62 Australian Geographic
- which can include up to 100 or more animals
at a time – appear to be merely feeding aggre-
gations within which mating occurs randomly.
In essence, they function like big herds of cattle.
There is also evidence that, even though
there is some limited movement of animals
between Moreton Bay and Hervey Bay, the two
populations are genetically distinct. Research
elsewhere also suggests that various local dugong
populations around the country are genetically
separate, and this could have major implications
for the species’ long-term management.
Recently, Janet’s team has begun to inves-
tigate dugong communication. Above water,
you won’t detect much noise from them. But
if you put your head under water near a group
of dugongs you’re likely to hear chirping. “They
sound like little tweeting birds and we’ve found
that the animals here [in Moreton Bay] sound
dif erent from the animals in Hervey Bay: they
vocalise at dif erent frequencies,” says Janet.
Research has also shown that the chirping
rises exponentially with the increase in group
size. It’s not just more individuals chattering,
but more ‘conversations’ occurring as a group
grows bigger. “It suggests there is some sort of
social behaviour going on in the herds,” Janet
says. There’s anecdotal evidence that animals
released at a distance from their herd will fi nd
their way straight back, and that a frightened
herd will move together.
It’s not clear, however, whether group move-
ments involve ‘chatter’, or some sort of tactile
pressure-sensitive sense, such as the ‘lateral line’
electro-sensory system that provides fi sh with
information about their surroundings. Dugong
skin is not smooth like a dolphin’s. Surprisingly,
it’s covered in sparse hairs spaced a centimetre
or two apart. There’s a theory that these could
function as pressure sensors that detect vibra-
tions and movements in the surrounding water,
but that will take more research to prove.
Janet’s team has also been conducting annual
health assessments of the Moreton Bay and
Hervey Bay populations for the past seven years,
taking blood samples and recording aspects of
body condition. There are indications that what
happens on land can af ect dugong health.
After the Brisbane fl oods in 2011, signifi cant
rises in heavy metals were seen in the blood of
Moreton Bay dugongs, a likely consequence of
the infl ux of coastal run-of into the bay. About
nine months later, researchers documented a
drop in body condition of the animals, and they
suspect there is a link between the two.A
LTHOUGH DUGONGS are a rare sight for
much of Australia’s population dwelling
on the temperate east coast, the animals
are an intrinsic part of the culture of northern
coastline communities. Their signifi cance is indi-
cated by the fact that many Aboriginal and TorresDugong delicacy. Seagrass meadows stabilise marine sediments and provide food and
habitat for a range of animals in tropical and temperate waters.