Marsupial Mole

Marsupial moles (genus Notoryctes) are burrowing mammals that belong to the family Notoryctidae. They are endemic to the south-central and northwestern deserts of Australia and rely on insects, small lizards, beetles, centipedes, and even plant seeds for food. Like true moles, these marsupials have adapted themselves to life underground and are equipped with claws on their feet. They have a conical head and reduced vestigial eyes and, hence, are functionally blind. Their bodies are covered by creamy-white hair with a golden, iridescent sheen.

Description

Size

They are typically around 4.7 to 6.3 in (12 to 16 cm) long and weigh between 1.4 and 2.1 oz (40 to 60 gm).

Body Plan

They have a streamlined, tubular body adapted for burrowing, with a cone-shaped head and a leathery shield covering their muzzle. Their short, stub-like tail is also encased in a tough, leathery layer. The entire body is covered in fine, creamy-white fur with an iridescent sheen similar to that of golden moles.

These animals are functionally blind, as their eyes are reduced to vestigial lenses hidden beneath the skin. They also lack external ears; instead, they have two tiny auditory holes hidden under their body hair.

Despite being marsupials, they possess a true cloaca (a common opening for digestive, urinary, and reproductive tracts) and exhibit testicondy, in which the testicles are retained within the abdomen rather than descending into a scrotum.

Marsupium

As marsupials, marsupial moles have a well-developed pouch or marsupium to nurture their young. The pouch is small and contains two teats, allowing only two offspring to nurse at a time. Positioned backward, the pouch provides a crucial adaptation that prevents sand from entering while the animal burrows through the ground.

Limbs

They have short limbs with considerably reduced digits. The forefeet are large and spade-shaped, equipped with flat claws on the third and fourth digits, while the hindfeet are flattened, with three claws. 

While the forefeet help excavate the soil in front of the animal, the hindfeet push the replaced soil behind.

Dentition

The upper molars of marsupial moles are triangular and zalambodont (lambda-shaped). Their dental formula is (4–3.1.2.4/3.1.3.4) x 2 = 42-44.

Taxonomy and Evolution

Currently, there are 2 extant species under the genus Notoryctes.

• Genus: Notoryctes
  • Species: Notoryctes typhlops (Southern marsupial mole)
  • Species: Notoryctes caurinus (Northern marsupial mole)

Fossils of the family Notoryctidae are represented by remains of the extinct genus Naraboryctes unearthed from Riversleigh in Queensland, Australia.

Marsupial moles resemble the true moles of North America and the golden moles of South Africa since these groups have undergone convergent evolution.

Distribution and Habitat

These marsupials are restricted to the deserts and sandy wastes of south-central and northwestern Australia.

• Northern marsupial moles are found in the northwestern deserts of Australia, including the Great Sandy, Little Sandy, and Gibson Deserts, where they occupy plains, dune fields, and interdunal flats.
• Southern marsupial moles, though abundant in the southern deserts of Australia, are also found in the southern parts of the Northern Territory. Though fewer in number, they are also found in the Gibson Desert of Western Australia, an area they share with their northern relatives.

Diet

• Southern marsupial moles are primarily insectivorous and consume insects at every stage of their life cycle. They also feed on lizards and seeds.
• The northern marsupial mole typically feeds on small lizards, beetles, centipedes, and seeds.

Behavior

• Like golden moles, marsupial moles dig just below the soil using their claws in an up-and-down motion (parasagittal plane). They become highly active for short stretches of time and then fall asleep for brief periods to conserve their energy.
• Those in captivity tend to emit squeaking sounds when they are held or kept from feeding.

Reproduction and Lifecycle

Very little is known about their reproductive habits, but it is believed that they give birth to one or two young at a time, which develop in the mother’s pouch before becoming independent.

Predators

Their primary predators include birds of prey, snakes, and goannas.

Adaptations

• The last five cervical vertebrae of these animals are fused, providing their heads greater rigidity while digging, a feature that supports their subterranean lifestyle. 
• Though marsupial moles have a generally low metabolism, they can shoot it up by 60 times when they need high energy for burrowing.

Conservation Status

The IUCN Red List estimates that the Northern marsupial mole has between 10,000 and 50,000 mature individuals, while the Southern marsupial mole population ranges from 10,000 to 100,000. Both species belong to the Least Concern (LC) category and have a stable population trend.

Interesting Facts

• Instead of generating heat through increased metabolism, these mammals can increase their body temperature from around 23°C to over 30°C (73°F to 86°F) primarily through passive heat conduction from their sandy surroundings.