Populations of New Holland mice that live in Tasmania, have a slightly larger body weight than those that are from New South Wales and Victoria.

[8] Most New Holland mice are born between the months of August and January, and their breeding patterns are based on the amount of food obtained, which depends on rainfall.

[7] The New Holland mouse's geographic range consists of fragmented populations throughout Tasmania, Victoria, New South Wales, and Queensland.

Based on genetic evidence, it is believed that the New Holland mouse existed in one large population on mainland Australia.

Furthermore, based on the distribution of subfossils, it has been suggested that the species has experienced a dramatic contraction of its normal range since the region was settled by Europeans.

[4] The New Holland mouse is as of 2021[update] listed as a vulnerable species due to its population size (estimated at 8,000) and density, and their rates of decline.

[10] The New Holland mouse has since been discovered in Victoria at a number of near coastal locations, mostly to the east of Melbourne, including Cranbourne, Langwarrin, Yanakie Isthmus, the south-western end of the Ninety Mile Beach and a number of sites near Loch Sport, Mullundung State Forest and Providence Ponds.

The Anglesea population, discovered in 1980, comprises a number of sub-populations which were intensively studied by Deakin University researchers throughout the 1980s and 1990s.

Also, equally as dangerous to the existence of the mice is the inappropriate management of fire and the subsequent environmental constraints such events have on the ability for populations to access the necessary sustenance to survive and reproduce.

Many scientists have speculated on various climatic environmental processes in a given location and created detailed models to project the status of the species in the future.

The most severe and pressing danger in regards to the existence of the New Holland mouse comes directly from the threat of predators in the environment.

At first the loss of habitat was mainly caused by clearing, but now frequent fires and predation by the introduced red fox and cat are potential threats to this species.

In 1990, after many studies of small mammals in Victoria were conducted, Deakin University received $10,000 from the National Estate Grants Program to review the populations and distributions of the New Holland mouse, and to identify the processes of habitat modification which threatens the species.

[citation needed] Long-term persistence of this species will probably require well-planned fire management regimes within its habitat, throughout its range.

The New Holland mouse occurs in association with other native mammals, including the brown antechinus (Antechinus stuartii), white-footed dunnart (Sminthopsis leucopus), southern brown bandicoot (Isoodon obesulus), bush rat (Rattus fuscipes), swamp rat (Rattus lutreolus) and Eastern pygmy possum (Cercartetus nanus).

[citation needed] The 2021 survey and conservation assessment in north-eastern Tasmania, funded by the Commonwealth Government, will inform a national recovery plan for the mouse.