Browsing by Author "Casper, Erin"

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    Development of Dynamic Indicators of Resilience in Wild Rodent (Peromyscus maniculatus)
    (2024-08-26) Casper, Erin; Pruvot, Mathieu; Kutz, Susan; Mastromonaco, Gabriela
    One of the primary reasons for global species decline is environmental disturbance which pose multiple stressors on wildlife populations. However, understanding the complex effects of multiple stressors has been difficult to assess. Resilience, or the ability of a system to cope with disturbance, may pose as a framework to assess the effects of multiple stressors on individuals. To develop a method to measure the resilience of individuals, physiological and immunological markers downstream of the hypothalamic-pituitary-adrenal (HPA) axis were assessed for use as dynamic indicators of resilience (DIORs) in deer mice (Peromyscus maniculatus). Candidate markers were assessed for the presence of a dynamic response to acute stress, and if that dynamic response changed under the influence of chronic stressors, indicating a change in individual resilience. To complete these objectives, a standardized sampling method was optimized, and markers were assessed for the presence of a consistent dynamic response profile and intraindividual repeatability. This refined the methodology that was needed to test candidate markers for use as DIORs. Next, we investigated how this response changed for each marker after animals had experienced different types and numbers of chronic stressors. We observed that effects of different types of stressors were not additive, and that the interaction between different types of stressors may be antagonistic. To determine if these markers could be used as DIORs, individual changes to their response and recovery slopes were compared after stress treatments to assess if these metrics could indicate change in individual resilience. We did not observe a decrease in recovery rate in any marker after treatment. We attributed this to the stress treatments not achieving the intensity or duration of stress needed to induce modulation of the HPA-axis. Due to this, it was difficult to make conclusions on the markers tested regarding their use as DIORs. However, this project highlighted key issues within the study design, that if corrected, would allow for a proper assessment of their application. While conclusions about these markers as DIORs could not be made, this study has laid important groundwork in developing testing protocols for biomarkers that may be used as DIORs for free-ranging wildlife populations.