Researchers have found the oldest European hedgehog (Erinaceus europaeus) on record in Denmark, according to a study published this month in the Animals journal.
The hedgehog – named Thorvald, per the University of Oxford – was a male who lived to be 16 years old. That’s seven years older than the previous record holder.
European hedgehogs are one of several species of “insectivores possessing several thousand short, smooth spines,” explained Encyclopedia Britannica. Of these species, European hedgehogs and African pygmy hedgehogs are often kept as pets.
In Britain, a widespread loss of Erinaceus europaeus was observed in 2011, said the British Hedgehog Preservation Society. By 2020, the species was put on the IUCN Red List as vulnerable for extinction in Great Britain.
To conduct the recent study on hedgehog longevity, Dr. Sophie Lund Rasmussen of Oxford University’s Wildlife Conservation Research Unit began something called The Danish Hedgehog Project. She asked Danish citizens to participate by collecting dead hedgehogs they encountered in 2016.
More than 400 volunteers “collected an astonishing 697 dead hedgehogs originating from all over Denmark, with a roughly 50/50 split from urban and rural areas,” said Oxford.
Using these specimens, researchers “determined the age of the dead hedgehogs by counting growth lines in thin sections of the hedgehogs’ jawbones, a method similar to counting growth rings in trees,” the university explained. Since hedgehog calcium metabolism slows down when they hibernate in the winter, their jaws develop growth lines.
“Although we saw a high proportion of individuals dying at the age of one year, our data also showed that if the individuals survived this life stage, they could potentially live to become 16 years old and produce offspring for several years,” said Lund Rasmussen, who is also known for her “Dr.
Hedgehog” YouTube videos. “This may be because individual hedgehogs gradually gain more experience as they grow older. If they manage to survive to reach the age of two years or more, they would have likely learned to avoid dangers such as cars and predators.”
In addition to Thorvald, the researchers found a 13-year-old hedgehog and an 11-year-old hedgehog – both older than the previous 9-year-old record holder. However, the average lifespan for hedgehogs found as part of The Danish Hedgehog Project was only around two years and one-third died before reaching their first birthday.
“Most (56%) of the hedgehogs had been killed when crossing roads, whilst 22% died at a hedgehog rehabilitation centre (for instance, following a dog attack), and 22% died of natural causes in the wild,” said Oxford.
Unlike many other mammals, researchers found that male hedgehogs like Thorvald lived 24% longer than females. Even so, male hedgehogs “were also more frequently killed in traffic, especially in rural areas and during the month of July, which is the peak of the mating season for hedgehogs in Denmark.”
Lund Rasmussen said that “the tendency for males to outlive females is likely caused by the fact that it is simply easier being a male hedgehog,” as male hedgehogs rarely fight and females raise offspring on their own.
Researchers were also surprised to find that inbreeding did not appear to impact hedgehog longevity in Denmark.
“Sadly, many species of wildlife are in decline, which often results in increased inbreeding, as the decline limits the selection of suitable mates,” Lund Rasmussen said. “Our research indicates that if the hedgehogs manage to survive into adulthood, despite their high degree of inbreeding, which may cause several potentially lethal, hereditary conditions, the inbreeding does not reduce their longevity. That is a rather ground-breaking discovery, and very positive news from a conservation perspective.”
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