Bondi, an 8-month-old toy poodle, had just returned from a walk when he began stumbling. His head wobbled and soon he could barely stand, so his owner, Colleen Briggs, rushed him to the vet.

The good doctor quickly made a diagnosis: Bondi was stoned.

On his walk, a sniff must have led Bondi to a discarded joint, which he ate.

“He was just doing his usual — exploring everything, sniffing everything,” said Briggs, who began to notice the pot shops sprouting up around New York City, the frequent whiffs of marijuana while circling her Manhattan neighborhood and the unfinished joints now littering sidewalks.

In places like New York City, where the first legal recreational pot dispensary opened last year, users can smoke it in the open. As a result, more dogs are coming across — and eating — discarded joints and edibles, prompting alarm among veterinarians and pet owners who blame the steep rise in poisonings on smokers oblivious to the harm they can do by littering.

Marijuana poisonings, which are almost never fatal, were once rare among pets, even when medical dispensaries started opening, according to Dr. Amy Attas, a New York City veterinarian. Until recently, many occurred at home, when pets got into their owners’ stashes.