A zoo in the United States had a pleasant surprise when its oldest animal became a father of three for the first time - at the grand old age of 90.

Mr Pickles, a radiated tortoise at the Houston Zoo, and his mate, Mrs Pickles, welcomed three hatchlings: Dill, Gherkin and Jalapeno.

The little ones were a surprise to staff.

A herpetology keeper happened upon Mrs Pickles as the tortoise was laying her eggs at closing time, according to the zoo.

The animal care team then quickly went to work uncovering the eggs and getting them to the safety of the Reptile and Amphibian House.

“The soil in Houston isn’t hospitable to the Madagascar native tortoises, and it’s unlikely the eggs would have hatched on their own if the keeper hadn’t been in the right place at the right time,” the zoo said in a blog post.

The three hatchlings are considered a big deal as their father, Mr Pickles, is the most genetically valuable radiated tortoise in the Association of Zoos and Aquariums’ (AZA) Species Survival Plan.

They will remain away from the spotlight in the Reptile and Amphibian House until they are big enough to safely join their parents, the zoo said.

Mr Pickles has been at the zoo for 36 years and has been with his companion, Mrs Pickles, since she arrived in 1996.

Houston broadcaster ABC13 reported that the Pickles welcomed a little one in 1997.

Radiated tortoises are critically endangered due to loss of habitat and illicit pet trade. They also produce few offspring.

A native of southern Madagascar, the tortoises are known for their beautifully patterned yellow lines that radiate in a star pattern from the centre of each of plate on the shell.