World’s oldest European hedgehog has been discovered

By Alice Clifford via SWNS

The world’s oldest European hedgehog has been discovered at age 16, seven years older than the previous record

A scientist known as "Dr. Hedgehog" and her team found the critter, called Thorvald, in Denmark.

Thorvald managed to live roughly 13 years longer than the average hedgehog which usually only survive for around two to three years.

In recent years hedgehog populations have declined dramatically across Europe.

In the UK, urban populations have fallen by up to 30 percent, with rural populations dropping even further by at least 50 percent since 2000.

The worrying trend has led researchers and conservationists to launch various projects to monitor hedgehog populations to inform initiatives to protect them in the wild.

In 2016, Danish communities were asked to collect any dead hedgehogs they found for a citizen science project called The Danish Hedgehog Project.

The aim was to better understand the state of the Danish hedgehog population by establishing how long hedgehogs typically live.

More than 400 volunteers collected 697 dead hedgehogs from all over Denmark.

Around half found were from urban areas while the other half came from rural habitats.

The 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 team said the lines are a good tell as each year when hedgehogs hibernate their calcium metabolism slows down. This causes bone growth to reduce or even stop, creating growth lines, with each line representing every yearly hibernation.

While they found hedgehogs aged 13 and 11, the crown went to Thorvald who lived for 16 years, making him the oldest scientifically documented European hedgehog ever found. The previous record holder lived for nine years.

Despite these long-lived individuals, the average age of the hedgehogs was only around two years.

About a third of the hedgehogs died by the time they had reached the age of one.

Of the hedgehogs, 56 percent were killed when crossing the road, while 22 percent died at hedgehog rehabilitation centers, following incidents such as dog attacks.

Just over 20 percent died of natural causes in the wild.

Male hedgehogs lived up to 24 percent longer than females, mounting up an average of 2.1 years versus females’ 1.6 years.

However, males were more likely to be killed in traffic accidents. This could be because males often travel further than females, bringing them into contact more frequently with roads.

For both male and female hedgehogs, road deaths peaked during the month of July.

This is the height of the mating season for hedgehogs in Denmark, meaning hedgehogs cross more roads in search of mates.

Dr. Sophie Lund Rasmussen - known to colleagues as 'Dr Hedgehog' - led The Danish Hedgehog Project.

She said: “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.

“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.”

She added: “The tendency for males to outlive females is likely caused by the fact that it is simply easier being a male hedgehog.

“Hedgehogs are not territorial, which means that the males rarely fight. And the females raise their offspring alone.”

The team also took tissue samples to investigate whether the degree of inbreeding influenced how long European hedgehogs live.

Previous studies have found there to be little genetic diversity amongst Danish hedgehogs, indicating high degrees of inbreeding.

This can reduce the fitness of a population by allowing hereditary, and potentially lethal health conditions to be passed on between generations.

Surprisingly, the results showed that inbreeding did not reduce the expected lifespan of the hedgehogs.

Dr. Rasmussen said: “Sadly, many species of wildlife are in decline, which often results in increased inbreeding, as the decline limits the selection of suitable mates.”

“This study is one of the first thorough investigations of the effect of inbreeding on longevity.

“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 groundbreaking discovery and very positive news from a conservation perspective.”

Dr. Rasmussen added: “The various findings of this study have improved our understanding of the basic life history of hedgehogs, and will hopefully improve the conservation management for this beloved and declining species.”

The findings were published in the journal Animals.