"The development is spectacular," said Reinhard Schnidrig, who heads the Federal Office for the Environment's department for hunting, wild animals and biodiversity.

"All species are growing in number in one way or another," he told the Le Temps daily.

"Bears are returning each year in summer" and wolves had "started to reproduce on Swiss soil", he said.

In addition, he said, the first golden jackal had made its way to Switzerland in recent weeks from the Balkans, while lynxes, wild cats and foxes were also prospering.

Even beavers were "testing the air" in Switzerland, he said.

Reports of wild animal sightings are common in Switzerland, where many carnivores are protected.

One of the reasons for the sudden increase in the numbers of wolves appeared to date back to the arrival of the first females in 2006, Schnidrig said.

Females were less likely to move on than more itinerant males, he explained.

"Bears share the same kind of behaviour," he said, adding that female bears had also been making their way to Swiss territory.

With the first wolf litters born in the country this year, "we have entered a new era. Wolves will only go on growing in number," Schnidrig said.

Growing forest cover and an abundance of prey such as deer were together facilitating the rise in wild carnivores in Switzerland, he added.

He cautioned however that while most wild animals represented no threat to people "bears are different" as they were "less predictable" than most other animals.