Key findings

• Globally, populations of Rangifer have mostly declined since the 1990s, some dramatically; however, there are notable exceptions. In addition, there are changes in distribution, range, and fragmentation.
• Conservation of Rangifer often focuses on ecotypes based on genetics and behaviour. Four ecotypes are widely accepted—migratory tundra, Arctic islands, mountain, and forest. The majority of migratory tundra and forest Rangifer herds have declined in population size. Trends for Arctic island and mountain Rangifer tend to be stable or unknown
• Rangifer trends are confounded by infrequent monitoring, variable methods, as well as introductions, local management and in some cases, mixing of domestic, feral, and native populations.
• Current circumpolar abundance estimate for muskoxen is higher than estimates from 2013 and 2017. Recent variations indicated that 23 muskox populations/regions were increasing, nine were stable, six were decreasing, while variation was unknown for 17. Of note, the two with steepest declines were, in 2000, the largest endemic populations in the world. Infrequent monitoring and variable methods confound comparisons.
• Trend is not detectable in pan-Arctic lemming populations over the last 25 years.
• Considering lemmings in different small mammal communities revealed a negative trend for low Arctic populations outside of Fennoscandia sympatric with voles. There were also indications of a negative trend in Russia, where several of the decreasing mixed community populations were located. 
• With one exception, all low Arctic lemming populations occurred in mixed small rodent communities including one or more species of voles.
• Change in species composition was noted at two low Arctic monitoring sites with vole species appearing in 2010 and 2013 in Churchill Manitoba and south-eastern Taymyr, respectively.
• Although highly variable, Arctic fox abundance was either stable or increasing at the majority of monitoring sites with only a few in decline. Trend was unknown at a few of the sites.
• Arctic fox abundance, reproductive effort and litter size was assessed in almost all populations. Better harmonization of protocols and data sharing would allow for greater understanding among sites, identify data gaps and direct future research.
• Currently, international monitoring networks exist for only three of the six mammal FECs. Future monitoring efforts would benefit from the establishment or expansion of monitoring networks to collect data on the remaining three FECs.

Monitoring Advice

The START reports on half of mammal FECs including large herbivores (caribou/reindeer, muskoxen), small herbivores (lemming), and medium-sized predators (Arctic fox). Data deficiencies prohibited reporting on medium-sized herbivores, and large and small predators.

• Develop synchronized protocols that include more attributes and reduce geographical knowledge gaps.
• Establish or expand international monitoring networks for medium-sized herbivores and large and small carnivores.
• Emphasize spatial structure and diversity in monitoring efforts due to the northward advance of southern competitors and vegetation changes.
• For large herbivore, small herbivore, and medium-sized predator FECs:
  • Agree on priorities and harmonize data collection across sites and programs;
  • Share and standardize protocols, in cooperation with relevant partners including Indigenous Peoples and organizations, to include abundance, demographics, spatial structure, health, phenology and, for harvested species, harvest rates; and
  • Ensure monitoring programs employ existing methods with new harmonized methods to allow data comparisons.
• Monitor health as an attribute and develop standardized health assessment protocols due to the anticipated impact of climate change on distribution and prevalence of disease.
• Monitor abiotic factors and drivers of change, across greater spatial distributions to assess the cumulative impacts of climate and other anthropogenic change on populations across their ranges.
• Conduct research on the vulnerabilities of populations to climate change and human impacts, and on genetic diversity and spatial structure of FECs.
• Increase collaboration using interdisciplinary and multi-knowledge approaches to share site- and population-specific information. This can improve monitoring and lead to better models to assess the vulnerabilities and resilience of specific populations.
• Address challenges in assessing abundance of FECs across the Arctic, including:
  • reliability of abundance estimates, such as lack of precision and accuracy;
  • changing baselines, such as changes in species distribution, sampling methodology, and areas monitored; and differences in frequency and spatial extent of monitoring.