Researchers warn in Science of reducing the Swedish wolf population

The Swedish wolf population is genetically isolated and highly inbred, according to the researchers. Photo: Christina Hansen Wheat

Why are you writing this letter in Science?

”All of the authors are deeply concerned about the Swedish Parliment’s desire to halve the size of the wolf population. The wolf population is, and has long been known to be, in a very difficult genetic situation. The Swedish wolf population is genetically isolated and highly inbred. The current population was founded by only three individuals in the 1980s and has been genetically isolated for decades. In recent years, only three genetically distinct individuals have succeeded in reproducing and spreading genes that still remain in the population. The results is a population that has a very small genetic pool, which results in an inbreeding level that is on average as high as the one obtained when full siblings mate with each other (an inbreeding rate of approximately 0.25).”

What do you hope to achieve with the letter?

Christopher Wheat.
Photo: Christina Hansen Wheat

”We hope to spread the information that continued hunting and reduction of the Swedish wolf population is not a reasonable conservation option. On the contrary, such measures are expected to significantly worsen the conservation situation. Few wild animal populations in the world are as well studied as the Swedish wolves and decades of studying these and other animal populations all point in the same direction – the Swedish wolf population is in a difficult genetic situation, especially since individuals are already showing negative effects of strong inbreeding. Additional recent studies using genome data has further confirmed the very low levels of genetic variation and extreme inbreeding in Swedish wolves.”

What is your most important message to politicians about what needs to be done?
”Two simple steps. First, in order for the genetic situation to improve, the population needs to be allowed to increase in size. Second, genetic exchange between the Swedish and Finnish populations needs to be significantly increased. Researchers have long suggested this, but this result has not yet been achieved effectively.”

“Additionally, the currently used guideline states that one wolf per generation that immigrates to the Swedish population is sufficient to provide genetic supplementation. This is not correct. Significantly more immigrants are needed for the Swedish wolves’ genetic health to come back. In addition, it is important that the exchange goes in both directions so that Swedish wolves also migrate to Finland. The management goal should be to create a well-cohesive population of wolves across the Scandinavian peninsula and Finland, which together are significantly larger than the current population in these areas. For a good conservation situation with the possibility of long-term survival, the value of the genetically effective size of the cohesive population needs to amount to at least 500, which in practice means at least 2000 individuals.”

Can you give an example of another country where you think that politicians have listened to research on the wolf issue?
”Several of my co-authors have experience with wolf management in other countries. Professor Carles Vilà says, for example, that in Spain the wolf now has full protection throughout the country and the population is estimated at 300 packs and over 2000 animals. He is very surprised that Sweden is going in the exact opposite direction. Another co-author, Dr. Cristiano Vernesi, says that Italy has about 3000 wolves and the authorities have not proposed that number to be reduced. France, Poland, Germany, Romania are additional countries that also have larger wolf populations than Sweden.

Professors Linda Laikre, Love Dalén, and Nils Ryman at Stockholm University are also authors of the letter to Science.

Read letter in Science: Planned cull endangers Swedish wolf population