A penguin swims past as a keeper counts the birds during a stock take at London Zoo.

London - It is touted as a wild night out. But after-hours parties at London Zoo are becoming a little too wild – and it’s the guests rather than the animals who are to blame.

Drunken revellers have been taunting and abusing the animals at Zoo Lates events, which are held on Friday nights over the summer.

Recent incidents include a woman punching a bird, a male visitor pouring beer on a tiger, a reveller stripping off before attempting to enter the penguin enclosure and butterflies routinely squashed underfoot.

There are also claims that a drunken woman tried to get into the lion enclosure.

The animals are said to have been disturbed by loud noise and flash photography at the parties.

Sources at London Zoo are said to have raised serious concerns about the impact on animals’ sleep and stress levels.

The world’s oldest zoo has been hosting the sessions for several years to attract a younger demographic, generating £800 000 a year to fund its conservation work.

A source at the zoo said: “During the day, welfare and conservation is of the utmost priority. In the evening, that seems to go out of the window, and the animals become a commodity.

“That’s not what zoos are about, but there’s a lot of money in it.”

More than 6 000 people attend each Zoo Lates event. Tickets cost up to £35 (about R600), and the price includes some free wine.

One visitor in June reported seeing a woman accidentally punching a bird in the aviary. “I don’t know how drunk she was but clearly she had been drinking for a while,” the female witness told the Guardian.

“She stumbled and inadvertently punched the side of the bird and the bird took off. I could not believe it.”

She added: “I saw animals being taunted, and saw people banging on the glass. One man was rubbing himself on the glass in the snake enclosure. In the butterfly exhibit, people were so careless, crushing butterflies on the ground.” London Zoo confirmed the tiger and penguin incidents, but said there was no record of a woman trying to enter the lion enclosure.

A spokesman said the zoo believed the events were safe.

“We would ban alcohol if we thought it was necessary but at the moment we see no need to do so,” she said, adding that only three people were ejected from the events during 2013 and 2014. - Daily Mail