They're designed to protect the future of the world's most vulnerable animal species, but regional zoos in Queensland are taking desperate measures to avoid extinction themselves.

Still recovering from the financially crippling COVID-19 pandemic, two privately owned zoos at opposite ends of the state are facing their next fight for survival — absorbing skyrocketing operating costs without hiking entrance fees to visitors.

Darling Downs Zoo is home to 600 animal residents from Africa, South-East Asia, South America and Australia.

A large percentage of these have specialised vegetarian diets.

Owners Steve and Stephanie Robinson said the exorbitant cost of produce had increased their weekly grocery bill by 25 per cent.

"The zoo isn't essential … so if we put our prices up to cover our rising prices, [customers] will leave us, and that's having an impact because we have so many more mouths to feed."

As price increases and produce availability bites, Ms Robinson said they had made changes to get by.

"You've got to try and adjust your diet so that the animals aren't missing out … you also look at other sources to keep us going in those downtimes," she said.

"It definitely gets hard to juggle, what you're feeding and how much, to try and make sure the animals are getting the right nutrition."

Zoo visitor Danielle Fowler said with a family of five, any potential future increase to entry fees would have to work in with the family budget.

"Unfortunately, the cost of everything's gone up, so we've got to factor that in too."

Animals missing treats like sweet corn

It's a similar struggle in north Queensland.

Billabong Sanctuary general manager Beau Peberdy said they were still making up for two years of COVID restrictions.

"Week by week, we're trying to recover what we can," he said.

"Throughout COVID, there was massive cutbacks on staffing and not being able to pick up produce … [that's] easier now, but prices have gone up significantly." 

To keep costs down, Mr Peberdy said the sanctuary animals were going without their usual "treat food" like sweet corn and sweet potato.

While at the Darling Downs Zoo, the resident rhinoceros iguana and giant Adalbra tortoises feed largely off expensive salad greens, so a cheaper alternative has been found in one of Australia's most noxious plants.

"We've had to supplement their diet to include prickly pear to alleviate the hefty cost of lettuce," Mr Robinson said.

Supplier says absorbing some costs

Percy Pugliese has been supplying the Darling Downs Zoo with fresh produce for more than two decades.

He said it had been challenging filling orders to not only meet the animals' nutritional needs but also fit the weekly budget.

"It's extremely difficult. The prices have gone through the roof, and they're $80 to $90 a box, and they [markets] will cut you down from 20 boxes to two," Mr Pugliese said.

"I'm sympathetic to their cause because I know they are in a predicament."

It's not just the cost of produce causing headaches for the zoos — it's everything else too, from electricity to insurance to staffing.

"We've reached the stage now where we're probably going to have to let at least one staff member go," Mr Robinson said.

"And for the others — including ourselves, we work for nothing — we're all going to have to work harder."

Staffing is also a concern for Billabong Sanctuary, but for a very different reason.

"So to try and find a rental for someone that's moving to the area is hard."

Impact on the tourism dollar

While the average monthly household fuel bill pales in comparison to the Robinsons' $2,000, the impact has left the drive tourism market hurting.

"Our Brisbane market is dropping off enormously because people think they can't afford the fuel to get out here, not because they don't want to take the kids to the zoo," Mr Robinson said.

"During the term time, our school markets are reducing because the price of the bus has gone up because the bus operators are facing those extra pressures as well."

Despite their financial fatigue, the zoos remain upbeat about the future.

"At least we are getting visitor numbers through the door," Mr Peberdy said.

"We just kind of hope people keep on coming in and visiting, even though their lives are getting significantly more expensive."

Ms Robinson agrees.

"You've got all these mouths that are so dependent upon us they can't do without you, so you just pick yourself up, and you keep going," she said.

But when it gets a bit too much, Ms Robinson turns to her feathered and furry friends.