Poisons are commonly used to kill non-native animals in New Zealand. Animals that have been poisoned show behaviours consistent with sickness such as inactivity or lethargy and increased time resting in a curled position, and abnormal behaviours such as crouching, lying prostrate, and pushing or pulling themselves across the ground. Other signs of poisoning can include vomiting, external bleeding, pale extremities, muscular weakness, loss of body control, and full paralysis. Some poisons will cause extensive bleeding in muscles and joints and throughout the body including the chest cavity, which is associated with pain and breathing difficulties. An animal can experience pain and distress from poisoning for a prolonged period before they are unconscious and dead, leading to severe welfare harm.

SPCA opposes the use of poisons in pest management because of the high risk of unintentionally poisoning animals that are not the target of pest management.

Animals that are not the target of pest management are at risk of ingesting poisons, especially if they are not placed in secure containers such as locked and anchored bait stations. Some poisons have a high risk of secondary poisoning where an animal not the target of pest management has preyed upon or scavenged the carcass of an animal that has already been poisoned (for example, a ruru has consumed a rodent that has eaten rat bait).

SPCA advocates that only methods that minimise negative welfare harms caused to targeted and non-targeted animals be used to kill animals for pest management.

SPCA acknowledges that it is sometimes necessary to manage populations of animals for a variety of reasons, including protecting biodiversity. In these instances, management activities must only use target-specific and effective methods that minimise negative impacts on animal welfare.