The life history and decline of the threatened Australian frog,Litoria raniformis

Abstract

A popular idea amongst ecologists last century was that animals which exploit dynamic environments often display 'fast' life history strategies (high fecundity, rapid growth and maturation, and low or variable adult survival rates) relative to those which occupy more stable environments. Whilst the underlying theory has been discredited, the categorization remains of interest, because species with 'fast' life history traits are thought to be more robust to human-induced environmental change than those with 'slow' life history traits.We examined the life history traits of the endangered Australian frog Litoria raniformis, to determine whether it displays 'fast' life history traits (like its sister species L. aurea and L. castanea), and to assess the role of these traits in the decline of this species. Mark-recapture data confirmed that L. raniformis displays rapid growth and maturation. The data also suggest that L. raniformis displays relatively low adult survival rates. We propose that the 'fast' life history traits of this species are adaptive to metapopulation dynamics. In turn, we suggest that the rapid decline of L. raniformis may have resulted from metapopulation collapse, driven ultimately by habitat loss, degradation and fragmentation, and proximately by severe stochastic perturbations.

Surface water network structure, landscape resistance to movement and flooding vital for maintaining ecological connectivity across Australia’s largest river basin

“…We used surface water, land cover (including vegetation), and transportation features to develop resistance surfaces as these have been found to strongly affect the distribution and movement of Australian floodplain amphibian species (Jansen and Healey 2003;Hazell et al 2004;Wassens et al 2008;Heard et al 2012b;Ocock et al 2014). Resistance surfaces were developed at the resolution of the Australian 250 m Dynamic Land Cover Dataset (DLCD), the highest resolution land cover data available for the entire MDB (Table 1).…”

Wetland characteristics influence disease risk for a threatened amphibian

“…Eight spotlight surveys were conducted at all sites in the 2004-2005 season, and 10 surveys were conducted at five sites in the 2005-2006 season. Surveys were conducted on a two-or three-week rotation, as described by Heard et al (2012b). Weather variables were recorded during each survey.…”

“…Previously unmarked individuals were retained overnight and tagged in the laboratory the following day, using either a Passive Integrated Transponder (PIT) tag (Trovan, Melton, East Yorkshire, UK) or a Visible Implant Alphanumeric (VIA) tag (Northwest Marine Technology, Shaw Island, Washington, USA). Tagging procedures are described in detail by Heard et al (2008) and Heard et al (2012b). Frogs retained for tagging were released at their point of capture within 24 h.…”

“…Similar to the occupancy approach described above, CJS models are built on the assumption that the detection (1) or nondetection (0) of each individual i on each survey s during a mark-recapture study results from two processes: (1) the probability of survival of individual i between surveys s À 1 and s (/ is ), and (2) the probability of recapture of individual i on survey s (r is ; Lebreton et al 1992). Given variation in the length of the interval between capture occasions, we rescaled / is to be the daily probability of survival by raising it to the power of the number of days in the interval s À 1 to s (see Heard et al 2012b for further details).…”

Interspecific variation in the phenology of advertisement calling in a temperate Australian frog community

“…Survey timing sought to optimize detection rates of Litoria raniformis in most cases; this endangered species having been studied intensively in this region since 2001 (Heard et al. ,b, , ). However, aural surveys during the spring and early summer months optimize detection rates across the frog community in this region (Canessa and Parris ).…”