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Koala
Phascolarctos cinereus
Olivia Thornton
42 Murdock Dr
UC Box 579
Unity, ME 0498
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Koalas
The koala is now Australia’s animal icon and one of the world’s most charismatic
mammals, but this has not always been the case. The first European settlers considered
koalas stupid and killed millions for their pelts. Other serious threats to the animal’s
survival came from the impact of forest clearance, large-scale forest fires, and the
introduction of zoonotic disease. (Encyclopedia of Mammals)
The threat to koalas peaked in 1924 when two million were exported to slaughter
sanctuaries. They were exterminated in south Australia and almost wiped out the species
in Victoria and New South Wales. In 1944, bans were put on hunting and this made the
decline stop rapidly. The species was able to recover, but their population is still threatened
today by habitat loss. It is very serious in the semi-arid woodland areas, such as
Queensland, which is only one of my areas the koalas live. One million acres are cleared
annually for pastoral and agricultural needs.
Koalas can live up to 18 years old. They have a gray coat that is white on the chin,
chest, inner side of the forelimbs, and their ears are fringed with white long hairs. The rump
of a koala has patches of white on it as well.
Koalas spend most of their lives living in eucalyptus trees. An adult eats 500
grams or 1.1 pounds of eucalypt leaves per day. They spend 80% of their lifetime
sleeping and less than 10% of their life is spent for feeding. They have well insulated
bodies with dense covering of fur. They have large paws that are equipped with strong,
curved, needle sharp claws on most of their digits. Koalas are expert climbers and use their
claws and powerful forearms to grip the trunks of trees to heave upwards, while bringing
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their hind legs up in a bounding motion. Their first and second digits are opposable to the
other three ones. This enables them to be able to grip the smaller branches and to climb up
to the outer canopy of the trees. Koalas are much less agile are on the ground. They tend
to move to a different tree at least every couple of days, using a slow, quadruped walk.
One adaptation that the koalas need to eat the eucalypt leaves is their extremely
fibrous teeth. Using their cheek teeth, they chew the eucalypt leave into very fine paste. In
the digestion phase, microbial fermentation occurs in the cecum, a cavity in which the large
intestine begins. Relative to the koala’s body size, is the largest of any mammal. Another
adaptation for this low-energy diet is the koala’s tiny brain. In relation to their body size,
the brain is .2% of the koala’s body weight. This is one of the smallest brain sizes in
marsupials.
There are over 600 of eucalypt trees to choose from for the koala. However, koalas
prefer only 30 of these species. In the south, they tend to stick to Eucalyptus viminalis and
Eucalyptus ovate. In the North, Eucalyptus camaldulensis, Punctata, Tereticornis, and
Microcorys are preferred. Eucalyptus leaves contain toxic substances such as cellulose and
lignin that are inedible. The koala’s liver is able to detoxify this substance. From these
leaves, they obtain all the water that they need to survive.
Koala populations are widely separated and fragmented from each other by
extensive tracts of cleared land. The koala species can be found over several hundred
thousand square kilometers. This range stretches from east Australia from the edge of
Atherton Tablelands in north Queensland to Cape Otway at the southernmost tip of
Victoria. Koalas can live in many different types of environments such as the wet montane
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forests, vine thickets in the tropical North, and woodlands.
Koalas are solitary animals. They have fixed home ranges that are related to the
productivity of the environment. In the South, a male’s range tends to be around 3.7-7.4
acres and a female’s is 1.2-2.5 acres. In the semi-arid areas, a male’s territory will be
larger, possibly over 250 acres. On average this territory overlaps with up to nine females
on average.
Males body size is 50% larger than females. They have a broader face,
smaller ears, and a very large sternal chest gland, that they use for marking their scents on
trees during mating seasons.
The reproduction of koalas starts with the female reaching sexual maturity at age
two, and the males having to wait until age three or four until they are fully mature. Once
females reach maturity, they may not begin to breed right away, some wait to achieve full
physical maturity at age four. In New South Wales, this period usually starts in
September and can run all the way through January. In the year 1978, a man by the name of
Eberhard studied koalas on Kangaroo Island and found that the births of the koalas
occurred from late December to early April, and peaked in February.
During breeding season, males attend a territory that contains several females.
They tend to move around frequently during the summer nights. They bellow loudly with a
series of harsh inhalations during the early months of breeding season. This is usually
followed by a growling expiration. This is used for a warning threat to other males and also
as an advertisement to any close females. Very often, a fight will break out if a male runs
into another male. Copulation itself, only lasts two minutes, and takes place in a tree. The
male will mount the female from behind and hold her between himself and a branch. The
only vocalization ever heard from female koalas is a wailing distress call made when a
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male is harassing them.
Females are seasonally polyestrous, going through a success of estrous cycles
during a particular time of the year, with an estrous cycle of about 27-30 days. Koalas
usually breed once a year and have a gestation period of about 35 days. The father does not
have any role in taking care of the baby. The litter size is one, however twins are known to
have been born. The baby koala is known as a joey and is hairless, earless and blind. At
birth the joey no bigger than a jelly bean, crawls into the mother's downward-facing pouch
and attaches itself to one of the two teats. (Pearce, 2004). The young weigh as little as .36
grams when born and live in the pouch for five-seven months. As it grows older, the young
makes it’s way towards the end of the pouch, during so it feeds on material passed through
the digestive tract for up to six weeks. The mother weans the joeys when they are
six-twelve months old. The young will now feed on partially digested leaf materials that
is produced by the mother’s anus. The mother clears the normally hard fecal pellets from
the lower bowel before producing this soft material, also known as pap. Pap contains high
concentration of microorganisms and is thought to inoculate the gut of the young with
microbes it needs to digest eucalyptus leaves. After seven months, the baby leaves the
pouch and will travel around on the mother’s back. The young will become independent
after eleven month but sometimes will stick around for a while after. Young males may
stay within their mother's home territory until they are two or three years old. (Pearce,
2004). The young will usually stay with the mother until the appearance of next year’s
joey. If the mother does not reproduce each year, the baby koala will stay longer and will
have a greater chance of survival.
When it comes to the handling and care of any captive animal, like the koala, the
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general guidelines are typically the same. The trainer or keeper of the koala should observe
and keep a record of the animal’s daily behavior. They should also be physically checked at
least once a month, and observed every day for any signs of injury or sickness. There are
several symptoms that sick or injured koalas will display and that a keeper or trainer should
constantly be on the look for. One symptom is puffy or inflamed eyes, which may make
the koala look as if he or she was crying or have a crust or discharge surrounding them.
Salivating excessively from the mouth, wet or matted fur, brown or dirty tail, appearing to
be abnormally skinny, and showing signs of trauma such as cuts and blood on the fur and
skin are all also physical symptoms of the koala. These signs might show that the koala is
being improperly handled or it’s environment is not ideal to fit all of the needs of a koala.
There are other symptoms that a keeper would notice when taking daily notes that aren’t
physical, but behavior signs of injury or sickness that a koala would display as well.
(Inger-Marie Vilcins) Any weakness or unusual behavior, remaining in the same tree for
more than a few days, sitting on the ground or in low branches, not moving when people
approach it, and not using all four limbs for climbing. If a koala is sick, or needs a check up,
there are ways to safely handle and catch the animal. You can use a long stick or rod with a
small sack attached at the end and the koala should climb down, with training, eventually
far enough to use your hands to make it go in the bag. (Tabart).
When doing a daily health check of a koala, the best time for this is the morning,
because that is when the koala will generally be the most active. The keeper should check
the coat and fur, dirt around the animal’s mouth, a wrinkled nose that suggests dehydration,
make sure the appetite is good, and the wetness of the cloaca and rump. An assistant animal
care manager, Travis, who works at the Cleveland Metroparks Zoo had this to say about the
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care and check up of koalas, “The daily routine for the koalas begins with food
preparations (i.e. removing the uneaten browse and providing fresh browse for
consumption). We weigh each koala every day - as an indicator of health. We also count
and weigh each fecal pellet daily - as an indicator of quantity of food eaten. They are placed
on exhibit (we have both indoor and outdoor viewing when weather permits) for public
viewing. They do sleep most of the day. It can be said if they are not eating they are
sleeping. There have not been any medical issues to speak of. Although being a northern
climate zoo we do concern ourselves with them getting enough UV light. They must also
check for ticks around their ears. Ticks can cause irritation and anemia. The eucalypts
leaves that the koala eats do not act as a parasite control, according to Tabart D.
If the
koala is in a hotter climate, they should be checked for heat stress. Symptoms for this are
lethargy and loose and dry skin on the nose. The koala’s droppings should be checked and
counted in order to see if the animal is having diarrhea, or other fecal problems. (Jackson
S.).
According to Jackson S. each captive koala is given a yearly examination where
blood samplings are taken to test for Chlamydia and Cryptococcus . A major disease for
koalas is Chlamydia, a bacteria involving the reproductive diseases in mammals. They
can also get an infection called fur mite. A koala with Chlamydia is affected in the
respiratory and intestinal tracts and a mother carrying this disease can pass it on to the
offspring if they are in the pouch. The symptoms of this disease are keratoconjuctivitis, a
discharge from the eyes, urogenital tract disease, inflammation of the urinary bladder
which causes the animal to lose its appetite and die from malnutrition, and reproductive
tract disease, affecting females. Other diseases that koalas can get are septicemia, cystic
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ovaries, nephritis, tubulointertitial nephritis, ophthalmic, rhinitis, pneumonia,
necrobalcillosis of the jaw, and salmonellas.
According to D. Tabart, The handling of koalas by guests is not allowed at any zoo
outside of Australia, but is allowed in a few zoos inside Australia. Usually the most contact
a guest is allowed to have is getting their picture taken while holding or being near the
animal. Excessive handling can result in the koala becoming stressed, that is why most
zoos around the world do not allow this.
There are several useful sexing techniques for koalas. A male has a distinguished
active sternal, chest gland that he uses for marking his scent on trees, leaving a brown stain
on his chest. Males are generally larger than females. Females have a more rounded face
that is more pointed than that of a male.
Early Europen settlelers can also be blamed for giving the koala it’s accustomed
nick name of koala “bear.” When infact, the koala is not a bear at all. The setterlers also
referred to the koalas as sloths and monkeys. The short, stocky build of these animals and
the absense of a tail gives a somewhat bear-like appearance. This mistake stuck around to
today’s times and people all over the world still refer to them as koala “bears.” A nickname
that will probably remain with them forever.
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Work Cited
Ronald M. Nowak. (1991). Walker’s Mammals of the World 5th Edition Volume. John
Hopkins Baltimore, Maryland University Press.
David MacDonald. (2001). Encyclopedia of Mammals Volumes III Marsupial, Insect
Eaters and Small Herbivores. Andromeda Oxford Ltd.
Gerry Pearce. (2004). Koalas. Information, pictures, cards, and gifts.
http://www.australian-wildlife.com/Koalas-information.html
Tabart D. Koalas in Zoos/Koala Handling. Australian Koala Foundation No Tree No Me.
https://www.savethekoala.com/koalazoos.html
Jackson S. Captive Husbandry Guidelines. Koala Phascolarctos Cinereus,
http://www.aszk.org.au/docs/koala.pdf
Travis. (2009, November 3rd). Asst. Animal Care Manager. (O. Thornton, Interviewer)
Inger-Marie Vilcins, Julie M. Old, Gerhard Körtner, and Elizabeth M. Deane. (2008) Ectoparasites
and Skin Lesions in Wild-Caught Spotted-Tailed Quoll (Dasyurus maculatus)
(Marsupialia: Dasyuridae). Comparative Parasitology 75:2, 271-277