Comparison of Three Individual Identification Algorithms for Sperm Whales (Physeter macrocephalus) after Automated Detection

Photo-identification of individual sperm whales (Physeter macrocephalus) is the primary technique for mark-recapture-based population analyses for the species The visual appearance of the fluke - with its distinct nicks and notches - often serves as the primary visual differentiator, allowing humans to make recorded sightings of specific individuals. However, the advent of digital photography and the significant increase in volume of images from multiple projects in combination with pre-existing historical catalogs has made applying the method more challenging.with the required human labor for de-duplication (reduction of Type II errors) and reconciliation of sightings between large datasets too cost- and time- prohibitive. To address this, we trained and evaluated the accuracy of PIE v2 (a triplet loss network) along with two existing fluke trailing edge-matching algorithms, CurvRank v2 and Dynamic Time Warping (DTW), as a mean to speed comparison among a high volume of photographs. Analyzed data were collected from a curated catalog of well-known sperm whales sighted across years (2005-2018) off the island of Dominica. The newly-trained PIE model outperformed the older CurvRank and DTW algorithms, and PIE provided the following top-k individual ID matching accuracy on a standard min-3/max-10 sighting training data set: Rank-1: 87.0%, Rank-5: 90.5%, and Rank-12: 92.5%. An essential aspect of PIE is that it can learn new individuals without network retraining, which can be immediately applied in the presence of (and for the resolution of) duplicate individuals in overlapping catalogs. Overall, our results recommend the use of PIE v2 and CurvRank v2 for ID reconciliation in combination due to their complementary performance.

Interaction between sperm whales (Physeter macrocephalus) and northern bottlenose whales (Hyperoodon ampullatus) and deep-water trawlers in the Northwest Atlantic

Interactions between various cetacean species and fisheries are geographically widespread and diverse. Foraging in association with fishing activities may increase prey encounter rates and possibly increase the quantity and the quality of the food consumed. This paper describes interactions between benthic trawlers, targeting mainly Greenland halibut, and two whale species: sperm whales and northern bottlenose whales, in the eastern Grand Banks of the northwest Atlantic. Whale behaviors were compared during four trawling-related activities: preparing/ shooting the net, towing, hauling and transiting between fishing sites. Sperm whales and bottlenose whales were more likely to be observed during hauling. We observed probable feeding behavior of both species close to the surface at the end of hauling which suggests they are taking fish escaping from the cod end of the net when it is close to the surface. It is not clear whether feeding attempts are made during other phases of the trawling cycle. Ten sperm whales were photo-identified and six of these individuals were resighted on different days. Resights of individuals indicated that sperm whales could follow trawlers through several sets over of distances up to 234 km. While some individuals were observed to move between fishing grounds others remained within one fishing area for some time. By contrast, even though twenty-three bottlenose whales were photo-identified, there were no resights of individual whales. While northern bottlenose whales have been studied quite extensively in some adjacent areas, particularly off Nova Scotia, their behaviour and distribution within the Grand Banks fishing areas has not been well described. No matches were found between northern bottlenose whales in this study and photo-identification catalogues for the Scotian Shelf or the Arctic. Whether and how northern bottlenose whales found in this area are connected to other subpopulations remains unclear.

New sperm whale remains from the late Miocene of the North Sea and a revised family attribution for the small crown physeteroid Thalassocetus Abel, 1905

In spite of a continuously expanding physeteroid fossil record, our understanding of the origin and early radiation of the two modern sperm whale families Kogiidae Gill, 1871 (including the pygmy and dwarf sperm whales, Kogia spp.) and Physeteridae Gray, 1821 (including the great sperm whale, Physeter Linnaeus, 1758) remains limited, especially due to the poorly resolved phylogenetic relationships of a number of extinct species. Among those, based on fragmentary cranial material from the late early to middle Miocene of Antwerp (Belgium, North Sea basin), the small-sized Thalassocetus antwerpiensis Abel, 1905 has been recognized for some time as the earliest branching kogiid. The discovery of a new diminutive physeteroid cranium from the late Miocene (Tortonian) of Antwerp leads to the description and comparison of a close relative of T. antwerpiensis. Thanks to the relatively young ontogenetic stage of this new specimen, the highly modified plate-like bones making the floor of its supracranial basin could be individually removed, a fact that greatly helped deciphering their identity and geometry. Close morphological similarities with T. antwerpiensis allow for the reassessment of several facial structures in the latter; the most important reinterpretation is the one of a crest-like structure, previously identified as a sagittal facial crest, typical for kogiids, and here revised as the left posterolateral wall of the supracranial basin, comprised of the left nasal (lost in kogiids for which the postnarial region is known) and the left maxilla. Implemented in a phylogenetic analysis, the new anatomical interpretations result in the new Belgian specimen and T. antwerpiensis being recovered as sister-groups in the family Physeteridae. Consequently, the geologically oldest kogiids are now dated from the Tortonian, further extending the ghost lineage separating these early late Miocene kogiid records from the estimated latest Oligocene to earliest Miocene divergence of kogiids and physeterids.