Metabolic costs and immune system impacts from chronic cortisol elevation and decreased energy acqui
Abstract
The US Navy has invested in the development of models that predict the impact of disturbance and/or multiple stressors to marine mam,ts affect the ability of animals to survive or reproduce, as these impacts can subsequently affect population sustainability. To imp,rove the predictive capability of these models, the Navy needs to better understand the link between stressors (e.g. chronic noise,,pollution) and the physiological responses of animals to the stressors that can affect life history functions (e.g. growth, reproduc,tion). Establishing these linkages requires relating the behavioral or physiological response of an individual to a ?cost,? which ma,y consist of missed reproductive opportunities, immune suppression, missed foraging opportunities, or increased metabolic expenditur,e. Ultimately, understanding the impact of multiple stressors requires understanding the mechanisms of impact from individual stress,ors in order to better realize the modes of interaction between stressors. Here, we describe an approach to quantitatively and quali,tatively assess the costs and mode of action of two potentially common responses to disturbance ? chronic elevations in cortisol (th,e ?stress? response), and reductions in energy acquisition. An elevation in cortisol is the primary endocrine indicator of stress in,immune function, illness, and decreased reproduction. Within other vertebrates, elevations in cortisol are positively correlated wit,h increases in metabolism. Within marine mammals, cortisol has been positively correlated with rates of body mass loss in Steller se,a lions, but relatively little information exists on the metabolic cost of elevated cortisol in other marine mammals and no such rel,ationships have been investigated in cetaceans (whales and dolphins). Similarly, trends between elevated cortisol and immune functio,n have received little attention in cetaceans.A reduction in energy acquisition (feeding) is another potential response to human-cau,sed disturbance. Reduced feeding could occur due to disruptions in foraging or the dispersion of prey. Prolonged reductions in energ,y acquisition result in metabolic rate reductions to protect energy stores, mobilization of fat reserves, and potentially altered im,mune function. Although reduced energy acquisition would presumably produce metabolic downregulation in odontocete cetaceans, the ma,gnitude of the shift and the rate at which it occurs is unknown. Furthermore, no information exists on the relationship between redu,ced feeding and immune function in odontocetes, although energy-dependent changes in immune function might have critical implication,s for wild cetaceans.Increased cortisol levels or reduced energy acquisition resulting from human-caused disturbance potentially imp,act immune function, metabolic hormones, and metabolic expenditure in cetaceans. These costs can be qualified and quantified. Their,determination in a representative odontocete (toothed whale) would go a long way in informing efforts to model the individual conseq,uences of disturbance in cetaceans and would benefit the US Navy in developing more accurate models of the impact of human-caused di,sturbance to marine mammals. In the proposed study, the metabolic costs associated with elevated cortisol (the stress response) and,reduced energy acquisition (disruption of foraging) will be measured in trained bottlenose dolphins by manipulation of circulating c,ort,e determined. The data obtained from the study will inform predictive Navy models on the potential costs to marine mammals exposed t,o Navy activities in the ocean.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Oct 07, 2022
- Source ID
- N000142212833
Entities
People
- Dorian S. Houser
Organizations
- National Marine Mammal Foundation
- Office of Naval Research
- United States Navy