Platypus

## Description

The platypus (Ornithorhynchus anatinus), sometimes referred to as the duck-billed platypus, is a semiaquatic, egg-laying mammal endemic to eastern Australia, including Tasmania. Together with the four species of echidna, it is one of the five extant species of monotremes. The platypus is one of the few mammals that lay eggs instead of giving birth to live young and it is one of the few species of venomous mammals. The unique features of the platypus make it an important subject in the study of evolutionary biology, and a recognizable and iconic symbol of Australia.

## Appearance

The platypus has thick fur that keeps it warm underwater. Most of its fur is dark brown, with a lighter patch near its eyes, and a lighter color on the underside. On its front feet is extra skin that serves as a paddle when it swims. The platypus walks clumsily on its knuckles in order to protect this webbed skin. Its bill is smooth, flexible, and rubbery, and feels like suede. The male features a venomous spike on its back foot which has enough poison to cause severe pain for a human.

## Distribution

Platypuses are found on the Eastern and Southeastern coasts of Australia as well as Tasmania, Flinders, and King Islands. There is also a small introduced population on Kangaroo Island. Platypuses are restricted to streams and suitable freshwater bodies, including some shallow water storage lakes and ponds.

## Behavior

Platypuses are solitary, particularly males. If their territories overlap, they will feed at different times to avoid each other. They are generally nocturnal and crepuscular, but individuals are also active during the day, particularly when the sky is overcast. Platypuses are excellent swimmers and spend much of their time in the water foraging for food. They spend a lot of time hunting for food, up to 10 to 12 hours and remain in their burrows when not hunting. When not in the water, platypuses retire to a short, straight resting burrow of oval cross-section, nearly always in the riverbank not far above water level, and often hidden under a protective tangle of roots.

## Venom

While both male and female platypuses are born with ankle spurs, only the spurs on the male's back ankles deliver venom, composed largely of defensin-like proteins (DLPs), three of which are unique to the platypus. The DLPs are produced by the immune system of the platypus. The function of defensins is to cause lysis in pathogenic bacteria and viruses, but in platypuses, they also are formed into venom for defense. Although powerful enough to kill smaller animals such as dogs, the venom is not lethal to humans, but the pain is so excruciating that the victim may be incapacitated. Oedema rapidly develops around the wound and gradually spreads throughout the affected limb. Venom is produced in the crural glands of the male, which are kidney-shaped alveolar glands connected by a thin-walled duct to a calcaneus spur on each hind limb. The female platypus, in common with echidnas, has rudimentary spur buds that do not develop (dropping off before the end of their first year) and lack functional crural glands.

The venom appears to have a different function from those produced by non-mammalian species; its effects are not life-threatening to humans, but nevertheless powerful enough to seriously impair the victim. Since only males produce venom and production rises during the breeding season, it may be used as an offensive weapon to assert dominance during this period.

Similar spurs are found in many archaic mammal groups, indicating that this is an ancient characteristic for mammals as a whole, and not exclusive to the platypus or other monotremes.

## Diet

Platypuses are carnivorous, feeding on annelid worms, freshwater shrimp, insect larvae, and freshwater yabby dug out with its snout from the riverbed or caught while swimming.

## Reproduction

Platypuses are polygynandrous (promiscious), and males and females both have several partners. Females can first mate at the age of 2, but some don't until they are 5. The breeding season is between the Australian winter months of June and October. When females are ready to give birth, they burrow into the ground to seal themselves off in one of the rooms. She lays 1 or 2 eggs and keeps them warm between her rump and tail. The eggs hatch after about 10 days. The little bean-sized young remain nursing for 4 to 5 months. They stay in their burrow until they gain about 80 percent of their adult weight, around 6 months.

## Population

### Population threats

The largest threat to this species is the loss of habitat due to land clearance and water pollution. Predators are snakes, goannas, water rats, and foxes.

### Population number

The IUCN Red List and other sources don’t provide the number of the platypus total population size. Currently, this species is classified as Near Threatened (NT) on the IUCN Red List, and its numbers today are decreasing.

### Ecological niche

The platypus, being a carnivore controls the populations of the species that it eats.

## Fun Facts

European naturalists first thought the platypus was a hoax, and that someone had sewn together a duck's bill and an otter's tail and created an animal like a beaver.

The name "platypus" comes from the Greek "platys," meaning broad, and "pous," which means foot.

The platypus can growl like a puppy.

The platypus uses its snout to search for prey. Its mouth is under the snout.

The platypus uses its tail to store fat, about 50% of its body is fat.

Platypuses use their front feet to paddle and steer with their back feet and tails.