Pregnant wolf Veluwe had pneumonia, but was otherwise in good condition

Published on
June 7, 2021

In early March, a female wolf was roadkilled on the Zuidwest Veluwe. The animal appeared to be pregnant with eight embryos. She also had a serious case of pneumonia, but despite this she was in good condition. This was investigated by Wageningen Environmental Research (WENR) and the Dutch Wildlife Health Centre of Utrecht University (DWHC).

Researchers from WENR looked at the animal's age, sex, reproductive status, stomach contents and identity, while researchers from DWHC focused on diseases and abnormalities.

Pregnant wolf

The wolf weighed over 35 kg. Her muscles and lower body fat showed that she was in good nutritional condition. Based on dental wear, her age was estimated at around 2 years. The animal was in early pregnancy with 8 embryos. The stomach contents weighed over 500 grams and contained mainly hair and skin remains. In it, the researchers found some legs that appeared to belong to an adult and a young hare. The rest of the stomach contents will be examined at a later date in a diet study of wolves. Genetic research showed that the animal turned out to be GW1729f, the daughter of the pack on the North Veluwe that has settled on the South-West Veluwe since 20 June 2020. The embryos were still too small to yield DNA of sufficient quality to determine the father.


The wolf had been traumatised all over its body by a major impact, like a collision with a car. Extensive samples were taken to exclude various (animal) diseases, including distemper and Covid-19. These were all negative. The wolf did have an extensive pneumonia caused by an infection with the so-called French heartworm (Angiostrongylus vasorum). A wolf can become infected by eating infected intermediate hosts, such as snails. The fox is a natural host for this type of worm. This worm can cause severe pneumonia in dogs and foxes. In 2017, three out of ten foxes examined by DWHC were positive for this worm, and in three of those cases the worm contributed to death. The presence of these worms in the habitat of wolves could potentially pose a health problem for the animals. It is not certain whether pneumonia contributed to the animal's behaviour and thus to an increased risk of a traffic accident.

The wolf research was part of the Interprovincial Wolf Plan.