Australian Wildlife Part 1
About 50 million years ago Australia was joined to a giant landmass called Gondwanaland but it then became separated and it is its isolation that has led to its unique wildlife. There are lots of creatures and plants that live on the Australian continent that can’t be found anywhere else!
Australia is the sixth largest country in the world and is an island continent that lies in the southern hemisphere.
About 70% of Australia is unable to support agriculture, and at least one third of this area is desert, with the remainder being dry shrub land (or bushland). Only about 15% of the land mass falls within the temperate zone (mostly in the southeast) and some of the remainder is tropical rainforest (mostly in the Northern Hemisphere).
About 50 million years ago it was joined to a giant landmass called Gondwanaland but it then became separated and it is its isolation that has led to its unique wildlife. There are lots of creatures and plants that live on the Australian continent that can’t be found anywhere else! In fact Australia, New Zealand, Tazmania and the surrounding islands are the only places in the world where you can find the group of animals called marsupials (those that have a pouch for carrying the immature young).
The platypus of Australia is the only survivor of an original species which lived 110 million years ago. Four species related to the platypus have been found in fossil deposits in Australia.
Platypus are grouped in a separate order of mammals known as Monotremata - a group of mammals that lays eggs! Today’s platypus is much more specialised than its ancestors. It has horny pads instead of teeth.
What foods do platypus eat?
The platypus body is about 36cms long, and has a tail roughly 13cms in length. They are covered in a soft, dense layer of fur that varies in colour from yellowish to dark brown.
The male is slightly larger than the female and has hollow spurs connected to venom glands on the ankle of each hind leg. The poison, although not fatal to humans, can be quite painful. The male uses these spurs in competitive mating fights and to protect their territory.
Platypus can only be found in the river systems of eastern Australia.
Why do platypus live in and around rivers?
Although it’s bizarre to look at, the platypus is perfectly adapted to its semi-aquatic life in lakes and streams. It is an excellent swimmer and diver and is able to stay submerged for up to five minutes. It forages at night and rests during the day in burrows dug out of nearby banks.
Its only enemies are large fish and perhaps, snakes.
Imagine how platypus might look in a million years as it keeps evolving!
The Australian Dingo is a type of dog. They are thought to have originated in Asia, are evolved from a subspecies of the Grey Wolf.
It seems likely that seafarers transported Dingos from mainland Asia to Australia and other parts of the Pacific during their voyages.
Fossil evidence suggests that Dingos arrived in Australia around 3500 – 4000 years ago, and quickly spread to all parts of the Australian mainland and offshore islands, with the exception of Tasmania.
It is thought that the Dingo caused the fall in numbers of the Thylacine – a type of marsupial – either through competition for food or through the introduction of diseases such as rabies.
In Tasmania there were no Dingos, and the Thylacines survived until the 1930s further proving that Dingos were a major cause of the decline of Thylacines on the mainland.
The Funnel-Web Spider
Funnel-web spiders are found in eastern Australia, Tasmania and as far west as the Gulf Ranges.
At least 40 species of funnel web spiders have been identified.
Funnel-web spiders burrow in moist, cool, sheltered habitats – under rocks and rotting logs.
The most characteristic sign of a Funnel-web’s burrow is the irregular silk trip-lines that radiate out from the burrow entrance of most species. These trip lines alert the spider to possible prey, mates or danger.
Most funnel-web spiders are nocturnal – that is active at night.
Funnel-web spiders are large, about 1.5 – 4.5 cm body length, with a glossy dark brown to black carapace. The abdomen is usually dark plum to black and not patterned.
Female funnel-web spiders spend most of their life in their burrows.
The males leave their burrows in search of females in summer and autumn, which is when they often come into contact with humans.
The female spins a pillow-shaped silk egg sac, into which she lays over 100 eggs. She cleans and turns the egg sac several times during incubation and will defend it vigorously if disturbed. The spiderlings hatch about three weeks later, and stay with the mother for a few months. After two moults, they leave the burrow to make their own burrows.
When juvenile males leave the burrow they become wanderers.
Funnel-webs mature in about two to four years, with the females living to ten or more years, and the males dying about six to nine months after maturity.
The spider’s famous bite is dangerous and can cause serious illness or death. The venom appears to particularly affect humans, whereas other mammals – such as cats and dogs – are relatively resistant.
The male Sydney Funnel-web Spider is more dangerous than the female, because it carries the toxic venom that attacks the human nervous system so severely.
The Wedge-tailed Eagle
The wedge-tailed eagle is Australia’s largest living bird of prey and one of the largest eagles in the world.
It measures 0.85-1.05m in length and has a wingspan of 2.3m. The female is larger than the male, reaching an average weight of 4.2kg and sometimes reaching 5.3kg! Males usually weigh between 3.2kg and 4.0kg.
Young wedge-tailed eagles are mid brown in colour with reddish-brown heads and wings. They become progressively blacker for at least the first ten years of their lives. An adult female is generally slightly paler than her mate. The bill is pale pink to cream, the iris brown to dark brown and the feet off-white.
The Wedge-tailed Eagle is found throughout mainland Australia. It prefers wooded and forested land and open country, but avoids rainforest and coastal regions. They can be seen soaring overhead at altitudes of up to 2,000m.
Wedge-tailed eagles build their nests in open locations with a good view of the surrounding countryside, usually in the tallest trees.
Why do they build their nests in tall open places?
If a breeding pair are disturbed when they are preparing to lay eggs they may abandon their nest.
The nest is a large structure of dead sticks, called an eyrie, which is usually reused for years and is often of a considerable size. The nest will usually hold two to three eggs.
When the chicks hatch they are covered in a light feathery down, and after two weeks they get their first feathers.
Each egg needs 42-45 days incubation and because of the intervals between laying, they do not hatch all together. The first chick hatches larger than the second, which in turn is larger than the third. Only one or two chicks will survive depending on local conditions.
What are the conditions needed for survival?
The chicks are then fed by both adults for five weeks or so. After five weeks they will recognise bits of food on the floor of the nest and feed themselves. Usually the largest chick will survive its brothers or sisters and if food is scarce it may eat its siblings!
If threatened, the chicks will lie flat in the nest and will defend themselves if necessary. They defend their nest vigorously and have been known to attack helicopters, hang-gliders, fixed-wing aircraft and model airplanes!
Juvenile eagles will remain with the adults for about 11 weeks after leaving the nest.
The wedge-tailed eagle’s diet reflects the availability of prey, but up to 92% its prey is rabbits and hares. They also eat lizards, birds, small mammals, and they will scavenge already dead birds and lambs. If food is scarce they will store their catch in a nearby treetop. Wedge-tailed eagles hunt alone, in pairs or in groups. Twenty birds may feed from a single carcass but only two or three will eat at any one time.
Wedge-tailed eagles mate for life. If one bird is killed the remaining one will find a new mate.
The Koala Bear
Koala bears are not bears at all. In fact they are related to wombats and opossums and are actually marsupials.
The name koala comes from an Aboriginal word meaning ‘no drink’ and it rarely does so. Koalas live in the topmost branches of Eucalyptus trees and eat the leaves and shoots. It consumes over 1kg a day.
Koala fur is different colours in different parts of Australia.
During the breeding season a male koala will gather several females to his small harem and guard them closely from rivals.
After 34-36 days gestation, there is normally only one baby born. It measures only 2cm in length and weighs a mere 0.5g. The tiny creature climbs into its mother’s pouch, and stays there for 5 or 6 months. It then leaves and rides ‘piggy back’ for another 5 or 6 months, and its mother feeds it with partly digested food.
The koala is independent by 11 months, but may still live close by its mother for a further few months.
There are less than 80,000 koalas in the wild. The population of the Australian Koala has dropped by 90% in less than a decade.
In the early days of European settlers, millions were shot and often used for their skins. Also, the Koala has lost much of its habitat through logging, agriculture and urban development. Since Europeans settled in Australia, it has lost 80% of its eucalyptus forests. Most of the remaining 20% is not protected. Other modern threats include cars and dogs.
Image: australian-wildlife-part-1 by ucumari / Valerie
Information sourced from:
Australian Museum (2013), Funnel-Web Spiders [online], Available from: http://australianmuseum.net.au/funnel-web-spiders-group [accessed 21/05/2015].