Weasels are the smallest carnivores in the world and ecologically vital controllers of small mammal populations. Their welfare is threatened by prey population crashes and secondary poisoning.
Weasels are physiologically vulnerable to food shortage because of their extremely high metabolic rate. Vole population crashes leave weasels in a state of rapid nutritional decline that is effectively starvation over days rather than weeks. Secondary poisoning from eating rodenticide-killed prey causes prolonged internal bleeding — a significant welfare harm for a species rarely considered in rodent control risk assessments. Improving trap selectivity and reducing rodenticide use benefits weasels directly.