Mammals, reptiles and amphibians

Aim

To identify the properties of habitat mosaics produced by fire that enhance the persistence and status of mammals, reptiles and amphibians in eucalypt-dominated mallee habitats.

Key research questions

1. What are the broad-scale biogeographic distributional patterns of mammals, reptiles and amphibians in the region?

2. What are the landscape-level properties of fire mosaics that determine:

a) the richness and composition of assemblages? and
b) the occurrence and abundance of individual species?

3. What are the site-level attributes shaped by fire that determine:

a) the richness and composition of assemblages? and
b) the occurrence and abundance of individual species?

4. What are the habitat requirements of individual species?

Methods

Each mosaic was surveyed at 10 survey points. The location of these survey points has been stratified based on the proportion of each fire age class in the mosaic. For example, if an age class makes up 50% of a mosaic then it was allocated 5 sites. Where possible, survey points were placed to include:

  • topographic variation within each age-class (dune/swale)
  • sites with different fire frequencies within the same Time-Since-Fire class
  • at least one survey point in each quadrant of the study mosaic
  • all sites being at least 100m from fire boundaries, at least 25m from access roads and at least 200m apart.

At each survey point a pitfall line consisting of ten 20L buckets connected by a 50m drift fence was installed. Each pitfall line was surveyed for five days in each of the spring and summer of 2006-2007 and 2007-2008 and will result in a trapping effort of 56,000 trap nights. Elliot traps were placed at each site during spring sampling sessions to survey mammals, such as Mitchell’s Hopping Mouse, that are not readily captured in pitfall traps resulting in 14,000 trap nights. Captured small mammals were marked and weight, age-class, reproductive condition and sex recorded.

Larger mammals (macropods, echidnas, foxes) were recorded at each site based on the presence of tracks, diggings, scats and incidental observations. Records from each site in a mosaic were pooled to represent the mammal, reptile and amphibian assemblages for each of the 28 mosaics.

Statistical models were built to examine the influence of mosaic properties and faunal composition, diversity and occurrence/abundance. The influence of the following sets of variables will be tested:

  • elements within the fire mosaic (size, shape, perimeter: area ratio, context, nearest neighbour/proximity)
  • mosaic properties (extent, composition, configuration, geographic position)

A number of predictor variables were collected at each spatial scale:

  • At a mosaic-scale predictor variables included the extent of long unburnt mallee, and the composition and configuration of other post-fire seral stages, including seral stage diversity (i.e. based on the proportion of mosaic area exposed to different times since fire).
  • At a site-scale predictor variables included seral stage, number of times site has been burnt in last 34 years, length of intervals between fires, the percent-cover of: Triodia, canopy cover, fine leaf litter, course leaf litter, shrub cover, bare ground and coarse woody debris. Other predictor variables included a measure of mallee DBH, amount of trees, number of hollows (divided into canopy and coppice hollows), and leaf litter depth. Each site was stratified according to its topographic location (for example, dune or swale).
  • At a bucket-level predictor variables included percent cover of: Triodia, canopy cover, fine leaf litter, course leaf litter, shrub cover, bare ground and course woody debris, as well as leaf litter depth. Other variables such as number and size of trees within plots were also recorded.

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