Ground-breaking surgery to help save chimp's ear

Cara has lived at Wellington Zoo since 1992. Photo / Supplied

A 33-year-old chimp at Wellington Zoo will have a ground-breaking procedure this week in a last-ditch effort to save her remaining ear.

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

"For several years Cara suffered from a chronic ear infection in her left ear, and it wasn't resolving with oral antibiotics," said Dr Lisa Argilla, Veterinary Sciences Manager.

The infection became life-threatening once it spread into Cara's inner ear and part of her skull, so in 2010 Dr Argilla and her team performed a highly complex surgery with help from ear, nose and throat specialist surgeon Dr Rebecca Garland and specialist veterinary surgeon Dr Andrew Worth. The pioneering surgery, which cured the infection and saved Cara's life, had never before been performed on a chimpanzee.

But in 2014 zoo staff discovered that Cara had a new infection in her right and remaining ear. Veterinarians monitored her closely, with regular check-ups to flush and clean the ear, and performed a CT scan to examine her ear canal and chest to rule out signs of pneumonia.

However, the chimp had her own inventive approach to treating the infection.

"Cara has a habit of jamming sticks and other objects into her ear, which most likely gives her a bit of immediate relief," said Dr Argilla. "Unfortunately these break off inside the ear canal, causing a blockage that further inflames the infection, damages the ear drum, and interferes with the medication before it has a chance to work."

Wellington Zoo called on Dr Garland again and she proposed a revolutionary solution. In June she and audiologist Flora Kay made a mould of Cara's ear canal. This was used to design a custom-made mesh earplug - which, if successful, will serve as a barrier between the ear canal and any foreign objects.

"On Tuesday Cara will receive a general anaesthetic so that we can administer more antibiotics and insert the plug. If all goes well this will prevent Cara putting sticks in there and will trap the medication into her ear so it works more effectively," said Dr Argilla.

"This is our last chance to save Cara's ear, so we're very hopeful for a good outcome."

A third procedure in 4-6 weeks will assess how the plug has worked.

This week's procedure is scheduled to take place at The Nest Te Kohanga, Wellington Zoo's animal hospital and centre for native wildlife, at 1pm tomorrow.

Zoo visitors can watch through a window, and staff will talk them through each step of the operation.