Underfloor heating, an incubator and an indoor pool are among the luxury amenities that have ensured that animals at a zoo in Jiangsu province have remained warm and comfortable over the winter.

Keepers at Nanjing Hongshan Forest Zoo even give some of the animals food that has been prepared in a microwave oven.

An incubator designed for premature babies has been installed for the zoo's mongooses.

"We introduced the mongooses from South Africa in 2013," said Hu Lanhua, who looks after the animals.

"During the first year we had them, we noticed that they gathered together and hid in underground holes they dug during cold winter nights. The nighttime temperature in Nanjing often remains below 0 C.

"Their body weight dropped by 5 percent one night when they slept in the holes. The first thing they did on sunny mornings was to go to the yard to get some sunshine."

The animals now sleep in the incubator, which is set to a comfortable 20 C, on cold nights.

"The mongooses stay in their holes when the temperature is above 0 C, and sleep in the incubator when it gets colder," Hu said. "They know exactly what they want."

Hu microwaves meat before giving it to the mongooses.

"We used to simply chop up the meat, but they did not eat much and appeared wary. After we started heating the meat they began to eat more, and we realized they like to have warm food in winter."