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Individual variation creates diverse migratory portfolios in native populations of a mountain ungulate

Citation

Lowrey, Blake et al. (2020), Individual variation creates diverse migratory portfolios in native populations of a mountain ungulate, Dryad, Dataset, https://doi.org/10.5061/dryad.80gb5mknj

Abstract

Ecological theory and empirical studies have demonstrated population‐level demographic benefits resulting from a diversity of migratory behaviors with important implications for ecology, conservation, and evolution of migratory organisms. Nevertheless, evaluation of migratory portfolios (i.e., the variation in migratory behaviors across space and time among individuals within populations) has received relatively little attention in migratory ungulates, where research has focused largely on the dichotomous behaviors (e.g., resident and migrant) of partially migratory populations. Using GPS data from 361 female bighorn sheep (Ovis canadensis) across 17 (restored = 4, augmented = 6, native = 7) populations in Montana and Wyoming, USA, we: 1) characterized migratory portfolios based on behavioral and spatial migratory characteristics, and 2) evaluated the relative influence of landscape attributes and management histories on migratory diversity. Native populations, which had been extant on the landscape for many generations, had more diverse migratory portfolios, higher behavioral switching rates, reduced seasonal range fidelity, and broad dispersion of individuals across summer and winter ranges. In contrast, restored populations with an abbreviated history on the landscape were largely non‐migratory with a narrow portfolio of migratory behaviors, less behavioral switching, higher fidelity to seasonal ranges, and less dispersion on summer and winter ranges. Augmented populations were more variable and contained characteristics of both native and restored populations. Differences in migratory diversity among populations were associated with management histories (e.g., restored, augmented, or native). Landscape characteristics such as the duration and regularity of green‐up, human landscape alterations, topography, and snow gradients were not strongly associated with migratory diversity. We suggest a two‐pronged approach to restoring migratory portfolios in ungulates that first develops behavior‐specific habitat models and then places individuals with known migratory behaviors into unoccupied areas in an effort to bolster migratory portfolios in restored populations, potentially with synergistic benefits associated with variation among individuals and resulting portfolio effects. Management efforts to restore diverse migratory portfolios may increase the abundance, resilience, and long‐term viability of ungulate populations.

Methods

Elevation and geographic distances between individuals core seasonal ranges

These data represent the elevational and geographic distances between individual core seasonal ranges of bighorn sheep from 17 populations across MT and WY. The IndID field is an individual ID, which has a different format in each population. The State field denotes the state (MT, WY) where the population was located. The population name is shown in the HuntUnit field. Note, populations have been aggregated as described in Appendix S1. Origin denotes the restored, augmented, or native classification as described in the methods section of the paper’s main text. The elevational difference between individual seasonal range centroids (in meters) is shown in the EleDistM column. The geographic distance between individual seasonal range centroids is shown in the GeoDistKM column.