The yellow-bellied glider is the largest of the Australian
gliders, with the average length of head and body 280 mm and
tail 433 mm.
It is grey above and whitish to yellow below, with gliding
membrane extending from wrists to ankles, an oblique black stripe
on it's thigh and large bare ears. It's belly fur is white when
young and changes to yellow as it reaches maturity.
Yellow-bellied gliders are restricted to tall, mature eucalypt
forests in temperate to subtropical eastern Australia in regions
of high rainfall.
They are nocturnal, during the day they nest in the hollows
of eucalypts and need hollows that have an entrance size of at
least 100 cm2.
Several studies have shown that yellow-bellied gliders are
very sensitive to logging and are mainly found in old growth
forests, sometimes moving into adjacent regrowth areas. This
is because of their dependence on large hollow bearing trees
associated with old growth and because the gliders like to feed
on nectar which is produced in abundance by the older eucalypt
trees. Old growth areas are also more likely to have appropriate
trees for sap tapping.
Yellow-bellied gliders fill a very unusual ecological niche
in our forests, feeding on the sap from certain eucalypt species
by making incisions in the bark, nectar from licking flowers,
searching under loose bark for arthropods and honeydew, and manna.
Honeydew is a nice name for insect excretions. Many sap eating
insects have to consume enormous amounts of sap to extract enough
nitrogen, and excrete the unused sap as honeydew. Manna is similar
to sap, it forms on leaves and small stems when a small wound
is made.
The incisions made in bark to lick sap are often called notches.
These notches can vary in shape, the most obvious being the V-notch.
These notches will be used again and again until the sap clogs
up and then a new notch is made. Vigorous trees of particular
species (including Grey Gum, Red Gum and Spotted Gum) are used
and often one tree will be covered in notches and the nearby
trees untouched.
Yellow-bellied gliders are very active, spending 90% of their
time outside the den foraging for food and feeding. Only 2% of
their time outside the den is spent resting.
They usually live in small territorial groups of between 2-3
individuals consisting of an adult male, adult female and subadult
offspring. The groups occupy exclusive home ranges of about 30-65
ha which makes them exceedingly low in density, between 0.05-0.14
individuals per hectare in preferred habitat.
Gliders have such large home ranges and occur at such low
population densities, that assessing the population size that
is needed for the gliders to survive long term, and the area
required for that population size, can give a good indication
of the size that conservation reserves need to be.
Yellow-bellied gliders court by grooming each other and through
scent-exchange. They mate while clinging to the bottom of large
branches. Gliders will mate for life, and sometimes when one
dies, the other will die or leave its home range soon after.
They may find a new mate and establish a new family group.
The female can breed at about 2 years of age and produce 1
offspring every 1 or 2 years. The young are carried in the pouch
for about 100 days and will stay in the nest for another 2-3
months before independently foraging for food. They will leave
their parents home range between the ages of 18-24 months. They
may live up to 6 years.
Yellow-bellied gliders have been living in our old growth forests for thousands
of years and are far too precious to lose. Their extinction would be tragic
and is perhaps still avoidable, but we must act now and protect enough of
their available habitat to make their chances of long term survival as certain
as we can.