Kangaroos

Habitat (1)

Kangaroos can adapt to almost any kind of habitat, although they mostly live on grassy plains, savannahs, or desert-like areas. A unique adaptation that allows them to live in dry areas is the ability to go without water for months at a time. Some smaller kangaroos can be found in New Guinea, but most kangaroos are found in the Australian Plains. Kangaroos usually stay in one place until they have a drought, at that time they can travel more than 100 miles in search of water and food.

Fig 1: Kangaroo Territory in Australia.

General (2)

The peculiar movement and the size of their pouches make the kangaroo the best-known marsupial. There are several species of kangaroos (Red, Eastern Grey, Western Grey, Wallaroo, etc.), the main difference being size, territory, and habits. The largest kangaroo is the Red; it can reach up to seven feet in height. The average male kangaroo will weigh about 65 kg but can be as heavy as 85 kg.Females only weight about 26 kg. Kangaroos typically are nocturnal, but will feed during the day if the temperature is cool.

Fig 2A: Teeth.

When traveling at speeds above 7 MPH, only the two hind feet are used with the tail held almost horizontal as a balancer. Max speed can be as high as 45 MPH, depending on species. They can clear obstacles with leaps of up to 26 feet long. Usually these leaps do not carry the kangaroo more than five feet off the ground, but there have been reports of larger kangaroos jumping over 9 foot high fences.

Fig 2B: Claws.

Kangaroos usually live and travel in large groups called Mobs. Mobs can have as many as 100 Kangaroos. When living in a mob, some kangaroos act as guards and stay on look out for danger. If they sense danger they will bang their tails on the ground and leap suddenly, scattering the mob.

Occasionally, males will fight (box) to get a female or limited water on a hot day. During the fight, they balance themselves on their tail and jump up in the air, then kick their opponent in the stomach. Since kangaroos have such strong hind legs, this can be fatal.

Fig 2C: A female rejects this male.

Food (3)

Kangaroos are herbivores and consumers and mainly eat grass and any other foliage, but aren’t necessarily threats to cattle and sheep grazing in Australia. They can go for several months at a time without water, as it can be drawn from vegetation. Kangaroos’ main predator is the dingo and humans, but birds will also prey on joeys.

Fig 3: Kangaroo Food Chain.

Human Interaction and Population (4)

Kangaroo populations fluctuate by how much humans are hunting them and how conditions are in their habitat (availability of food, water, or the threat of dingos). They are never low enough to be considered an endangered species, and currently are twice the number of the cattle population in Australia.

Kangaroo Population Over Time

Body Systems (5)

The majority of the kangaroo’s body systems are the same as all other mammals, including humans. A heart circulates blood through the body oxygenated by the lungs and respiration. The skeletal system is odd, and looks like across between a human, rabbit, and cat skeleton, specialized for jumping, balance, and versatility.

Kangaroo Skeleton

Kangaroo Digestive Tract

The nervous system works typically of a mammal; the brain connects to the body via nerves that pass down the spinal column. Excretory glands are also common to mammals; kidneys filter into the bladder, where urine is later released nearby the genitalia. The major difference is in the ruminant, multi-chambered stomach, which is similar to a camel. It’s designed for grazing on tough grasses. The intestines are also lengthened to allow for maximum absorption of water.

Reproduction (6)

When a female completes her oestrus (35 to 45 days, differing between species) cycle and is not actively lactating for a joey, she is ready to mate again. Males will constantly sniff her pouch or cloacal to check for her readiness to mate. Normally, the female will also urinate when she is willing to copulate. It’s common for males to scratch the female’s tail and rub their head along her back as a kind of kangaroo foreplay. Typically, only large, dominant males will be allowed to mate with the female. If necessary, males will fight to determine who will mate. The male’s penis is prehensile so it can get around the female’s large tail.Copulation lasts up to fifteen minutes.

Fig 6A: Kangaroos mating.

Gestation lasts for about five weeks in kangaroos.  Just before birth, the female cleans out her pouch, which secretes a waxy compound, from the last joey. For birth, she will lay on her back propped up against a tree. When it is born, the joey is in a sac called the amnion. It must tear its way out of the amnion and crawl up to the pouch, where it will suckle a nipple for the next three months. The female will cleanup feces and urine from the joey and recycle it to make more milk.

Fig 6B: Female with joey in pouch.

At around six months, the joey will begin exploring outside the comfort of its mother’s pouch. At first, it will leave for only a minute, but increasingly until it stays outside the pouch at all times except when danger is present. If alarm arises, its mother will call for it and the joey can jump back into the pouch in a matter of seconds. Eventually,the mother will force the joey out of her pouch permanently and it will be on its own.

Fig 6C: Female with older joey in pouch.

A large, healthy kangaroo can live into its twenties in captivity, but their average life span in the wild is 10 years. Males are typically larger than females, and don’t have the necessary pouch and nipples. Obviously, females have a vaginal opening and males have a penis and testicles. Internal differences between male and female reproductive systems are very similar to all other mammals.

Fig 6D: Male kangaroo cleans his testicles.

Scientific Identification (7)

Kingdom: Animal
Phylum: Chordata
Class: Mammalia
Order: Marsupialia
Family: Macropodidae
Genus: Macropus
Species: canguru

Poem (8)

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