Effect of fire on northern bettong Bettongia tropica foraging behaviour

1
Effect of fire on northern bettong (Bettongia
tropica) foraging behaviour
Paula Freeman, Department of Biological and
Physical Sciences, University of Southern
Queensland, Australia
Introduction The Northern Bettong is an
endangered, small, solitary and nocturnal
marsupial. Its habitat is restricted to the fire
prone forest in NE Australia. Their diet
consists primarily of truffles, making up 60
of their diet. Truffles are usually detected in
their highest abundance after fire. Fire can have
important effects on vegetation, food resources
and animal behaviour at a variety of scales (1,
2). The aim of this study was to
examine the movement patterns of northern bettong
and the effects of fire on their foraging
patterns and habitat.


Figure 2 The rate of foraging observed on both
control and experimental areas before and after
fire, a) dug for truffles and b) investigating
pre-existing diggings.

• Results
• Significantly more Individuals chose to forage on
  control sites during the period before fire.
• The period after fire significantly more
  individuals chose to forage on the experimental
  location.
• A slight but not significant increase in diggings
  for truffles on burnt ground compared with the
  unburnt ground (p0.065) (Figure 2a).
• The probability of observing a bettong foraging
  at a previously existing diggings on the
  experimental location was significantly lower
  during period before fire in comparison to
  control (plt0.001) (Figure 2b).

Methods This experiment was conducted during
the period July 1996 to February 1997 at Davies
Creek, on the western edge of the Wet Tropic
world heritage area in NE Australia (figure 1).
Two adjacent areas each divided by a narrow
forestry road approximately 40ha were studied.
One side of each forestry road was burnt in late
October 1996 using a low intensity fire. Unburnt
sites were the control while burnt sites were the
experimental. Twelve cage-traps baited with
peanut butter, honey, oats and vanilla essence
were spaced 50m apart along each forestry road.
Bettongs were trapped two periods before fire
during July and October 1996 and two after fire
during November and February 1997. Fungal
sporocarps were collected from 18 x 1 m2 quadrats
in both sites before and after fire. Movement by
the bettongs was mapped and measured from cotton
spool 750 m in length that had been glued to the
bettong fur and the other end tied to vegetation.
Correlation of random walks (CRW) models were
calculated for each movement event, step length
and angle. Analysis of foraging behaviour was
also calculated between step length and angles.

Discussion The movement of animals ranges
differently according to their environmental
cues. These cues include whether or not the
bettongs had any recent foraging success. The
truffle samples determined that the bettongs
found much denser patches of truffles in the area
of the burnt ground. The biomass of the truffles
is not known before the bettongs began foraging,
but the results observed indicate that more
truffles remain after fire, presumed due to
larger more productive clusters being available.
The recent produced diggings by the bettongs on
the burnt area were on average scattered with
remnants of truffles. The fruit bodies had
usually been opened and only the most nutritional
core section eaten. This suggested that the
truffle were in such a great abundance in the
burnt site that all but the most valuable area
was discarded. Bettongs had a much greater
proportion of truffle discovery in the burnt area
after finding a truffle in a previous step,
though there was no significant difference in
bettong ability to detect truffles through scent
before or after fire. This greater likelihood of
foraging success in a burnt area when a patch of
good forage has been found may reduce the
bettongs need to use extraneous cues, like
foraging area of another individual when looking
for food.


Conclusion Bettongs significantly preferred to
forage in the recently burnt area obtaining a
greater success rate of finding truffles. Changes
that may occur in the amount of food or type of
food available may affect the distance necessary
for the bettong to travel. In general this
result determines that the north-eastern bettong
demonstrates a somewhat flexible response to
alternation in their habitat and to changes
brought on by frequent and low intensity fires
that are characteristic of their habitat.
References 1. Gill, A. M., Groves, R. H. and
Noble, I. R. (1981). Fire and the Australian
Biota. Australian Academy of Science.
Canberra. 2. Whelan, R. J. (1995). The Ecology of
Fire. Cambridge University Press. New York.
Acknowledgements Vernes, K. and Haydon, D. T.
(2001). Effect of fire on northern bettong
(Bettongia tropica) foraging behaviour. James
Cook University. Townsville.
Figure 1 Map of the site area at Davies Creek
in QLD, showing the position of the trap site and
extent of area burnt.
Completed as part of BIO3314 Terrestrial Ecology
assessment - October, 2003