The Loro Parque employee was dressed in a gorilla costume as part of a practice drill to simulate the escape of a captive gorilla when he was shot in the leg with the high-dose dart.

It seems not everyone had been informed that a drill was taking place and when a zoo vet saw the “gorilla” running through the park, he thought an actual gorilla had escaped and took action. The vet fired the shot (designed for a 400lb gorilla) at the man and hit him in the leg.

According to La Opinion de Tenerife newspaper when the man was later located he was in his underwear.

The tranquilliser can be a sedative, anaesthetic, or paralytic agent, but it is unclear what the dart fired at the man contained.

The worker had a severe allergic reaction to the tranquiliser and was taken to hospital.

Drills like this happen regularly at zoos, but this is the first report of an incident of this kind.

The zoo said that the vet had only been working there for two months.

The zoo said in a statement: “Loro Parque simulated the escape of an animal from its enclosure in the gorilla park.

“As part of the simulation, which took place in the security zone of the area and was attended only by authorised personnel, they set off the emergency alarm.

“Once they had carried out the various procedures, one keeper in the wild mammals team was accidentally struck by the medical tranquiliser that vets use in these instances.

“As a result, emergency services were called and he was taken to hospital.”