Cover provides shelter, food, nesting opportunities, and protection from predators. The behavioural response of small mammals to reduced cover has been well documented. However, very little is known about the effect of cover on community and population dynamics. Australian small mammals generally inhabit extremely dynamic ecosystems, where cover and food supplies are greatly affected by fire. Species are described as early or late seral specialists, generally returning to a disturbed area once their habitat requirements are met. Habitat requirements have loosely been interpreted as cover and food supply, however, these factors are not mutually exclusive and few studies have attempted to determine the driving factors behind small mammal succession. In this study, we manipulated specific aspects of cover in the eucalypt forests of Fraser Island and show that the behaviour and population dynamics of small mammals were greatly affected. A reduction of cover from grass-trees (Xanthorrhoea johnsonii) did not affect small mammal species composition, however, the abundance and size structure distribution of the dominant species (Rattus fuscipes) decreased. Patch use by rodents also decreased after cover was reduced. Rattus fuscipes must trade-off remaining in an environment with increased risk of predation or disperse to an area with greater cover but increased competition. Juveniles dominated (>60%) populations of R. fuscipes after cover was reduced, however, size distributions of control sites were relatively more even (<25% juvenile). While adult R. fuscipes are either killed by predators or disperse to other areas, juveniles that remained or immigrated to an area of reduced cover gained a selective advantage over control sites, because reduced competition with adults increased body condition of juvenile R. fuscipes.

Stable social aggregations are rarely recorded in lizards, but have now been reported from several species in the Australian scincid genus Egernia. Most of those examples come from species using rock crevice refuges that are relatively easy to observe. For many other Egernia species that occupy other habitats and are more secretive, it is harder to gather the observational data needed to deduce social structure. Instead we used genotypes at six polymorphic microsatellite DNA loci of 229 individuals of E. frerei, trapped in 22 sampling sites over 3,500 ha of eucalypt forest on Fraser Island, Australia. Each sampling site contained 15 trap locations in a 100 x 50 m grid. We estimated relatedness among pairs of individuals and found relatedness was higher within than between sites, and that female relatedness within sites was higher than male relatedness, or between males and females. Within sites we found that juvenile lizards were highly related to other juveniles and to adults trapped at the same location, or at adjacent locations, but relatedness decreased with increasing trap separation. We interpret the results as suggesting high natal philopatry among juvenile lizards and adult females. This result is consistent with stable family group structure previously reported in other rock dwelling Egernia species, and suggests that social behaviour in this genus is not habitat driven.

A comparative study of environmental factors that affect nesting in Australian and North American freshwater turtles. Journal of Zoology.

Kenneth D. Bowen, Ricky-John Spencer and Fredric J. Janzen. 2005.

The timing of reproductive events is critical for fitness, and these events are often linked to weather and climate. Weather components are thought to influence the nesting behaviour of freshwater turtles, but to date there have been few quantitative studies and no comparative studies. We compared the environmental cues used by nesting Australian (Emydura macquarii and Chelodina expansa) and North American (Chrysemys picta) freshwater turtles, and quantified the differences in weather between days with and without nesting activity within the nesting season. We also characterised the diel time of nesting for each species. The results suggest that nesting behaviour is related to warm air and water temperatures in C. picta and to rainfall in E. macquarii and C. expansa. Chrysemys picta primarily nests in the afternoon and evening, E. macquarii is a crepuscular nester, and C. expansa nests diurnally. While changes in life history resulting from climate change are difficult to predict, we suggest that an increase in the number of El Nino events may have adverse effects on the two Australian species, whereasincreases in environmental temperature may expand the number of nesting opportunities for C. picta.