I’ve been spending some time working on an
aspect of research which is used the world over, and is one of the most
powerful tools available to those studying cetaceans – photo-identification.
As with almost any animal, no two
individuals will ever look exactly the same, there will be some unique feature
which marks them apart from others and can be used for recognising that
individual. The idea with photo-identification is to take a clear photograph of
that feature in order for it to be recognised again in the future. In some
species this will be easier to identify and photograph than others, and the
biggest problem with cetaceans is that they spend the majority of their time
underwater and out of sight. The fact that they are mammals comes to our aid
though, they must return to the surface at least occasionally to breathe, so we
can use this opportunity to photograph them.
Different body features are used in
identifying different species. In the giant blue whale, the pattern of spots
along the side of the body is used, in right whales it is the unique clusters
of white markings, or ‘callosities’ on their head, and in humpback whales it is
the distinctive black and white patterning on the underside of the tail flukes.
Here in Tenerife we are focusing on the resident species of short-finned pilot
whales and bottlenose dolphins, both of which are recognised by their dorsal
fins. Each dorsal fin is a slightly different shape, but this alone is not distinctive
enough. Over the course of their life an animal will acquire nicks, notches,
and scratches on the fin which make each one as unique as our fingerprints.
One set of photographs
of ten different pilot whales will not give you much information – other than
that you saw ten different individuals. But hundreds of sets of photographs of
pilot whales, taken over years of research, becomes an incredibly powerful
research tool. Not only can you say how many different individuals you have
ever seen, but you can also say how many times each individual has been seen,
if they have ever been seen with a calf indicating they are female, if they are
always seen with the same other individuals suggesting a social structure, what
times of day or year they are seen showing patterns in behaviour, where they
are seen indicating important locations… the list goes on and on.
