Hello colleagues, Co-authors and I have recently had a few papers published open access in Marine Mammal Science. References and links are pasted below.
best regards, Jared Executive Director Bay Cetology www.baycetology.org Barnhill, A., Towers, J.R., van Weelden, C., Rörup, T., Nöth, E., Maier, A., Bergler, C. (2026). Machine learning detection of scarring events in killer whales. Marine Mammal Science, 42:e70207. https://doi.org/10.1111/mms.70207 Abstract: Detection and analysis of body scars using photo-identification data of cetaceans can provide insights into life history, behavior, and exposure to threats, but such analyses typically require manual examination of large image datasets. To explore whether machine learning can assist this process, we developed a pipeline for automatically detecting and counting conspecific scarring events on killer whales. The approach combines an nnU-Net segmentation model, which generates binary masks containing individual scar lines, with hand-crafted feature representations and HDBSCAN clustering to group scars into events and estimate the number of events per image. Across a dataset in which images contained between 1 and 10 annotated scarring events (median = 2), the best-performing configuration produced a conservative estimator with a mean absolute error (MAE) of 0.82 events per image and exactly recovered the annotated number of events in just over 50% of cases. These results demonstrate that machine learning-assisted analysis can extract biologically meaningful information on scarring burden from standard photo-identification images of killer whales. While accurate recovery of absolute scarring burden from single images is achievable with useful reliability, detecting small inter-annual changes remains more challenging under heterogeneous field conditions. Rather than replacing expert annotation, the present system is best viewed as a semiautomated framework that can extend existing photo-identification workflows toward longitudinal scarring analysis and broader population-level assessment. It therefore provides a practical foundation on which more comprehensive detectors of cetacean scarring events can be built. Towers, J.R., Tixier, P., Guinet, C., Gasco, N., Arnould, J.P.Y., Cheeseman, T., Pitman, R.L. (2026). Total numbers and movements of photo-identified subantarctic (type D) killer whales. Marine Mammal Science, 42:e70192. https://doi.org/10.1111/mms.70192 Abstract: The distinctive Subantarctic (Type D) killer whale (DKW) (Orcinus orca) is a highly divergent and apparently inbred form previously known only from three mass strandings and several dozen at-sea sightings, primarily from Patagonian toothfish (Dissostichus eleginoides) longline vessels in the southern Indian Ocean and from tourism vessels in the Scotia Sea. Its range appears to be circumpolar throughout the Subantarctic, but very little is known about total numbers and overall movements. We summarize photo-identification data from 352 of 406 sightings collected between 44° S and 62° S from 2003 to 2024. Among 207 photo-identified individuals there were two distinct clusters of 78 and 29 toothfish depredators, one in the southern Indian Ocean and the other off southern Chile, respectively. An additional 100 DKW were photo-identified throughout the wider Subantarctic. Discovery curves indicate that DKW may be more abundant than some less divergent or inbred killer whale populations. Depredating DKW showed seasonal and interannual site fidelity, but 10 depredating individuals identified in the southern Indian Ocean were also resighted in the southern South Atlantic, 4428 km away. Probable re-sightings of two other DKW occurred in the Scotia Sea over distances of 1070 and 41 km, respectively. These latitudinally narrow, long-distance inter-ocean movements are unique among killer whales. During the study period, the entirely pelagic distribution of encounters appears to have shifted significantly southward. Scarff, T.M., Towers, J.R., Trites, A.W. (2026). The inside waters of Vancouver Island are critical foraging habitat for west coast transient killer whales. Marine Mammal Science, 42:e70205. https://doi.org/10.1111/mms.70205 Abstract: West Coast Transient (WCT) killer whales (Orcinus orca rectipinnus) hunt marine mammals along the west coast of North America from California to southeastern Alaska. However, little information is available on their seasonal use of nearshore areas and the relative importance of different parts of their range. Using sighting data from 2016 to 2023, we assessed their seasonal distribution and abundance in the inside waters of Vancouver Island (the Salish Sea and North Island Waters). WCT killer whales were seen an average of 250 days throughout each year. They were most frequently observed in the Salish Sea from March to September but had fewer sightings in July of even years when pink salmon returns were low. In contrast, occurrences of WCT killer whales in the North Island Waters peaked in September but were significantly lower overall. Peak occurrences in both areas corresponded with the seasonal presence of seals and sea lions, their primary prey. Overall, ~70% of the coastal subset of the WCT population occurred annually in a region that accounts for a relatively small portion of their range. This high concentration highlights the importance of the inside waters for their survival and emphasizes the need to assess other key areas within their range.
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