As she captured hedgehogs for her study in one of Hamburg's many parks, Lisa Warnecke discovered just how secretive these little creatures can be.
Most of the people she met had no idea that their town had a thriving hedgehog population, let alone that they roamed the city parks at night in search of food and mates.
“They told me there weren’t any hedgehogs in this park, and yet I had just tagged seven of them,” says Warnecke, a biology postdoctoral researcher at the University of Hamburg in Germany.
In studying these urban dwellers, Warnecke was surprised to find they've adapted to city life—for instance by shrinking their home ranges, according to results Warnecke presented July 4 at the Society for Experimental Biology annual meeting in Brighton, England.
“This is a really important finding. It helps those of us who are working to save these animals provide better conservation advice,” says Hugh Warwick, an ecologist with the British Hedgehog Preservation Society.
European hedgehogs on the mainland haven't declined like their British kin, and Warwick says this type of research could help prevent the continental hedgehogs from dropping in number.
City Hedgehog, Country Hedgehog
When Warnecke, who studies hibernation, looked through the scientific literature about the phenomenon in European hedgehogs, she found very little.
The few studies that had been completed were all done in the 1970s, and no one had any idea whether hedgehogs in urban areas had similar patterns of hibernation and lifestyle to rural animals.
With a team of undergraduate students, Warnecke and colleagues set out to compare these two populations near their university.
The group attached temperature-sensitive GPS trackers to 14 hedgehogs living in Hamburg and in surrounding farmland and suburbs.
The trackers, which collected data for seven to ten months, revealed how far the hedgehogs traveled for food and their location, as well as information on the animal’s body temperature, which indicates whether an animal was hibernating.
During the day, the city hedgehogs spent most of their time sleeping or resting in private gardens, hidden in brush or under shrubs where no one could see them.
Around 9 p.m., when most of the city’s residents had taken their dogs out for the last time, the hedgehogs began to emerge.
By midnight, the spiny mammals freely roamed Hamburg’s green spaces. The city hedgehogs limited their home range to around 12.5 acres (five hectares), unlike their rural counterparts, whose range was 10 times as large.
When it came to hibernation, however, the two populations were remarkably similar: They hibernated for around the same amount of time each year.
Overall, the research suggests the roly-poly Internet stars are more resilient than people thought.
“How can you not love hedgehogs?” Warnecke says.