Small, isolated populations are driving inbreeding in Norway’s wild reindeer, leaving them increasingly vulnerable. New DNA analyses also reveal extensive genetic mixing with semi-domesticated reindeer.
Norway’s wild reindeer herds are fragmented into small, isolated populations, many of which show high levels of genetic input from semi-domesticated reindeer. The Snøhetta herd is one of the few notable exceptions to such genetic mixing. Photo credit: Roy Andersen, NINA
Genetic diversity is essential for species to adapt to environmental change. New research from the Norwegian Institute for Nature Research (NINA) shows that the genetic diversity of Norway’s wild reindeer (Rangifer tarandus tarandus) is changing rapidly. Habitat fragmentation, particularly in small populations, is causing loss of genetic variation and rising inbreeding — both well-known risk factors for long-term survival.
“Norwegian wild reindeer populations are characterized by small size, isolation, and substantial genetic mixing with semi-domesticated reindeer. All of these factors complicate efforts to conserve a truly wild species,” says senior researcher Brage Bremset Hansen at NINA.
National and international conservation goals aim to preserve both genetic diversity and the distinct identity of naturally occurring wild reindeer populations.
“Previous research has shown that semi-domesticated reindeer in Norway do not descend from the Norwegian wild reindeer, but likely originate from a more eastern subspecies”, explains senior researcher Olav Strand at NINA.
DNA from 1,400 Wild Reindeer
Researchers have now analyzed genetic material from hair and tissue samples collected from nearly 1,400 wild reindeer across 22 of Norway’s 24 wild reindeer regions.
Their findings are presented in a new report, which proposes genetic criteria to guide future wild reindeer management decisions.
A National Goal: Viable Wild Reindeer Populations
The Quality Standard for Wild Reindeer was developed to meet international conservation commitments and national policy goals. Its overarching objective is to maintain viable wild reindeer populations within their natural ranges.
Genetic diversity is one of the key indicators in the quality standard. In the new report, researchers evaluate loss of genetic variation, effective population size, inbreeding levels, and the extent of semi-domesticated reindeer ancestry.
Effective population size indicates how well a population can adapt genetically over time. It depends not only on how many animals exist, but on how many successfully pass on their genes.
Alarmingly Low Genetic Health
“In several of the smaller wild reindeer areas, all with semi-domesticated genetic origin, genetic diversity has declined rapidly. Effective population sizes are alarmingly low, and inbreeding is both high and increasing. These populations are small and isolated,” says Bremset Hansen.
“Low gene flow between herds further accelerates loss of genetic diversity and reduces adaptability”, adds NINA researcher Bart Peeters.
Fragmented Landscapes
Historically, wild reindeer ranged across large, continuous mountain landscapes. Roads, cabins, power lines, and other infrastructure have since divided these areas into isolated habitat fragments.
Today, Norway has 24 designated wild reindeer areas. All have little or no genetic exchange with neighboring populations, and several are further split into isolated subpopulations.
A Conservation Dilemma
Some of the herds of semi-domesticated ancestry now number fewer than 100 animals. Their effective population sizes are much smaller.
“This creates a difficult management dilemma,” explains Bremset Hansen. “Reducing barriers to other populations could restore gene flow and improve genetic diversity. But it could also increase semi-domesticated reindeer ancestry in herds that still retain largely native wild genetics.”
Efforts to reconnect populations may also raise the risk of spreading infectious diseases such as the fatal chronic wasting disease (CWD). Different regions face distinct challenges, requiring tailored management strategies.
Clear messages for management actions
The researchers recommend that the Quality Standard explicitly includes criteria for genetic diversity loss, effective population size, and semi-domesticated reindeer genetic influence — in line with earlier recommendations and international conservation genetics principles.
Half of Norway’s wild reindeer populations trace their origins to semi-domesticated reindeer and are therefore excluded from the national Red List assessment of wild reindeer. Several other herds are also heavily influenced by so-called genetic introgression, challenging the goal of preserving the species’ wild identity.
Ultimately, the researchers stress, it is up to government authorities to decide what condition is acceptable and what Norway’s wild reindeer should be in the short and long term — balancing ecological, cultural, and economic values.
“Our recommendations are based solely on genetic analyses and established conservation biology principles,” says Bremset Hansen.
Contact: Brage Bremset Hansen
Read the report here (Summary in English): Genetics in the Quality Standard for Norwegian wild reindeer: new tools and opportunities.
Learn more: A quality standard for conservation of wild reindeer
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