44 Australian Geographic
linked to significant genetic variations. “It was unknown if these
different colour variations might also be genetically distinct,
and whether or not we had more than one species,” she says.
The results, published in 2017, showed frillnecks can be separated
into three different genetic groups with slightly different DNA.
These are consistent with different frill colour, but not genet-
ically different enough to be separate species. Mitzy believes
this is because different populations have remained well con-
nected in recent evolutionary history, helped by the land bridge
that connected northern Australia and New Guinea 18,000
years ago, when sea levels were lower and savannah stretched
across the Torres Strait. “This was a very interesting result,” she
says, “because there are countless examples of other lizards with
very deep genetic divergences across this part of Australia.”
Claire McLean, in the Devi Stuart-Fox lab at Melbourne
University, has been exploring the physiology behind this and
how frillnecks produce the pigments behind their colour. Both
red and yellow pigments are carotenoids: frillnecks acquire these
from their insect diet and concentrate them in their skin. This
implies frillnecks with brighter frills are healthier and stronger,
with better diets, than those with less vividly coloured frills.
Red carotenoids, such as those that give f lamingos pink plum-
age, often come from shrimps or algae. “This is particularly
interesting, because red carotenoids are rare in the diet of frill-
necks,” Claire says. Instead, frillnecks are thought to be able
to convert yellow carotenoids in their diet to red carotenoids in
their skin. “Because it’s costly to produce skin colour using red
carotenoids, it’s thought this could be an honest signal of an
individual’s quality,” Claire says, explaining that redder indi-
viduals are likely to be more fearsome competitors and better
mates. Her work now aims to understand the genetic basis of
how the different pigments are produced.
T
HE FOCUS OF Christian’s research has been how the sud-
den erection of the frill, and the behaviours that go with
that, can be used to frighten off predators. “We’re still
in the data-analysis phase, but it seems that the defensive behav-
iour is what we would expect from a deimatic display,” he says.
Deimatic displays are typically used by reptiles as a last line
of defence against an attacking predator (see Wild Australia,
AG 146), intended to startle and confuse an attacker. To this
end, they are often swift, highly conspicuous and over quickly.
They’re mostly bluff, but work well against predators that depend
on the element of surprise to catch prey, such as birds and snakes.
Currently based in the USA, Christian is planning to return
to Australia for more fieldwork, this time measuring the reac-
tions to the lizards’ display of predators such as hawks. “This
could ultimately break down the deimatic display, to see what
elements are effectively broadcasted to stall or halt the incom-
ing threat,” he says.
Rick looks back fondly on his work on frillies during the
1980s, and often still encounters them during fieldwork on
other species. The species’ ability to walk at a leisurely pace on
its hind legs particularly appeals to him. “One of the lizards
I was watching, on a little tree, saw a beetle walking past.
He scurried down to the ground and grabbed it,” he says. “But
the bit that astonished me was that, as soon as he got back to
the base of the tree, he reared back and walked across on his
hind legs. Very few animals do that, and it’s hilarious.”
While many lizards run on their hind legs, they need to
get up a fair speed to do so. Rick speculates that because
frillies have evolved such a long neck to accommodate the frill,
they can lean back and get it into such a position that they are
unusually stable on their hind legs.
For many years, numbers of frillneck lizards have seemed
relatively secure and the species’ IUCN (International Union
for Conservation of Nature ) threatened status is currently listed
as ‘least concern’. However, Rick says that recently there has
been evidence of worrying declines across parts of the species’
range. The cause is currently one of the most important unan-
swered questions about the species. Rick thinks changing fire
regimes and vegetation communities, driven by the spread of
invasive grasses that burn very intensely, could be part of the
problem, but there have also been reports of frillnecks dying
after eating cane toads.
For Christian, observing a frillneck in the wild in the NT
for the first time was an emotional experience. “They are quite
charismatic, extremely aware of their surroundings and quick
to perceive any movement or sound,” he says. “Since I was very
young, I’ve wanted to encounter a frilly in the wild. It is a
childhood dream come true to conduct research on these iconic
dragons and come to know individual frillies so intimately.” AGThe species’ ability to walk at a
leisurely pace on its hind legs
particularly appeals to him.
Like other dragons, frillnecks prefer to display from elevated
spots such as termite mounds, as seen here in northern QLD.
PHOTO CREDIT: DAVE WATTS/MINDEN PICTURES