ESR 11:271-278 (2010) - doi:10.3354/esr00277
Habitat relationships and presence of the threatened heath frog Litoria littlejohni (Anura: Hylidae) in central New South Wales, Australia
ABSTRACT: The heath frog Litoria littlejohni has been recorded from only scattered locations in south-eastern Australia, and habitat specificity may determine this rarity. I tested for relationships between the presence/absence of this species and habitat at 2 scales. A logistic regression was used to compare 10 presence and 36 absence sites to habitat variables at ponds located in central New South Wales. Habitat information derived from Geographic Information System (GIS) datalayers was compared to 51 known presence and 13000 absence (null) sites located within 220 km of Sydney. A predictive regression tree was also created using the 51 presence and 1000 of the absence sites. In the Watagan Mountains, heath frog presence showed a significant negative relationship with the percentage of grass cover in the surrounding forest. Heath frog presence sites in the Sydney region were positively associated with moist environments (Prescott Index) and negatively associated with terrain roughness. The regression tree indicated a 94% probability of presence where the Prescott Index was >1.2 and the solar radiation index was >13.4. These results indicate that heath frogs are present in moist, sunny areas that are relatively flat. However, these variables are too broad to accurately predict heath frog presence at a specific water body. Based on this information, the heath frog is absent from many apparently suitable sites. Thus, its patchy distribution, if habitat related, results from a yet to be measured variable.
KEY WORDS: Habitat relationships · Litoria littlejohni · GIS · Presence
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