Patna zoo will inaugurate a "nocturnal house" for creatures that venture out only after dark and release a souvenir to mark its foundation day - after 44 years.

Sanjay Gandhi Biological Park director Nand Kishore said: "After going through the history of the zoo, we decided to organise a special programme on June 22 to celebrate the foundation day as a formal notification of this zoo was made on this very date in 1973."

The nocturnal house will accommodate owl, bat, civet cat, porcupine, slow loris (the only venomous primate), hedgehog and jackal.

The souvenir will depict the history of the Sanjay Gandhi Biological Park.

A nocturnal house, sometimes called a nocturama, is a building in a zoo or research establishment where nocturnal animals are kept for public viewing. The lighting is dark during day and lit at night to enable visitors and researchers to study nocturnal animals during daylight hours.

Visitors will have to buy an entry ticket to visit the nocturnal house. For persons up to height of 4 feet 6 inches the entry ticket will be Rs 5 and for those taller it will be Rs 10.

Kishore said: "As the nocturnal animals go into hiding during daylight, we have specially designed the interiors of this house so that the animals remain active when visitors come to see them during the daytime."

He added: "The basic structure of the nocturnal house was ready for the past 25 years but for some reason or the other, it could not be put to use. After doing the necessary modifications in the structure, we will now make it functional. A small interpretation centre has been set up inside the nocturnal house so that visitors could have basic information about the traits of these animals before actually watching them in their respective enclosures inside the house."

The first step towards setting up the zoo was taken in 1969 when the then governor of Bihar, Nityanand Kanungo, donated 34 acres to set up a botanical garden. In 1972, the state revenue department provided 58.20 acres while the public works department provided 60.75 acres to set up the zoo.

The zoo got its present name in October 1980 when, while inaugurating a Wildlife Week event, then chief minister Jagannath Mishra announced that the zoo will be known as Sanjay Gandhi Biological Park.