Adapting photo-identification methods to study poorly marked cetaceans: a case study for common dolphins and harbor porpoises

Social and community structure of striped dolphins in a semienclosed Mediterranean embayment

“…A further selection was based on photographic quality criteria, independent of fin markings (high sharpness, entire dorsal fin visible and perpendicular to camera, no underwater images), restricting the sample to 34,711 photographs. These images were then matched visually based on dorsal fin markings (no automated matching software was used; Bearzi et al, 2011; Würsig & Würsig, 1977) while also considering possible mark changes over the 7‐year period (Elliser et al, 2022; Gowans & Whitehead, 2001; Urian et al, 2015; Wilson et al, 1999). Individuals were stratified into different distinctiveness categories corresponding to the degree of natural markings on the dorsal fin, as done by Bearzi et al (2011).…”

“…Only the more reliable marking categories were used for the social analyses described in this study, namely D1 (dorsal fin deformities), D2 (one or more large notches), and D3 (multiple nicks), totaling 8,943 high‐quality, high‐resolution photographs of single individuals. Dorsal fins with less distinctive marks (categories D4–D6; Bearzi et al, 2011), or with absent/inconspicuous markings were not considered in this study, considering that a 7‐year time frame would increase uncertainty and matching errors for poorly marked individuals (Elliser et al, 2022; Urian et al, 2015).…”

Feasibility study for a pilot program: catching and tagging harbour porpoises in the Netherlands

“…• Photo(-ID): harbour porpoises can be individually identified based on pigmenting, the shape of their dorsal fin and scars and marks (Elliser et al, 2022;Stichting Rugvin, 2022b). Taking a photo of the animal on both sides allows for comparing with earlier or later photos and thus for potential identification.…”

Application of multi-species photo-ID database management systems: a user’s perspective

“…While for some animals their primary identifiable features do not change in appearance whether viewed from the left or right sides, such as the pattern of notches on the dorsal fin of many dolphin species (e.g., Würsig and Würsig 1977;Read et al 2003;Verborgh et al 2022); for many other, such as elephants where identification of individuals is based on the pattern of natural markings on their membranous ears (e.g., Ardovini et al 2008;de Silva et al 2022) or the pattern of facial wrinkles (Whitehouse and Hall-Martin 2000;Chui and Karczmarski 2022), or the coat pattern of giraffes (Bolger et al 2012;Muller 2018), or that of several species of felids (Oberosler et al 2022;Pereira et al 2022) and canids (Dorning and Harris 2019;Marneweck et al 2022), or pigmentation and scars of some poorly marked cetaceans (Karczmarski and Cockcroft 1998;Elliser et al 2022), these primary identifiable features display different patterns on the left and right sides of the animal. For that reason, DIS-COVERY offers options to verify new IDs by either a particular aspect (Fig.…”