Common Water Rat vs Gray-backed Tern

Hydromys chrysogaster compared with Onychoprion lunatus

Taxonomic Classification

Rank	Common Water Rat	Gray-backed Tern
Kingdom same	Animalia (Animals)	Animalia (Animals)
Phylum same	Chordata (Chordates)	Chordata (Chordates)
Class	Mammalia (Mammals)	Aves (Birds)
Order	Rodentia (Rodents)	Charadriiformes (Charadriiformes)
Family	Muridae (Mice & Rats)	Laridae
Genus	Hydromys	Onychoprion
Species	Hydromys chrysogaster	Onychoprion lunatus

Evolutionary Relationship

Common Water Rat and Gray-backed Tern share a common ancestor at the Phylum level: Chordata. (Chordates)

Conservation Status

Common Water Rat

LC — Least Concern

Gray-backed Tern

LC — Least Concern

Physical Characteristics

Attribute	Common Water Rat	Gray-backed Tern
Diet	—	—
Average Lifespan	—	—
Average Length	—	—
Average Weight	—	—

Habitat & Geographic Range

Common Water Rat

Habitat

Typically found in diverse terrestrial and aquatic ecosystems.

Gray-backed Tern

Habitat

Typically found in various aerial, terrestrial, and aquatic environments.

Range

Found in Norway.

Common Water Rat

<em>Hydromys chrysogaster</em>, commonly known as the common water rat or rakali, is a semi-aquatic rodent in the family Muridae, native to Australia and New Guinea. It is classified as Least Concern by the IUCN, reflecting its relatively stable population across a broad range of freshwater and estuarine habitats on the Australian continent and associated islands. The species typically inhabits the banks of rivers, lakes, wetlands, and estuaries, where it constructs burrows in streambanks. It is highly adapted for an aquatic lifestyle, with partially webbed hind feet, a flattened head, and a dense waterproof coat. <em>Hydromys chrysogaster</em> is a carnivore, typically feeding on fish, crustaceans, mussels, frogs, and aquatic invertebrates, which it often carries to elevated feeding platforms to consume. The species is nocturnal and crepuscular, most active during early morning and evening hours near the water's edge. Biological traits including average lifespan, body length, and weight remain poorly documented in standardized databases, though adults are generally robust for a rodent, reportedly reaching body lengths of 20–35 cm excluding the tail. Geographic range details for this particular record remain incompletely documented in available data sources. Ecologically, the common water rat is an important apex predator in small-scale freshwater food webs and serves as an indicator species for wetland health in Australian riparian systems.