Volunteers 'the back bone' of NZ charities, but some roles prove hard to fill.

Each Wednesday, the volunteers for the SPCA Auckland all receive the same email. It's a call for help - for the charity's unpaid workers to step up.

"Sunday PM - No volunteers - who will feed the baby rabbits!?" said a recent email asking for help. Each week it's the same story - staff shortages, shifts gone unfilled, and more help desperately needed.

Non-paid staff at the SPCA outnumber paid staff 10 to one across nearly every part of the organisation, and if it's running low on volunteers, the results can be potentially disastrous.

"When we are low on volunteers, staff are put under a huge amount of pressure. Every day, you never know what might happen," SPCA CEO Andrea Midgen told Newshub.

“A litter of very young puppies might be brought in without their mum, or a severely abused dog might be rescued by an SPCA inspector. Having the support of our volunteers means we can tend to these unexpected, special cases, while ensuring everything else run as normal.”

Canine volunteer Alan Wooley says he finds the work rewarding and he knows the importance of his role in the organisation. "The SPCA relies on volunteers quite a lot to do the work that they need to do," he said.

"We need volunteers, we need the commitment that the volunteers provide, we need the help that the volunteers can provide in terms of assisting what is a very worthwhile charitable cause."

The SPCA and St John together run a joint outreach therapy pets programme, which allows volunteer Jasmine Hweh and her dog Peachy to visit mental health wards, rest homes and even university students to give them a chance to relax and pet the animals. Ms Hweh says it's great to see those who may need a break interacting with Peachy and the chance to see the animals clearly makes a big difference in some people's lives.

"Animals bring you so much happiness and it just makes me really happy to see other people enjoy [Peachey's] personality and that it can make a difference," she said.

One of the volunteer recruitment challenges SPCA experiences is with positions that may not involve close contact with cats and dogs. These volunteer positions can often prove challenging to fill. "The one exception is small animals (specifically rabbits) volunteers, perhaps because the role is a little more specialised and requires some experience," Ms Midgen said.

"We also find that volunteers for our op shops can be quite difficult to find – our volunteers at the shops are so important, and although they don’t have direct animal contact, they are invaluable."

"We rely so heavily on our volunteers in all areas of the organisation,” Ms Midgen said.

"They are the backbone of the organisation. We truly wouldn’t be able to run the SPCA without them."

It's also often on the lookout for foster parents like Jody Kelly, who in five years has helped seven rabbits and 84 cats prepare for adoption.

"It’s a really good way to volunteer and give something back without having to spend lot of time out of your house," she told Newshub.

"I work from home so it's great for me - I've always got kittens on my desk or under my desk or on my printer or whatever."