A hedgehog previously recorded as the longest living in history lived eight times longer than the typical lifespan. This small Denmark-based mammal reached at least 16 years, a remarkable age given that hedgehogs commonly survive about two years on average.
Despite their spines and shy nature, hedgehogs (Erinaceus europaeus) have earned affection for their plump bodies and endearing faces. Yet numbers of this species are dropping sharply in many regions.
In the United Kingdom, recent findings from the British Hedgehog Conservation Society show urban hedgehog populations declining by roughly 30% and rural groups by as much as 50% since the start of the century. The concern over this trend sparked deeper curiosity about the hedgehog life cycle and its ultimate fate.
To address this concern, Denmark launched the Hedgehog Project, a citizen science effort that enlisted volunteers to collect deceased hedgehogs for laboratory study. The aim was to uncover patterns in age and causes of death across different environments.
Researchers looked at age and death triggers by counting growth lines in the hedgehogs’ chins, a method similar to reading tree rings. This technique helps scientists gauge how often the animal hibernates and, as a result, its age.
The newborn hedgehog is small and delicate, a reminder of the species’ tender beginnings.
The jawbones of hedgehogs display growth lines because metabolism slows during hibernation, which can lead to lower calcium levels and slower or paused bone growth. These lines allow scientists to count hibernation cycles and estimate age.
Biggest threats: traffic and cars
With more than 400 volunteers, researchers collected 697 deceased hedgehogs from towns and countryside across Denmark, with roughly equal representation from urban and rural areas. The results, reported in a scientific journal, point to traffic as the leading danger. More than half, about 56%, died while crossing roads, around 22% died after vehicle-related incidents or were found on roads, and another 22% died from natural causes.
Even though several long-lived individuals aged 16, 13, and 11 were documented, the average lifespan remains about two years. Nearly one-third, around 30%, of the hedgehogs studied died before reaching their first birthday.
The researchers note that counting growth rings on a hedgehog’s chin helps determine age, and that the timing of some deaths aligns with travel during the mating season in July. Hedgehogs often move long distances in search of mates, which increases exposure to traffic risks.
In addition to age, tissue samples were collected to assess kinship and whether shared ancestry might influence susceptibility to diseases passed through generations. The analysis confirmed a degree of inbreeding within hedgehog populations, yet this did not appear to shorten lifespans. In populations where mates are scarce, inbreeding concerns can rise, even if immediate effects on lifespan remain unclear.
Experts say the findings hold promise for conservation efforts, signaling potential avenues to strengthen protection for hedgehogs in both cities and the countryside.
Notes: the environment department will not be contacted here; direct inquiries are not included in this rewrite.