Fingerprinting Bottlenose Dolphins

Photo-identification of marine mammals is a mark-recapture method that is used for a variety of species around the globe. Here in Cardigan Bay, the Sea Watch Foundation uses this non-invasive technique to assess the population, habitat use and social structure of the semi-resident population of bottlenose dolphins (Tursiops truncatus). Whilst on land watches and during boat surveys the dorsal fins of bottlenose dolphins are photographed for later analysis. The dorsal fin of a bottlenose dolphin is likened to human fingerprints in that each individual’s fin is unique and therefore identifiable. Over time the dorsal fin acquires nicks, scratches and scars from encounters with other dolphins and potential boat strikes and these, along with the shape of the fin, are used for identification.



Catalogue I.D. number: 017-03W_R (nickname: Smoothy)


The process is like a detective game in that you have a host of photographed individuals, your suspects, and you need to identify each of them. Each night the photos from the digital camera are downloaded onto the computer and the day’s encounters are divided up into separate files. Each land-watch shift and boat survey is considered a separate encounter and ‘spacers’ (for example a photo of a shoe) are taken to mark the end of an encounter. When on day-long, dedicated surveys each new group of dolphins is considered a new encounter.

Photos not useful for identification are then deleted from the folders. These include missed or late shots; photos at the wrong angle, ideal photos are taken at 90º to the fin; photos taken against the light; shots that are too far away; and photos with too much water in the way of the fin. The remaining photos are then renamed with the date, encounter number, boat name (or land), photographers name and numbered consecutively.

The kept, good photos are then copied and a new folder created. Within this new folder all photos are cropped so that only the dorsal fin and part of the dolphin’s body are kept in the shot. If a photo contains more than one individual it is replicated and each dolphin cropped out. If the animals are too close together for successful cropping, paint is used to draw an arrow to the intended fin. Where a mother and calf have been photographed, the photo is duplicated and cropped to keep both individuals in the frame so that a database can be constructed of recent mothers and their calves. An arrow is used to identify the separate fins, see photo below. This stage can take a surprisingly long time especially when a large number of photos have been taken.



Unidentified I.D. number: U1(U2calf)_110414_001_seekat_PEV_058b_1


Next up is the matching stage. This is the most significant stage of the process whereby the suspects are identified and abundance estimates obtained. Firstly, internal matching is carried out. Using their uniquely marked dorsal fins, all pictures of the same individual within an encounter are given a temporary name (A, B, C, etc). This stage is relatively trouble-free as you become familiar with the shapes and nicks of each dolphin from that encounter. The suspects are then compared one-by-one to the I.D. catalogue in an attempt to find out who was at the scene.

This stage involves dedication and precision as each nick and scar needs to match in the way that jigsaw pieces need to match up to finish the puzzle. The detective needs to be aware at this stage that nicks and scars may change over time as scars fade and new nicks may be obtained. This is why it is important to regularly photograph individuals so that positive matching is achievable. Of course it is still possible that the dolphin in question can not be successfully matched to the catalogue as it may be a new individual; a juvenile who has not acquire any nicks yet; or the suspect does not have a well-marked dorsal fin.



Catalogue I.D. number: 066-10L_L


Any unidentified suspects that have certainly not been photographed before are added to the catalogue as well as up-to-date photos of individuals whose fins have changed. Once the photo-identification process is started, you can become quite devoted to the task and do not want to stop until all the suspects in question have been identified.

Youtube video:
Sea Watch Volunteers - Dolphin Photo Identification
http://www.youtube.com/watch?v=o_peF4r8eKk&feature=related


Sea Watch Foundation Team

www.seawatchfoundation.org.uk

Chris and her calf seen!

Great news! Adoptable female dolphin Chris has already been seen on several occasions this season, including a very close encounter from a survey trip on the Gallois on the 11th of May, accompanied by her now grown and inquisitive (not to say cheeky) calf. The pair was seen last year (picture below), when he was still the size of a newborn. We were delighted to see them both looking healthy. The calf has become quite big and is particularly curious with boats: he even splashed monitoring officer Gemma Veneruso during the survey trip, while showing off next to the boat!

The pair should be seen around again soon, and a closer look at the sighting pictures from this morning, which included at least one calf, should confirm their presence.

New sightings and information on recent strandings

Our Friday 13th started on a high with a morning spent in the company of a large group of dolphins just off New Quay pier. In the afternoon, we had the pleasure of meeting Rod Penrose, the Welsh strandings coordinator from the Marine Environmental Monitoring. Rod gave us a talk on his work and marine mammal/turtle/shark strandings around the UK. It was very instructive, allowing us to gain a good insight on anatomy, how to diagnose the cause of death of animals. Rod mentioned a particularly interesting case of “corkscrew seals” which remains a mystery to this day –for about three years, number of seals have been found stranded with very strange looking wounds, resembling the spiral movement of a corkscrew-hence the name- from nostril to tail – if you come across anything like it let us know! For more information on cases like this and on marine mammal strandings in general, have a look on www.strandings.com.

Coincidentally there were 3 strandings reported in the New Quay area on 13th and 14th. First on the 13th, a female harbour porpoise, probably pregnant, was found on Barmouth beach. The following day, Saturday 14th, a juvenile harbour porpoise and a fresh adult female bottlenose dolphin were found respectively in New Quay and Aberaeron. Putting theory into practice, the Sea Watch volunteers and staff were able to inspect the bodies of the stranded animals and were given a run through of basic things to look for (blubber thickness, external injuries etc.).

HAVING A WHALE OF A TIME IN WALES!!

The 2011 marine mammal research season in New Quay, Wales kicked off on Easter Monday and there has already been an abundance of sightings. Although no whales have yet been spotted, we have high hopes for the season.



Top left: Juliette, Alisha (MSc student), Katrin (Research Assistant & Volunteer Co-ordinator)
Bottom left: Elena, Rachel, Deborah (Education & Awareness Assistant), Vanessa, Fabio


The first 7 volunteers, plus one MSc student (all pictured above), have already been introduced to a bottlenose dolphin (Tursiops truncatus) mother-calf pair regularly seen frequenting the New Quay harbour area.




The mother has been identified as ‘Chris’, one of our adoptable dolphins (www.adoptadolphin.org.uk). Over the past few weeks we have seen the calf become more independent and adventurous in its movements and playful displays. It has been sighted swimming on its back with its white underside in full view; much to the amusement of curious onlookers.

Another familiar face is that of a grey seal (Halichoerus grypus) which swims past the harbour wall with its head out of the water having a good nosy around.




We have all also been out on daily 1-2 hour Ermol trips which take us along the coast, past the fish factory which is a key foraging ground for the dolphins, seals and bird species. Public awareness of the Sea Watch Foundation and the local marine mammals is carried out during these trips as well as on the harbour wall. This has proved to be a little challenging what with the wind taking every opportunity to blow our leaflets away, leaving the volunteers chasing after them.

We are anxiously waiting for the wind to die down so that we can get out on the Dunbar Castle II for our day-long survey trips. These should prove to be exhilarating and enjoyable days. In the mean time the team has been swatting up and improving our general knowledge ready for the weekly pub quiz at the Dolau Inn!


Sea Watch Foundation Team

www.seawatchfoundation.org.uk