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Data from: Morphological traits are not consistently related to population size in four migratory caribou populations across North America

Vuillaume, Barbara1; Leblond, Mathieu2; Festa-Bianchet, Marco3; Côté, Steeve4

Published Oct 31, 2024 on Dryad. https://doi.org/10.5061/dryad.n2z34tn59

Data files

Oct 31, 2024 version files 1.32 MB

Abstract

To develop effective management to maintain or restore populations of large herbivores, wildlife managers require sound empirical data on their variations in size and associated parameters. Many studies have highlighted links between morphological traits of individuals and population density; however, less attention has been devoted to whether or not morphological traits can reliably inform on population size in years when no population estimates are available. We evaluated the relationships between three morphological traits (hind foot length, body mass, and body fat) and population size interpolated over three decades, for four migratory caribou (Rangifer tarandus) herds in northern Canada and Alaska. Our sample included 8,865 measurements of 4,473 individuals. We used a Bayesian modelling approach to evaluate the relationships between morphology and population size across different sex and age classes, considering different temporal scales and, when possible, phases of population growth or decline. We found that morphological traits were not consistently linked to population size. Statistically significant relationships existed for some combinations of herd and age classes, but weak to absent relationships were more common. Our study suggests that morphological traits alone cannot replace data obtained from aerial surveys to approximate population size when population trends are unknown. We discuss the usefulness of morphological traits to explain population size, and recognize their role as complementary metrics to inform the management and conservation of large herbivore populations, but conclude that generally morphological data should not be used to predict population size without prior information on population trends.