From Tropical Topics newsletter, No. 78 June 2003,
produced by Stella Martin at the Queensland Environmental
Protection Agency. Download the PDF to read the whole issue.
Acknowledgements to Russell Best, Queensland Parks and Wildlife
Service and Tony Griffiths, Key Centre for Tropical Wildlife,
Charles Darwin University.
How fire affects lizards | Comparisons between burnt
and unburnt areas | Impact of exotic species |
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Recent research has found that fires can benefit these
lizards, mainly by removing ground cover and allowing them a better
view of potential prey.
Photo: Tony Griffiths
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Fires are common in savanna woodlands so how do they affect the
frilled lizards which live there? Researchers found that, on the
whole, fires benefited these lizards, mainly by removing ground
cover and allowing them a better view of potential prey.
However, different types of fires have different effects. Fires
occurring early in the dry season are less intense and do not seem
to threaten the frilled lizards, which avoid them by staying in
tree canopies. Late dry season fires, on the other hand, are much
more dangerous killing up to 30 per cent of the lizards. Many of
those studied chose to leave their treetop retreats and seek
shelter in termite mounds—a successful strategy which saved
their lives. Many, however, stayed in the trees which was much more
hazardous. Nonetheless, areas burnt by late dry season fires seem
to provide more food for frilled lizards. Generally, abundance of
invertebrates in the lizards’ stomachs
decreases—termites by more than 40 per cent—but there
is an increase in numbers of ants, which seem more active and
abundant in burnt areas. Importantly, however, the lack of
vegetation cover means that the lizards can find more, and larger,
prey.
When compared, frilled lizards from areas unburnt for many years
were not in as good condition as those from regularly burnt areas;
areas unburnt for prolonged periods tended to have low populations
of frilled lizards. On the whole, areas which are burnt regularly
in the early dry season are most likely to benefit these lizards by
increasing food supplies but not threatening the animals’
lives. Although late season fires seem to provide more food,
they also kill off such a large proportion of the lizards that the
population is unlikely to be sustainable if such fires are too
frequent. Only if increased food supplies attract sufficient
numbers of lizards from neighbouring unburnt areas would the
population remain viable.
Reptiles have fared much better than mammals and birds following
the arrival of Europeans in Australia. More than 12 percent of
mammals have become extinct and more than 17 per cent have
declined, compared with just one possible reptile
extinction.
Medium-sized mammals weighing between 35 g and 5.5 kg have been
worst affected.
During droughts, larger mammals and birds can often move to
wetter areas. Smaller mammals, however, have probably always lived
a boom/bust existence, those lucky enough to retreat to wetter
refuges eventually re-colonising areas where less fortunate animals
died out. These refuges, however, now attract cattle which compete
for the same resources. In addition, rabbits have severely reduced
ground cover and foxes and feral cats are serious predators.
Changed fire regimes also make life difficult for many mammals and
birds. Reptiles seem more resiliant to the same pressures.
