Using Aerial Photogrammetry to Estimate Body Condition and Assess Sexual Dimorphism in Narwhals

The Arctic is warming rapidly, impacting ice‐dependent species and communities that rely on them for resources. Body condition indices (BCI) are widely used to assess individual health within populations. We adapted the methodology to improve accessibility for estimating narwhal body condition from drone footage, using body length, body width, and neck width measurements. We compared indices across sexes and age classes of individual narwhals and evaluated measurement consistency across observers. Both neck width‐to‐body length (BCI neck ) and body width‐to‐body length (BCI body ) did not differ significantly between sexes. The BCI neck measure was more difficult for observers to reproduce than the BCI body . However, the BCI body was found to be repeatable and reproducible among raters. We also found dimorphism in fluke shape, which could be used to distinguish sexes. This study demonstrates that using a freely available image‐processing program and drone footage is an effective and accessible method for estimating BCI in narwhals, with the potential to be implemented in future studies examining narwhal health.