The researchers have looked at data from the past 30 years, and have found that it is more likely that these three species are hunted in so-called protected areas than in surrounding unprotected areas. Geir Rune Rauset, a wildlife biologist who contributed to the study, tells Swedish Radio News that a total of 80 animals were killed illegally within or around three national parks in northern Sweden during this time.
"We expected that these restrictions would have a positive effect on species and the ecosystem, not the opposite," Geir Rune Rauset says.
He says that they have monitored the animals using GPS trackers.
"We have assumed that these animals have been killed illegally if several trackers in the same area have stopped working at the same time or if an animal carrying multiple trackers have had all of its trackers shut off at the same time," Rune Rauset says.
The study also shows that these animals were mainly killed in the protected areas during the winter months, in remote areas that would have been difficult to reach by any other form of transportation than a snowmobile.
But the reindeer herder Jakob Nygård, who frequently visits these national parks, thinks that the study is based on too many assumptions.
"Technology is still only technology. I don't think you can assume that an animal has been killed illegally just because a tracker stops working, and I don't know anyone who has been found guilty of illegal hunting," Nygård says.