a half years old, and have a life expectancy of 3–4 years. A territorial species, they are mostly solitary excluding the periods of mating and rearing their young. Their social organisation suggests adults are intra-sexually aggressive with their limited home range and overlapping sex and age classes. In captivity, only the dominant female in the hierarchy will successfully reproduce. Fecundity is lower than that of other murid species producing only four to five litters, but fertility is very high which can create high population growth in a period of favorable breeding conditions. This can be also influenced by the rapid growth in juveniles who can reach maturity and size within their first year. H. chryogaster in comparison to the Rattus species mature late and have long reproductive lifecycles. They have lower reproductive output, delayed implantation, lactation anoestrus, winter anoestrus, longer estrous and longer gestation cycle. Their development occurs in stages associated with the eruption of incisors, hearing and eye-opening, eating solid foods, puberty and full reproductive maturity. Status Although nationwide the populations appear stable there are individual populations facing a significant threat. Near threatened in Western Australia's Wheatbelt, urbanisation, salinisation, waterway degradation and pollution have all attributed to this status change. In the Northern Territory, Queensland, Tasmania and New South Wales they are classified as 'least concern'. In the Victorian Lake Wellington, Lake Victoria and Lake Tyers region, numbers have declined in the past fifty years attributed to commercial eel-fishing, predation, loss of habitat due to commercial development and poisoning from baiting programs placing this species at risk. References External links Australian Museum Factsheet Australian Platypus Conservancy CSIRO Water for a Healthy Country Water Rat - Description and Characteristics Oz Animals Hydromys Mammals of Tasmania Mammals of Western Australia Mammals of South Australia Mammals of the Northern Territory Mammals of New South Wales Mammals of Queensland Mammals of Victoria (Australia) Rodents of Australia Mammals described in 1804 Rodents of New Guinea Taxa named by Étienne Geoffroy Saint-Hilaire