Only about 20 boars die of disease in the Hoge Veluwe reserve annually.
But the figure so far this year is more than triple that. And experts have never seen something like that.
As many as 70 wild boars have died of an unexplained illness at a nature reserve in the eastern Netherlands.
Erik Koffeman of the Gelderland Wildlife Management Department says the death rate is “unprecedented – experts have never seen anything like this before.”
Wild boars are allowed to live in only a few parts of the country, in case they cause damage or disrupt traffic, and the Hoge Veluwe reserve alone has a population of more than 6,000.
“About 150 boars die every year, often in traffic collisions, but these animals are just dropping dead,” Mr Koffeman told the Hart van Nederland news programme.
Wildlife wardens have ruled out African swine fever, as the boars are routinely tested for it, and hunger is not an issue because this has been a “very plentiful food year for them,” he added.
The Dutch Wildlife Health Centre has performed autopsies on six carcasses, and excluded the possibility of 30 other boar diseases and found no common denominator.
One died of pneumonia but, as for the others, “they looked healthy, but were dead,” said veterinarian pathologist Dr Marja Kik of Utrecht University.
One theory is that the boars are being “stressed out” by the wolves that have made their way into the Hoge Veluwe in recent years, but Erik Koffeman doubts this.
“The location of the carcasses don’t always match the wolves’ habitat,” he says, adding that the oak processionary caterpillar – another invasive creature that has made the headlines in the Netherlands this year – wasn’t around in January when the first dead boards were found.
Erik Koffeman says the wardens are “now particularly alert” to signs of sick boar, and the disease does seem to be on the wane.
It is unlikely to affect the overall boar population of Veluwe, as thousands are culled each year just to keep numbers down, but Mr Koffeman told Hart van Nederland that the wardens are “still left with questions” as to what’s been happening.
Is it a new man-made disease… Or a test for the next bio-weapon?