Dolphin ID Project: 2020-2021
During our guest dolphin cruises, we have started to take photographs of the cetaceans we encounter, to use for identification purposes. We take as many photos as possible at each encounter, especially on the calm, clear days.
We use only high quality photographs (correct angle, sharpness, lighting) for the identification process, but we do keep the lower quality images of any marked fins to use for future comparisons. Re-sightings are recorded in an excel sheet and the photos added to the individual dolphin’s collection. Periodically, we look through our archive of old photos to look for possible matches and re-sightings, and to remove any poor quality or indistinguishable images.
Taking good ID shots can be challenging under the variable conditions onboard (sun’s position, choppy sea) and it’s often not possible to angle the shot perpendicular to the dolphin’s body (to see the full outline of the dorsal fin). On average, out of 100 photographs taken, only 30 are good for analysis.
We photograph close-ups of dolphin dorsal fins
to record and identify the unique patterns
The photographs of the dorsal fin are cropped and analysed using image-matching software (we are trialling ‘Darwin’ at Kuda Huraa and I3S ‘Interactive Individual Identification System’ at Landaa Giraavaru).
Dolphins can be identified individually based on the notches, scars and markings present on their dorsal fin. Small wounds are known to heal within months, while large wounds caused by predation attempts or human impacts tend to persist (Lockyer & Morris, 1990 [PDF]). As missing tissue does not regenerate, dorsal fin mutilations are permanent marks that can be used for identification purposes.
We have created photographic databases for each of the four most commonly sighted Cetacean species in Maldives:
Spinner dolphins (Stenella longirostri) are by far the most commonly encountered Cetacean species in Maldivian waters. They are usually observed in pods of 40 to 100 individuals, exhibiting active and social behaviours including playing in the wake behind the boat and showing off their acrobatic skills (jumping, spinning, porpoising and bow-riding). They are the only species to actually spin in the air whilst jumping.
Young calves (30-90cm length) are often seen swimming alongside their protective mothers, and on some occasions even practising their jumping and spinning skills. Spinner dolphins are difficult to identify individually as most have “clean” dorsal fins with a smooth outline, lacking any distinct markings.
Bottlenose dolphins (Tursiops truncates and T.aduncus) are larger than Spinners, and often have more identifiable scars. They live and travel in much smaller family groups (even individually). Bottlenose are the most common species globally, and they have more fat so they can live in colder waters. They are sometimes seen jumping from the water, but never spin.
There are 2 different species sighted in Maldives – the ‘Common Bottlenose’ (Tursiops truncates) and the ‘Indo-Pacific Bottlenose’ (Tursiops aduncus), both very similar in appearance and difficult to tell part (‘Common’ is larger and found worldwide).
False killer whales
False killer whales (Pseudorca crassidens) are sighted seasonally in the Maldives, and are not so common. They can reach around 6 metres in length, although cold water populations have more fat insulation making them larger and heavier. They are usually sighted in family groups of 10-20 members (occasionally in huge groups of 500+) and often have uniquely identifying scars.
The mother is head of the group (‘matrifocal’ family structure) compared to pilot whales where the father plays a more important role.
Short-finned pilot whales (Globiocephala macrorhynchus) are sighted in family groups of around 15-30 members, but they will often migrate larger distances in groups of 100+. Here in the Maldives, pilot whales are often seen travelling together with pods of dolphins. Their large size and fat insulation means they can live in colder waters, and they often have many scars which makes for easier identification of individuals.
They were named ‘pilot’ whales as they follow a leader, and sometimes if that leader becomes sick or disoriented, the whole pod can end up stranding on a beach.
Spinner dolphin, photographed on a guest excursion from Kuda Huraa, Maldives (February 2020)
Dolphin Diary 2020
At Kuda Huraa, during a total of 15 guest excursions, we recorded 325 Spinner dolphins swimming in pods of between 10-75 individuals in encounters lasting from 5-44 minutes. We were also lucky to sight a pod of 10 pilot whales this month.
At Landaa, 380 Spinners plus 10 Bottlenose dolphins were sighted during 12 excursions in encounters lasting from 1-45 minutes. 7 new Spinners were added to the database, and there was 1 confirmed resighting (Rudolph SL0015).
At Kuda Huraa, we recorded sightings of 350 Spinners, in pods of 20-75 individuals, over 16 dolphin cruise excursions, with encounter times ranging from 13-40 minutes. The seas tended to be choppy, with white capped waves making it more difficult to spot cetaceans, so we were very lucky to spot a pod of 10 Pilot whales too this month.
At Landaa, we recorded sightings of 1520 Spinners and 53 Bottlenose dolphins this month, during 12 guest excursions, in encounters lasting between 1 to 45 minutes. From our photo sets, we were able to confirm re-sightings of 3 named individuals (Norhen, Laserstone, Steffi) and positively identify 10 new Spinners to add to our database.
At Kuda Huraa, we recorded 110 Spinners, sighted during 8 dolphin cruises, in pods of 15-50 individuals and in encounters lasting from 10-37 minutes. Calves were spotted on every occasion. We also encountered 2 pods of Pilot whales and 1 pod of Bottlenose dolphins (both species are rarely seen at Kuda Huraa, so this was exciting for the guests and for our team.)
24 quality ID photos were taken (representing all 3 species), and our current database of Spinners now totals 145 uniquely identified individuals.
At Landaa, we recorded 705 Spinners, sighted during 8 excursions, with encounter times varying from 25-40 minutes. From our ID photos, we were able to add 2 new Spinners to our database, and we confirmed re-sightings of 3 individuals (Barty, Hobnob, Pikachu).
Our database now totals 105 Spinners and 78 Bottlenose dolphins.
APRIL – MAY
Quiet, due to travel restrictions in place during the global pandemic.
Rare sighting of Pilot whales, photographed on a dolphin-watch at Kuda Huraa (Maldives, March 2020)
During June, we held one sunset excursion at Landaa Giraavaru, and sighted a pod of approximately 15 Spinner dolphins close to the island of Voavah. The encounter time was an enjoyable 20 minutes, with good weather and calm ocean.
From the photos taken during this trip, we were able to uniquely identify 2 new Spinner dolphin individuals, bringing our database totals to 107 Spinners plus 78 Bottlenose.
At Kuda Huraa, we arranged 1 dolphin cruise for 8 guests. We were all delighted to watch a medium-sized pod of 50 Spinners, swimming, jumping and playing behind our boat for an enjoyable 45 minutes.
At Landaa Giraavaru, we held 3 excursions but only managed to sight 2 elusive Spinners. The ocean was choppy and variable, making it tricky to spot (and photograph) any cetaceans nearby.
At Kuda Huraa, we held 6 separate dolphin-spotting trips for a total of 26 guests, and sighted 330 Spinners plus 10 Bottlenose dolphins in encounters lasting between 15 to 60 minutes.
At Landaa, we held 9 excursions (for a total of 31 guests) and sighted 194 Spinners in encounters lasting from 10 to 45 minutes.
From the photographs taken on our trips, we were able to uniquely identify 26 new Spinners to add to our database, and confirm resightings of a further 18 named individuals.
Spinner dolphins photographed at Landaa Giraavaru during June,
and newly added to our database
Spinner photographed on a dolphin-spotting excursion
Kuda Huraa, July 2020
Spinner dolphin, Kuda Huraa, August 2020
At Kuda Huraa this month, we held 5 excursions and recorded sightings of 370 Spinners. The dolphins were observed for periods of between 12 to 45 minutes, in pods varying from approximately 60 to 100 individuals, with calves sighted in each pod.
At Landaa, we recorded 185 Spinners across 5 excursions, with encounter times of 25-30 minutes.
From our dolphin identification photographs, we were able to uniquely identify 5 new Spinners to add to the database, and confirmed resightings of 6 named individuals: Diana, Giuly, Gaetan, Doge, Norhen [x2].
At Kuda Huraa, 760 Spinners were sighted during 8 Dolphin Cruises, enjoyed by a total of 34 resort guests. Dolphin pod sizes varied from 50 to 150 individuals, in encounter times lasting between 8 and 40 minutes. Calves were sighted swimming with most of the pods, and the sea was generally calm.
At Landaa, we recorded 230 Spinners during 7 excursions, in encounters lasting from 15 to 70 minutes.
We failed to capture any good quality photographs this month, in part due to cloudy weather resulting in lower light levels.
At Kuda Huraa, approximately 1100 Spinners were recorded, swimming in pods of between 50-300 individuals (including calves). Encounters lasted from 6-49 minutes, during 9 separate guest excursions (totalling 49 guests).
We were also lucky to spot 2 separate pods of Shortfin Pilot whales (4-5 individuals in each pod).
From the photographs taken this month, we were able to uniquely identify 45 Spinners plus 3 Pilot whales, all new to our identification database.
At Landaa, we sighted 610 Spinners plus 16 Bottlenoses during 8 separate guest excursions, in encounters lasting from 2-45 minutes.
From our ID photography, we added 23 new Spinners to the database (and confirmed 32 resightings) plus 2 new Bottlenoses (with 2 resightings).
At Kuda Huraa this month, we sighted 3 Bottlenose and 550 Spinners across 10 excursions (totalling 56 guests), during encounters lasting 25 to 56 minutes. From our ID photographs, we were able to successfully identify 7 new Spinner individuals, plus resightings of 17 dolphins already entered in our database. Our year-end database totals now stand at 152 uniquely identified Spinners, using a total of 364 ID photographs.
At Landaa, we sighted 615 Spinners plus 35 Bottlenose dolphins across 13 excursions, during encounters lasting from 2 to 60 minutes. This month, we identified 27 new Spinner individuals, and confirmed an impressive 38 resightings, to bring our year-end database totals to 81 Bottlenose and 185 Spinners.
Spinner dolphins photographed at Landaa Giraavaru during August,
and newly added to our database
Spinner dolphin (left) and Pilot whale (right) showing fin shapes and characteristics unique to each individual (Kuda Huraa, January 2021)
Dolphin Diary 2021
The Dolphin ID Project is making good progress, with large numbers of new individuals being added to the system. To ensure quality and accuracy, it is important that we spend additional time reviewing all our existing data (photos, matches, identifications). We dedicate time to periodically review our ID photos, to create templates of each ‘damage category’ (fin patterns) used by the Darwin ID software to reinforce the main matching areas. We also archive the low-quality images and identifications to improve database integrity.
At Kuda Huraa during January, we held 12 guest excursions and recorded: 670 Spinners, 25 Bottlenose and 12 Pilot whales (Globiocephala macrorhynchus). The Spinner dolphins were observed for periods of 9-46 minutes, in pods of 20-150 individuals.
From our dolphin ID photographs, we successfully identified 26 Spinners (9 new individuals, 17 resightings), bringing the total of uniquely identified Spinners to 161 individuals (from a total of 391 database photos). We also positively identified 10 Pilot whales (7 new individuals plus 3 resightings), increasing our database total to 18 individuals (from 21 photos).
At Landaa this month, we sighted 445 Spinners plus 2 Bottlenose dolphins during 5 excursions, in encounters lasting between 15-70 minutes. From our photographs, we successfully identified:
– 20 Spinners (14 new individuals plus 6 resightings);
– 12 Bottlenose (7 new individuals plus 5 resightings);
This brings our database totals to 87 Bottlenose and 199 Spinners.
At Kuda Huraa during February, we held 8 Dolphin Cruises and recorded sightings of a total of 310 Spinners, during encounters lasting from 6-35 minutes. In addition, we were excited to observe 2 separate pods of the rarely-seen Risso’s dolphins (Grampus griseus) totalling 35 individuals, plus one as-yet unidentified large whale species.
From our ID photos, we uniquely identified 5 Spinners (plus 5 confirmed resightings), plus 5 Risso’s (thereby doubling our database of Risso’s to 10 individuals).
At Landaa this month, during 9 guest excursions, we sighted 510 Spinners plus 9 Bottlenose dolphins (Tursiops truncatus), in encounters of 15-45 minutes. The seasonal good weather and calm oceans enabled us to successfully capture hundreds of quality identification photographs, leading to the identification of 3 new Bottlenoses and 44 new Spinners (plus 67 re-sightings).
Selection of our uniquely identified Spinner individuals, photographed on guest excursions during January 2021 (Landaa Giraavaru).
Risso’s dolphin [GG008]
whale tail (unknown cetacean species)
More ? > Dolphin Diary 2018-19
Cetacean Sightings Around the Maldives
Big thanks to our fellow Cetacean fans, for posting these rare and exciting sightings to social media for us all to enjoy ! 🙂
Manta rays were a consolation today, On the way to #HanifaruBay with @AveylaMaldives we encountered 2 massive #BlueWhales outside Hanifaru Reef. It was just incredible.#BaaAtoll #Maldives #bluewhale #whalewatching #whales #ocean #scubadiving pic.twitter.com/v7t72YNQfk— LiquidSaltDivers (@LiquidSdivers) November 11, 2018
A day with @liquidsaltdivers— LiquidSaltDivers (@LiquidSdivers) December 6, 2018
Repost from @jonschutte - Let's go for a dive! Just a casual day heading out on the boat for a few dives when guess what we saw? You'll have to watch to find out! 🎬💙🌊 #dharavandhoo #maldives #islandlife pic.twitter.com/pbdwySMVBl