Aerial survey and telemetry data analysis of a peripheral caribou calving area in northwestern Alaska

Abstract

With industrial development expanding in the Arctic, there is increasing interest in quantifying the impacts of development projects on barren ground caribou (Rangifer tarandus granti). The primary data source to assess caribou distribution and predict impacts in remote areas of Alaska has shifted in recent decades from aerial survey data to telemetry data, but these techniques have different strengths and weaknesses. The ranges of two caribou herds, the Western Arctic Herd and the Teshekpuk Herd, overlap in northwest Alaska between Wainwright and Atqasuk, Alaska. Based on long-term telemetry data sets, this region was thought to be outside of the core calving ranges of both herds. Calving has long been reported to occur in this general area, but early reports assumed caribou were from the Western Arctic Herd and only one systematic aerial survey of caribou density and distribution during calving has been conducted in this area in recent decades. Following interest in industrial development in this area, we conducted aerial strip-transect surveys during early to mid-June 2013–2015 to directly assess the density and distribution of caribou in the area and we used existing telemetry data to compare our results to the seasonal distribution of both herds. Total caribou densities varied between 0.36 and 1.06 caribou/km² among years, and calf densities varied 0.04 and 0.25 calves/km² among years. Contrary to assumptions by early researchers in the area, telemetry data indicated that caribou in this area during early to mid-June were from the Teshekpuk Herd. The use of telemetry data alone underestimated the importance of this area for calving, but the combination of aerial surveys and telemetry data provided complementary information on caribou use of this area showing the importance of collecting the appropriate types of data for assessing potential impacts of development on caribou.

Achieving a representative sample of marked animals: a spatial approach to evaluating post‐capture randomization

“…This scenario could occur when population substructure exists that is not accounted for, such as subgroups, divergent migratory strategies, or sexual segregation during parts of the year. Differences between the expected distribution and the actual distribution may be discovered when unmarked animals are observed outside the expected distribution (Davis and Valkenburg 1978, Prichard et al 2019).…”

“…The TCH uses the area near Teshekpuk Lake, in northern Alaska, as its primary calving area (Figure 1; Kelleyhouse 2001, Person et al 2007, Prichard et al 2019), uses the area north of Teshekpuk Lake for its primary mosquito relief area during mid‐summer (Parrett 2007, Yokel et al 2009, Wilson et al 2012), and has a partially migratory wintering strategy (Fullman et al 2021). Approximately 30% of the herd, including a disproportionate number of males, winters in the Brooks Range mountains, but the rest of the herd winters on the coastal plain in most years (Person et al 2007, Prichard et al 2020, Fullman et al 2021).…”

Variation in winter site fidelity within and among individuals influences movement behavior in a partially migratory ungulate

“…The TCH numbers approximately 56,000 caribou [ 33 ]. The herd primarily calves around Teshekpuk Lake in northwestern Alaska ( Fig 1 ) [ 30 – 32 ], though some calving has been noted farther west [ 34 ]. After calving, the herd clusters along the coast and in riparian areas seeking relief from mosquitoes ( Culex spp.)…”

Simulation modeling accounts for uncertainty while quantifying ecological effects of development alternatives

“…3b). Recent work noted some TCH calving further west (Prichard et al 2019), but the vast majority remained in areas around Teshekpuk Lake (BLM 2019 a ) indicated as suitable by Wilson et al (2012). This habitat suitability layer remains the best available representation of TCH calving.…”