91色情片

If a dog鈥檚 sense of smell is thousands of times more sensitive than ours, why do they have to get so close to smell each other鈥檚 bottoms?

Jay Brookhiemer, London, UK

We pay 拢25 for every answer published in New Scientist. To answer this question 鈥� or ask a new one 鈥� visit newscientist.com/lastword. Terms and conditions apply.

This article appeared in print under the headline 鈥淪niff test鈥�