But the injured female monkey was later found hiding in the enclosure, still frightened after the encounter.
After entering the zoo through an unsecured gate that night, Casford headed to the squirrel monkey enclosure, where the animals were asleep in a corner.
He broke through two padlocks to get into the enclosure.
"Your intention was to capture one and bring it home to your girlfriend," the judge said during sentencing.
"Your attempt was not successful.
"I don't know what happened in the squirrel monkey enclosure. The squirrel monkeys know. You say you couldn't find them and I don't speak squirrel. What I know is that by daybreak all the monkeys were distressed, two of them were injured, and you had a broken leg, two fractured teeth, a sprained ankle, and bruises on your back."
None of the monkeys chose to escape through the gates Casford left open.
After pleading guilty to the burglary, Casford attended a Restorative Justice meeting with zookeepers, who said it was a blessing he was unable to catch any of the monkeys, for his sake and the monkeys' sake.
Casford told the zookeepers he broke his leg jumping the boundary fence.
"You said you were, and I quote 'high as a kite'."
The judge said one of the monkeys still continues to experience stress months after the incident.
The monkeys' injuries indicated they had been grabbed, chief executive Karen Fifield said at the time.
One monkey had a haematoma on its elbow and others had scratch marks after the break-in.
Casford was also being sentenced today for an unrelated spate of violent offending over the summer.
He had pleaded guilty to a number of incidents, including an unprovoked assault on a man waiting in his car at traffic lights, an alcohol-fuelled attack at a dairy in Westport, and assaults on a Wellington City Council community safety officer and a night shelter resident who refused to hand over cigarettes.
The judge sentenced him to two years and seven months in prison for all of the offending.
Although rare in New Zealand, animal thefts from zoo enclosures have happened all over the world.
In 2015 National Geographic reported golden lion tamarins were stolen by professional animal dealers from Zoo Krefeld in Germany.
The magazine reported that in 2011, 400 animals were stolen from European zoos and in 2015, 25 members of the European Association of Zoos and Acquaria reported thefts.
One French zoo had 79 tortoises stolen.
At the time the director of the Association of Zoological Gardens in Germany, Volker Homes, said zoo thefts were "a really severe problem".
Earlier this year, Charisma the alpaca was stolen from Dairy Flat, Auckland, leaving his blind mate Bambi adrift.
In December 2016, The Sun reported a group of teenagers broke into London Zoo at night and filmed themselves exploring the enclosures.
One teenager was bitten by a llama during the escapade, and another jumped into a penguin enclosure.
The escapade was posted on YouTube.
In 2008 Hamilton Zoo recovered a stolen pair of Madagascan day geckos and two bearded dragons.
Thieves cut through chained and padlocked doors to get into the reptile house to steal the lizards.
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 35cm (plus a 35 to 42cm tail) 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".
