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Animal Adaptations - Monotremes
There are three different groups of mammals: placentals; marsupials and monotremes. Monotremes are generally considered to be a more primitive kind of mammal. They are warm-blooded, have fur, and produce milk to feed their young just like all mammals. The thing that is different about them is that they lay eggs instead of bearing live young. Some parts of their skeletons are more similar to a reptile than to a mammal.
More primitive kinds of mammals such as monotremes would generally have been expected to be outcompeted when more advanced mammals like the placentals evolved. But Australia became an island when it split away from what is now Antarctica millions of years ago. It contained no advanced mammals at that time, and its island isolation prevented advanced placental mammals from finding their way there. With no competition from other mammals, the monotremes survived. It is for this same reason that Australia contains so many marsupials which are also considered to be a more primitive kind of mammal.
Platypuses
The platypus is the only animal that has a bill, webbed feet, fur, and feeds in water. They inhabit freshwater creeks, rivers, and lakes and can live in both hot and cold climates. They live in the eastern part of Australia and in Tasmania.
Platypuses can stay under water for 2 to 8 minutes, and then it must surface to breathe through nostrils which are located at the front of its bill.
Unlike female echidnas, female platypuses do not have a pouch.
Sample the following internet sites and complete the platypus tasks.
Kratt's
Creatures
http://www.pbs.org/kratts/world/index.html
From this page, click on "Australia" and then click on "Platypus".
- What is stored in the tail of a platypus?
- How does it find its food underwater?
- How powerful is the venom from the spurs on the back legs of a platypus?
Platypus
http://www.discovertasmania.com/home/index.cfm?SiteID=133&subsiteid=590
- How does a platypus hunt?
Echidnas
There are two species of echidnas. Echidnas have long snouts and spiny-like fur similar to a porcupine. The echidnas with the shorter snouts live in Australia and the lowlands of New Guinea and are called short-beaked echidnas. The ones with the longer snouts live in the highlands of New Guinea and are called long-beaked echidnas.
The spines of an echidna do not look like fur, but they are. The spines themselves are stiff hairs. Normal fur grows between the spines and on the face, belly, and legs.
Short-beaked echidnas feed almost exclusively on ants, although they will eat termites if no ants are available. Long-beaked echidnas eat ants and other small insects and earthworms.
Echidnas protect themselves from danger by curling up into a ball to protect the soft part of their bellies where they are most vulnerable. When confronted with danger, echidnas also use their powerful claws and quickly dig a hole and sink their soft bellies into the hole to protect them. Predators to echidnas are dingoes and goannas.
Echidnas use their strong claws to dig into ant nests and termite mounds. When an echidna digs into an ant or termite nest, it smells out the ants or termites and feels for them with its sensitive snout. It sticks the snout in and out of the broken nest, flicking out its tongue which is covered in a special sticky saliva. When many ants or termites are stuck to the tongue, the echidna pulls it in, dirt and all and swallows. Echidnas often eat as much dirt as they eat ants or termites. Echidnas have no teeth. They crush the insects between the spiny base of their tongue and the roof of the mouth, and the grains of dirt help with the crushing. The crushed ants and dirt are then swallowed down into the stomach. Echidnas and other ant-eating mammals have a stomach with a special lining that can accommodate alot of dirt.
The long snouts, long, sticky tongues, toothless mouths, and claws for digging are all adaptations that allow echidnas to successfully eat ants and termites.
About 3 weeks after mating, a female echidna lays 1-2 eggs. Female monotremes have a pouch like marsupials. The female echidna lays her eggs directly into her pouch. After about 10 days, the leathery eggs hatch. In marsupials like kangaroos and koalas, the newborn anchors itself in its mother's pouch by attaching itself to a teat. However, monotremes do not have teats, so baby echidnas and platypuses use their front legs to hold on to the hairs in the pouch. The mother secretes milk from pores in her skin. The newborns suck or lap up the milk from the skin and hairs. The baby stays in the pouch for about 2 months until it starts to grow spines. After that, the mother digs a burrow for the baby to shelter in. She continues to nurse the baby until it is about 5 months old.
Sample the following internet sites and complete the echidna tasks.
Echidna
http://www.discovertasmania.com.au/home/index.cfm?siteid=592
- What do male echidnas have on their hind feet?
Echidna
http://www.koala.net/ed/animals/ech1.htm
- From the main menu on the left, click on "Echidna" under the category "Monotremes".
- What is another name for echidnas?
- How do echidnas protect themselves from danger?
- How is the tongue of an echidna adapted for what it eats?
Echidna
http://www.greggman.com/pages/echidna.htm
- How do you pronounce echidna?
Bibliography
Short, Joan, Green, Jack, and Bird, Bettina. Platypus. Mondo: Greenvale, New York, 1996.
Stodar, Eleanor. The Austalian Echidna. Houghton Mifflin: Boston, 1991.
Image is copyrighted by ArtToday. Used by permission. All rights reserved. Author: LINDA MOSBACKER - Email linda.mosbacker@slc.k12.ut.us