Wood bison migration metrics and environmental covariates
Data files
Nov 19, 2024 version files 108.39 MB
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README.md
5.97 KB
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SSFAnalysis_public.csv
105.23 MB
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StudyArea_MaxDates_published.csv
3.15 MB
Abstract
Migration is an evolutionarily stable adaptation when movement costs are outweighed by fitness gains. Migration is defined as the predictable movement between seasonal ranges in response to differential resource availability. However, migrations to locate suitable mates, and calving or nursery grounds are also common across taxa. For ungulates, the growth of new vegetation (i.e., green-wave) has been identified as a key mechanism influencing migration between seasonal ranges. We investigated how the green-wave influenced migration in a wood bison (Bison bison athabascae) population in northern Alberta, Canada, while also considering risk of calf predation by wolves (Canis lupus). Each year, all collared females in the population migrated an average of 28-kilometers over 6-days to a region at the western edge of their annual range between late-May and early-June. By late-June they migrated back to their core range, averaging a 40-kilometer migration distance over 10-days. We found that the green-wave influenced both the timing of migration and selection of habitats during migration. Risk of predation was not found to influence habitat selection during migration. However, the herd congregating and leaving their spring range as a group suggests risk of predation may be an evolutionary mechanism contributing to this migratory behavior. The timing of migration and congregation aligns with the expected timing of parturition giving further support that both the green-wave and predation risk influence migration. We provide a framework to assess interrelated mechanisms influencing migration, which is important to those studying, managing, and/or conserving migratory ungulates.
https://doi.org/10.5061/dryad.hdr7sqvt4
Description of the data and file structure
Between 2013 and 2019, 58 females were fitted with Global Positioning System (GPS) collars by Alberta Environment and Protected Areas at a 1.5-hr fix-rate for various lengths of time (n = 38 Lotek Newmarket, Canada; 10 Vectronics Berlin, Germany; 10 Tellus Lindenberg, Sweden). We observed an annual spring migration by all females (i.e., complete migration; Avgar et al., 2014) in May or early-June to a distinct region near where the McIvor River exits the Birch Mountains (hereafter referred to as the “spring range”; Figure 1). We calculated instantaneous rate of green-up (IRG) as the first derivative of the positive slope of the normalized difference vegetation index (NDVI; MOD9Q1 product from MODIS terra satellite) curve for a given 250×250-m cell
Files and variables
File: StudyArea_MaxDates_published.csv
Description: Dataset including dates of of maximum normalized difference vegetative index and instantaneous rate of green-up across the bison’s home range.
Variables
- Date_Time: Date and time single variable in the Mountain Time Zone.
- Date: Date (MM/DD/YYYY), Mountain Time Zone
- Time: Time (HH:MM:SS), Mountain Time Zone
- Latitude: latitudinal decimal coordinates (WGS 1984)
- Longitude: longitudinal decimal coordinates (WGS 1984)
- Year: Year
- Day: Julian day
- Migration: ingress (migration to the calving range) or egress (migration out of the calving range)
- EWC: Duck’s Unlimited’s enhanced wetland classification for landcover types
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1 Open Water 2 Aquatic Bed 3 Mudlfats 5 Emergent Marsh 6 Meadow Marsh 7 Graminoid Rich Fen 8 Gramonoid Poor Fen 9 Shrubby Rich Fen 10 Shrubby Poor Fen 11 Treed Rich Fen 12 Treed Poor Fen 13 Open Bog 14 Shrubby Bog 15 Treed Bog 16 Shrub Swamp 17 Hardwood Swamp 18 Mixedwood Swamp 19 Tamarack Swamp 20 Conifer Swamp 21 Upland Conifer 22 Upland Deciduous 23 Upland Mixedwood 24 Upland other 25 Cutblock 26 Agriculture 27 Antropogenic 28 Cloud 29 Cloud Shadow 30 Burn 33 Upland Pine
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- ndvi: normalized difference vegetative index
- IRG: instantaneous rate of green-up
- 16MaxIRGJD: Julian day of MAXIMUM IRG value per cell
- 16MaxNDVI: Julian day of Maximum NDVI value per cell
File: SSFAnalysis.csv
Description: Covariates associated with bison and random locations used to conduct step selection function (SSF) analysis. Due to the conservation status of the Ronald Lake wood bison population and our data sharing agreement with Alberta Environment and Parks (manager of collar data) the coordinates associated with each location have been removed. However, the SSF analysis can still be conducted as the BPoint_ ID * *and Random_ ID vectors identifying the sequence of bison locations and the associated random locations.
Variables
- ID: Identification unique to each point.
- Location: Bison or random
- Binomial: 1= bison or 0 = random
- BPoint_ID: Bison point ID. NA for all random locations.
- Unique_ID: Same as “ID”.
- Device_ID: Bison collar number. NA for all random locations.
- Random_ID: Random ID to associate it with a bison location. NA for all bison locations.
- Date_Time: Date and time single variable in the Mountain Time Zone. Note that no date or time is included for random locations as they are determined based on the bison location.
- Date: Date (MM/DD/YYYY), Mountain Time Zone. Note that no date or time is included for random locations as they are determined based on the bison location
- Time: Time (HH:MM:SS), Mountain Time Zone. Note that no date or time is included for random locations as they are determined based on the bison location
- Year: Year
- Day: Julian day
- Migration: Ingress or egress migration period
- NDVI: normalized difference vegetative index
- IRG: instantaneous rate of green-up
- NDVI2: squared NDVI
- inWolf_BBM: kernal density estimate of wolf dBBM during ingress
- egWolf_BBM: kernal density estimate of wolf dBBM during egress
- LC: Duck’s Unlimited’s enhanced wetland classification for landcover types
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1 Open Water 2 Aquatic Bed 3 Mudlfats 5 Emergent Marsh 6 Meadow Marsh 7 Graminoid Rich Fen 8 Gramonoid Poor Fen 9 Shrubby Rich Fen 10 Shrubby Poor Fen 11 Treed Rich Fen 12 Treed Poor Fen 13 Open Bog 14 Shrubby Bog 15 Treed Bog 16 Shrub Swamp 17 Hardwood Swamp 18 Mixedwood Swamp 19 Tamarack Swamp 20 Conifer Swamp 21 Upland Conifer 22 Upland Deciduous 23 Upland Mixedwood 24 Upland other 25 Cutblock 26 Agriculture 27 Antropogenic 28 Cloud 29 Cloud Shadow 30 Burn 33 Upland Pine
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- DWater: distance to water
- CTI: compound topographic index
- Dline: distance to linear disturbance
- iNDVI: integrated NDVI
- Distance: Distance between steps
- BisonRandom_ID: Bison location ID used to associated random locations
Code/software
All analyses conducted in R studio.