Diabetes prevented Hsing Hsing from getting cake for his 40th birthday, but Perth Zoo’s beloved alpha male orangutan still enjoyed a special treat to mark the milestone.

Recognised by his dreadlocks and a vocal call that can often be heard across South Perth, Hsing Hsing on Sunday devoured boxes covered in yoghurt and full of snacks, including carrots and nuts.

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He then reused the boxes to take cover when the rain started to pour.

Senior primate keeper Kylie Bullo says Hsing Hsing has been trained to present his arm to keepers so they can give him insulin and check his glucose levels every day.

“We do monitor his diet very closely because of his diabetes, but he still gets a very wide variety of food,” she said.

“We do hope Hsing will be with us for many years to come.”

Hsing Hsing was born at Singapore Zoo and arrived at Perth Zoo as a teenager as part of the Sumatran orangutan breeding program.

Now weighing 90 kilograms, Hsing Hsing leads Australasia’s largest orangutan colony as a father of five females and a grandfather to three more apes.

Among his offspring was Temara, who became the world’s first zoo-born orangutan to be released back into the wild in 2006.

The average life span for an orangutan is 35 to 40 years in the wild, but can reach the 50s in captivity.

Perth Zoo currently cares for 62-year-old Puan, who is believed to be the oldest orangutan in the world.