Litoria booroolongensis (Booroolong Frog) is a medium-sized frog from the Family Hylidae (“tree frogs”). Females are larger than males, reaching a maximum snout-to-vent length (SVL) of 55 mm, while males reach 40 mm SVL. The dorsal surface is smooth or with scattered low tubercles and may be grey, olive, or reddish-brown, with faint black reticulations and scattered salmon-coloured flecks. The ventral surface is finely granular and a white or cream colour. The Litoria booroolongensis (Booroolong Frog) backs of the thighs may be dark brown or covered in a yellow and black reticulated pattern. The head is slightly broader than it is long, and the snout is rounded. A faint, thin, black stripe begins at the snout, passes through the eye, then widens to enclose a small distinct tympanum before terminating at the shoulder. The eyes are prominent and golden, with the upper half of the iris often brighter than the lower half. Males have small dark flecks on their throats and lack a distinct vocal sac. Disks on the fingers and toes are well developed. On the hands, the second finger is longer than the first, and on the feet, a small but prominent inner metatarsal tubercle and tiny outer metatarsal tubercle are present. Fingers are free from webbing, while the toes are nearly fully webbed with webbing reaching the disc of the fifth toe. The species can be further identified from the male’s breeding call, which is a soft “qrk, qrk, qrk” purring sound lasting two or three seconds.
Booroolong Frog |
Litoria booroolongensis
Status: Endangered on the EPBC Act list
Government evidence of impact of climate change:
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Australian Government, Conservation Advice, Litoria booroolongensis
Threat factor Threat type Evidence base and status Climate change Stream drying Known current Climate change is expected to cause a pronounced (drought) increase in extinction risk for frogs over the coming century (Hagger et al. 2013 Pearson et al. 2014).
Climate projections for eastern Australia include reduced rainfall; increased average temperatures; and more frequent droughts (CSIRO 2007 CSIRO Bureau of Meteorology 2015).
Bd impacts have been observed to be most severe following metamorphosis (Berger et al. 1998; 1999; 2016 Garner et al. 2009); with mortality of adults and juveniles eroding the capacity of subpopulations to sustain recruitment losses associated with drought (see climate change section; above) and from predation of eggs and tadpoles by introduced fish (see invasive species section; below).
Compounding this predation rate; the number of predators attracted to the area (Hradsky et al. 2017) and predator activity (Leahy et al. 2015) increase where habitat has been modified through frequent or intense burning (see climate change section; above).
Any action or event that reduces stream permanency (e.g. water extraction or climate change) or results in loss of rock crevices (e.g. smothering by weeds; sediment; or post fire ash slugs); threatens the persistence of subpopulations of this species (OEH 2012).
However; fire can adversely affect stream breeding habitat; increasing water temperature; altering water chemistry (Lyon O Connor 2008); and creating sediment ash runoff slugs that can form in waterways following rainfall (Lyon O Connor 2008 Alexandra Finlayson 2020).
However; an analysis by a team from the National Environmental Science Program (NESP) Threatened Species Recovery (TSR) Hub showed that a significant proportion of the range of the Booroolong Frog was affected; with 5 burnt in high to very high severity fire; and a further burnt in low to moderate severity fire (Legge et al. 2021).
Surveys immediately after the fire event indicate that some subpopulations have been severely impacted by a combination of fire; flood; and disease (West Johnson 2020).
A structured expert elicitation process was used to estimate the proportional population change for this species from pre fire levels to immediately after the fire and then out to three generations after the fire; when exposed to fires of varying severity.
For comparison; experts also estimated the population change over time in the absence of fire; finding that by three generations the overall population of Booroolong Frogs after the fire to be one percent lower than it would have been had the 2019 20 fires not occurred (Legge et al. 2021).
Fire impact surveys for the species have yet to be conducted in NSW; but in Victoria; surveys have revealed the fires affected the Burrowye Creek subpopulation (distributed over Burrowye and Guy Forest creeks).
Recent surveys have revealed the extent of the impact of drought on the species; particularly in the Northern Tablelands where many subpopulations are close to extirpation (see Criterion 1); and analysis of the impact from the 2019 20 bushfires estimates an overall population decline of up to 27 percent from pre fire levels one year after the bushfires (see Criterion 1).
Surveys conducted in Victoria have revealed post fire flooding burying the best breeding habitat in ash; mud; and other debris at some sites (West Johnson 2020); and analysis of the impact estimates an overall population decline of 16 44 percent from pre fire levels over the next 10 years (see Criterion 1).
Any reduction in stream flow can increase the likelihood of stream drying during periods of drought and can increase sedimentation.
Over the last 10 years; the species has been impacted by severe drought (2017 20) across its entire distribution and the 2019 20 bushfires; with burnt areas overlapping with 14 percent of the distribution (see Criterion 1).
The case for being precautionary; and listing in the Endangered category; is strengthened by the lower plausible value including sites that have been extirpated by the recent drought (2017 20) (see Criterion 1) and other sites that are likely significantly impacted by the 2019 20 bushfires (both of these events occurred towards the end of the 10 year period that point records were taken).
However; the extent and severity of the recent drought (2017 20) and the 2019 20 bushfires has recalibrated the size of an area that can potentially be considered one location; particularly for species that have a biology and ecology that makes them more susceptible to these threats; such as the Booroolong Frog (see above).
Recent surveys have revealed the extent of the impact of drought on the species; particularly in the Northern Tablelands where many subpopulations are close to extirpation (see Criterion 1); and analysis of the impact from the 2019 20 bushfires estimates an overall population decline of up to 27 percent from pre fire levels one year after the bushfires (see Criterion 1).
A continuing decline in EOO; AOO; extent and or quality of habitat (and therefore number of locations or subpopulations); and number of mature individuals may be inferred based on the ongoing threats to the Booroolong Frog; primarily through habitat loss from drought (see Criterion 1) and changes to riparian zone structure (either directly or indirectly) from primary industries.
Across the distribution range of the Booroolong Frog; a number of subpopulations are under threat of local extinction due to their small size and the risk of stream drying (see Criterion 1).
Impacts from the drought have been exacerbated by the 2019 20 bushfires.
Therefore; the Committee has inferred a significant cumulative decline of minimally 10 percent over the next 10 years; in line with the NESP TSR Hub analysis; together with the threat posed by further stream drying through more frequent drought events; and the additive impacts from fish predation and Bd infection on different life stages (see Criterion 1).
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