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

Abstract

Many animals migrate to take advantage of temporal and spatial variability in resources. These benefits are offset with costs like increased energetic expenditure and travel through unfamiliar areas. Differences in the cost-benefit ratio for individuals may lead to partial migration with one portion of a population migrating while another does not. We investigated migration dynamics and winter site fidelity for a long-distance partial migrant, barren ground caribou (Rangifer tarandus granti) of the Teshekpuk Caribou Herd in northern Alaska. We used GPS telemetry for 76 female caribou over 164 annual movement trajectories to identify timing and location of migration and winter use, proportion of migrants, and fidelity to different herd wintering areas. We found within-individual variation in movement behavior and wintering area use by the Teshekpuk Caribou Herd, adding caribou to the growing list of ungulates that can exhibit migratory plasticity. Using a first passage time–net squared displacement approach, we classified 78.7% of annual movement paths as migration, 11.6% as residency, and 9.8% as another strategy. Timing and distance of migration varied by season and wintering area. Duration of migration was longer for fall migration than for spring, which may relate to the latter featuring more directed movement. Caribou utilized four wintering areas, with multiple areas used each year. This variation occurred not just among different individuals, but state sequence analyses indicated low fidelity of individuals to wintering areas among years. Variability in movement behavior can have fitness consequences. As caribou face the pressures of a rapidly warming Arctic and ongoing human development and activities, further research is needed to investigate what factors influence this diversity of behaviors in Alaska and across the circumpolar Arctic.

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

“…Females of the 2 herds have the highest fidelity to specific areas and are most highly aggregated during calving and mid‐summer (Joly et al 2021). They have lower levels of aggregations during other seasons, may be widely dispersed during winter (Fullman et al 2021, Joly et al 2021), and movement rates are highest during mid‐summer and lowest during winter (Prichard et al 2014). The patterns of aggregation and movement were important influences on how rapidly newly collared caribou became mixed with previously collared caribou.…”

“…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). Individual caribou do not appear to show strong fidelity to wintering areas (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). Individual caribou do not appear to show strong fidelity to wintering areas (Fullman et al 2021). The TCH was estimated at ~56,000 animals in 2017 (Klimstra 2018).…”

A parametric model for estimating the timing and intensity of animal migration

“…This herd moves annually between their more southern winter grounds and their calving and summer ranges further north. Caribou do not always display high inter-annual fidelity to their wintering grounds (Fullman et al, 2021) but, in part due to the gathering of large herds which facilitates social learning, the herd displayed high fidelity to their calving grounds for at least 40 years (Gunn et al, 2012). Pregnant females that arrive on the calving grounds give birth to their calves shortly after, and dramatically reduce their movement for up to two weeks (DeMars et al, 2013; migration has management implications, especially as climate change and anthropogenic modifications to the landscape alter the phenology and availability of their food resources (Chen et al, 2018;Mallory et al, 2020).…”

Changes in local interaction rules during ontogeny underlie the evolution of collective behavior

“…Social behaviors in animals are critical for survival, and extensive variation in sociality is found across animal species. Collective motion, which includes flocking in birds, herd migration in ungulates, and swarming in insects, is an example of collective behavior in which individuals’ responses to local social cues culminate in coordinated behavioral outcomes (Ahmed & Faruque, 2022; Bialek et al, 2012; Fullman et al, 2021; Götmark et al, 1986; Ling et al, 2019; Nagy et al, 2010; Naidoo et al, 2012; Wang et al, 2021). Collective motion is also observed in many species of fish, and includes shoaling and schooling (Greenwood et al, 2013; Ho et al, 2015; Katz et al, 2011; Seghers, 1974; Suriyampola et al, 2016; Z.-H. Tang et al, 2017).…”