Out of the shed and into the field: an immune toolkit for measuring wild ungulate immune phenotypes at multiple scales

TL;DR

This paper introduces a new immune toolkit to measure immune responses in wild bighorn sheep across different levels, from individuals to entire populations.

Contribution

The paper presents a novel field-tested immune toolkit for assessing immunological variation in wild ungulates at multiple scales.

Findings

Most immunological traits showed significant variation at both metapopulation and individual levels.

The toolkit identified two main axes of immune response segregation: innate vs. adaptive immunity and inflammatory states.

Age and sex of bighorn sheep influenced immune response patterns.

Abstract

Understanding factors that shape immune responses in wild animals is critical to predicting population resilience and long-term persistence. Immune function modifies the survival of individuals facing infectious disease, trauma, and environmental stressors, yet remains understudied. An individual’s immune response is shaped not only by current and historic pathogen exposures but is mediated by both individual (e.g. host genetics, metabolic plane, age, and sex) and population-level (e.g. population size, density, and connectivity) factors. Bighorn sheep (Ovis canadensis, bighorn) occupy populations of varying sizes, nested within larger metapopulations, creating a hierarchical structure. This organization provides a useful framework to understand how immune parameters vary across individual, population, and metapopulation levels. Unfortunately, measurement of immune parameters in ungulates is limited.

To address this limitation, we measured 18 immunologic traits across 581 wild bighorn to evaluate this toolkit’s ability to detect immunological differences between individuals, populations, and metapopulations.

Most immunological phenotypes illustrated significant variation at the metapopulation level and individual level. Our assays revealed immune phenotypic variation consistent with two main axes of segregation—one that distinguished tradeoffs in bighorn innate versus adaptive immune responses, and another reflecting alternative inflammatory states, defined by distinct cytokine patterns. Bighorn age and sex also mediated immune response patterns.

Our immunological toolkit sets the stage to further clarify landscape-level immunological variation in wild ungulate populations and provides a template for deploying integrative eco-immunological tools in any natural population to further understand wildlife health.

Here we demonstrate the utility of our field-tested “immune toolkit” in describing the immune phenotypic heterogeneity of bighorn sheep (Ovis Canadensis) across individuals and large spatial scales within California.

Graphical AbstractFor image description, please refer to the figure legend and surrounding text.

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