ECOLOGY

Environment temperate or tropical rivers
Organization solitary
Treasure none

The unusual appearance of this egg-laying, venomous, duck-billed, beaver-tailed, otter-footed mammal baffled sages when first discovered, with some considering it an elaborate fraud. It is one of the few venomous mammals, the male platypus having a spur on the hind foot that delivers a venom capable of causing severe pain.

The platypus is semiaquatic, inhabiting small streams and rivers over an extensive range from cold highlands to tropical rainforests. Natural predators include snakes, water rats, goannas, hawks, owls, and eagles.

Habitat

Its habitat includes rivers and river banks where it can dig resting and nesting burrows. It may have a range of 4-5 miles, with a male's home range overlapping those of three or four females.

Biology

The platypus is endothermic, maintaining its body temperature at about 90°F, lower than most mammals, even while foraging for hours in water below 41°F.

Diet

The platypus is a carnivore: it feeds on annelid worms, insect larvae, freshwater shrimps, and yabbies (freshwater crayfish) that it digs out of the riverbed with its snout or catches while swimming. It uses cheek-pouches to carry prey to the surface, where it is eaten. The platypus needs to eat about 20% of its own weight each day, which requires it to spend an average of 12 hours daily looking for food.

Behavior

The platypus is generally regarded as nocturnal and crepuscular, but individuals are also active during the day, particularly when the sky is overcast. It is an excellent swimmer and spends much of its time in the water foraging for food. When swimming, it can be distinguished from other mammals by the absence of visible ears. Uniquely among mammals, it propels itself when swimming by an alternate rowing motion of the front feet; although all four feet of the platypus are webbed, the hind feet (which are held against the body) do not assist in propulsion, but are used for steering in combination with the tail.

Dives normally last around 30 seconds, but can last longer, although few exceed the estimated aerobic limit of 40 seconds.

When not in the water, the platypus retires 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. The average sleep time of a platypus is said to be as long as 14 hours per day, possibly because it eats crustaceans which provide a high level of calories.