Conserving habitat for migratory ungulates: How wide is a migration corridor?

Merkle, Jerod A.; Lowrey, Blake; Wallace, Cody; Hall, L. Embere; Wilde, Luke R.; Kauffman, Matthew J.; Sawyer, Hall

doi:10.1111/1365-2664.14473

Cited by 5 publications

References 31 publications

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Estimating ungulate migration corridors from sparse movement data

McKee,

Fattebert,

Aikens

et al. 2024

Ecosphere

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Many ungulates migrate between distinct summer and winter ranges, and identifying, mapping, and conserving these migration corridors have become a focus of local, regional, and global conservation efforts. Brownian bridge movement models (BBMMs) are commonly used to empirically identify these seasonal migration corridors; however, they require location data sampled at relatively frequent intervals to obtain a robust estimate of an animal's movement path. Fitting BBMMs to sparse location data violates the assumption of conditional random movement between successive locations, overestimating the area (and width) of a migration corridor when creating individual and population‐level occurrence distributions and precluding the use of low‐frequency, or sparse, data in mapping migration corridors. In an effort to expand the utility of BBMMs to include sparse GPS data, we propose an alternative approach to model migration corridors from sparse GPS data. We demonstrate this method using GPS data collected every 2 h from four mule deer (Odocoileus hemionus) and four elk (Cervus canadensis) herds within Wyoming and Idaho. First, we used BBMMs to estimate a baseline corridor for the 2‐h data. We then subsampled the 2‐h data to one location every 12 h (a proxy for sparse data) and fitted BBMMs to the 12‐h data using a fixed motion variance (FMV) value, instead of estimating the Brownian motion variance empirically. A range of FMV values was tested to identify the value that best approximated the baseline migration corridor. FMV values within a species‐specific range (mule deer: 400–1200 m2; elk: 600–1600 m2) successfully delineated migration corridors similar to the 2‐h baseline corridors; overall, lower values delineated narrower corridors and higher values delineated wider corridors. Optimal FMV values of 800 m2 (mule deer) and 1000 m2 (elk) decreased the inflation of the 12‐h corridors relative to the 2‐h corridors from traditional BBMMs. This FMV approach thus enables using sparse movement data to approximate realistic migration corridor dimensions, providing an important alternative when movement data are collected infrequently. This approach greatly expands the number of datasets that can be used for migration corridor mapping—a useful tool for management and conservation across the globe.

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Estimating ungulate migration corridors from sparse movement data

McKee,

Fattebert,

Aikens

et al. 2024

Ecosphere

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Construction of ecological corridors in complex terrain areas based on the ’cost-function-ecological benefit’ model

Luo,

Chen,

Luo

et al. 2024

Ecological Indicators

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Conserving habitat for migratory ungulates: How wide is a migration corridor?

Merkle

Lowrey

Wallace

et al. 2023

Journal of Applied Ecology

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Conserving migratory ungulates relies on the analysis of GPS collar data and associated maps of migration corridors to inform management and policy actions. Current methods for identifying migratory corridors use complex statistical models designed to account for movement uncertainty rather than estimating the amount of space required by animals to migrate. Furthermore, such methods can complicate conservation efforts by producing highly variable corridor widths and non‐contiguous corridors that do not fully connect seasonal ranges. To remedy, we propose an intuitive line buffer approach for delineating individual migration corridors that is simple to implement and focuses on the functional corridor widths needed by migratory ungulates. By buffering a line that connects successive GPS locations, we can delineate individual migration corridors with consistent widths that are robust to variable parameters (GPS fix rate, travel speed, tortuosity) and provide contiguous connection between seasonal ranges. Using a combination of expert knowledge, simulation and 10‐min GPS collar data collected from mule deer (Odocoileus hemionus) and pronghorn (Antilocapra americana), we suggest 400–600 m are reasonable estimates of functional migration corridor widths for individuals of those species. Synthesis and applications. Our line buffer approach is intended to simplify migration corridor delineation, improve transparency and encourage a broader discussion of functional corridor widths. These considerations help advance efforts to conserve habitat within migration corridors and prioritize conservation efforts within a single corridor or across multiple corridors.

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Conserving habitat for migratory ungulates: How wide is a migration corridor?

Cited by 5 publications

References 31 publications

Estimating ungulate migration corridors from sparse movement data

Estimating ungulate migration corridors from sparse movement data

Construction of ecological corridors in complex terrain areas based on the ’cost-function-ecological benefit’ model

Conserving habitat for migratory ungulates: How wide is a migration corridor?

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