Migration and winter use data for the Teshekpuk Caribou Herd in northern Alaska, 2004-2021
Data files
Jun 12, 2026 version files 198.65 KB
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README.md
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TCH_Data_Fullman_et_al_2025-07-21.csv
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Abstract
In variable environments animals can remain in place and tolerate changes or move to favorable conditions. Species must balance the costs and benefits of site fidelity and behavioral plasticity in adapting to rapidly changing environments. Caribou (Rangifer tarandus) are known for their migratory behavior, making some of the longest overland migrations in the world. However, this iconic migratory behavior is combined with a high degree of behavioral plasticity in timing and destination. These data were used to investigate winter fidelity, behavioral plasticity, and migration dynamics of the Teshekpuk Caribou Herd in Alaska. Records are based on GPS telemetry location data for 192 female caribou from 2004-2021. Using this information, we classified winter use and compared patterns to four null models to identify whether site fidelity was occurring. We investigated how intrinsic and extrinsic factors related to winter use and migratory behavior using generalized additive mixed models. Increasing pressures for infrastructure development and rapid warming of the Arctic present challenges to many migratory species, including caribou. Our findings that caribou exhibit both winter fidelity and plasticity and that patterns may vary across scales contribute to a better understanding of behavioral plasticity among migratory species. Knowledge of the degree of site fidelity and migratory flexibility shown by caribou can help inform spatial and temporal mitigation measures as managers seek to balance responsible development with conservation of natural systems.
Dataset DOI: 10.5061/dryad.nzs7h453r
Description of the data and file structure
We classified movement behavior and winter use for 192 female caribou (Rangifer tarandus) of the Teshekpuk Caribou Herd in northern Alaska from 2004-2021. We ran GPS telemetry data through a first passage time – net squared displacement analysis (Fullman et al. 2021) to classify annual movement into migratory, resident, and other behaviors. Wintering areas were identified based on percentage contours of the population-level winter utilization distribution and we assigned caribou use to the wintering area with which they showed the greatest spatial overlap. We extracted intrinsic and extrinsic covariate data across locations based on field surveys and remotely sensed data products. The resulting dataset was used to investigate patterns of winter fidelity, migration dynamics, and their associated environmental and intrinsic covariates.
Files and variables
File: TCH_Data_Fullman_et_al_2025-07-21.csv
Description: Analysis-year summary information for movement behavior, winter use, and associated covariates of female caribou of the Teshekpuk Caribou Herd in northern Alaska. Each row of the dataset represents one analysis-year for one caribou.
Variables
- individual: Unique alphanumeric identifier representing one analysis-year for a single caribou analyzed in the dataset. The individual identifier is comprised of the animal ID and analysis-year, separated by an underscore.
- animal: Unique alphanumeric identifier for each caribou in the dataset.
- analysis_year: Numeric representation of the analysis-year of the given record. We divided data for each caribou into “analysis-years” stretching from July 1 of one year to June 30 of the subsequent year, following Fullman et al. (2021). These were named by their start year, such that the 2019 analysis-year spanned 1 Jul 2019–30 Jun 2020.
- mvmt: Character indicator of the movement behavior identified for the given individual. Possible values include ‘migrant’, ‘resident’, and ‘other’.
- winter_area: Character indicator of the primary wintering area used by the individual in the given analysis-year. The four possibilities include W_Coastal, E_Coastal, W_Brooks, and E_Brooks. We assigned each analysis-year to one of four wintering areas based on the degree of spatial overlap. See Fullman et al. (in review) for depictions of each wintering area and details of wintering area identification and assignment.
- mig_fall_start, mig_fall_end, mig_spring_start, mig_spring_end: Date-time indicator of the start or end dates of fall and spring migration (YYYY-MM-DD HH:MM:SS). Only reported for migrants. Time records are recorded in UTC in the dataset but were converted to local Alaskan time (timezone = 'America/Anchorage') in our analyses.
- mig_fall_dir, mig_spring_dir: Numeric indicator of the directedness of fall or spring migration, giving a sense of the tortuosity of migration. Directedness was calculated as the Euclidean distance between migration start and end points divided by the path distance along each step of the migration (Fullman et al. 2021). Possible values span from 0 – 1, with lower values indicating a more tortuous migration path and higher values indicating more directed movement. Only reported for migrants.
- age: Integer value indicating the minimum age for each individual, reflecting known ages for individuals captured as yearlings or those with dental records and otherwise estimating a minimum age at capture of 3 years for caribou collared as adults.
- parturition: Binary indicator of parturition status for each individual. Parturition status reflected whether a caribou had a calf in the spring of a given analysis-year based on aerial observations of calf at heel, retention of antlers, or distended udders by trained observers. Parturition surveys were not conducted in 2007, and not all individuals could be relocated during each survey, resulting in no data for many individuals, indicated by a value of NA.
- sTemp, fTemp, wTemp, pTemp: Numeric indicator of seasonal average air temperature (°C at 2m above ground) across caribou locations. Data were obtained from the hourly ERA5-Land reanalysis dataset (Muñoz-Sabater et al. 2021), accessed from Google Earth Engine (Gorelick et al. 2017; Muñoz-Sabater 2019) using the rgee R package (version 1.1.5; Aybar et al. 2020, Aybar 2022). Preceding lowercase letters indicate the season: s = summer, f = fall, w = winter, p = spring.
- sPrecip, fPrecip, wPrecip, pPrecip: Numeric indicator of seasonal average precipitation (m) across caribou locations. Obtained as with air temperature. Preceding lowercase letters indicate the season: s = summer, f = fall, w = winter, p = spring.
- insect: Numeric insect harassment index value indicating the proportion of observations during the insect harassment season in which biting insects were considered active based on equations relating air temperature and wind speed to mosquito and oestrid fly activity (Russell et al. 1993). The index indicated harassment if either mosquitos or oestrid flies were considered active (index values above 0.4).
- sNDVI, pNDVI: Numeric indicator of the seasonal average vegetation greenness at caribou locations based on the Normalized Difference Vegetation Index (NDVI). NDVI data from the MCD43A4 MODIS-derived product (Schaaf and Wang 2015) were obtained from Google Earth Engine using the rgee R package. Values < 0.1 were set to NA prior to averaging to avoid impacts of snow, ice, or bare areas. Preceding lowercase letters indicate the season: s = summer, p = spring.
- sAO, fAO, wAO, pAO: Numeric representation of the seasonal average Arctic Oscillation (AO) climate index. We averaged monthly AO values from the National Weather Service Climate Prediction Center (NOAA/NWS 2005) to seasonal means. Because data were at a monthly resolution, seasonal assignment was done differently from the other variables, with summer AO covering July – September, fall comprising October values, winter spanning December – April, and spring consisting of May values. Preceding lowercase letters indicate the season: s = summer, f = fall, w = winter, p = spring.
References
Aybar C (2022) rgee: R bindings for calling the Earth Engine API. Version 1.1.5. https://CRAN.R-project.org/package=rgee
Aybar C, Wu Q, Bautista L, et al (2020) rgee: An R package for interacting with Google Earth Engine. JOSS 5:2272. https://doi.org/10.21105/joss.02272
Fullman TJ, Person BT, Karpovich S, et al (in review) Flexibility in winter fidelity of a partially migratory arctic ungulate varies with weather conditions and other factors. Landscape Ecology
Fullman TJ, Person BT, Prichard AK, Parrett LS (2021) Variation in winter site fidelity within and among individuals influences movement behavior in a partially migratory ungulate. PLoS ONE 16:e0258128. https://doi.org/10.1371/journal.pone.0258128
Gorelick N, Hancher M, Dixon M, et al (2017) Google Earth Engine: Planetary-scale geospatial analysis for everyone. Remote Sensing of Environment 202:18–27. https://doi.org/10.1016/j.rse.2017.06.031
Muñoz-Sabater J (2019) ERA5-Land monthly averaged data from 1981 to present. Copernicus Climate Change Service (C3S) Climate Data Store (CDS). https://developers.google.com/earth-engine/datasets/catalog/ECMWF_ERA5_LAND_HOURLY
Muñoz-Sabater J, Dutra E, Agustí-Panareda A, et al (2021) ERA5-Land: a state-of-the-art global reanalysis dataset for land applications. Earth Syst Sci Data 13:4349–4383. https://doi.org/10.5194/essd-13-4349-2021
NOAA (2022) Monthly mean Arctic Oscillation index since January 1950. National Oceanic and Atmospheric Administration/National Weather Service. Available from: https://www.cpc.ncep.noaa.gov/products/precip/CWlink/daily_ao_index/ao.shtml. Accessed 2022-11-18
Russell DE, Martell AM, Nixon WAC (1993) Range ecology of the Porcupine Caribou Herd in Canada. Rangifer 13:1–168. https://doi.org/10.7557/2.13.5.1057
Schaaf C, Wang Z (2015) MCD43A4 MODIS/Terra+Aqua BRDF/Albedo Nadir BRDF Adjusted Ref Daily L3 Global - 500m. Version 006. NASA EOSDIS Land Processes Distributed Active Archive Center. https://doi.org/10.5067/MODIS/MCD43A4.006
Access information
Data were derived from caribou telemetry data obtained from GPS collared caribou. Caribou collaring was a collaborative effort involving the Alaska Department of Fish and Game, North Slope Borough, United States Bureau of Land Management, and Conoco Phillips Alaska, Inc. Caribou location data are protected under Alaska statute 16.05.815(d). For access requests please contact the Alaska Department of Fish and Game.