'Sneaky' sloths' new arrival is an unexpected surprise for London Zoo

Sloths Marilyn and Leander broke the mould to successfully mate within six months of first meeting

The sex of the baby sloth is not yet known (PA)

They are creatures that are hardly renowned for their speed – but two sloths at ZSL London Zoo have shocked their keepers by producing the menagerie’s first baby sloth.

Staff were taken by surprise upon discovering that two-toed sloth Marilyn had fallen pregnant right under their unsuspecting noses, after mating with her male partner Leander, who arrived from Germany in 2012.

Despite adhering to a more “treat them mean, keep them keen” strategy in public, things were hotting up between the “sneaky” sloths after hours.

Factoring in an 11-month pregnancy, it is believed that Marilyn and Leander successfully mated after just six months, thereby speeding up a process that has been known to take nearly a decade.

Zookeeper Tegan McPhail said: “To say we were surprised when Marilyn fell pregnant is something of an understatement - we weren't aware that she'd even been near the male.

"When Leander arrived at the zoo at the end of 2012, he and Marilyn just didn't appear particularly interested in each other, but we knew that with sloths these things can take some time.

“However, with the arrival of the first sloth to be born at ZSL London Zoo, it appears that it was all an act on their behalf and our two very sneaky sloths were getting amorous behind our backs.”

Keepers do not know the sex of the new arrival, which is spending its days clinging on to Marilyn, and will not be able to tell if it is a boy or a girl until it is scanned by vets as there are no external differences between males and females.

Sloths are slow-moving, tree-dwelling, nocturnal animals which feed on plants in their native tropical forests in Central and South America.

They have long, sharp claws, good for hanging from trees, but making walking laborious. Sloths are strong swimmers and can drop from trees into a river to swim across it.

Additional reporting by Press Association