Watson's Tree Frog  |  

Litoria watsoni

Status: Endangered on the EPBC Act list

Watson’s 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 64 mm, while males reach 59 mm SVL. The dorsal surface is weakly granular, becoming more granular laterally and on the venter and thighs. Dorsal surfaces of the body and limbs are a light brown, mottled with dark and light flecking of brown and yellow. The sides of the face are lighter still. The ventral surface is granular and white. Distinctive bright orange-red markings are present on the back of the legs and onto the foot, groin, and posterior flanks, and on the upper axial of the forelimbs. The head is longer than it is wide with a rounded snout. The eyes are large and yellowish-gold. The tympanum is circular and visible. A dark stripe extends from the tip of the snout to the eye, continues less intensely behind the eye and over the tympanum, and then onto the flank where it gradually dissipates. The legs are moderate to long. The fingers and toes are long with prominent terminal discs. The fingers are not webbed, while the toes have basal webbing.

Government evidence of impact of climate change:

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  • Australian Government, Conservation Advice, Litoria watsoni

    In addition; across the distribution range; habitat has been degraded by climate change (including increased severity and frequency of bushfires and drought) and visitors to National Parks.
    Mortality associated with Bd erodes the Extent across the entire capacity of the population to sustain loss of recruitment range associated with drought and reduces resilience to climate change (Scheele et al. 2016).
    Climate change Increased severity Status current Climate change is expected to cause a pronounced increase in and frequency of extinction risk for frog species over the coming century Confidence known heatwaves and (Hagger et al. 2013 Pearson et al. 2014).
    Climate projections change to Consequence severe for south eastern Australia include reduced rainfall; precipitation increased average temperatures; and more frequent Trend increasing patterns droughts.
    Climate change is expected to impact frog recruitment by reducing the availability and altering the seasonality of breeding sites (Lemckert and Penman 2012 DEPI 2014 Lowe et al. 2015).
    This sort of event is increasingly likely to reoccur as a result of climate change.
    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 Watson s Tree Frog; in particular disease (Bd); habitat loss; and climate change (see Criterion 1); thereby meeting subcriterion (b)(i;ii;iii;iv;v).
    Increased Status current Localised extinction of frogs has been observed through intensity frequency bushfire events.
    They Confidence known of bushfire are unable to flee and have a low tolerance of extreme Consequence severe temperatures and desiccation (Gillespie et al. 2016).
    An analysis by a team from the National Environmental Science Program (NESP) Threatened Species Recovery (TSR) Hub showed that 85 of the distribution of Watson s Tree Frog was affected by these fires (with 44 burnt in high to very high severity fire); and the estimated proportional population change for this species from pre fire levels to one year after the fire was an overall decline of 41 from pre fire levels; but that the decline could be as large as 62 (bound of 80 confidence limits) (Legge et al. 2021).
    The fires may have accelerated any population decline; through direct mortality; and the unfavourable post fire conditions (loss of shelter; increased susceptibility to predators; and loss of prey); as well as a reduction in future recruitment (egg and tadpole death and breeding site degradation).
    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 by three generations; the overall population of Watson s Tree Frogs after the fire was estimated to be percent lower than it would have been had the 2019 20 fire not occurred (Legge et al. 2021).
    Despite the uncertainty over the extent of the impact of the bushfires; evidence suggests percent decline in site occupancy during drought; likely sustained or amplified by fire effects on mortality; predation and habitat suitability.
    Adding to a loss of forest habitat; the availability of breeding sites; particularly ephemeral ponds; was likely reduced during recent extreme drought events.