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Brown Toadlet

Brown Toadlet (Bibron's Toadlet). Image: Peter Robertson.

The Brown Toadlet Pseudophryne bibronii, also known as Bibron’s toadlet, is a small brownish coloured toadlet only 2 - 3 cm long. It is endemic to south-eastern Australia including Tasmania  and is found in a variety of habitats not necessarily associated with permanent water.

The Brown Toadlet is found from south-eastern Queensland, through eastern NSW, central Victoria, eastern South Australia to Kangaroo Island and eastern Tasmania ( Hoser 1989, Hero et al.1991). it is considered to be the most widespread of its genus (Hero 1991) and covers an estimated area of 721,300 km2 and occurs at elevations from between 20-1000 metres above sea level (Anon 2006).

Brown Toadlet (Bribron's Toadlet)
Pseudophryne bibronii 
Kingdom:   Animalia
Phylum:             Chordata
Class:   Amphibia
Order:   Anura
Family:   Myobatrachidae
Status
World:  near threatened (IUCN 2004)
Australia:  not listed (EPBC Act)
Victoria:  endangered (DSE 2013)
Victorian FFG:  not listed

Identification

The Brown Toadlet is brown to black on its back, with a scattering of darker flecks and red spots. Its underbelly is marbled black and white and there is a bright yellow patch around its cloaca. A faded yellowish stripe usually occurs down the middle of its lower back. On the base of each arm there is always an orange or yellow patch. The skin on the back is smooth and usually scattered with a few tubercles (warts), while the belly is either smooth or slightly granular. Its toes are not webbed and it tends to moves by walking. Adult female toadlets are slightly larger than males, measuring between 25-32mm, compared to the male toadlets 22-30mm length (Walker et al. 1999, Gillespie et al 2004, Anon 2005).

Distribution in Victoria

All known records of the Brown Toadlet. Source: VBA 2016

In Victoria, the Brown Toadlet is distributed from the north-east through to central and western Victoria with scattered records in Gippsland. To the north of Melbourne there are records from Diggers Rest across to Craigiburn and Warrandyte. In Victoria's south-west most records are grouped on the Volcanic Plains bioregion north of Werribee, the Greater Grampians bioregion and the Lowan Mallee bioregion in the Little Desert.

Habitat & ecology

The Brown Toadlet utilises a wide variety of habitats, including dry forests, woodland, shrubland, grassland, coastal swamps, heathland, and sub-alpine areas (Anon 2006). They live in areas that are likely to be inundated after rain (Robinson 2002). They shelter in damp areas under leaf litter, logs, or other forms of cover.

Eggs are deposited terrestrially either under moist leaf litter, in sphagnum moss, or under stones or logs, near water. These eggs hatch after rain floods their area, providing water for the tadpoles (Pengilley 1973). It is thought that within its broad geographical distribution, the local distribution of  the Brown Toadlet may be influenced by soil pH,  with a preference for low soil pH. A study by Chambers et al. (2006) found that soil pH at sites where P. bibronii were recorded as present was significantly lower than pH at sites where P. bibronii were recorded as absent. They conclude soil pH and/or fungi associated with high-pH soils (>5) may play a major role in influencing the local distribution of this species.

Breeding

The breeding season is autumn (March to May) when males initiate breeding by calling from nest sites. Calling activity by Brown toadlet males may begin in February and continue through until August (Natureserve 2006). Males call in response to seasonal and environmental triggers, with the most intense calling on still evenings, after rain in April to early May (Howard et al 2010).

The males call from within a burrow or nest (a concealed area under a rock or log, or within damp leaf-litter) near water (Robinson 2002). The structure of the call by the male is variable, and can be described as a grating “ark” sound, or a short, grating “cre-ek” noise and the call is repeated every few seconds. (Gillespie et al. 2004; Anon 2006). Distinguishing the call from the Southern Toadlet is virtually impossible.

Females are believed to have a minimum reproductive age of less than 2 years, and lay only one batch of eggs each breeding season (Anon 2005).

Eggs are deposited in the nest at the calling site, or nearby in a concealed place near water. Eggs are large and pigmented, and are spawned in loose clumps of between 70-200 eggs (Anon 2006). When rain floods the nest site, these eggs hatch and the tadpoles develop in the water. Tadpoles vary in colour from dark brown to grey, and the clear tail fin is mottled with black or brown flecks. However, if rain does not occur soon after laying, the eggs can survive unhatched for many weeks, and the tadpoles begin to develop inside these unhatched eggs (Gillespie et al. 2004).  Metamorphosis takes between 3-7 months (Anon 2005)

Decline 

Declines in Victoria are occurring co-currently with declines in other states. (Hazel 2001). Currently, the specific reasons for many of the reported declines are not known.

A survey of the Greater Melbourne district for the Melbourne Water frog census failed to find the species at any of the 40 sites where it had previously been found. A decline in records inVictoria's Biodiversity Atlas also suggests that the species has reduced in numbers and their range has contracted. It has been predicted that the Brown Toadlet is in significant decline, at a rate of less than or equal to 30% over ten years (IUCN 2006).

In March to May 2010, surveys of 106 sites were sampled in for Bibron’s Toadlets (Brown Toadlets) in response to 2009 Black Saturday Bushfires.  The surveys were conducted the vicinity of Darraweit Guim in the west, to Yea in the north, Buxton in the east and Wonga Park in the south. Only two Bibron’s Toadlets (Brown Toadlets) were detected, both in unburnt area. However, researchers noted that it was likely Bibron’s Toadlets had already undergone severe declines in at least some parts of the study area well before the fires, possibly due to many years of below average rainfall (Howard et al 2010).

 

Threats

Habitat alteration and degradation - possible causes:

  • Livestock and high grazing intensities.
  • Cropping.
  • Infrastructure development.
  • Previous and current mining activities.

Waterway degredation, possible causes:

  • Increasing salinity
  • High nutrients and sediments in waterways
  • Waterway weeds such as willows
  • Changes to hydrology (groundwater pumping, altered flow patterns, drainage).

Other potential threats possible causes:

  • Global and regional climate change, including the current drought.
  • Chytrid fungus. 
  • Land and atmospheric pollution.
  • Pest animal species such as cats, foxes, dogs etc.
  • Small population sizes, which makes populations more susceptible to localised extinctions

Suggested conservation maeasures in Victoria

The overall and long term objective should be to guarantee that the Brown Toadlet survives and prospers in the wild, and maintains it’s potential to evolve.

1. Accurately measure Brown Toadlet numbers, locations and habitats of existing populations.
  • Develop a statistically sound method for assessing and comparing population sizes and habitat.
  • Undertake population and habitat monitoring.
  • A statistically accurate long-term study is required to distinguish between natural fluctuations in populations and serious declines. Currently, there is not a very accurate idea of the total number of individuals of the species, and this is needed to measure future declines from. Also, as individual toadlets occur over a large range of habitats, a habitat survey along with the population study will show which type of habitat supports the largest populations of Bibron’s toadlets, as well as which habitats they are failing to thrive in as well. This will give a better indication as to which habitat communities to protect, as well as which populations are likely to be at the biggest risk.
  • Provide this information to Catchment Management Authorities, local government authorities, land managers and landholders as required.

Responsibility for population monitoring: DELWP, Parks Victoria, VicForests

 

2. Determine the exact cause/s responsible for the current decline of the Brown Toadlet.
  • Develop a method for studying populations to determine the impacts of believed threats, and carry this out.
  • Provide this information to Catchment Management Authorities, local government authorities, land managers and landholders as required.

Responsibility: DELWP, Parks Victoria

 

3. Reduce the impact of known threatening processes to Brown Toadlet habitat.
  • Integrate habitat improvement with existing programs such as pest plant and animal control and salinity reduction projects.
  • Continue to work on improving water quality (This can involve working with landholders to fence off their stock from rivers and creeks, creek bank revegetation, implementing sediment traps in waterways, willow removal etc.).
  • Evaluate proposed infrastructure developments for possible effects on the Brown Toadlet before they are carried out (This will prevent accidental harm to the species, and will allow compensatory measures to be put into place where required).
  •  

Responsibility: DELWP, Parks Victoria, Local Government, relevant Catchment Management Authorities

 

4. Planning to protect known Brown Toadlet habitats.
  • Incorporate actions to protect Brown Toadlet habitat into relevant Regional Catchment Strategies, through Biodiversity Action Plans,  Local Landscape Plans, Biodiversity Maps and Municipal Planning Scheme environmental overlays.

Responsibility: DELWP, Parks Victoria, relevant Catchment Management Authorities, relevant Local Governments.

 

Recent surveys

Macedon Ranges Shire has undertaken surveys in many of its reserves. Detection of the Brown Toadlet at Bald Hill Reserve in 2016 was significant as it had not been recorded in the area for over 20 years.

References

Anon (2005) Pseudophryne bibronii . Australian Frog Database. Frogs Australia Network. Victoria.

Anon (2006) Pseudophryne bibroni: Bibron's Toadlet. Frogs of Australia. 

Chambers, J., Wilson J.C., Williamson I. (2006) Soil pH influences embryonic survival in Pseudophryne bibronii (Anura: Myobatrachidae) Austral Ecology, Volume 31, Issue 1: 68-75. doi: 10.1111/j.1442-9993.2006.01544.x

DSE (2013) Advisory List of Threatened Vertebrate Fauna in Victoria 2013. Department of Sustainability and Environment, Victoria.

Hero, J-M., Gillespie, G., Lemckert, F., Littlejohn, M. & Robertson, P. (2004) Pseudophryne bibronii  IUCN Red List of Threatened Species. Accessed 17 May 2016.

Hazel, D., Osborne, W. & Lindenmayer, D (2003) Impact of post-European stream change on frog habitat: south-eastern Australia. Biodiversity and Conservation 12: 301-320

Hero, J-M., M. Littlejohn and G Marantelli (1991) Frogwatch Field Guide to Victorian Frogs. Department of Conservation & Environment, Victoria.

Hoser, R.T. (1989) Australian Reptiles & Frogs, Pierson & Co, Sydney, Australia.

Howard, K., Cleeland, C. and Clemann, N. (2010). Assessment of the status of the threatened Bibron’s Toadlet and Southern Toadlet in areas affected by the Kilmore East-Murrindindi fires: Black Saturday Victoria 2009 - Natural values fire recovery program. Department of Sustainability and Environment, Heidelberg, Victoria. pdf

NatureServe (2006) Pseudophryne bibronii - Bibron's Toadlet, Brown Toadlet. Amphibian Survival Alliance

Pengilley, R. (1973) Breeding Biology of some Species of Pseudophryne (Anura: Leptodactylidae) of the Southern Highlands New South Wales. Australian Journal of Zoology 18(1): 15-30.

Robinson, M. (2002). A Field Guide to Frogs of Australia. Australian Museum/Reed New Holland: Sydney

Tyler, M.J. (1997) The Action Plan for Australian Frogs. Environment Australia, Canberra.

VBA (2016) Victorian Biodiversity Atlas, Department of Environment, Land, Water & planning, Victoria.

Walker, S.J., Hill, B.M., & Goonan, P.M (1999) Frog Census-a Report on Community Monitoring of Water Quality and Habitat Conditions in South Australia using Frogs as Indicators. Environment Protection Agency. Department for Environment and Heritage

See also: Southern Toadlet

Please contribute information regarding the Bribron's Toadlet (Brown Toadlet) - observations, images, conservation projects or research.  Contact SWIFFT

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