So we have frequently mentioned ‘photo-ID’ and spotting known individuals. To a zoologist working with individual animals, photo-ID is our very own ‘wax-on/wax off’: the most basic of talents that you are expected to master before you get to do any more difficult techniques or before you can answer longitudinal questions. It is especially important for studying marine mammals that are notoriously difficult to find or handle, and it is required on just about every behavioural job posting you come across today. The work we do wouldn’t be possible without it. It’s what we spend a large proportion of the day in the field working on, and what encompasses most of our evenings.
The basic principle of photo-ID is that we can use the natural markings on animals to tell them apart within and between years. Be it a grey seal, giraffe, whale or leopard—patterns on the fur are consistent throughout life and unique to individuals. Now you might be thinking, “Why not use flipper tags or temporary marks to tell them apart instead of looking at blotches?” While in some cases these methods can, and are used, when dealing with a strictly observational and non-invasive project these options are often unavailable.
Instead we rely on the natural marks to recognize individuals. Some, we know quite well and can ID on-site in the field. While these individuals will always bring a smile to our face and make us feel like we’ve accomplished something—a job well done—they really only represent about 10-30% of the animals we will see in a single day of sightings. The others will be poorly marked, covered in mud, laying on their back or will without fail, always roll over when you are not pointing your camera at him/her. For these other animals, we will likely leave the field not having a clue who they are and will have to rely on the pictures, sketches or notes on their appearance to try to match them up back at home-base (hence the ‘photo’ part of “photo-ID”).
For some marine mammals, including grey seals, the process of sorting out who is who can be aided by software that looks for matches between the pelage patterns in pictures but in our case, most of the process is done manually. As frustrating as it can be to stare at a database of over 200 individuals trying to tell if the brown blur on one seal matches the slightly different brown blur on another seal (repeat ad nauseum for the over 200 males in the catalog) it is incredibly gratifying when you do make the match. Even more so, it is an amazing feeling when you recognize a male tearing through the colony with only a glimpse and a quick picture of his left side. It takes a keen eye, patience and self-restraint to not convince yourself of matching two males you want to be a match (second opinions can be VERY handy). It also means sometimes admitting to defeat. Some individuals, on certain days, you’ll just never sort out because they are covered in mud, refuse to move and show you their marks or are just really, really poorly marked.
As hard as this might sound, you do get used to it and in many cases giving the seals names can help. Sometimes I use names that are mnemonics to help me remember their marks (B23 aka ‘Y-dot-Dash’, or C17 aka ‘Mirror C’) but in other cases giving them a name itself can help me remember their marks (B7 aka ‘Fred’ has an ‘f’ on his left flank or B1 aka ‘Anchorman’ has an anchor shaped blot). In some ways it ends up as a bit of a Rorschach test “What do you mean you don’t see the man being chased by snakes??” but sometimes the more obscure the image/pattern you see, the easier it is to remember.
At the end of the day, knowing individual seals is essential to answering questions like “How long on average does a male stay on the breeding colony?” or “Do females return to the same spot every year?” and other individual based questions that our research group focuses on. With the advances in photo-ID software these techniques can even be used to track movements of animals between colonies. All it takes is a camera, a keen eye, patience and careful observations.