Chimpanzee and Tiger Cub

Two-year-old chimpanzee "Do Do" feeds milk to "Aorn", a 60-day-old tiger cub, at Samut Prakan Crocodile Farm and Zoo.

A baby gibbon

A baby gibbon sits on a swing in its enclosure in Vienna's Schoenbrunn zoo. The gibbon, born on September 23, 2009, has yet to be sexed and named.

Kira, a 3-month-old baboon

Kira, a 3-month-old baboon, looks on as it is fed by an employee of the Zoo in Russia's city of Krasnoyarsk.

Baby monkey

Emperor tamarin monkey

Emperor tamarin monkey twins Lara and Lucy look on from their home in the zoo's nursery. The twins are being cared for by zookeepers after they were orphaned on July 30 when their mother died from cancer, three weeks after giving birth to the pair.

Marmoset monkeys

This composite photograph shows newborn transgenic marmoset monkeys Kei (L) and Kou. Japanese researchers on Thursday reported they have genetically engineered monkeys whose hair roots, skin and blood glow green under a special light, and who have passed on their traits to their offspring, the first time this has been achieved in a primate.

Red-shanked Douc

Red-shanked Douc is on display at Dusit zoo in Bangkok.

Ring-tailed lemurs

Ring-tailed lemurs warm themselves in front of an electric heater at the Japan Monkey Center in Inuyama. The monkeys, native of Madagascar, are not good at maintenance of body temperature and usually bask in the sun or huddle together to keep warm but they got used to the new way from last season, the zoo said.

Emporer Tamarin monkey

Rollie, an Emporer Tamarin monkey is seen at Chicago's Lincoln Park Zoo.

Young squirrel monkey

A young squirrel monkey is seen amongst adults at the Zoo in Philadelphia. Squirrel monkeys are indigenous to northern South America.

A Sumatran orangutan

A Sumatran orangutan relaxes in a zoo in Medan, North Sumatra, Indonesia. Orangutans are one of the most endangered species in the world with a wild population of less than 7,000.

Sumatran Orangutan

Sumatran Orangutan Anita, left, feeds her offspring Atina at the Singapore Zoo. The Sumatran and Bornean Orangutans are categorized as being critically endangered.

Obese Rhesus monkey

An obese Rhesus monkey eats at Ohama park in Sakai, near Osaka. Since June 2007, the park has cut down on the amount of food being fed to the monkeys from 10 kg (22 lbs) per day to 2 kg (4.4 lbs) because the monkeys have become overweight. The park is also planning to build a fence to prevent visitors from throwing food to the monkeys, a park office worker said.

A baby Katta monkey

A baby Katta monkey (lemur catta) cuddles with its mother in their enclosure at the Hagenbeck Zoo in Hamburg. The Katta baby was born on March 17 at the Zoo while another Katta gave birth to twins on March 18.

Sumatran orangutan

Nonja, the Sumatran Orangutan at Miami Metrozoo, believed to be the oldest living Sumatran Orangutan in the world.

Gorilla tax

A gorilla cradles her young at Taronga Zoo in Sydney.Rwandan companies using the country's famous mountain gorillas' image for marketing purposes will have to pay a tax aimed at financing the endangered species protection.