Admiralty Giant Rat

The more isolated an island, the more likely a species will develop island gigantism.

Manus Island is the main island of the Admiralty Islands that are located to the northwest of Papua New Guinea. Today, the island is best known for its detention centre for Australian asylum seekers.

As recently as 2016, a new species of rats was discovered on Manus Island. To 'honour' the 'recent use of the island to detain people seeking political or economic asylum in Australia', this new addition to the genus Rattus was named Rattus detentus.

The Admiralty Giant Rat weighs nearly half a kilogram and is larger than almost any other rat across the Melanesian archipelago. It measures more than 40 centimeters in length. It has coarse, spiny, and dark fur with prominent black guard hairs; and sharply contrasting cream ventral pelage. The rat has a short tail. This species of rat may have been on the island hundreds of thousands of years.

Over millennia of isolation on Manus Island, the rat has adapted to specific conditions. It has powerful front incisors but small molars, suggesting it uses its front teeth to break open hard nuts.

Before confirmation of the Admiralty Giant Rats existed, scientists had suspected there was a large rat endemic to the island.

Sightings of the Admiralty Giant Rat are rare, thus it is possibly seriously endangered. Residents report it has previously been seen across Manus Island and sometimes on adjacent Los Negros Island (the two islands are connected by a bridge) but efforts by zoologists to find further evidence of it have been fruitless.