Nature Spot: Why Numbats Have Teeth

Numbats are cute little possum-like marsupials found in forest areas of the south-west of Western Australia. They grow to about 45 centimetres (18 inches) long, which includes their long-haired, brushlike tail. They have reddish-brown fur with white stripes, and have a rather long snout.

The most unusual feature of numbats is their teeth. Numbats have 50 or 52 permanent teeth—more than any other land mammal. Yet adult numbats do not chew! Their diet consists almost entirely of termites, which they flick up with their long, thin, sticky tongue and swallow whole. They spend most of their time scouring decaying logs and soil for termites, of which a single numbat may eat up to 20,000 a day.

If numbats swallow their food whole, why do they have so many teeth? Why do they have teeth at all? The evolutionary explanation at one time was that it may be because the teeth are a useless leftover from an ancestor that needed teeth to catch and chew tougher insect prey. This explanation is still presented in some popular books.¹ But now that a little more is known about this endangered species, it seems those teeth are useful after all.

Researchers have found that the teeth serve to grip and move small branches in the course of the numbat’s excavation and to carry nesting material.² They also may be used to shred the stringy bark of certain eucalyptus trees to produce their nest lining that has been found in hollow logs.³ It should be noted too that numbat babies do chew their termite food.

So even though adult numbats do not use their teeth to chew, the teeth are used by the young to chew, and by adults to help with excavation and nesting. They are therefore not useless evolutionary leftovers.

References

1. Reader’s Digest Book of Facts, Reader’s Digest Services, Sydney, p. 304, 1985.
2. Friend and Kinnear, Ed. Ronald Strahan, The Complete Book of Australian Mammals, Angus & Robertson, Sydney, 1983.
3. Ibid.