A rare golden lion tamarin monkey has been killed and eaten by otters after accidentally falling into a pond at a British zoo.

Bristol Zoo Gardens said the monkey was climbing on a branch when it fell and became trapped in the otter enclosure last month.

The zoo made the disclosure after a whistleblower unveiled a series of animal deaths at the institution.

In a recent incident, an endangered warty piglet was eaten by its father shortly after it was born.

The zoo's director of conservation, Christoph Schwitzer, said despite their best efforts, keepers were unable to prevent unforeseen accidents.

Speaking in a video posted on the zoo's website, he said the zoo had made a decision not to separate the piglet's mother from its mate so it did not cause the animals harm.

"This left not only our team of keepers and the vets very distressed but in fact all of us," he said about the piglet's death.

"We care for thousands of animals here at Bristol Zoo day in and day out and our keepers and all of us here form very strong bonds with these animals and you can imagine we were unhappy about this incident."

According to local media reports, three rainbow lorikeets escaped through a hole in their cage last week.

One of the birds is still missing.

The ABC has contacted Bristol Zoo Gardens for comment.