Litoria spenceri (Spotted Tree Frog) is a medium-sized frog from the family Hylidae (“tree frogs”). Females are larger than males, having a snout-to-vent length (SVL) to 60 mm, while males reach 45 mm SVL. Dorsal colouration is highly variable, ranging from chocolate or golden brown to olive-grey to bright green, with or without darker blotches. In brown specimens, the upper lip often remains green, and in green specimens there may be a gold stripe from the nostril to beyond the arm, which breaks into fine gold spots over the abdomen. The dorsal surfaces of the body and limbs typically have numerous small but distinct tubercles. The ventral surface is pale and granular, often becoming flushed with lemon yellow or orange towards the rear and the underside of the legs. The head is broad and short with a rounded snout. The eyes are golden. The tympanum is indistinct with a skin fold above. Toes and fingers are long and flattened with moderately expanded discs. On the hands, the second finger is longer than the first. On the feet, a small but prominent inner metatarsal tubercle is present. The fingers have distinct basal webbing, and the toes are fully webbed to the base of the pads.
Spotted Tree Frog |
Status: Critically Endangered on the EPBC Act list
Government evidence of impact of climate change:
Australian Government, Conservation Advice, Litoria spenceri
Mortality associated with Bd erodes the capacity of subpopulations to sustain loss of recruitment associated with drought and reduces resilience to climate change (Scheele et al. 2016).
Climate Change Increased severity Known Climate change is expected to cause a pronounced and frequency of current increase in extinction risk for frog species over the heatwaves and coming century (Hagger et al. 2013 Pearson et al. change to 2014).
Climate projections for eastern Australia include precipitation reduced rainfall; increased average temperatures; and patterns more frequent droughts.
Models of habitat suitability under climate change scenarios suggest that both habitat availability and population abundance of Spotted Tree Frogs may decrease to approximately 15 of current levels by 2100 (Keith et al. 2014).
These sorts of events are increasingly likely to reoccur as a result of climate change.
The Committee has inferred a significant cumulative decline of greater than 80 percent over three generations (including the past and into the future) in line with modelled declines from the threat posed by predation by trout and Bd infection; combined with the extent of the Spotted Tree Frog s distribution range that overlapped with the fire affected areas and the ongoing and anticipated threat from climate change.
Understand the influence of climate change on the long term survival prospects of the species; due to altered temperatures; rainfall patterns; bushfires; environmental stressors and diseases; through maintaining robust population and environmental monitoring.
Increased Known Localised extinction of frogs has been observed through intensity frequency current wildfire events.
Frogs have little defence against fire. of wildfire They are unable to flee and have a low tolerance of extreme temperatures and desiccation (Greenspan et al. 2017).
Wildfire 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).
This fire is thought to have adversely impacted Spotted Tree Frog recruitment within the catchment; with small recently metamorphosed frogs likely perishing due to their limited ability to move quickly and seek shelter in water.
However; an analysis by a team from the National Environmental Science Program (NESP) Threatened Species Recovery (TSR) Hub showed that a large proportion of the range of the Spotted Tree Frog was affected; with 10 burnt in high to very high severity fire; and a further 16 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 Spotted Tree Frogs after the fire to be 5 percent lower than it would have been had the 2019 20 fires not occurred (Legge et al. 2021).
Post fire ground truthing has revealed eight Spotted Tree Frog sites directly affected by fire; flood; and Bd and other sites impacted by ash and debris flows related to the fires.
Any reduction in stream flow can increase the likelihood of stream drying during periods of drought and can increase sedimentation.