Bottlenose dolphin (Tursiops truncatus) metabolic rate in relation to reduced energy acquisition

Authors: HOUSER, DORIAN - National Marine Mammal Foundation; INCITTI, ANGELO - National Marine Mammal Foundation; WILLIAMS, CASSONDRA - National Marine Mammal Foundation; CROCKER, DANIEL - Sonoma State University; Sacco, Randy

Submitted to: Integrative and Comparative Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/29/2026
Publication Date: 7/29/2026
Citation: Houser, D.S., Incitti, A.J., Williams, C.L., Crocker, D.E., Sacco, R.E. 2026. Bottlenose dolphin (Tursiops truncatus) metabolic rate in relation to reduced energy acquisition. Integrative and Comparative Biology. 66. https://doi.org/10.1093/icb/icag134.
DOI: https://doi.org/10.1093/icb/icag134

Interpretive Summary: The potential for reduced energy through alterations in eating behavior, movement from feeding areas, or reductions in food value is common to all animals. The impact of reduced energy, which may be caused by natural or human activity, is a result of the length of time and size of the energy loss and the response that curbs the loss of nutrients. To evaluate the response of dolphins to reductions in energy in the diet, dolphins were subjected to seven days of a normal diet followed by seven days of an energy-restricted diet that had 25% less energy per day than the normal diet. The number of calories burned at rest was determined for each animal on days three, five, and seven of the treatment periods. Blood samples were collected and processed to analyze hormone levels. Eating the energy-restricted diet reduced the number of calories burned at rest by an average of 10%. Females had lower overall number of calories burned at rest than males. Two molecules measured were significantly affected by a reduction in energy. Bottlenose dolphins show a reduction in calories burned under an energy-restricted diet that is similar to land mammals. The information from this study will be useful in examining the impacts to individuals and populations that experience both natural and human-caused reductions in body energy availability due to disruptions in feeding.

Technical Abstract: The potential for reduced energy acquisition through disruptions in foraging behavior, displacement from foraging habitats, or reductions in food quality is common to all animals. The impact of reduced energy acquisition, which may be caused by natural phenomenon or anthropogenic activity, is a function of the duration and magnitude of the energy reduction and the physiological response that mitigates the loss of endogenous nutrient reserves. To assess the response of bottlenose dolphins (Tursiops truncatus) to reductions in dietary energy consumption, five adult dolphins were subjected to seven days of a normal diet (ND) followed by seven days of an energy restricted diet (ERD) that had 25% less energy per day than the ND. The resting metabolic rate (RMR) was determined for each animal on days three, five, and seven of the dietary treatment periods. Blood samples were collected following each RMR measurement and processed for cortisol, free triiodothyronine (fT3), dehydroepiandrosterone, adiponectin, tumor necrosis factor-a and interleukin-6. Consuming the ERD significantly reduced the RMR by an average of 10% from baseline. A significant interaction between sex and treatment day suggested a possible sexual dimorphic response to being on the ERD, with females having lower overall RMRs than males and showing a progressive decrease in RMR with treatment day (i.e., the RMR declined from day three through day seven of the ERD). Both fT3 and adiponectin were significantly affected by the ERD, and whereas fT3 trended toward a direct relationship with RMR, adiponectin had a significant inverse relationship with RMR. Bottlenose dolphins show a reduction in RMR under an ERD that is similar to terrestrial mammals, and exhibit the hormone relationships expected of a downregulation in RMR, as well as a shift towards lipid oxidation and protein conservation. The quantitative information from this study will be useful in modeling the impacts to individuals and populations that experience both natural and human-caused reductions in energy acquisition (e.g., disruptions of foraging, reduced prey quality).