The beagle patrolling Toronto Pearson International Airport was prowling for the subtle scents of contraband when an unexpected odor tickled its olfactory receptors. The source was the luggage of a Canadian man who had just returned from Russia.

The dog knew what to do next and plonked down next to the traveler—sending a signal to Canada Border Services Agency personnel that something was amiss.

Officials peered inside the man’s bags and found hundreds of containers filled with slimy, writhing objects—5,000 live leeches. It was October 17, 2018, and the trusty beagle had helped authorities snag Canada’s first known leech “smuggler.” (Authorities are calling him an alleged illegal leech importer, rather than a smuggler, because he wasn’t necessarily purposefully hiding the contraband.)

The incident,