The Amazing Wombat …and other stories
During the break I was fortunate enough to visit Bonorong Wildlife Sanctuary outside Hobart, Tasmania. While at Bonorong, the Sanctuary Guide introduced us to the secret life of the humble wombat. I subsequently read James Woodford’s “The Secret Life of Wombats” and I now want to share what I learned. I also recommend Woodford’s book as highly informative and entertaining reading.
Wombats have an unexpected but effective defence mechanism. They have a thick bony plate in their posterior. The fur at their back end is thick. They have no tail. When chased by a predator they scurry to their burrows and wait at the entrance with their back facing their attacker. The entrance is designed to fit their posterior snugly, and in this way they can seal their home so that it is impenetrable. The predator can claw and scratch and bite but the wombat’s backside can sustain any attack. A predator biting the back of a wombat would feel as though they have bitten the business end of a toilet brush.
If the attacker persists, a wombat will flatten itself. As the intruder seeks to squeeze in over it, the wombat will then quickly raise him or herself and slam the attacker against the roof of the burrow. Investigators have found all manner of animals, including humans who were crushed at the entrance of a burrow.
Wombats are surprisingly fast. Wombats can run 100 metres in under 10 seconds. They can maintain a speed of 40 kilometres an hour over 150 metres – only a handful of men can sustain 36 kilometres an hour over 100 metres.
There are only three remaining species of wombat being the common wombat, the northern hairy-nose wombat and the southern hairy-nose wombat.
The southerns number a comfortable 300,000 and the common wombat number about a million but the northern hairy nose wombat is among the rarest big mammals on the planet. It is years away from extinction. This should not surprise us as Australia has one of the highest extinction rates for mammals on the planet!
The plasma concentrations of thyroid hormones in wombats is the lowest recorded of any mammal, indicating that their metabolism is phenomenally efficient.
Wombat poo is the driest mammal poo on the planet, because they are the most efficient consumers of water of any mammal.
A wombat’s gut capacity is a third larger than herbivores of a similar size. It uses slow fermentation in the digestion of its food. Unlike cattle and kangaroos, wombats use fermentation as a second step in their digestive process. The easy starches and proteins are absorbed first by the stomach and small intestine and the remaining food is then fermented by bacteria to extract every last drop of energy. This process may take several weeks
Wombats are the most intelligent of the world’s marsupials
Wombats are herbivores and live on grasses. Their diet contains a high level of silicone that would normally turn their teeth to powder but wombats have evolved with rootless teeth. Human teeth are grounded in the jaw by roots and once knocked out, will not grow back. Wombat teeth have no roots and grow continuously just like fingernails. Accordingly, a wombat’s lifespan is dictated by the longevity its teeth.
Wombats have reverse pouches that open towards their hind legs.
Wombat reproduction is bizarre. It has been rarely witnessed as wombats are very private and nocturnal. The male mounts the female at right angles and thrusts for about three and half minutes. The female then trots away with the male in pursuit. Typically the female will run in circles or figures of eight eventually allowing the male to catch her. Sometimes the male will bite the female hind-quarters to keep her in place as he mounts a second time. The whole show is repeated about seven times over a thirty minute period. The mating game will cover almost half a hectare. This may explain why it is extremely difficult for have wombats to breed in captivity.
Males play no role in the raising of young wombats.
When a wombat is born it weighs about a gram and is the size of a jelly bean. It takes only a few minutes to travel from the mother’s birth canal to the pouch. At a month it weighs 5 grams, at three months it weighs 250 grams and at four months it weighs 400 grams and its eyes are open. At six months it has developed teeth and is slowly introduced to grasses and it begins showing signs of fur.
Between eight and ten months the wombat is more than 2 kilograms and can leave the pouch permanently.
At two years of age a wombat is about 20 kilograms. At this age they become unusually aggressive towards their mother. They bite and scratch and act in a hostile manner. This is known as “the turning” and the young wombat is now ready to live independently. Sometimes they push their mother out of the burrow and take it over! Talk about unruly and pushy teenagers.
A human baby will mature to an adult weighing about 25 times its birth weight. A wombat will grow up to 30,000 times its birth weight!
Today a major threat to wombats are motor vehicles. Many “baby” wombats are rescued from mothers struck down by motor vehicles on our busy highways. There is a strict protocol for extracting a baby from its mother’s pouch. Babies are normally locked onto their mother’s teat deep inside the pouch. Tugging the baby may break its delicate jaw bones. The pouch needs to be cut open so that there is full access to the joey. The suction between the joey’s mouth and the mother’s teat needs to be broken (gently) before the joey can be removed. A joey should never be held close to a human as the smell of a human chest and the thumping of a human heart will frighten it. Instead rub a cloth over the deceased mother to collect its scent and wrap the joey in that cloth.
Marsupials are divided into nine orders and it is estimated that in the last 55 million years, 455 species of marsupials have evolved in Australia.
Just so that you develop an understanding of the depth of marsupial life in Australia, archaeologists have uncovered a marsupial lion weighing up to 164 kilograms. The only mammal that has come close to it in terms of savagery is the sabre tooth tiger weighing in at 170 kilograms. Compare it with the modern day African lion, weighing 130 kilograms and tigers at 150 kilograms.
The fossils tell us that the biggest wombat Phascolonus gigas probably weighed 250 kilograms and was around as late as 50,000 years ago. Accordingly it overlapped with the arrival of humans and may have been hunted to extinction.
Marsupials (pouched mammals) are a later development of placental (womb) mammals. How many Australian placental mammals can you name? What is striking, is that in Australia, marsupials have outcompeted placental mammals. Why? The question is almost unanswerable as we do not yet have sufficient fossil evidence to complete a full history of our fauna. But one plausible answer is that marsupials are better able to manage their reproductive process because they can terminate or abort a joey in adverse conditions where a pregnant placental mammal cannot and may subsequently be placed in jeopardy.
Cook and Bank’s voyage to Australia in 1770 was a boon for any curious scientist. The number of new fauna and flora discovered in Australia was staggering. Just to give you some sense of proportion, in the tenth edition of Linnaeu’s Systema Naturae there were on the entire planet only 184 known mammmal species, 544 birds, 218 amphibia, 378 fishes and others, a total of 4,380 animal species. By the conclusion of Cook and Banks’ exploration, Australia had yielded 616 new animal species, including 22 mammals, 93 birds and 14 reptiles. Just think about this when you hear or see a call for stricter quarantine. We must protect our native species!
Notwithstanding, neither Cook or Banks came across the wombat.
Much has been made of Matthew Flinders’ exploits in Australia, now that his resting place has recently been uncovered. He and George Bass figure greatly in the wombat story. We all know that the Flinders and Bass were officers aboard HMS Reliance, which in 1795, brought the second governor John Hunter to the colony. While here, Flinders and Bass embarked on many adventures. They travelled in a small whaleboat (8 oarsmen) Tom Thumb across what is now known as Bass Strait. They circumnavigated Tasmania in the sloop Norfolk to demonstrate that it was an island.
Flinders recommended that the strait be named “after my worthy friend and companion, as a just tribute to the extreme dangers and fatigues he had undergone in first entering it in a whaleboat.”
But I digress. Bass sighted and caught a wombat on the islands in the strait named after him and on returning to Port Jackson showed it to local Aborigines. None were familiar with the animal. But one aborigine, from the Blue Mountains, described the animal as a “wombat”, and the name stuck. Had Bass asked a Tasmanian, they would have called it “Publedina” or “Drogerdy”.
Bass wrote excitedly and eloquently to Banks, back in England, about the “wombat” and the modern story of the wombat began.
On 5 February 1803, Bass left Sydney to command the Venus for a voyage to South America. He was never heard from again and no trace has ever been found of his ship. He was only thirty-two.