Kea and rhino were given treats to mark Orana Wildlife Park's 40th birthday.

Beaks and horns tore into birthday presents as animals and keepers celebrated 40 years of Christchurch's Orana Wildlife Park.

New Zealand's only open-range zoo opened its doors on September 25, 1976, showcasing 28 animals from six species.

Visitors can now see more than 400 animals, spanning 70 species.

JOHN KIRK-ANDERSON/FAIRFAX NZ Tamu, 13, left, and Utani, 32, lock horns over a present, stuffed with lucerne hay.

Chief executive Lynn Anderson said strong community support helped the park open and continued support meant they could "remain the best community asset we can possibly be".

"Orana raises 100 per cent of funds for capital developments and to date, over $15 million has been raised to create the zoo," she said.

Locals made up the zoo's largest visitor demographic, Anderson said, particularly during school holidays, which started on Sunday.

JOHN KIRK-ANDERSON/FAIRFAX NZ Orana's kea enjoy a breakfast of grapes, nuts and vegetables to celebrate the park's 40th year of operation.

For years, Orana's biggest attraction was a drive-through lion encounter. People would queue in their cars for the chance to drive through the lion enclosure.

The experience closed in 1995 and a safer alternative was launched in 1999, where people were driven through the lion enclosure in a cage.

In 2015, Orana opened its $6 million Great Ape Centre, showcasing the country's first gorillas. It was awarded a Large Scale Exhibit Award from the regional zoo association in 2016.

JOHN KIRK-ANDERSON/FAIRFAX NZ Stumpy the southern white rhinoceros opens a present to mark Orana Wildlife Park's 40th birthday.

"The public are loving the gorilla boys," Anderson said.

"And of course in 2017, orangutans will be joining the gorillas in the Great Ape Centre."

Anderson said "a lot more research had been done into animal welfare" since the park opened, creating a better experience for both animals and visitors.

Since 1999, the lion encounter at Orana involved visitors being driven through the enclosure in a cage, while keepers fed the lions.

"We subscribe to ensuring that all of our animals not only have a good life, but a life worth living."

On Sunday, a crowd gathered for the morning kea feed, the native mountain parrots ripping open wrapped presents of fruits, nuts and vegetables.

"The grapes and nuts are their favourite," native fauna head keeper Alyssa Salton​ said.

Orana Wildlife Park ran a drive-through lion encounter until 1995. Since 1999, an alternate experience let visitors drive through the enclosure in a cage, while keepers fed the lions.

A new walk-through kea aviary in 2009 gave visitors unlimited access to the inquisitive birds, Salton said.

"It's one of the best features of the park, because people can get so close and spend so much time with them.

"They are really naturally curious birds, so even in the wild you'll find they come up and interact with you."

Salton said she was proud of the park's breeding efforts, particularly for brown teal and whio, two native duck species.

"There is also a captive kea breeding programme, which we are a part of. In captivity they can live over 50 years."

The park's six southern white rhinoceros' were also treated with birthday presents on Sunday, stuffed with lucerne hay.

"It's like chocolate for these guys," keeper Matt Warren said.

Warren said his previous work, in demolition and construction, was a far cry from zookeeping.

"I love this . . . I've found my thing, so I think I'll stick with it," he said.

"I just love the space we have here [at Orana] and my co-workers, we are a really tight team."

A history of Orana Wildlife Park:

1976: Orana Park, later renamed Orana Wildlife Park, opens to the public.

1984: Giraffes arrive. A successful breeding programme has meant more than 15 giraffes have since been bred at Orana.

1991: Meerkats arrive. The meerkat habitat opening remains one of the busiest days on record for Orana.

1995: Drive-through lion encounter closes, to be replaced by a safer alternative encounter in 1999.

1996: New Zealand whio arrive. They become one of Orana's most important conservation species, alongside brown teal, which arrive in 2004.

1999: The lion encounter and rhino encounter open. New Zealand's first rhino calf, Ibutho, is born.

2000: Orana takes over Southern Encounter Aquarium in Cathedral Square. The facility is lost in the February 2011 earthquake, but many animals are saved.

2006: A six-square-kilometre habitat for the Sumatran tiger opens.

2009: Walk-through kea habitat opens. It is later recognised for excellence in exhibit design.

2015: The Great Ape Centre opens. At a cost of $6 million, it remains Orana's most ambitious project.

2016: Orana Wildlife Park celebrates 40 years.