The motive in each case is simply utilitarian. The fact that we derive satisfaction from hunting in no way means that we 'kill for pleasure' despite our opponents' frequent and offensive allegations to the contrary. Wild populations are rarely stable in these days of intensive farming, with its resultant reduced habitat and extended water supplies in remote arid areas. Consequently, kangaroo populations now thrive in numbers vastly exceeding those prior to white settlement. Unfortunately, though, many of the more cryptic species, such as very small kangaroos, bandicoots and tiny carnivores, have simultaneously become endangered or extinct.
Extinctions generally result from loss of habitat and encroachment by alien species.
Cats and foxes eat small mammals directly, and thus their effects are easy to measure. Likewise, the damage wrought by rabbits has been well studied. But rabbits are not the only small, introduced vegetarians to cause ecological problems. Indeed, while plagues of mice are usually depicted in terms of their impact upon agricultural and other human activities, the reality is that such plagues can cause ecological ripples that bounce about unpredictably for a very long time. Sometimes, even the opposite of plagues can be detrimental.