The Warsaw zoo has said it will start giving its elephants medical marijuana as part of a pilot project to test how it reduces their stress levels, The Guardian reports.

Medical cannabis has been used worldwide to treat dogs and horses but “this is probably the first initiative of its kind for elephants,” Agnieszka Czujkowska, the veterinarian in charge of the project, said.

The zoo’s three African elephants will be given liquid doses of a high concentration of the relaxing cannabinoid CBD through their trunks.

The veterinarian said the CBD causes neither euphoria nor harmful side effects on the liver and kidneys.

“It’s an attempt to find a new natural alternative to the existing methods of combating stress, especially pharmaceutical drugs,” Czujkowska said.

The project, she said, comes at an opportune time because the zoo’s herd has recently had to cope with the death of its alpha female.

The zoo monitors the elephants’ stress by checking their hormone levels and through behavioural observation.