The Warsaw zoo will be giving its elephants medical marijuana as part of an experiment to test whether it reduces their stress levels.
The zoo's three African elephants will be given liquid doses of a high concentration of the cannabinoid CBD through their trunks.
It comes after the death of an elephant in March, leaving the herd of three young elephants mourning.
Agnieszka Czujkowska, the veterinarian in charge of the project, said although medical cannabis has been used worldwide to treat dogs and horses, "this is probably the first initiative of its kind for elephants."
"It's an attempt to find a new alternative to the existing methods of combating stress, especially pharmaceutical drugs," Czujkowska told AFP.
The zoo monitors the elephants' stress by checking their hormone levels and behavioural levels. If successful, the initiative could then be tried with other animals.
"Contrary to what some would imagine, the elephants won't be using cannabis pipes nor will they be getting huge barrels of it," Czujkowska said.
"The female Fryderyka has already had a chance to try it and she didn't say no."
The veterinarian said CBD causes neither euphoria nor harmful side effects on the liver and kidneys.