Next time you're irritated that ants have gotten into your kitchen, you might take a moment to consider their extraordinary powers of perception. These tiny animals can detect markers of illness, such as cancer. In fact, ants are just one of many creatures whose senses can register signs of human disease: dogs, rats, bees, and even tiny worms can as well. The silky ant, Formica fusca, a common species found throughout Europe, can be taught to identify the scent of breast cancer in urine. Research from the University Sorbonne Paris Nord in France published this year in Proceedings of the Royal Society B shows ants can learn to distinguish between the scent of urine derived from mice carrying human breast cancer tumors from that of healthy mice. Ants and other animals pick up signs of disease by perceiving various volatile organic compounds, or VOCs. These chemicals are produced in a variety of ways and can be found in exhaled breath, and in sweat, urine, and blood. Diseases can change the VOCs we emit, resulting in giving off a different odor. By placing a sugar reward near the cancer sample the ants learned to seek out that scent, a process called operant conditioning. Dogs can be trained to smell several types of cancers, including melanoma, breast and gastrointestinal cancers and some infectious diseases in humans, including malaria and Parkinson's disease. They can also smell infectious disease in other animals, including chronic wasting disease, which affects the brains of deer and can be fatal.