Islands and exclosures are being increasingly considered in the conservation of many mammal species exposed to threats across their broader historic range. However, the area available on islands and exclosures will often constrain the size of any mammal population. This has implications from a genetic perspective, particularly if founder size is small, growth rates are slow or there are large fluctuations in population size. Stochastic effects are likely to predominate in these situations resulting in chance matings between close relatives (inbreeding) and genetic drift playing a greater part in the evolution of these populations, as has been seen in many island-endemic species. Often, this will lead to a loss of fitness, reduced ability to evolve, and ultimately, an increased chance of extinction. Simple genetic translocation strategies can, however, be used to limit these effects and promote the maintenance of genetic diversity in island or exclosure populations. Importantly, a network of populations on islands or exclosures creates an opportunity to not only conserve genetic diversity, but also promote adaptive divergence in populations through time, which could ultimately flow on to an increased reintroduction success elsewhere. Here I will outline different genetic strategies aimed at maintaining genetic and adaptive diversity in islands and exclosures using examples from Australian threatened species, and highlight a key future priority for their use in mammal conservation genetics.