The
Global Amphibian Decline:
Trends, Causes, and Challenges
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The
Global Amphibian Decline: |
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Australian lace-lid |
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Global
Trends Causes
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Regional Trends: Australia In Australia, as in Central and South America, the many amphibian species experiencing dramatic population declines primarily include endemic species confined to montane areas. In all known cases, declines occurred with marked rapidity. Since the late 1970s at least fourteen frog species have declined sharply in montane areas of eastern Australia. All of these species breed in and live near rain-forest streams and are locally endemic. Some exist only in small pockets of montane rain forest, whereas others have larger ranges that include both montane and lowland areas. The earliest known species to decline were the southern day frog (Taudactylus diurnus) and the southern gastric brooding frog (Rheobactrachus silus) in the late 1970s. Both species occurred in subcoastal mountain ranges and were last observed in 1981. Concurrently, the cascade tree frog (Litoria pearsoniana), the giant-barred frog (Mixophyes iteratus), and Flea's barred frog (M. fleayi) declined by more than 90% in southeastern Queensland and nearby areas of New South Wales, although small extant populations still exist. In 1985, declines began to occur in the marginally tropical rain forest of central eastern Queensland and affected the Eungella dayfrog (T. eungellensis) and the northern gastric brooding frog (R. vitellinus). Nearly all known populations of these two species disappeared within six months, though very small populations of dayfrogs have been rediscovered in more recent surveys. The gastric brooding frog, however, has not been observed since 1995. The most recent declines have occurred in the tropical rain forests of far-northern Queensland, where large-scale population declines began in 1989. At least seven species declined suddenly, including the armored mistfrog (Litoria litoria), mountain mistfrog (L. rheocola), waterfall frog (L. nannotis), northern tinkerfrog (Taudactylus rheophilus), sharp-snouted dayfrog (T. acutirostris), and the Australian lace-lid (Nyctimystes dayi, above). Four of these species were limited to montane areas and have been extirpated in the wild. The other three species have disappeared from upland areas but persist at normal densities in the tropical lowlands. Several declines have also occurred among populations inhabiting upland streams in south-eastern Australia, including the spotted tree frog (L. spenceri) and the leaf-green tree frog (L. phyllochroa). Predation from introduced trout are suspected in these two declines. |
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