Muskoxen in a defensive posture. The muskoxen in the photograph are descendants of individuals translocated in 1935 from Eastern Greenland to the Arctic Wildlife Refuge, Alaska, USA.  (Photograph: ©Peter Mather, 2010).

There is encouraging news for muskox conservation – that is one of the findings from our just completed genome assembly of a Canadian Arctic Island (Banks Island) muskox.  Our research, led by Si Lok and Stephen W. Scherer (The Centre for Applied Genomics/CGEn, The Hospital for Sick Children and the University of Toronto, Canada), is the first reported chromosomal-level genome assembly for this iconic Canadian Arctic species.  

Over thousands of years, muskoxen have periodically gone through sharp reductions in numbers serious enough to reduce their genetic variability.  Those genetic bottlenecks have reduced their overall genetic variation to a worrisome level – one of the lowest recorded for mammals.  Genetic diversity is often a hallmark of the species’ resilience to adverse changes in the environment.  Among the fears of the low genetic diversity was that it likely meant a compromised immune system which raises concerns as muskox disease outbreaks and declines are being reported in the increasingly stressful and warming climate.  

The Inuit are the eyes on the ground and there has been a long-standing collaboration between Inuit and the University of Calgary’s Faculty of Veterinary Medicine under the leadership of Dr. Susan Kutz to detect unhealthy animals and share diagnoses.  The recent picture is alarming with outbreaks of disease and sharp drops of 74% in muskox numbers – alarming because in the 1990s, the central Arctic Islands of Banks and Victoria had almost 70% of the world’s muskoxen.

Two important findings from our assembled muskox genome suggest the resilience of the muskox to diseases and environmental disruptions might not be as dire as initially inferred from previously reported low genetic diversity.  The first good news is that annotation of our muskox genome essentially revealed a full repertoire of the known immune genes, pointing to no obvious signs of immune deficiencies in the muskox.  Importantly, we found the diversity of the major histocompatibility complex (MHC), a principal component for pathogen recognition, in our muskox specimen was surprisingly more diverse when compared to the overall low heterozygosity levels reported for the bulk genome.  Moreover, we also observed this finding in the MHCs in muskoxen collected from other Arctic islands, suggesting the recent outbreak in disease and decline in muskox population is not solely due to an inherent lack of genetic diversity or deficiencies the muskox’s immune system.  On the other side of the coin, the muskox pathogen’s adaptive capacity comes into play as evidenced by the recent emergence of multiple virulence genes in the pathogenic Arctic clone of the serious bacterial disease, erysipelas.  The identification of these virulence genes, together with our newly assembled and annotated muskox genome, will provide an important genomics resource to study the pathophysiology of emerging diseases in the Arctic.  

In addition to the genes of the immune system, we annotated genes that are rapidly evolving and positively selected, genes associated with adaptations to the Arctic’s taxing climate such as brown fat metabolism and circadian rhythm, and genes with possible socioeconomic benefits for Arctic communities including wool (qiviut) attributes.  Muskoxen have a remarkable wool layer under their dark guard hairs – the wool fibers are as fine as cashmere and the wool has a luxury market.

The muskox is an iconic animal of the Canadian High Arctic, its flowing dark hair standing huddled with its companions facing swirling snows and the menacing wolves or a grizzly bear as their feared predators going back deep into pre-history.  Muskox ancestors appeared some 12 million years ago with muskoxen themselves at least 1 million years ago and their numbers have waxed and waned with climate.  Their heyday when their global Arctic range was the most extensive across northern Russia, Europe and North America was 30,000 years ago.  Sweeping climate changes with the ebb and flow of glaciations meant by some 6,000 years ago, muskoxen had disappeared from Europe with their disappearance from Russia delayed until 2,000 years ago and from Alaska by the late 1800s.  By the first half of the 20^th century, muskoxen were only found in Arctic Canada and Eastern Greenland.  While early man certainly hunted muskoxen and the Thule Inuit relied on muskoxen as the people spread east across the Arctic, hunting likely did not have a hand in muskox collapses – that is until the 19^th century.  A voracious market for muskox hides – mostly exported to Europe - triggered collapses leaving only scattered survivors in a few places across the Canadian Arctic mainland by the early 1900s.  The drastic reductions in muskox numbers imposed a further bottleneck in genetic variability.

Remarkably though, muskoxen have the ability to bounce back: the pockets of muskoxen across the Canadian mainland in the early 1900s recovered and by the 1990s were spreading into areas not seen in living memory, even into the northern fringes of the boreal forests.  Despite their extraordinary low genetic variability, muskoxen are also thriving where they have been deliberately re-introduced (Alaska, Russia, Western Greenland and Northern Quebec).  Notably, muskoxen are found from the tree-line to the High Arctic – they have adapted to a wide range of latitudinal and longitudinal climate and vegetation.  However, the recovery of muskoxen and their apparent adaptability may not be that simple because where muskoxen have re-colonized their ranges, after decades, their recovery tapers off. Elsewhere, on the largest Canadian Arctic Islands, muskox numbers are sharply declining and much is uncertain about underlying mechanisms, which handicaps conservation.

Our high-quality reference genome is a first step toward unravelling the perplexing pattern of regional muskox increases and decreases and to explore just what is the muskox’s adaptive capacity.  More widely, our findings should encourage a more detailed examination of the assumptions underlying low levels of genetic diversity and allow exploration of the roles of earlier declines purging deleterious genes, or the roles of non-coding genome regions and epigenetic variation.  Our gene annotation is an important resource to measure connectivity between the geographically isolated populations and to assess how local adaptations could feed into conservation decisions.  We see urgency for this given that the Arctic is rapidly warming up and especially hot summers will likely stress the large-bodied muskox. 

Further Reading

1. Barr, W. The commercial trade in muskox hides in the Northwest Territories in 1860 - 1916. Rangifer 11(2), 81-81 (1991).
2. Cuyler, C. et al. Muskox status, recent variation, and uncertain future. Ambio 49, 805-819 (2020).
3. Hansen, C. C. R. et al. The muskox lost a substantial part of its genetic diversity on its long road to Greenland. Curr. Biol. 28, 4022-2028 (2018).
4. Li, M. et al. Convergent molecular evolution of thermogenesis and circadian rhythm in arctic ruminants. Proc. R. Soc. B 290, 20230538 (2023).
5. Pečnerová, P. et al. Population genomics of the muskox’s resilience in the near absence of genetic variation.  Mol. Ecol. 33(2), e17205 (2024).
6. Prewer, E. et al. Draft genome assembly of an iconic species: Muskox (Ovibos moschatus). Genes 13, 809 (2022).
7. Seru, L. V. et al. Genomic characterization and virulence gene profiling of Erysipelothrix rhusiopathiae isolated from widespread muskox mortalities in the Canadian Arctic Archipelago. BMC Genomics 25:691 (2024).
8. Tomaselli, M. et al. Iqaluktutiaq voices: local perspectives about the importance of muskoxen, contemporary and traditional use and practices. Arctic 71(1), 1-4 (2018).

Anne Gunn, PhD is a field biologist with extensive experience in designing and managing programs for territorial government and co-management boards in wildlife management and environmental assessment. Her work has been focused in the Canadian Arctic. Dr. Gunn is based in Salt Spring Island, British Columbia.