Monotremes - what exactly are they?!

Skyrail Nature Diary: September 2013


This month we will be looking at monotremes and small marsupials in Barron Gorge National Park. So what exactly are monotremes....? Well put simply, they are the most primitive of all mammals and lay eggs like reptiles and birds. Unlike reptiles and birds, monotremes have fur and produce milk. There are only three monotremes in the world, one in New Guinea and two in Australia. The one is New Guinea is a Long-beaked Echidna that specialises in eating worms. There is fossil evidence that they were found in Australia not too long ago. Interestingly, modern monotremes have no teeth as adults, only a special' egg tooth' which they use during the hatching process but is then quickly lost. There is now fossil evidence that there used to be large relatives of the platypus with teeth in years gone by.

All known monotremes are specialists which helps to explain why they are becoming more and more rare with every passing year. The platypus live in clear creeks and rivers. Due to Australia drying out the last few million years, permanent waterways are becoming more scarce and the platypus is therefore smaller than their ancestors. As for the small marsupials, they are little known. Part of the reason for this is the introduction of dingoes, cats and foxes which are slowly eating their way through our native fauna. The beautiful numbat is almost extinct, now only found in two tiny reserves in Dryandra State Forest in Western Australia due to a fox baiting program - previously, they could be found over large areas of southern Australia. Other small marsupials are also becoming scarce like several potoroos (rat kangaroos), bilbies (rabbit like desert relatives of the bandicoot) and quolls.

Quolls are arboreal carnivores covered in white spots and can be quite vicious hunters, rumoured to have hot tempers. Sadly this is no advantage when faced with a hungry dingo or cat. Even some Australian rodents are becoming more rare, most notably of which, the two species of 'Stick-nest' rats, one of which is already believed to be extinct. The species below are still reasonably common in the Cairns region but are only rarely seen. This has a lot to do with their nocturnal and secretive habits. Not surprisingly, the most successful of the survivors are those that have adapted to the human presence. None are quite as successful in exploiting human habitats as the American Raccoons but evidently successful enough.

The Yellow-footed Antechinus is a small marsupial carnivore often referred to as a 'marsupial mouse' which eat insects and any other small animal they can overcome. Antechinus only live for about a year with the females giving birth to up to 12 young who stay in the rudimentary pouch for up to five weeks. They are weaned after about three months.

The echidna is without a doubt the most widely distributed mammal in Australia. It is amazingly unfussy when it comes to their preferred habitat, living in every kind of environment from rainforest to desert. This has a lot to do with its oddly specialised diet, consisting of ants and termites. Both insects are so common all over Australia that it’s highly unlikely the echidna will run out of food. The echidna is covered in spines and has a moderately long snout with no teeth. They have an incredibly long, sticky tongue they use to collect ants and termites after they have dismantled the nest with their powerful claws. Echidnas are excellent diggers and are very difficult to contain outdoors. Echidnas have a backward facing pouch and a single egg is deposited directly into it. When the young hatch the hairs have not yet turned into spines.

The platypus is the most unusual mammal in the world. It’s basically a beaver with a rubbery bill attached to the front. The males have a spur connected to a venom gland on their hind legs. The platypus is a highly aquatic creature which eats insects, crustaceans, small fish and small frogs. They have no teeth and hunt with their eyes closed. They find their way underwater with a special electrical sense located in the  bill. When they catch something edible, they grind it with special plates on the bill. The platypus lays eggs in a riverside burrow and feeds the young with milk from their bellies. Platypus’ are essentially solitary creatures but make a surprising number of sounds, most commonly an annoyed growling sound when disturbed.

The long-nosed Bandicoot is one of the few common bandicoots left in the world. Being highly nocturnal, they are rarely seen in the wild. Their conical holes made whilst burrowing are often seen in suburban gardens. In many ways bandicoots are Australia’s version of the badger. Bandicoots have long snouts and relatively large ears. The hunt by smell, mostly underground and eat almost anything they can catch. The two small joined toes on the hind feet are used for grooming their fur. The fur nevertheless is often full of parasites, especially ticks. Bandicoots are the fastest breeders of the mammals with gestation lasting only 12.5 days. Litters consist of one to five young, usually two to three. They are weaned after two months.

Tore Lien Linde