Patna's Sanjay Gandhi Biological Park is by next year expected to receive the distinction of hosting the highest number of captive one-horned rhinoceroses (or rhinoceros unicornis or Indian rhinoceros) in a zoo around the world.

The biological park, popularly known as Patna zoo, has 10 one-horned rhinos, just one shy of the number of rhinos in San Diego Zoo, California, US. The number may soon change as sources said a couple of the female rhinos in Patna zoo are expected to give birth in the next few months.

Zoo director Nand Kishore told The Telegraph: "Every zoo wants to be number one and we also wish to. To be able to achieve it with regard to an animal as precious and endangered as the one-horned rhinoceros, is a big deal. We are already the number one in Asia."

The one-horned rhino is considered to be the largest in size and weight among the five existing species of the mammal, including the white, black, Sumatran and Javan rhinos. The zoo has five males and equal number of female one-horned rhinos.

According to data provided by the zoo, 77 zoos across the world house around 200 rhinos. San Diego and Patna hold the top two spots for the largest number of rhinos in captivity, while Basel Zoo in Switzerland has witnessed the highest number of live births of the Indian rhinoceros.

The Indian rhinoceros' natural habitat includes the forests and grasslands along the foothills of the Himalayas from Pakistan to Arunachal Pradesh in India. They reach a height of over two metres and on an average weigh up to 2,200kg. The horn, which can reach a length of two feet, is the reason behind the poaching of this endangered animal. It is popularly used in traditional medicine, and is also known for its ornamental value. The life-span of this species in the wild is around 40 years, and around 47 years when in captivity or a protected environment. The age of those at Patna zoo is around three to 28 years.

Zoo director Kishore said that the central zoo authority is yet to agree to a proposal to establish a special conservation and breeding centre for rhinos at the park. "The conservation and breeding centre will spread over 2.5 acres . The proposed area for the centre will have a lake and grassland to simulate its natural habitat and aid in mating," Kishore added.

A rhino brought in from San Diego has brought about genetic diversity at Patna zoo, said Kishore. He added that the Patna rhinos were in demand, but the zoo does not have exchange plans yet.