Overview

Distribution

Range Description

This species is present on Obi Island in the Moluccan Islands of Indonesia, the Kai Islands (Indonesia), the Aru Islands (Indonesia), the islands of Biak-Supiori and Yapen (Indonesia), it is found over much of the island of New Guinea (Indonesia and Papua New Guinea), on the D’Entrecasteaux Islands and the Trobriand Islands (Papua New Guinea), and ranges through parts of northern, eastern, south-eastern and south-western Australia, including the island of Tasmania and a number of offshore islands (e.g., Bernier Island, Western Australia). It ranges from sea level to 1,900 m asl.
Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© International Union for Conservation of Nature and Natural Resources

Source: IUCN

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Geographic Range

Hydromys chrysogaster dwells in freshwater lakes and rivers throughout Australia and Tasmania and on offshore islands. They are also found on New Guinea. (Watts and Aslin, 1981)

Biogeographic Regions: australian (Native )

Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© The Regents of the University of Michigan and its licensors

Source: Animal Diversity Web

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Physical Description

Morphology

Physical Description

About the size of a rabbit, H. chrysogaster is well adapted for water. The toes are webbed on front and hind feet, which are broad and act as paddles. Hydromys chrysogaster has numerous whiskers at the end of a long, blunt muzzle. The head is flat with small ears and eyes. The most notable characteristic is the water rat’s thick white tipped tail. Hydromys chrysogaster varies in color from a brown black to gray, making them somewhat cryptic in their surroundings. Some are uniform in color, while others have lighter undersides. The one unifying feature is the white tipped tail. (Watts and Aslin, 1981)

Other Physical Features: endothermic ; bilateral symmetry

Average mass: 850 g.

Average basal metabolic rate: 2.97 W.

Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© The Regents of the University of Michigan and its licensors

Source: Animal Diversity Web

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Ecology

Habitat

Habitat and Ecology

Habitat and Ecology
This species is associated with a wide variety of permanent aquatic habitats. It can be found in most types of freshwater habitats, including artificially irrigated sites, and can also occur in mangrove and estuarine areas (Flannery 1995a,b; Olsen 2008). Animals nest in bankside tunnels or logs, and while most food is taken from the water, they may forage in riparian vegetation (Olsen 2008). Females may annually have up to five litters (usually one or two) of three or four young (Olsen 2008).

Systems
  • Terrestrial
  • Freshwater
  • Marine
Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© International Union for Conservation of Nature and Natural Resources

Source: IUCN

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Hydromys chrysogaster individuals live mainly near permanent fresh water. They live on land but depend on the water for food. Also present along the coastline, H. chrysogaster do not need completely fresh water. They can also survive in areas where rivers and streams have become polluted or are brackish. (Watts and Aslin, 1981)

Habitat Regions: tropical ; saltwater or marine ; freshwater

Aquatic Biomes: lakes and ponds; rivers and streams; coastal

Wetlands: marsh ; swamp ; bog

Other Habitat Features: urban ; suburban ; agricultural ; riparian ; estuarine

Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© The Regents of the University of Michigan and its licensors

Source: Animal Diversity Web

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Trophic Strategy

Food Habits

Hydromys chrysogaster feeds mainly on crustaceans, mollusks, and fish, although they have been observed feeding on aquatic insects, frogs, house mice, the eggs and young of waterfowl, poultry, and turtles, and even attacking bats. Hydromys chrysogaster have also been observed eating cane toads, an introduced species that is toxic to many other predators. They often have a favorite feeding platform on which they collect piles of food before eating it. Hoarding food in the nest site is also common. Mussels are opened by their strong incisors.

Animal Foods: birds; mammals; amphibians; reptiles; fish; eggs; insects; terrestrial non-insect arthropods; mollusks; aquatic crustaceans

Foraging Behavior: stores or caches food

Primary Diet: carnivore (Piscivore , Eats non-insect arthropods, Molluscivore )

  • Fanning, F., T. Dawson. 1980. Body temperature variability in the Australian water rat, *Hydromys chrysogaster*, in air and water. Australian Journal of Zoology, 28: 229-238.
  • Watts, C., H. Aslin. 1981. The rodents of Australia. Sydney: Angus & Robertson Publishers.
Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© The Regents of the University of Michigan and its licensors

Source: Animal Diversity Web

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Associations

Ecosystem Roles

Water rats are abundant and are an important prey base for many small to medium-sized predators. Their burrowing and foraging activities probably also help in the redistribution of nutrients in systems.

Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© The Regents of the University of Michigan and its licensors

Source: Animal Diversity Web

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Predation

Eagles, buzzards and kites prey on water rats, as well as snakes and small mammalian carnivores. Water rats mainly escape predation by escaping to burrows or into the water. (Watts and Aslin, 1981)

Known Predators:

Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© The Regents of the University of Michigan and its licensors

Source: Animal Diversity Web

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Known predators

Hydromys chrysogaster is prey of:
Serpentes
Accipitridae

This list may not be complete but is based on published studies.
Creative Commons Attribution 3.0 (CC BY 3.0)

© SPIRE project

Source: SPIRE

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Known prey organisms

Hydromys chrysogaster preys on:
non-insect arthropods
Actinopterygii
Mollusca
Arthropoda
Insecta
Amphibia
Aves
Mammalia

This list may not be complete but is based on published studies.
Creative Commons Attribution 3.0 (CC BY 3.0)

© SPIRE project

Source: SPIRE

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Life History and Behavior

Life Expectancy

Lifespan/Longevity

Longevity in water rats is unknown.

Average lifespan

Status: captivity:
7.3 years.

Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© The Regents of the University of Michigan and its licensors

Source: Animal Diversity Web

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Lifespan, longevity, and ageing

Maximum longevity: 7.3 years (captivity)
Creative Commons Attribution 3.0 (CC BY 3.0)

© Joao Pedro de Magalhaes

Source: AnAge

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Reproduction

Little is known of the mating system of water rats.

Water rats breed in the spring and summer. Females have an estrous cycle of approximately eleven days. The gestation period is about 35 days. Females can enter estrus immediately after giving birth, so litters can be produced only 35 days apart. Usually, water rats have litters of four to five young. During a good breeding season, females can have two or three litters.

At birth, the young are blind. They are usually lighter in color than the adults, but already have the characteristic white tipped tail and partially webbed feet. The young grow quickly and are usually independent after about 35 days. However, after this initial growth, maturity to adulthood takes longer. Breeding does not occur until the young are at least one year old and full size is attained at about two years of age. (Watts and Aslin, 1981)

Breeding season: Breeding occurs during spring and summer.

Range number of offspring: 8 to 15.

Average gestation period: 35 days.

Average weaning age: 35 days.

Average age at sexual or reproductive maturity (female): 1 years.

Average age at sexual or reproductive maturity (male): 1 years.

Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); fertilization (Internal ); viviparous

Average birth mass: 24.39 g.

Average gestation period: 36 days.

Average number of offspring: 3.8.

Average age at sexual or reproductive maturity (male)

Sex: male:
135 days.

Average age at sexual or reproductive maturity (female)

Sex: female:
163 days.

Young are born helpless and are cared for by their mother in her nest burrow until they are weaned, at about 35 days old.

Parental Investment: altricial ; female parental care

Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© The Regents of the University of Michigan and its licensors

Source: Animal Diversity Web

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Molecular Biology and Genetics

Molecular Biology

Statistics of barcoding coverage: Hydromys chrysogaster

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 0
Specimens with Barcodes: 1
Species With Barcodes: 1
Creative Commons Attribution 3.0 (CC BY 3.0)

© Barcode of Life Data Systems

Source: Barcode of Life Data Systems (BOLD)

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Conservation

Conservation Status

IUCN Red List Assessment


Red List Category
LC
Least Concern

Red List Criteria

Version
3.1

Year Assessed
2008

Assessor/s
Aplin, K., Copley, P., Robinson, T., Burbidge, A., Morris, K., Woinarski, J., Friend, T., Ellis, M. & Menkhorst, P.

Reviewer/s
Lamoreux, J. (Global Mammal Assessment Team) & Amori, G. (Small Nonvolant Mammal Red List Authority)

Contributor/s

Justification
Listed as Least Concern in view of its wide distribution, presumed large population, and because it is unlikely to be declining at nearly the rate required to qualify for listing in a threatened category.
Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© International Union for Conservation of Nature and Natural Resources

Source: IUCN

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Water rats are widespread and abundant, they are not threatened.

US Migratory Bird Act: no special status

US Federal List: no special status

CITES: no special status

IUCN Red List of Threatened Species: least concern

Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© The Regents of the University of Michigan and its licensors

Source: Animal Diversity Web

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Population

Population
It is generally a common, but sparsely distributed, species. There have been some declines in parts of Australia.

Population Trend
Unknown
Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© International Union for Conservation of Nature and Natural Resources

Source: IUCN

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Threats

Major Threats
There are no major threats to this species. In New Guinea, some populations are locally threatened by aquatic pollution resulting from mining activities. In south-western Western Australia, populations have declined likely due to increased salinity from clearing in agricultural areas. Extinction in the Montebello Islands (Western Australia) was probably due to a high density of introduced black rats (Rattus rattus) and cats.
Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© International Union for Conservation of Nature and Natural Resources

Source: IUCN

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Management

Conservation Actions

Conservation Actions
It is present in many protected areas in Australia and New Guinea. Further studies into the taxonomy of this species are needed.
Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© International Union for Conservation of Nature and Natural Resources

Source: IUCN

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Relevance to Humans and Ecosystems

Benefits

Economic Importance for Humans: Negative

Active burrowers, H. chrysogaster individuals have damaged channel banks and water-control structures. (Watts and Aslin, 1981)

Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© The Regents of the University of Michigan and its licensors

Source: Animal Diversity Web

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Economic Importance for Humans: Positive

Hydromys chrysogaster are able to withstand pollution in cities and even thrive there. They are often observed by humans because they are sometimes active during the day. Farmers benefit from H. chrysogaster because they often destroy yabbies, other small rodents, which destroy irrigation systems. By eating pond snails, water rats also protect livestock from the parasites that are transmitted through snails. (Watts and Aslin, 1981)

Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© The Regents of the University of Michigan and its licensors

Source: Animal Diversity Web

Trusted

Article rating from 0 people

Default rating: 2.5 of 5

Wikipedia

Rakali

Hydromys chrysogaster, commonly known as Rakali or Water-rat, is an Australian native rodent. The species lives in burrows on the banks of rivers, lakes and estuaries and feeds on aquatic insects, fish, crustaceans, mussels, snails, frogs, birds' eggs and water birds. Rakali have a body 231–370 millimetres (9.1–14.6 in) in length, weigh 340–1,275 grams (0.750–2.811 lb), and have a thick tail measuring around 242–345 millimetres (9.5–13.6 in). They have webbed hind legs, waterproof fur, a flattened head, a long blunt nose, many whiskers and small ears and eyes. They are black to brown in colour with an orange to white belly, and dark tail with a white tip.

Common names[edit]

Until the 1980s, this species was commonly known as Water-rat, but during the 1990s there was a push for such descriptive English common names to be replaced with indigenous names. In 1995 the Australian Nature Conservation Agency released a document in which the following indigenous names were recorded for H. chrysogaster. They recommended that the name Rakali be adopted as the common name,[2] and the Australian Department of Environment and Heritage has taken up this suggestion. Both common names are now widespread.

References[edit]

  1. ^ Aplin, K., Copley, P., Robinson, T., Burbidge, A., Morris, K., Woinarski, J., Friend, T., Ellis, M. & Menkhorst, P. (2008). Hydromys chrysogaster. In: IUCN 2008. IUCN Red List of Threatened Species. Retrieved 10 October 2008.
  2. ^ a b Braithwaite R. W. et al. (1995). Australian names for Australian rodents. Australian Nature Conservation Agency. ISBN 0-642-21373-9. 
Creative Commons Attribution Share Alike 3.0 (CC BY-SA 3.0)

Source: Wikipedia

Unreviewed

Article rating from 0 people

Default rating: 2.5 of 5

Disclaimer

EOL content is automatically assembled from many different content providers. As a result, from time to time you may find pages on EOL that are confusing.

To request an improvement, please leave a comment on the page. Thank you!