A group of squirrel monkeys left injured and frightened after a break-in at Wellington Zoo last month have recovered from their ordeal.

Would-be thieves armed with bolt cutters broke into the monkeys' enclosure overnight in the first week of April and tried to snatch one of the monkeys, leaving some of them with scratches and bruising.

Zoo staff initially reported one of the female monkeys as stolen when she could not be found during searches of the enclosure. She was later discovered in hiding.

The offenders have not been found yet.

One squirrel monkey was presumed stolen because she hid so well after the break-in that keepers could not find her in several searches of the enclosure. Photo / Wellington Zoo 

A little under a month since the incident, the zoo's team leader of primates, Harmony Neale, said it was business as usual for the monkeys.

"The squirrel monkeys have been really good. It took them kind of a couple of days to settle back down, but now they're back to normal," she said.

"They were a little bit, I guess, hesitant to come towards their keepers on that first day.

The monkeys do not like to be handled, so would have been trying to escape the intruders as though they were predators in the wild, she said.

"In that first day afterwards it was very much 'I don't know what's going on, I'm scared, I'm going to stay away'."

But the keepers were able to gain back the animals' trust by offering them their favourite treats.

Neale said the monkeys were coaxed with "high-value rewards" such as raisins, other dried fruits, and bugs.

"Bugs are a really big one for squirrel monkeys. So anything that's that reward, or they know is positive, they will then associate you with that.

"As their relationship with us grew again and they knew that they were safe, they went back to normal and knew that it was safe to come down and act normally."

Part of helping the monkeys recover from the incident was keeping them together as a group.

"For squirrel monkeys, being in a big family group is really important for them so keeping them together and keeping things as normal as possible for them is the best, quickest way to get them over anything like that."

After the break-in, the zoo's chief executive Karen Fifield said squirrel monkeys were social animals and would be terrified if they were stolen and separated from their mates.

"We want to say to whoever tried to do this, this is really just not acceptable and it's not appropriate to try to take one of these animals," she said.

A police spokeswoman said police were still pursuing "positive lines of inquiry" into the break-in.

What is a squirrel monkey?

• According to the Zoological Society of London the primate, also known as Saimiri, is an endangered species that grows to 35m and weigh up to just 1100g.

• They have the largest brain of all primates with a brain-to-body mass ratio of 1:17.

• They live together in large troops of up to 500 and have a polygamous mating system.

• When threatened they make vocal calls, including warning sounds, and have been called "small, nervous primates".