the attempted killing of any such wild mammal as an act of mercy if he shows that the mammal had been so seriously disabled otherwise than by his unlawful act that there was no reasonable chance of its recovering;

the killing in a reasonably swift and humane manner of any such wild mammal if he shows that the wild mammal had been injured or taken in the course of either lawful shooting, hunting, coursing or F1lawful pest control activity;

doing anything which is authorised by or under any enactment;

any act made unlawful by section 1 if the act was done by means of any snare, trap, dog, or bird lawfully used for the purpose of killing or taking any wild mammal; or

the lawful use of any poisonous or noxious substance on any wild mammal.