A new study from Aalborg University in Denmark reveals that European hares (Lepus europaeus) are not only surviving—but thriving—in urban environments. Using a combination of citizen science and thermal imaging technology, researchers have documented surprisingly high hare densities in two of Denmark's largest cities, raising new questions about the role of cities in European wildlife conservation.
"We were surprised to find such high numbers of hares right in the middle of the city. In several areas, the population density rivals or even exceeds that of the best rural habitats in Europe," says senior researcher Sussie Pagh from the Department of Chemistry and Bioscience at Aalborg University, lead author of the study published in Urban Science.
Urban green spaces may be key to hare recovery
Across Europe, the European hare has declined significantly due to intensive agriculture and habitat fragmentation. But cities, long overlooked as wildlife habitats, may be offering new hope—especially when urban planning focuses on biodiversity.
"In both cities, local authorities are actively working to reduce pesticide use and promote urban biodiversity. This allows wild herbs and plants to flourish in green areas—plants that hares rely on for food," says Pagh. "We believe this could be part of the explanation for the high densities, and we've now launched a student project to investigate which wild plants are actually growing in urban lawns and used by the hares."
In central parts of Aalborg and Aarhus, the researchers measured up to 40 hares per square kilometer using thermal monitoring. This figure is significantly higher than typical densities in surrounding farmland.
From average citizens to spotters: a new way to track urban wildlife
The study is based on a combination of nearly 1,900 hare observations submitted by the general public in Aalborg and Aarhus and targeted monitoring using a thermal spotter—a handheld device that detects animals based on their body heat, without the need for disruptive lighting.
"The thermal spotter was key to understanding the actual density of hares in the areas reported by the public. It allowed us to detect them quietly and effectively, even between buildings and cars," explains co-author Hanne Lyngholm Larsen.
While citizen observations are excellent for identifying hotspots, the researchers found they often overestimate actual population size. By combining both methods, the team could map where hares live, breed, and move throughout the cityscape.
Urban Europe: a new frontier for wildlife
The findings echo a broader trend seen in other European countries where species like foxes, hedgehogs, and badgers are increasingly making cities their homes. With urban areas becoming greener and more ecologically minded, researchers believe hares may become another flagship species for European urban biodiversity.
"If cities can offer better conditions than the countryside—more food and no hunting—they may act as source habitats for regional populations. That's a shift in how we think about cities, from concrete jungles to key conservation areas," says Cino Pertoldi, professor of conservation genetics at Aalborg University and Aalborg Zoo.
