Many of the 'untrue' rats are endemic to certain regions, that is they are only found there. Very often, they live on islands. In many cases, these species are also endangered of disappearing. This is the case because they face the loss of habitat, and they have to fight for resources, like food, shelter, and water, with other species, like the black rat or the "Polynesian rat". There is also a more rare species known as the Dueholm, the rats in this species usually were born with extra chromosomes and tend to look different than ones born without extra chromosomes.