Integrating Across Species: A New Multi-Method Approach to Whale Energetics

Whether you’re moving between labs, or between continents, transitions always engender a bit of apprehension and uncertainty in academia. Over the last months, I’ve made quite a transition, from Hawaii to North Carolina (working remotely), and from one project to another within the MMRP. This new project is built on the foundation that the lab and I have been building over the last ~3 years. In essence, we will be taking the analytical framework outlined in our recent publication on short-finned pilot whales (Gough et al., 2025) and expanding in scope to estimate the energetic expenditure of species ranging in size from the harbor porpoise up to the blue whale.

Energetic expenditure (i.e., the amount of energy used over a given period of time to power life-sustaining functions such as metabolism, locomotion, and growth) can be very difficult to measure accurately, for a number of logistical reasons. New technologies allow us to answer old questions in new ways, but each one has distinct limitations. Suction-cup tags, for example, give an excellent multi-hour picture of behavior and movement for a single animal, but give no information on morphometrics or physiology (barring new “physio-logging” sensors that are in development by a handful of research groups). Unmanned Aerial Systems (UAS) drones, on the other hand, allow for high-resolution morphometrics of multiple animals in quick succession, but they offer nothing about the movements of those animals once they leave the camera’s field of view. Controlled experiments on animals under human care offer another avenue with significant promise, allowing for high-quality physiological measurements. But these studies are limited to smaller species that can be safely housed in aquaria, and the inferences obtained from these species are not always relevant to larger animals, either due to differences in behavior between monitored vs. free-ranging individuals, or simply as a result of body-size scaling.

The goal of our new project will be to estimate energetic expenditure and use those values as inputs to inform the Population Consequences of Disturbance (PCOD) framework for species of cultural, scientific, and economic importance. In recent years, this PCOD framework has become increasingly important for our understanding of anthropogenic impacts on free-ranging marine mammals (Pirotta et al. 2018). And how these species expend energy is a vital piece of any species-specific PCOD model. As evidence of this importance, a recent survey of marine mammal biologists identified “Field Metabolic Rate” (Daily Energetic Expenditure) and “Allocation of Energy” as the first and third most important questions in marine mammal bioenergetics, respectively (McHuron et al., 2022).

For this project, we will be leveraging extensive paired multi-sensor tag and UAS drone datasets across 18 species (10 baleen whales, 1 beaked whale, and 7 other tooth-whales) totaling >370 deployment from ~13 data contributors. Where possible, we will supplement these datasets with behavioral and physiological information from additional sources (e.g., long-duration satellite tags, stomach content analysis, controlled physiological experimentation). With this wealth of data, we will be able to estimate daily energetic expenditure using three distinct methods:

• Thrust Generation - combining fine-scale movements from suction-cup tags and body morphometrics from UAS drones.

• Breathing Frequency - using respiration rates taken from suction-cup tags or UAS drones and physiological estimates from controlled animal studies.

• Overall Dynamic Body Acceleration - using fine-scale accelerometer measurements from suction-cup tags and validated scaling relationships from controlled animal studies.

Despite the breadth and importance of this research avenue, the current body of literature lacks a comprehensive overview or in-depth comparison of these energetic expenditure estimates within and between cetacean species. Recent analyses of cetacean energetic expenditure have focused on one method and / or a single species (e.g., Allen et al. 2022; Christiansen et al. 2023; Fahlman et al. 2023; Gough et al., 2025). We hope that this new project will be an invaluable tool to assess the merits of each method for different species and behavioral contexts.

Figure: Population Consequences of Disturbance (PCOD) model (modified from Pirotta et al. 2018). Estimates of energetic expenditure are expected to inform the “Behavioral Change”, “Health”, and “Vital Rates” portions of the PCOD model. Data collection avenues (Multi-sensor suction-cup biologger [Tag] and UAS drone [UAS]) and methods of calculating energetic expenditure (Thrust Generation, Breathing Frequency, Overall Dynamic Body Acceleration) are outlined. Illustrations show the 18 species to be included in methods comparisons - pink are baleen whales, blue is a beaked whale, and green are other toothed whales.

This work is funded through a generous grant by the Office of Naval Research (no. N00014-25-1-2553), and will be supported by a wonderful team of friends and collaborators.

References

Allen, A. S., Read, A. J., Shorter, K. A., Gabaldon, J., Blawas, A. M., Rocho-Levine, J. and Fahlman, A. (2022). Dynamic body acceleration as a proxy to predict the cost of locomotion in bottlenose dolphins. Journal of Experimental Biology 225, jeb243121.

Christiansen, F., Sprogis, K. R., Nielsen, M. L. K., Glarou, M. and Bejder, L. (2023). Energy expenditure of southern right whales varies with body size, reproductive state and activity level. Journal of Experimental Biology 226, jeb.245137.

Fahlman, A., Allen, A. S., Blawas, A., Sweeney, J., Stone, R., Trainor, R. F., Jensen, F. H., McHugh, K., Allen, J. B., Barleycorn, A. A., et al. (2023). Surface and diving metabolic rates, and dynamic aerobic dive limits (dADL) in near- and off-shore bottlenose dolphins, Tursiops spp., indicate that deep diving is energetically cheap. Marine Mammal Science 39, 976–993.

Gough, W.T., Madrigal, B., Hollers, A., Currie, J.J., Baird, R.W., West, K., Fahlman, A., Fish, F.E., Evans, L., van Aswegen, M., Stirling, B., Pacini, A., Olson, G.L., Stack, S.H., Blawas, A.M., Walker, W.A. and Bejder, L. (2025). Daily energetic expenditure and energy consumption of short-finned pilot whales. Journal of Experimental Biology 228, jeb249821.

McHuron, E. A., Adamczak, S., Arnould, J. P. Y., Ashe, E., Booth, C., Bowen, W. D., Christiansen, F., Chudzinska, M., Costa, D. P., Fahlman, A., et al. (2022). Key questions in marine mammal bioenergetics. Conservation Physiology 10, coac055.

Pirotta, E., Booth, C. G., Costa, D. P., Fleishman, E., Kraus, S. D., Lusseau,D., Moretti, D., New, L. F., Schick, R. S., Schwarz, L. K., et al. (2018). Understanding the population consequences of disturbance. Ecology and Evolution 8, 9934–9946.