At the end of last month NOAA released a publication of over 1,000 pacific-coast bottlenose dolphin pictures. The Catalogue [https://swfsc.noaa.gov/publications/TM/SWFSC/NOAA-TM-NMFS-SWFSC-566.pdf] is made up of close-ups of the dorsal fin, each one showing a unique scar and notch pattern with an identification code next to each fin. The scarring and notch pattern on the dorsal fin is used to identify individuals when they are seen again because they are persistent over time. A similar method is used to identify individuals of all species of cetacean. The underside of humpback whale flukes have distinctive black and white markings to varying degrees that persist over time, right whales have specific callosity patterns on their rostrum which can be photographed from above, and beaked whale can even have distinctive cookie cutter shark scars along their bodies which they obtain when they dive into deep water.
I encourage any amateur cetacean photographer that has pictures of or want to get pictures of bottlenose dolphin’s dorsal fins to have a look through. You never know, you might recognize or be able to match up a few fins. I remember the first time I saw a dolphin I recognized by dorsal fin and the memory sticks with me because it was so rewarding. Now a mainstream in modern cetacean research with many longitudinal studies of whale and dolphin populations going on around the world, photo ID has not always been so. Below is a history of the technique.
Although it may seem strange that modern photo ID techniques originated from studies of birds, the skies (like the oceans) were another example of a habitat that man could not go. When stalks would disappear from Europe during certain times of the year in the 18th century it was hypothesized, among other things, that they hibernated in the mud at the bottom of lakes. It was not until a stalk was unfortunate enough to get skewered through the neck by an African spear, travel to Europe, and then get shot out of the sky again that we first learned where they were going. Ornithologists were also the first to recognize the potential benefits of reliably identifying specific individuals in the late nineteenth century by banding birds. This greatly enhanced migration research because individual birds could be recognized without recapture simply by looking through binoculars at the bird’s ankle.
Since the 1920’s individual whales had been monitored with the use of foot-long stainless steel cylindrical tags shot into the whale with date, address and promise of reward engraved onto them. These couldn’t be recovered until the whale was killed and its body rendered for oil. Whalers were encouraged to post them back to London where they could plot the location the whale was tagged and the location the tag was recovered in order to get an estimated migration path. Back then the purpose of collecting information was more related to controlling numbers of whales caught rather than protecting them outright.
Many cetacean researchers felt lethal tags should be replaced by non-invasive individual recognition techniques and in the late 1960’s and 1970’s biologists started to realize that many marine and terrestrial animals could be identified by natural markings. The Würsigs were among the first to apply photographic techniques for recording individuals by their natural markings to bottlenose dolphin at Peninsula Valdes, Argentina.
Another very successful study in British Columbia at that time focused on the marking of the Killer Whale. Before photo ID methods were employed it was widely believed there was thousands of Orca in the local waters around British Columbia because so many had been spotted in the region. There was no way to identify individuals and it didn’t occur to people that they might be seeing the same whale over and over again. Mike Bigg was enlisted to conduct a survey of the Orca population so he ingeniously enlisted the help of everyone he could think of that worked on the water in the area and printed out thousands of surveys so everyone could count the number of Orca’s they saw on one particular day, June 27th 1971. This way he could get around the problem of counting repeated individuals. The results shocked everyone because they found that instead of the thousands that were expected to be in the waters there were only estimated to be 350 individuals.
After noticing that one of the whales had a distinctive mutilated dorsal fin, Mike tried to find and identify her again, which he did. The female was called “whale A1”. By photographing, the researchers in Mike’s team noticed the individuality of the scarring patterns along the dorsal fin and body as well as the shape of the saddle patch. They also found they could find these individuals over and over again. Once a catalogue of individuals was set up, researchers set out to collect data on longevity, reproduction, travel patterns, births and deaths. The research identified the pod structure of the Orca and the fact they were divided into residents and transients. They also found that capture of Orca at certain locations in British Columbia had left significant reproductive dents in several populations. After this, many cetacean field workers learned to discriminate the often subtle natural marking that distinguished individual whales and dolphins.
The progression away from lethal tagging done in the 1920’s to the non-invasive, non-lethal method used from the late 1960’s onwards marked a shift in cetacean research. Photo Identification yielded great insights into behavior, life history and social structure of cetaceans and has helped to identify many of the species needing protection. Whaling and live capture of cetaceans represented the largest culling of any species on the planet in terms of biomass and it is good to say that these practices are mostly behind us here in the United States, in a large part thanks to the research conducted using photo Identification.
Written by Matthew Scott.
Post graduate marine biologist; spotter of whales; writer for ACS SF chapter; swimmer of oceans; companion to dogs.