A squirrel monkey finds nuts hidden in Christmas stockings during a media photo call at Whipsnade Zoo in Dunstable, England, Tuesday Dec. 18, 2018.

Six-month-old Amur tiger cub Makari plays with a Christmas stocking during a media photo call at Whipsnade Zoo in Dunstable, England, Tuesday Dec. 18, 2018.

Kumbuka, a critically endangered Western Lowland Gorilla, finds brussel sprouts in a giant advent calendar placed in his enclosure at London Zoo, Thursday, Dec. 20, 2018.

A lioness investigates a 'Christmas pudding' - a giant ball scented with classic yuletide spices - cinnamon and nutmeg in her enclosure at London Zoo, Thursday, Dec. 20, 2018.

Kumbuka, a critically endangered Western Lowland Gorilla, finds brussel sprouts in a giant advent calendar placed in his enclosure at London Zoo, Thursday, Dec. 20, 2018.

Bhanu, a male asiatic lion, and a lioness investigate a 'Christmas pudding' - a giant ball scented with classic yuletide spices - cinnamon and nutmeg in her enclosure at London Zoo, Thursday, Dec. 20, 2018.

Bhanu, a male Asiatic lion, walks under a giant ball scented with classic yuletide spices - cinnamon and nutmeg in his enclosure at London Zoo, Thursday, Dec. 20, 2018.

A Bactrian camel takes grass placed in a stocking as animals are given meals styled along a Christmas theme in London, Britain, December 20, 2018.