the elongate, cylindrical fingers and toes. Extremely variable in colour and dorsal patterning, It may range from pale to dark grey and light to darker brown which may have a bronze tinge.Often with irregular darker markings, and sometimes a pale U-shaped nape patch, which may extend along the back to form an hourglass shape. There may also be no marking on the dorsal area at all which is often covered with a scattering of small warts. The upper labial surface may be banded. The ventral surface is whitish. The limbs, especially hind limbs, which are short and robust (compared to the slim forelimbs), are usually banded. It has prominent eyes set to the side with dark irises and a very indistinct tympanum.The fingers are unwebbed and the toes only slightly webbed, if at all. A large shovel-like inner metatarsal tubicle is present and is longer than the second toe. In breeding season glandular nuptual excrescenses appear on the first 3 male fingers. Females have finger flanges on the first two digits.

Size (snout-vent). Although the recorded average for species is 45mm., females are said range between 35mm and 42mm apx with males smaller, from 31mm.to 37mm. apx.

Adult

 

 

 

 

Calls

(Baker, 1999, Barker et al., 1995, Cameron and Cogger, 1992, Clyne, 1969, McDonald, 2000, , Tyler, 1982, Tyler et al.,1994, Tyler and Davies, 1986; Tyler et al,. 1994;)


Although this frog can produce a variety of sounds the calling males make a sound that has been described a slow repeated "short nasal unk" or gulping sound.

 

Geographic range.

(Cameron and Cogger, 1992, Barker et al., 1995, Cogger,1988, Clyne, 1969, Frith, 1987: McDonald, 2000, Swan, 2001; Tyler and Davies, 1978, Tyler et al,. 1994)

An adaptable frog that is found south to NSW, Limnodynastes ornatus is often considered a 'tropical frog' as its range is greater in hotter climes.

L. ornatus is found throughout Northern Australia (down to Dampier Downs, Fitzroy Crossing and Halls Cr.in the west) , down to just beyond Boroloola in the N.T. and in most of eastern Australia (down to mid south NSW) Including islands in the Torres Straight but not New Guinea. According to Tyler of the nine frogs found in Cape York that are also found in New Guinea, L. ornatus is the only species that almost made it with the range ending on the intermediate islands.

 

 

 

Biology/physiology

(Warburg, 1964; Clyne, 1969;)

Limnodynastes ornatus has a limited bladder water storage ability, compared to the true water storing frogs which perhaps allows it limited aestivation time. At an ambient temperature of 37.5°C, in dry conditions, in the laboratory L. ornatus has been known to survive for 8hrs. without water or food uptake. Live adult specimens that have been in water for some time appear viably to swell.

 

 

Typical breeding habitat for this species on Magnetic Island

 

 

Habitat, Ecology and Behaviour

(Barker et al., 1995; Cameron and Cogger, 1992; Cogger, 1988; Clyne, 1969; Friend and Cellier, 1990; Frith, 1987/1995; McDonald, 2000, Swan, 2001; Tyler and Davies, 1986; )

According to some sources they are found everywhere except in rainforest, but others have them anywhere from rainforest through wet schlerophyll forest, vine thicket and arid woodland to grasslands. In Kakadu one survey showed L.ornatus to be more often found in treed areas than grasslands.

A capable burrower, L. ornatus diurnally retreats often preferring a sandy substrate. This species burrows obliquely backwards often referred to as a "backwards-sliding burrower" as opposed to the more common burrowing style termed 'circular burrowers'. It can remain underground for long periods of time.Once thought a mainly 'arid' species, it is often found buried in dry creek beds far from permanent water. Warm humid nights is a good time to find foraging adults.

This species is recorded as being part of the diet of the Green Tree Snake
(Dendrelaphis punctulata) and of of the Keelback Snake
(Tropidonophis mairii) and is possibly in the diet of most frog eating snakes in the same range.

 

 

 

 

 

Reproduction.

(Anstis, 2002; Barker et al., 1995, Cameron and Cogger 1992, Cogger, 1988; Crossland, 1998; Frith, 1995; McDonald, 2000, Swan, 2001; Tyler and Davies, 1979; Tyler et al,. 1994;)

Calling begins with the first summer rains in November/December, On Magnetic Island Limnodynastes ornatus are the first species to call and will spawn as soon as ground water accumulates. (pers. Obs) In 2006 they spawned early but the water did not last more than 1 week and the tadpoles died, they then recommenced calling with the next batch of heavy rain (pers. obs). Metamorphs can be present late in the season at the same time as calling males, in some regions. In W.A. L. ornatus will call throughout the Wet season and are likely to spawn on more than one occasion, with a preference for flooded areas. This species is widely distributed so the breeding season will vary geographically and climatically. Males call from floating positions (with spread out arms and legs) in the water. If the water is too shallow to float they will call from a wading position (pers. obs) The amplectant couple produce a dome shape foamy nest of spawn that is laid and fertilized with females using their flanged feet to paddle/aerate the mixture to buoy it up. This collapses within hours to form a floating layer.

Clutches can range from a couple of hundred up to more than 1600 pigmented eggs, With the animal pole ; black and the vegetal; off-white to grey. Ova size in this species is between 1.02 - 1.10 apx. and the capsule size between 1.6-2.07mm. After 18-30 hours the apx. 4.4mm hatchlings will emerge.

The size of tadpoles is up to 47mm(apx.) in the tail and up to 19.6mm (apx.) in the body length. Tadpoles range from pale to dark brown and are a roughly oval shape with a somewhat pointed snout when viewed from above. The narrowly separated eyes are situated on top of the head area with gold rimmed pupils and a diamond shaped, gold sprinkled iris. The tail fins are relatively shallow, tapering to a rounded end, when viewed laterally. From above the tail appears quite thin.

The omnivorous tadpoles of L. ornatus have been known to be a major aquatic predator on eggs and hatchlings of other native anurans with no preference for species. In some ponds, if in sufficient numbers, they may even eliminate them entirely. On Magnetic Island they spawn well before other species giving them a size advantage when other spawn appears (pers. obs). Although classed as bottom dwellers, this author has observed many times that this species will rise to eat and compete for floating food and will eat in all water levels in captivity. Tadpoles have been known to over-winter and hatchlings from the same clutch may develop at very different rates (pers. obs)

Metamorphosis is accomplished in between 21 and 90 days apx. depending on local environmental conditions. From December - March the diurnally active (pers obs), brown patterned or unpatterned metamorphs may be observed hopping on the ground (should not be confused with B marinus metamorphs which, although a similar size and also day active in the same season and similar places, will be black).

 

Amplectant pair

Collapsing 'nest '

 

 

Metamorph variation

 

 

All photos and Audio by author unless otherwise captioned

 

References

Anstis, M (2003) Tadpoles of South-eastern Australia, Reed New Holland, Sydney, NSW

Barker, J,Grigg, G. and Tyler, M.(1995) A Field Guide to Australian Frogs: Surrey, Beatty and Sons, NSW. Cogger, H. G., 1988. "Reptiles and Amphibians of Australia ". Reed Books, N.S.W.

Burton, Thomas C., 2001. "Variation in the foot muscles of frogs of the family Myobatrachidae". Australian Journal of Zoology, 49, 539–559.

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

Clyne, D., (1969) Australian Frogs, Lansdowne Press, Melbourne.

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

Crossland, M.R., (1998) A comparison of cane toad and native tadpoles as predators of native anuran eggs, hatchlings and larvae,Wildlife Research, 25: 373–381

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

Frith, D. and Frith C., (1995), Cape York Peninsula - A Natural History, Reed Books, NSW.

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

Littlejohn, M.J., Roberts, D., Watson, G.F. & Davies, M. (1991) Family Myobactachidae - Fauna of Australia Series, Australian Government Publication, C.S.I.R.O., Australia

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

Shauble, C.S., Moritz, C., and Slade, R.W. (2000) A Molecular Phylogeny for the Frog Genus Limnodynastes (Anura: Myobatrachidae),Molecular Phylogenetics and Evolution:16: 3: 379–391

Swan, G.,(2001) Frogs of Australia,New Holland Publishers, Melbourne

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

Tyler M.J.and Davies, M. (1979), Foam Nest Construction by Australian Leptodactylid Frogs (Amphibia, Anura,Leptodactylidae),Journal of Herpetology, 13: 4: 509-510.

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.

Tyler, M.J., Martin, A. A. and Davies, M. (1979), Biology and Systematics of a New Limnodynastine Genus (Anura : Leptodactylidae) from North-western Australia
Aust. J. Zool., 27: 135-50

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

Warburg, 1965,Studies on the Water Economy of some Australian Frogs,Aust. J. Zool., ; 13: 317-30

 

 

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