The Pygmy Blue Tongued Skink
General Information

This species was discovered in the 19th century, but then not seen for so many years that it was believed extinct until several small populations were discovered in 1992. Understandably, this very rare species is unlikely to come into private hands for the foreseeable future, but several zoos are working with it to increase its numbers. Little is known of its ecology, but it`s suspected that it`s an ambush predator that lives mostly on invertebrates with some plant matter. They are found in Adelaide, Australia. It is estimated that only about 5000 remain.

Past and Present Distribution

Very little information exists on the past distribution of T. adelaidensis, with the few known localities extending from the Adelaide Plains to the North Mount Lofty Ranges (Ehmann 1982, Hutchinson 1992). Prior to this study, only 20 specimens were known, of which half have no precise capture data, whilst some localities may only be addresses of the consigners of the specimens (Armstrong et al 1993). The relative abundance of pygmy bluetongues in European collections in the 19th century (11 of the 20 specimens) suggests that the species was formerly common, and has undergone a marked decrease in distribution (Shea 1992).

The pygmy bluetongue is now known from ten spatially discrete subpopulations, ranging from south of Burra to south of Peterborough. Preliminary estimates of population size suggest that the total number of pygmy bluetongues is 5500, with most sites supporting fewer than 500 individuals. This estimate is based upon lizard numbers within plots extrapolated against the area of prime grassland habitat within each site. The estimates given are a minimum count, as the boundary zone of poor habitat around each population would support additional pygmy bluetongues, although at a lower density. The total population estimate is still preliminary, and a need for greater precision exists. More accurate sub-population estimates will be addressed as part of the Recovery Plan.

Reasons for Decline

The initial impression that lizards require unploughed areas has been reinforced by the absolute correlation at all known sites between the presence of lizards and absence of ploughing. Observations at these sites show that lizards barely penetrate into patches of ploughed land adjacent to known bluetongue sub-populations. Native grassland similar to that in which the species occurs at Burra once extended south onto the Adelaide plains, but being prime agricultural land, was one of the first areas in South Australia to be cleared and ploughed. Ploughing permanently alters the vegetation and ground cover, converting a native, largely perennial flora into an introduced, largely annual one. In addition, ploughing would destroy the burrows, killing lizards directly and leaving the survivors without shelter and at the mercy of predators. The fact that most specimens were collected last century may simply be correlated with the fact that this was when most of their habitat was being converted to agriculture.

The presence of a relatively large number of apparently unploughed native grasslands that contain no pygmy bluetongues suggests that other threatening processes may have contributed to the endangered status of this animal. Preliminary observations suggest that the degree of ground cover is correlated with the presence/absence of pygmy bluetongues. Ground cover is affected by several land use practices, including fertilising, seeding, fire and degree of grazing. These potential threatening processes require further study in order to propose management actions for pygmy bluetongue habitat.

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