Effects of repeated low-intensity fire on terrestrial mammal populations of a mixed eucalypt foothill forest in south-eastern Australia
Research Report No. 63
Authors: Marc Irvin, Martin Westbrooke and Mathew Gibson
A total of 17 mammal species, excluding bats, were recorded for the Wombat Fire Effects Study Areas (FESAs). Of these, nine species were terrestrial and eight were arboreal. Two of the terrestrial mammals were the introduced European Rabbit and Red Fox. Only two of the terrestrial species were present in sufficient numbers for quantitative analysis—Rattus fuscipes (Bush Rat) and Antechinus agilis (Brown Antechinus).
Two main methods of study were used: trap and release, and radio telemetry. Trapping provided a good basis for studying population dynamics and dispersal while radio telemetry provided a good basis for studying habitat usage. The terrestrial mammal study was concentrated in three of the five FESAs, namely Blakeville, Barkstead and Musk Creek.
Five burning treatments were replicated in each FESA: short-rotation spring, short-rotation autumn, long-rotation spring, long-rotation autumn and a long-unburnt control.
The ability of small mammal populations to recover from fire was related to the survival rate of individuals in burnt areas, the presence of unburnt refuges and the rate of vegetation recovery.
Radio telemetry of A. agilis indicated that leaf litter and logs were important foraging microhabitat. It was also found that nests for this species were in cavities in trees and fallen logs and in the ground under trees, stumps, logs and tussocks. Radio tracking of R. fuscipes indicated that it was mainly restricted to dense thickets of sedges, rushes and ferns in gullies.
A significant decline in A. agilis numbers was noted after the 1985 spring and 1987 autumn fires. Spring fires reduced abundance by approximately 50% for 12 months after the fire. However, the population recovered in the second year due to a combination of high breeding rate, a significant proportion of the population surviving in the burnt area and the rapid accumulation of leaf litter in which to forage.
Rattus fuscipes population declined following fire in all treatments. It took three breeding seasons (two years) for the population levels to recover from a single spring fire when more than half their habitat was burned, compared with recovery after one breeding season following a single autumn fire, when less than half of the habitat burned. This relatively slow population recovery rate may be related to the longer recovery time of the dense sedge-dominated vegetation preferred by R. fuscipes. Rattus fuscipes also has a slower reproductive rate than A. agilis.
No single burning treatment favoured either species, but habitat preferences were observed. Although A. agilis and R. fuscipes have different habitat preferences, the survival and recovery of both species depends largely on retention of unburnt habitat patches.
Fire Research Report No. 63