Body condition as an indicator of long-term ecosystem change: evidence from common dolphins
- 1Instituto de Investigaciones Marinas, Consejo Superior de Investigaciones Cientificas
Abstract
As climate change continues to disrupt marine ecosystems, reliable body condition indices (BCIs) for sentinel megafauna species such as dolphins will become increasingly important tools for long-term ecosystem monitoring. We developed novel BCIs from routinely collected morphometric measurements and applied them to a 22-year dataset (1998-2019) of 597 stranded common dolphins (Delphinus delphis) from Northwest Spain. BCIs were calculated as residuals from Generalized Additive Models relating body length to girth and blubber thickness measurements, thereby controlling for body size effects. The indices were first validated against visually assessed nutritional status and then used to investigate long-term trends and potential environmental and trophic drivers of body condition. The girth-based BCI outperformed the blubber thickness-based index in predicting nutritional status. The indices differed in their sensitivity to confounding variables. Both indices revealed an increase in male body condition until 2009-2010 followed by a sustained decline through 2019, whereas no long-term trend was detected in females. By integrating data on climate variability (North Atlantic Oscillation), oceanographic conditions (upwelling intensity, sea surface temperature, chlorophyll-a), prey availability, and prey quality, we found evidence that changes in body condition was associated with climate- and oceanography-driven changes in prey communities and reductions in the quality of prey available to dolphins. Our findings suggest that body condition in common dolphins integrates signals across multiple components of marine ecosystems and can serve as a sensitive indicator of ecosystem change. Given growing reports of declining body condition in marine predators worldwide, the approach presented here provides a practical and transferable framework for long-term ecosystem monitoring using existing stranding network datasets.
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BibTeX
@misc{petitguyot2026body,
title = {{Body condition as an indicator of long-term ecosystem change: evidence from common dolphins}},
author = {M. A. C. Petitguyot and J. Champsaur and A. Hernandez-Gonzalez and A. Lopez and P. Covelo and J. Martinez-Cedeira and X. Pin and M. Gonzalez and U. Vazquez and G. J. Pierce},
howpublished = {bioRxiv},
year = {2026},
month = sep,
doi = {10.64898/2026.09.08.750080},
url = {https://www.biorxiv.org/content/10.64898/2026.09.08.750080v1},
note = {CC BY-NC-ND},
}
RIS
TY - UNPB
TI - Body condition as an indicator of long-term ecosystem change: evidence from common dolphins
AU - M. A. C. Petitguyot
AU - J. Champsaur
AU - A. Hernandez-Gonzalez
AU - A. Lopez
AU - P. Covelo
AU - J. Martinez-Cedeira
AU - X. Pin
AU - M. Gonzalez
AU - U. Vazquez
AU - G. J. Pierce
PY - 2026
DA - 2026/09/08
PB - bioRxiv
DO - 10.64898/2026.09.08.750080
UR - https://www.biorxiv.org/content/10.64898/2026.09.08.750080v1
AB - As climate change continues to disrupt marine ecosystems, reliable body condition indices (BCIs) for sentinel megafauna species such as dolphins will become increasingly important tools for long-term ecosystem monitoring. We developed novel BCIs from routinely collected morphometric measurements and applied them to a 22-year dataset (1998-2019) of 597 stranded common dolphins (Delphinus delphis) from Northwest Spain. BCIs were calculated as residuals from Generalized Additive Models relating body length to girth and blubber thickness measurements, thereby controlling for body size effects. The indices were first validated against visually assessed nutritional status and then used to investigate long-term trends and potential environmental and trophic drivers of body condition. The girth-based BCI outperformed the blubber thickness-based index in predicting nutritional status. The indices differed in their sensitivity to confounding variables. Both indices revealed an increase in male body condition until 2009-2010 followed by a sustained decline through 2019, whereas no long-term trend was detected in females. By integrating data on climate variability (North Atlantic Oscillation), oceanographic conditions (upwelling intensity, sea surface temperature, chlorophyll-a), prey availability, and prey quality, we found evidence that changes in body condition was associated with climate- and oceanography-driven changes in prey communities and reductions in the quality of prey available to dolphins. Our findings suggest that body condition in common dolphins integrates signals across multiple components of marine ecosystems and can serve as a sensitive indicator of ecosystem change. Given growing reports of declining body condition in marine predators worldwide, the approach presented here provides a practical and transferable framework for long-term ecosystem monitoring using existing stranding network datasets.
ER -