Adding burrows to enhance a population of the endangered pygmy blue tongue lizard, Tiliqua adelaidensis

The endangered pygmy blue tongue lizard, Tiliqua adelaidensis, occupies spider burrows in a population near Burra, South Australia. In each of twelve 20 × 20 m plots at that population, we added 36 artificial burrows, providing about a ten fold increase in suitable burrows for lizards. Over three surveys during the spring and summer of 2001/2002 there were significant increases in lizard numbers in the experimental plots relative to the controls, both for adult lizards and for new recruits after clutches were produced. This local increase in population density may be due to lizards locating suitable burrows more easily where burrow numbers were supplemented. The increased availability of high quality burrows may also reduce mortality among lizards searching for suitable burrows. Additional burrows also led to an increase in local density of a burrow-dwelling centipede that is a potential predator of lizards, but there was no evidence of predation, and any negative predation impact was outweighed by the beneficial effect of providing more burrows. Overall the results suggest that adding artificial burrows could enhance local population density and recruitment success, and that this could be a valuable tool in the conservation management of this endangered species.     

Regrowth and revegetation in temperate Australia presents a conservation challenge for reptile fauna in agricultural landscapes

Secondary vegetation, associated with changes in land use, presents a conservation issue in the preservation of biological diversity in agricultural landscapes. We examine the interactive effect of eucalypt regrowth and rock habitat on reptile species richness and assemblage structure in fragmented agricultural landscapes in south-eastern Australia. Zoogeographic and geomorphic factors influenced species richness and community composition. Saxicolous and arboreal species were less abundant in grassy woodland regrowth, whereas Bassian and fossorial species responded positively to forest regrowth (and tree plantings). Regrowth with rock habitat had higher reptile richness, and more old growth-associated taxa, than regrowth without rock habitat. Thus, the presence of saxicolous habitat can reduce the time required for regrowth to attain a climax community structure and elements of old growth fauna. However, in the absence of vegetation management, secondary vegetation can reduce habitat suitability for a broad range of reptiles. In agricultural landscapes historically supporting savannah-like vegetation, habitat manipulation may be necessary to maintain reptile diversity. Furthermore, tree plantings in temperate agricultural landscapes should aim to restore historical vegetation composition and structure, thereby reflecting the habitat requirements of extant species and facilitating evolutionary processes. In grassy woodland ecosystems, this may involve heterogeneous plantings which emulate natural levels of canopy cover and solar penetration. Maintaining biodiversity in agricultural landscapes will therefore involve managing trade-offs to preserve areas of dense regeneration for regrowth-dependant fauna, while at the same time, creating open-canopy environments to enhance habitat for ectothermic organisms.     

Habitat deterioration affects body condition of lizards: A behavioral approach with Iberolacerta cyreni lizards inhabiting ski resorts

We analyzed whether habitat deterioration due to ski slopes affected lizards’ behavior, and whether these changes in behavior had consequences for the body condition and health state of lizards. Results suggested that habitat deterioration in ski slopes not only implied a loss of optimal habitat for lizards, but also led to an increase in perceived risk of predation. Males seemed to adjust their movement patterns to differences in risk, increasing their movement speed during their displacements across risky areas within ski slopes, but as a consequence, they incurred loss of body condition. A laboratory experiment supported that fleeing at high speeds in areas without refuges can be a factor responsible for reduced body condition. However, changes in body condition did not affect sprint speed of lizards. Our study provides new evidence that behavioral strategies to cope with increased predation risk, due to human-induced habitat deterioration, may affect body condition of lizards. Our results have applications for the design of conservation plans for this endangered lizard species. Environmental impact studies should be performed before opening new ski slopes, but taking into account not only the presence of lizards but also their body condition. An effective way to decrease the effects of habitat loss may be the artificial restoration of some refuges to create safe corridors for movement.     

Habitat requirements of the endangered pygmy bluetongue lizard, Tiliqua adelaidensis

The pygmy bluetongue lizard, Tiliqua adelaidensis, occupies spider burrows as home sites. It is an endangered species, known from only 19 small natural grassland sites in the mid-north of South Australia, all on privately owned land. Habitat requirements of the pygmy bluetongue lizard were investigated at four sites. Both within and between sites, lizards were more likely to be found in areas with a greater number of deep spider burrows. Areas where lizards were not found tended to lack these burrows. Strong site similarities were found for a range of habitat parameters examined. Within these grasslands there was no specific vegetation community associated with areas occupied by pygmy bluetongue lizards. However there was a distinct vegetation community associated with an absence of lizards. Generally there was no difference in the abundance and diversity of ground dwelling invertebrates between areas with and without lizards. As the only protected area of natural grassland within the known distribution, Mokota Conservation Park was assessed as a potential reintroduction site. It was found to be unsuitable due to a low number of deep spider burrows and a vegetation community similar to that found in uninhabited areas of known lizard inhabited sites. Unless other conservation areas can be established, preservation of this lizard will rely on habitat management by private land holders. Community goodwill and informed advice to the land holders will be essential in this process.     

Effects of bush encroachment on an assemblage of diurnal lizard species in central Namibia

Bush encroachment is a serious environmental and economic problem in Namibia, but little is known about impacts on native reptile diversity. Area-confined visual surveys were used to examine a diurnal lizard assemblage in central Namibian commercial ranchlands. Surveys were conducted in plots of open savanna habitat and proximal bush-encroached habitat. The following four species comprised 97.5% of all lizard observations: Pedioplanis undata, Mabuya varia, M. striata, and Lygodactylus bradfieldi. Pedioplanis undata was terrestrial, and the remaining three species were largely arboreal in our study plots. Mabuya varia was found in all savanna plots but was absent from all bush-encroached plots. Two species (P. undata and L. bradfieldi) were less abundant in bush-encroached plots. One species (M. striata) was more abundant in bush-encroached plots than in open savanna plots. Arboreal lizards demonstrated an avoidance to invasive woody plant species. Decreased diversity of habitat structure in bush-encroached habitats appears to influence native savanna lizard assemblages. Our results are consistent with accumulating evidence suggesting that bush encroachment and its associated ecological impacts are reorganizing savanna ecosystems throughout southern Africa.