The colony of the red-necked Bennett's wallabies, which look similar but are much smaller than kangaroos, are originally from Tasmania and were brought into a zoological reserve in the village of Emance, about 70 kilometres southwest of Paris.
A group of them escaped through holes in the fencing in the 1970s into the surrounding verdant forests.
They subsequently bred and researchers now believe that there are about 100 of the marsupials living in the wild in a climate very similar to that of Tasmania.
The spottings have sparked incredulity and light-hearted exchanges and banter.
"A neighbour asked me: 'Did you see the kangaroo?'" said Marylene, a grocer in the village of Hermeray, about 10 kilometres from Emance.
"I said: 'Are you high?" she recalled about an exchange in June last year.
But it was no hallucination. Marylene saw the evidence for herself.
The animal was there, "in front of the gate as if it was waiting for the grocery to open. Then it went off down the road with little regard for traffic signs," she said.
Bruno Munilla from the forestry centre in nearby Rambouillet, said their numbers could range from between 100 and 150.
Most of them live around Emance but some have migrated as far as Ulis, some 40 kilometres farther east.
(Photo: Theen Moy/Flickr)
'It was taboo!'
Wallaby researcher Laure Raad said the marsupials -- whose life span can go up to 15 years -- "integrated really well into the local ecosystem because they found food and shelter here".
"They're safe because the forest gives them shelter and they find plenty to eat, feeding mostly on wild berries and green plants."
Apart from the abundance of food, they also don't have to worry about predators. The 80-centimetre, 15 kilogram animals are too big for the local foxes.
Their biggest danger is cars.
"We probably have about 30 to 40 collisions per year. Not all are deadly but 15 to 20 animals do get killed," said Munilla.
Sceptical insurance companies have a hard time believing people who claim a wallaby caused their accident, said Emance's Mayor Christine David, adding that she has to provide "certificates saying that there are in fact wallabies in the area".
Attitudes towards the wild wallabies have shifted over the years. There was a time when their presence caused confusion.
Spotting a wallaby after an evening tipple could even make one swear off drinking.
"About 20 to 25 years ago, it was all taboo! There was a sort of code of silence," said Stephane Walczak from the Hunting Federation of the
Ile-de-France, which encompasses Paris and its surrounding areas.
A hunting ban on wallabies has helped them to multiply, he said.
"Kangaroos fall into a legal void. We can't hunt them because in France species are listed as either game, pests, protected species or pets. Kangaroos appear nowhere."
In 2003, some yellow signs featuring a leaping wallaby silhouette installed by local pranksters helped lighten the mood, and "loosen tongues", Walczak said.
Now the animal has become a sort of mascot, Emance's mayor said.
Marylene never saw the wallaby again, but she said she is keeping her eyes peeled just to be sure.
"So now if I see a pink elephant I wouldn't immediately brush it off."