Chimpanzee's life-saving surgery unsuccessful

Cara will have to undergo another operation. Photo / Supplied

A chimpanzee at Wellington Zoo has found a way to foil the ground-breaking surgery vets carried out last week in a last ditch effort to save her remaining ear.

Now the 33-year-old chimp will have to undergo another operation.

Cara, who has lived at the Zoo since 1992, is easily distinguished from the rest of the chimpanzee troop by her barely-there left ear, and the story behind it.

For several years the chimp suffered from a chronic ear infection that couldn't be resolved by oral antibiotics.

The infection became life threatening when it spread into Cara's inner ear and part of her skull.

So in 2010, zoo staff performed a highly complex and pioneering surgery which cured the infection.

Unfortunately in 2014 Wellington Zoo staff discovered that Cara had a new infection in her right and remaining ear.

Last Tuesday Cara underwent surgery to clear the infection at The Nest, Wellington Zoo's animal hospital and centre for native wildlife.

Ear, nose and throat specialist surgeon Dr Rebecca Garland came up with a creative solution to cure the ear infection - a custom-made plug to prevent the Chimpanzee inserting sticks and pieces of straw in her ear.

The procedure went smoothly after several last-minute adjustments to the plug were made.

However, Cara wasn't a fan of her new ear accessory - and the clever primate found a way to remove the plug shortly after waking up from general anaesthetic.

Veterinary Sciences Manager Dr Lisa Argilla said while zoo staff hoped for a good outcome, they knew it was possible that Cara, or another member of the chimpanzee troop, would succeed in removing the plug.

"This was our last shot to save Cara's ear before resorting to ear canal ablation surgery, which means removing the entire ear canal, so it was absolutely worth trying.

"Cara has already undergone this life saving surgery on her left ear, so unfortunately repeating this procedure on her remaining ear will mean that she may lose her hearing completely."

Losing her hearing might effect Cara's future in the group, Dr Argilla said.

Chimpanzees communicate through a system of vocalisations, gestures, body postures and facial expressions.

Cara's loss of hearing may lead to changes for her in the Wellington Zoo Chimpanzee troop, which has a complex hierarchal system that can change easily.

Dr Craig Johnson, Professor of Veterinary Neurophysiology at Massey University will also come in and test Cara's hearing while she is anaesthetised.

He would use a technique called Brainstem Auditory Evoked Potentials which would allow him to objectively evaluate Cara's ability to hear.

"By testing Cara's hearing before and after the surgery, we'll be able to gain a better understanding of how to monitor her interactions with the group after her surgery," said Dr Argilla.

"This also means we can get a good idea of her hearing ability without having to do a separate procedure, which will mean Cara wouldn't need to be anaesthetised again."