The Canberra snake catcher had been called out by a staff member who spotted the bright red, black and yellow reptile (that's milk snake not milkshake) lurking under the franchise's bins.

Milk snakes are native to the Americas and illegal in Australia, but a common pet in the US. They are also alarmingly similar in colour to the venomous coral snake so Mr Dunn wasn't taking any chances.

"It was dark, I didn't know what I was dealing with, I just threw it in the bag and got it home," he said.

While the exotic snake turned out to be the safer kind of reptile, it still spent the Easter long weekend under careful quarantine with the Dunn family.

Authorities granted Mr Dunn and his partner Emma Carlson, who also runs Canberra Snake Rescue & Relocation, special permission to hold the animal until it could be handed over on Tuesday.

"We're not sure whether or not it escaped from an apartment in the city or if this was an illegal reptile trade in the Maccas carpark gone wrong," Ms Carlson said.

ACT Parks and Conservation director Daniel Iglesias said the territory was concerned about any exotic reptiles found in Canberra as "they have the potential to adversely impact local ecosystems".

"A decision on the fate of the animal will be made on the advice of the government veterinary officers, who will consider animal welfare and biosecurity issues," Mr Inglesias said.

The snake was reported to the Commonwealth and it is understood the animal will be put down.

"All exotic reptiles found or surrendered in the ACT are investigated, although there is often little or no information to go on," Mr Inglesias said.

Just a month earlier, Alex Borg, who runs Canberra Snake Catcher service, removed another exotic reptile, this time an albino corn snake, from outside a house in Calwell.

Neither snake was fully grown, sparking fears that illegal breeding might be more rampant in the ACT than previously believed.

"It clearly wasn't imported in, someone must be breeding them here," Mr Borg said.

"It's too cold in Canberra for them to survive without people."

The corn snake was seized by authorities and euthanised, Mr Iglesias confirmed on Tuesday.

When Mr Borg posted a photo of the reptile to Facebook, he said he was "overwhelmed" by the amount of people who came forward claiming it was their snake.

Ms Carlson agreed it was a "very worrying" trend.

"We'd never come across an exotic snake before, the other ACT handlers hadn't either, and now we've had two turn up in the space of a month," she said.

"There's potentially a bigger illegal trade than we realised in Canberra."

Mr Dunn said he had raised his concerns about illegal breeding directly with authorities but said it was difficult to police when animals were kept in secret.

Ms Carlson has since written to the territory to suggest holding an exotic snake amnesty, similar to one conducted in Queensland in 2016, to encourage people to hand in illegal species, which could often carry disease if imported.

But ACT Parks and Conservation said staff had only encountered two exotic snakes and one exotic turtle in the past 18 months.

"Any amnesty in Canberra would need to be done in close cooperation with NSW authorities," Mr Inglesias said.

"ACT Parks and Conservation will continue to consider all options to prevent unlawful wildlife trade."

In the ACT, most reptiles cannot be commercially traded through pet shops and require a licence to own. Exotic snakes can only be kept by zoos or for scientific research.

A spokeswoman for the Department of Environment and Energy confirmed the reptile found at McDonald's was a milk snake but said ACT authorities were investigating.

"Trafficking of wildlife and wildlife products is a serious international problem," the spokeswoman said.

"Globally, it is estimated to cost up to US$24 billion each year."

The maximum penalty for wildlife trade offences was 10 years imprisonment and fines of up to $210,000 for individuals or more than $1 million for corporations.

Holding the milk snake in his hands, Mr Dunn sighed when he considered the animal's fate.

"It's a shame, he's a really nice snake."

On Tuesday afternoon, he took another surprise call out to Wanniassa High School, where a venomous tiger snake had been discovered in a cupboard.

The snake, it turned out, had squeezed underneath the sink cupboard in the canteen but after a "small amount of demolition works" Mr Dunn said he was able to catch and relocate it safely.

ACT Parks and Conservation encouraged people to report any suspected illegal trade of wildlife to Access Canberra on 13 22 81. All reports will be investigated and can be made anonymously.