Nikki Thurgate with one of her reptilian
Australia's reptiles aren't as tough as we thought—those
are the findings of James Cook University student Nikki Thurgate
who completed a Tropical Savannas CRC Honours scholarship at the
end of 1997.
Nikki studied the impact on reptiles of cattle grazing at a
unique Queensland location, the Great Basalt Wall, and found that
grazing had seriously affected both the abundance and diversity of
reptiles in the area.
Nikki conducted studies comparing geckos, skinks and goannas
between grazed and ungrazed sites north-west of Charters
These sites are found within a natural barrier provided by
Queensland's Great Basalt Wall—the result of a volcanic flow
that probably took place 13,000 years ago. The lava flowed into
low-lying areas leaving pockets of vegetation on higher ground but
those pockets now lie lower than the basalt, effectively keeping
out grazing animals such as cattle.
What she found was that there were almost twice as many
individual animals in the ungrazed sites as in the grazed sites.
Species diversity was also significantly higher in ungrazed sites.
Assoc. Prof. Ross Alford, one of Nikki's supervisors, says the
study could have implications for conservation managers throughout
"Essentially the thinking has been that if you keep grazing
pressure to a moderate level, don't clear trees and don't defoliate
then grazing would not have much effect on the native reptile
fauna," he said. "This study suggests that grazing has stronger
effects than previously realised.
"It's a very good study in that it compares completely ungrazed
areas with grazed sites which is a difficult thing for people to
do," he said.
Nikki worked in nine separate areas of habitat on two different
properties and found 27 species of geckos, goannas, skinks and
The four species that had suffered the greatest impact were the
gecko Gehyra catenata and three skinks: Morethia taeniopleura
(fire-tailed skink); Ctenotus robustus and Carlia jarnoldae. Of the
fire-tailed skink, Nikki found 40 in ungrazed sites, and six on the
grazed sites. G. Catenata was twice as abundant in the ungrazed
areas compared to the grazed, and of the C. Jarnoldae 20 were found
in ungrazed sites and two in the grazed areas.