A mystery disease has killed up to 70 wild boar at the Hoge Veluwe nature reserve, local broadcaster Omroep Gelderland reports

‘This is unique. Experts are mystified as to the cause,’ Erik Koffeman, spokesman for the Gelderland wildlife management agency told the broadcaster.

In a normal year some 20 boar succumb to disease and the number has now more than tripled. Koffeman said African swine fever has been ruled out because the boar are routinely tested for it. They are not dying of hunger either.

Some of the carcases have been sent to the Dutch Wildlife Health Centre for analysis and so far 30 known diseases to affect boar have been ruled out. ‘One of the animals had pneumonia and some showed some anomalies but nothing that pointed to a common denominator’.

It has been suggested the boar are stressed because of the presence of wolves in the area but, Koffeman said, some of the dead boar were found outside the wolves’ habitat.

The disease, which seems to be retreating, is not going to affect the total number of boar at the Veluwe, thousands of which are culled each year.

Wild boar are only allowed to live in two parts of the Netherlands – in Limburg and in the Veluwe heath region – although a small group near Utrecht are being tolerated – unless they start causing too much damage to crops or cars.