Western spotted In the wheat and sheep farming country of WA’s Wheatbelt, a noisy little is defying the odds and providing a soundtrack to the night from small, isolated temporary ponds made possible by autumn rains. f you’re lucky enough to find yourself adding to a symphony until the air around In most areas of the Wheatbelt, less in the semi-arid parts of WA’s south- you is pulsing. Congratulations, you than 10 per cent of the native vegetation Iwest from March to April and there’s have found yourself a thriving breeding now remains, mostly as small, isolated been some rain, you should go out at night population of western spotted ! remnants. The value of the approximately and listen carefully. If you’re even luckier, 1000 small nature reserves, parks, reserves you may hear a shrill ‘whoop, whoop’ call GOOD CALL and private property bush cannot be that doesn’t stop all night. If you brave This has a unique breeding underestimated as they provide valuable the darkness and track down the source biology. Males arrive shortly after the protection for like frogs and areas of this strange call, you’ll likely end up at first autumn rains between March and from which they can recolonise when a dry small wetland, roadside ditch, dam, May. They excavate a burrow in a sandy conditions are favourable. Such rapid and salinity drain or old quarry. depression and begin calling. If successful widespread landscape change has had a Looking around on the ground may in attracting a mate, a foamy egg mass is significant impact on local fauna and flora. reveal a large mound of freshly turned up deposited in the base of the burrow in the are the world’s most sand with no obvious entrance hole. The moist soil. threatened class of vertebrate and there calling has probably stopped by now, so At this stage, the frogs leave the has been great concern about both the stand still, turn off your torch and look at burrow. The eggs develop to some degree cause and scale of declines of amphibians the stunning southern skies and enjoy the within the protection of the jelly-like foam globally. The most significant causes of stars and soon enough, the calls will start surrounding the eggs. If all goes well, the decline are the chytrid fungus, climate up again, one at first and then one by one, season breaks, and rains fill the breeding change and loss. Habitat loss sites with water. The flooded burrows is the leading cause for the decline of collapse, the eggs hatch and complete their Australian frogs, yet we have a very limited development as free-swimming tadpoles. understanding of how frogs persist in fragmented landscapes, or even if they do. THE FIGHT FOR SURVIVAL The western spotted frog is distributed PREDICTING THE FUTURE Previous page widely throughout the semi-arid region of To understand the impact of a drying Main Western spotted frogs. Western Australia from near Kalbarri in climate and habitat loss, a comprehensive Photo – Jiri Lochman the north-west to Esperance in the south- dataset is needed that can be used to Above Western spotted frog emerge to forage east. Much of this distribution coincides model population processes and predict on warm wet nights outside the breeding with the wheat-sheep farming region the future survival of frogs on a landscape season. of Western Australia, and accordingly, scale. Over six years, starting during much of the range of this species has been his PhD at the University of Western Above right A granite outcrop breeding subject to habitat loss, fragmentation and Australia in 1999, Robert Davis studied site near Kellerberrin. The larger salt river in the foreground separates this site from salinisation as European settlers cleared 30 populations of the western spotted frog populations in the north. 140,000 square kilometres in less than albopunctatus in the Central Photos – Robert Davis 150 years. Wheatbelt region of WA near Kellerberrin.

44 LANDSCOPE He installed pitfall traps to capture migrating adults during the autumn breeding season. Adults were marked so he knew which adults survived from year to year. Egg clutches were collected, and the number of eggs counted. He followed the metamorphosis of tadpoles into frogs from May to Perth ● September. While the western spotted frog may appear to be widespread and secure, Rob’s ● Distribution of detailed studies of genetics and adult, western spotted frog tadpole and egg survival, suggest that western spotted frog populations are small and isolated, with low tadpole and juvenile frog survival. So, he teamed up with research scientist Cheryl Lohr from DBCA to increased the probability of persistence for Top left Western spotted frog burrow. predict the probability of persistence for this species. Top Western spotted frog tadpole. That is to say that populations that this species. “We used population viability became extinct or were declining could Above Western spotted frog. analysis (PVA) to model the sensitivity be saved by new individuals moving Photos – Jiri Lochman of populations to a decline in breeding- in. Several similar studies on frogs and season rainfall and the length of time other animals have come to the same that breeding ponds held water,” said conclusion. In Rob and Cheryl’s study, Rob. “We wanted to predict the likely the metapopulation facilitated population persistence of this species in a highly persistence, despite increases in the modified agricultural landscape that frequency of drought. still has opportunities for successful “ ...western spotted frog breeding.” A DRYING CLIMATE The analysis showed the western Atmospheric research predicts a still occurs across all its spotted frog still occurs across all of its drying climate for the south-west of WA. known range and uses known range and uses a wide range of But western spotted frogs are a long-lived a wide range of water water bodies such as livestock dams for dryland frog that may be resilient to some breeding. Regular dispersal among small dry years because they don’t try to breed bodies for breeding such breeding populations (metapopulations) every year. as livestock dams.”

LANDSCOPE 45 “Consequently, we assumed drought such as in salinity interceptor banks and have focused considerable resources on did not have a catastrophic effect on small pastoral soaks,” said Rob. understanding and preventing the spread of juvenile frog survival,” said Rob. “Some frogs are choosing breeding chytrid fungus and determining the impact However, as the drying climate sites based on cues such as soil moisture of climate change on amphibians, sound worsens, the reduction in rainfall and or the presence of a depression, but baseline population demographic data is runoff will further reduce the size and these sites do not tend to hold water essential to inform the complex models duration of temporary ponds which may long enough for tadpoles to develop and required to understand these threats. result in widespread failure of recruitment breeding attempts fail when sites do not With baseline life history data lacking for (the successful development of tadpoles fill with water during winter. most species of , it is critical that into juvenile frogs), which requires the “In the future, consideration may need such studies are resourced and continued,” pond to be full of water for at least six to be given to designing breeding wetlands said Rob. weeks. to ensure the presence of core breeding If this happens, the maintenance of a sites that continually succeed, even in a well-connected metapopulation may be series of low rainfall years.” even more critical to the species viability. Above left Western spotted frog habitat, Another major finding was that the WHAT’S NEXT Eagle Rock.

survival rate of juvenile frogs was a key to Juvenile and adult survival is critical Top Western spotted frog. populations persisting in the long-term. to the long-term persistence of western Photos – Ann Storrie If there was an increased death rate of spotted frogs and this may be the case for juvenile frogs e.g. by predation or car many amphibians with similar life histories. Above A newly metamorphosed western spotted frog emerges from a breeding pond. strike, then the model suggested that Finding that a metapopulation with as Its tail will be slowly reabsorbed. populations would be driven to extinction few as five sub-populations reduced the Photo – Robert Davis sooner. To increase the accuracy and extinction risk for western spotted frogs resolution of future models, more research gives cause for hope that WA’s frogs may Robert Davis is a senior lecturer at on the survival of juveniles is required. have the adaptive capacity required to Edith Cowan University and can be survive drying climates, particularly if contacted at [email protected] LOCATION, LOCATION connectivity is maintained or enhanced. Cheryl Lohr is a DBCA research “A fascinating observation during our “Our work highlights the importance scientist and can be contacted at [email protected] or work is the attraction of breeding adults of furthering our fundamental knowledge (08) 9405 5750. to sub-surface water and sandy substrates of amphibian species. While recent efforts

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