Gilbert's Potoroo

## Description

Gilbert's potoroo or ngilkat (Potorous gilbertii ; formerly Hypsiprymnus gilbertii ) is Australia's most endangered marsupial, the rarest marsupial in the world, and one of the world's rarest critically endangered mammals, found in south-western Western Australia. It is a small nocturnal macropod that lives in small groups.

It was thought to be extinct for much of the 20th century, having not been spotted for around a century, until its rediscovery in 1994. The only naturally located population is found in Two Peoples Bay Nature Reserve in Western Australia, where they co-exist with quokkas (*Setonix brachyurus* ), but in 2015 a huge fire destroyed 90% of their habitat. Small populations are being established at Bald Island, off Albany, and more recently on Middle Island, off Esperance, all on the southern coast of WA. Numbers have increased in recent years, and as of December 2018 the entire population was estimated to comprise at least 100 individuals, with 10 on Middle Island, 70 on Bald Island, 20 at Waychinicup National Park and two at Two Peoples Bay (also known as the Mt Gardner population).

## Appearance

Gilbert’s potoroo is a small marsupial species, which was believed to be extinct since the early 1900s and rediscovered in 1994 at Two Peoples Bay Nature Reserve near Albany (Western Australia). When moving fast, these animals hop on their hind legs. When moving slowly, they put their forefeet on the ground. The forefeet of these marsupials are well-developed and used in digging. When standing, the potoroo seems to be hunched. Instead of looking directly, its eyes look slightly upwards. The animal is able to dig as well as easily grasp and handle objects due to its long and curved claws. There is no reliable information on the life expectancy on these animals. However, they are thought to live as long as their close relatives, Long-nosed potoroos, which usually live up to 7 years in the wild and as much as 12 years in captivity.

## Distribution

Currently, Gilbert's potoroos occur exclusively on Mount Gardner headland at Two Peoples Bay par (Western Australia). In the past, however, the species was widely distributed and common across all of south-western Australia. These animals used to inhabit areas around King George Sound and near the Margaret River. Gilbert's potoroos are primarily found in tall shrubland of 1.5 - 2 meters with dense Melaleuca growth. Nesting sites of these animals are typically secluded, bowl-shaped recesses under low bushes, sheltered by the shrub canopy.

## Behavior

There is very limited information on social habits and behavior of these animals. According to information, acquired from radio-tracking and trapping, they are likely to form small, isolated groups, which are scattered throughout their range. Some sub-adult individuals and older males are known to move from one group to another. Within a group, home ranges of individuals of the same sex rarely overlap, whereas territories of male and female protoroos usually do overlap. These nocturnal animals spend their daytime hours nesting. In addition, they can occasionally nest at night, typically in secluded, bowl-shaped recesses under low bushes, sheltered by the shrub canopy. According to studies, these animals make one-kilometer foraging trips each day from their daytime hideaways, returning to their shelters in the morning. Although there is no information on communication behavior of Gilbert's potoroos, they are thought to associate with conspecifics through visual stimuli, noises and smells, like other marsupials.

## Diet

Gilbert’s potoroos are believed to be primarily herbivores. Throughout the year, they feed upon fruiting bodies of underground fungi known as truffles, which compose more than 90% of their diet. The rest of their diet consists of occasional berries, fleshy seedpods as well as some insects.

## Reproduction

Reproductive habits and behavior of this species is currently insufficiently explored. Gilbert's potoroos are believed to have polygynandrous (promiscuous) mating system, like their close relatives, Long-nosed potoroos. Births may occur throughout the year. Young are born approximately in 4 - 6 weeks after mating. The newborn babies remain in the pouch of their mother for the first 3 - 4 months of their lives, after which they begin appearing from the pouch; this lasts for a week, after which they leave the pouch, continuing to feed upon maternal milk for another month. Then, during the following 1 - 2 months, they live on the territory of their mother, leaving by the age of 6 months. There is no accurate information on the age of sexual maturity in this species: males appear to become mature after 2 years old, whereas females are known to give birth at one year old.

## Population

### Population threats

Gilbert’s potoroos presently suffer from destruction of their natural habitat as well as feral predation. However, the primary threat to the only known, small population of these animals in the wild is fire: living in an area, covered with vegetation, which is exposed to wildfire, Gilbert’s potoroos are highly threatened with complete extinction.

### Population number

According to the IUCN Red List, the total population size of the Gilbert’s potoroo is 30-40 individuals. This species is currently classified as Critically Endangered (CR) on the IUCN Red List and its numbers are decreasing.

## Fun Facts for Kids

Discovered in 1840, this species was named after John Gilbert, an English naturalist and explorer, in 1841.

In his note, John Gilbert mentions potoroos as “the constant companions” of the Quokka.

This little-known animal is the rarest marsupial in the world, which was believed to be extinct for 120 years, until 1994, when it was rediscovered.

When Gilbert’s potoroos were discovered, they were nicknamed as “rat-kangaroos”.

These marsupials were found due to urbanization, after which Prince Philip (husband of Queen Elizabeth II), organized protection of the area, where they lived, for the noisy-scrub bird, which was believed to be extinct until 1961, when it was rediscovered. As a result, this conservation campaign helped survive the small local population of Gilbert’s potoroos.