Morphology of nares associated with stereo-olfaction in baleen whales

The sensory mechanisms used by baleen whales (Mysticeti) for locating ephemeral, dense prey patches in vast marine habitats are poorly understood. Baleen whales have a functional olfactory system with paired rather than single blowholes (nares), potentially enabling stereo-olfaction. Dimethyl sulfide (DMS) is an odorous gas emitted by phytoplankton in response to grazing by zooplankton. Some seabirds use DMS to locate prey, but this ability has not been demonstrated in whales. For all 15 extant species of baleen whale, nares morphometrics (imagery from unoccupied aerial systems, UAS) was related to published trophic level indices using Bayesian phylogenetic mixed modelling. A significant negative relationship was found between nares-width and whale trophic level (β = -0.07, Lower 95% CI = -0.12, Upper 95% CI = -0.02), corresponding with a 36% increase in nares-width from highest to lowest trophic level. Thus, species with nasal morphology best suited to stereo-olfaction are more zooplan..., Morphometric measurements were made for free-ranging whales mostly using UAS or aircraft-based imagery, including stills from video footage. The selection criteria for images were that they were vertical, in focus and clearly showed the nares. Altitude was typically between 10 – 60 m, however accurate altimetry data were not available for all flights and therefore relative measurements (i.e., pixel counts) were used. Because images were compiled from a range of different studies, the UAS, camera, camera sensor, lens focal length, altitude and thus pixel resolution will have varied among sampling events . Similarly, lens distortion will vary in its effect on whale measurements due to differences among UAVs. To mitigate for possible effects from image distortion, only images where the subject of interest (head) was in the center of the frame (≥ 30% from all frame edges) were used . 
Absolute measurements were not generated in this study, rather those previously published (total body lengt..., , # Morphology of nares associated with stereo-olfaction in baleen whales

The dataset contains one .csv file and the necessary code to reproduce our results using the data therein. The .csv file contains nares measurements, made using UAV (drone) imagery with some additional underwater, ship-bourne and airplane-bourne images for rarely observed whale species. This .csv data file also contains trophic index information derived from the literature and the citations to these sources are listed therein. Both .csv and .tre files described below are required to produce the Bayesian phylogenetic mixed model presented in the paper. We controlled for the expected similarity in trait values due to common descent among species using a distance matrix of the phylogenetic distance between these species. The code for this phylogenetic tree is provided in the .tre file, as described in the methods section of the paper. R (R Core Team, 2022) code to run the analysis is included as a .pdf file which al...