What do Customs and Border Protection detector dogs primarily search for?

Customs and Border Protection (CBP) detector dogs are primarily trained to identify harmful plant pests and animal diseases. These dogs play a crucial role in safeguarding agriculture and natural resources by detecting biosecurity threats that could be introduced through international trade and travel. Their expertise in identifying these specific threats allows them to help prevent the spread of diseases and pests that could have detrimental effects on native ecosystems, agriculture, and animal populations.

In the context of the other options, while some detector dogs may be trained for specific searches—such as drugs or evidence of animal cruelty—the primary focus of CBP's detector dogs, particularly in relation to safeguarding agricultural interests, is indeed on harmful pests and diseases. Illegal wildlife trade may involve detection of illegal species but is not the main function of CBP canine units. Thus, the correct answer emphasizes the critical role that these detector dogs play in protecting against threats related to agricultural biosecurity.