Animal invasions threaten native biodiversity globally and are the most important threat to Australian faunal biodiversity. Lethal control predominates efforts to manage invasive animal impacts upon agricultural and ecological values, but increasingly there are calls for its substitution by non-lethal methods. Here we ask whether killing of invasive animals is essential for wildlife conservation. Firstly, we define wildlife conservation and its population ecology requirements. Secondly, we discuss ethical considerations and then we answer our question using the scientific method, proposing that killing is not essential (the null hypothesis) and offering two working alternatives. The hypotheses are addressed with three conservation case studies of increasing likelihood that killing is essential. Examining spotted-tailed quoll, rabbit-affected ecosystems and New Zealand bird recovery efforts, we conclude that killing invasive animals is sometimes essential to achieve conservation outcomes.