ZSL Whipsnade Zoo is due to celebrate its 90th birthday this month, with 11 days of special activities.

The zoo celebrates its birthday on Sunday, May 23 and to kick off the celebrations, the 90th visitor of the day will be invited to feed the herd of reticulated giraffes.

Over the birthday weekend (May 22 - 23) and throughout the May half term (May 29 - June 6), a birthday treasure hunt will be held, and any child that finds a hidden treasure token will win a prize. Families will also be able to follow the birthday trail and collect a free sticker when they have completed it.

Herts Advertiser: Adult rockhopper at ZSL Whipsnade ZooAdult rockhopper at ZSL Whipsnade Zoo (Image: ZSL)

Visitors can also create birthday-themed crafts including origami elephants to celebrate one of the zoo's most iconic animals.

Those who are interested in learning more about the zoo’s history as a centre for conservation can pre-book for a ‘What makes a Whipsnade?’ tour, running through half term.

The animals themselves will be enjoying special treats to celebrate the birthday, including colossal snacks for the elephants to enjoy.

The Zoological Society of London was founded in 1826 with the aim of 'promoting worldwide conservation of animals and their habitats', and a derelict farm on the Dunstable Downs was purchased by the society in 1926, with animals first arriving in 1928.

Herts Advertiser: Amur tiger Czar at ZSL Whipsnade ZooAmur tiger Czar at ZSL Whipsnade Zoo (Image: ZSL)

On May 23, 1931, Whipsnade Park Zoo opened as the first easily accessible ‘open zoo’ in Europe and was an immediate success, welcoming tens of thousands of visitors in its opening week.

Whipsnade’s distinctive chalk figure of a white lion, measuring 147 metres, was completed in 1933 but had to be camouflaged with green paint, turf and netting during the Second World War. During this period, the zoo also acted as a refuge for animals evacuated from London Zoo.

Herts Advertiser: Asian short-clawed otters at ZSL Whipsnade ZooAsian short-clawed otters at ZSL Whipsnade Zoo (Image: ZSL)

Now known as ZSL Whipsnade Zoo, it is home to 3,500 animals, including its herd of endangered Asian elephants, two species of rhinoceroses, brown bears and Amur tigers.

The zoo has contributed to the reintroduction of species which were previously extinct in the wild, such as the Przewalski horse and the scimitar horned oryx.

Advance tickets for the summer can now be booked at www.zsl.org.

Herts Advertiser: A dwarf crocodile in a pool at ZSL Whipsnade ZooA dwarf crocodile in a pool at ZSL Whipsnade Zoo (Image: TONY MARGIOCCHI)

Herts Advertiser: Asian elephants at ZSL Whipsnade ZooAsian elephants at ZSL Whipsnade Zoo (Image: ZSL)

Herts Advertiser: ZSL Whipsnade Zoo recently reopened to visitorsZSL Whipsnade Zoo recently reopened to visitors (Image: ZSL)