‘WELL SPOTTED’: PANTROPICAL SPOTTED DOLPHINS IN ABACO


Pan-tropical Spotted Dolphins, Abaco Bahamas (BMMRO)

‘WELL SPOTTED’: PANTROPICAL SPOTTED DOLPHINS IN ABACO

Two species of spotted dolphin are found in Bahamas waters. The most common is the ATLANTIC SPOTTED DOLPHIN Stenella frontalis, a species confined to the Atlantic. Less commonly seen – though with a global range – are Pantropical Spotted Dolphins Stenella attenuata

Pan-tropical Spotted Dolphins, Abaco Bahamas (BMMRO)

The BMMRO research boat is out whale-spotting right now, and the team is finding a good variety of cetacean species, from dolphins right up to SPERM WHALE mother and calves. A couple of days ago, the pantropicals surfaced and these great shots of them were taken.

Pan-tropical Spotted Dolphins, Abaco Bahamas (BMMRO)

The two spotted dolphin species are very similar to the untrained eye. Identification is further complicated by the fact that both species start life without spots and go through stages ranging from no spots at all to completely spotted. These stages are sometimes referred to as ‘two-tone, speckled, mottled, and fused’. The pantropicals are relatively small, reaching lengths up to 7 feet and weighing c250 pounds at adulthood. Their beaks are longer and more slender than the familiar but larger bottlenose dolphin. The beak has a white tip, a useful identifier.

Atlantic Spotted and Pantropical Spotted range maps for comparison

The pantropicals favour shallower water by day, and at night they move to deeper water where they can dive down for food such as squid. Although they are IUCN listed as ‘Least Concern’ and their world-wide numbers are estimated to be abundant, they face the usual man-related threats to the species throughout their range, especially in the Pacific region. As we see time after time, complacency can turn to concern in a very short time.

Pan-tropical Spotted Dolphins, Abaco Bahamas (BMMRO)

THREATS TO THE SPECIES

  • Entanglement in fishing gear – captured as bycatch in the course of commercial fishing
  • Entangled in discarded fishing gear
  • Illegal feeding and harassment – this is a problem in particular locations eg Hawaii
  • Overexposure to and interaction with eager tourists in inshore areas
  • Hunting – these dolphins are prolifically hunted for food in several parts of the world
  • Hunting – they are caught ‘accidentally’ in large numbers in nets set for tuna
  • Persecution in eastern tropical Pacific fisheries, according to WDC
  • Pollution, plastic ingestion etc – basically, mankind’s negligence over 60 years or so
  • General habitat degradation, disturbance and marine noise pollution – mankind again

Pan-tropical Spotted Dolphins, Abaco Bahamas (BMMRO)Pan-tropical Spotted Dolphins, Abaco Bahamas (BMMRO)

Credits: BMMRO for all photos; research credits NOAA; WDC

BAHAMAS WHALES & DOLPHINS IN ABACO & ANDROS WATERS


Melon-headed Whale breaching - BMMRO copy

Melon-headed Whale breaching – BMMRO

BAHAMAS WHALES & DOLPHINS IN ABACO & ANDROS WATERS

The Bahamas Marine Mammal Research Organisation (BMMRO)  has its HQ at Sandy Point, Abaco. We recently went out in their research boat, a RHIB, to spend an unforgettable day with Blainville’s beaked whales and bottlenose dolphins. I posted some of the dolphins HERE; and a two-part beaked whale post is a work in progress.

Male Blainville’s beaked whale with its extraordinary barnacle-encrusted teeth that protrude upwards from its lower jaw. The prominent beak is plainly visible. Sighted off the south-west point of Abaco during our second encounter with a group of these whales – the only male we saw that dayBlainville's Beaked Whale KS 1

Abaco waters are ideal for marine mammals, especially off the southern shores where the walls of the Great Bahama Canyon drop vertiginously down from the shallow coastal waters to depths of up to 3 miles below. This is one of the deepest ocean canyons in the world.  The area provides a rich source of food and nutrients for the whales and dolphins and many different species are regularly sighted there, from huge sperm whales to small pilot whales (including plenty of species I had never heard of before). 

Great Bahama Canyon Map edit

As the name suggests, the BMMRO’s remit extends far beyond Abaco. The researchers often spend time exploring and recording cetaceans in other Bahamian waters. For the last few weeks the team have been off Andros and have encountered quite a few target species. I have included a selection below taken within the last month to illustrate the importance of the area for a remarkable assortment of wonderful whales and dolphins.

BLAINVILLE’S BEAKED WHALEBlainville's Beaked Whale copy

DWARF SPERM WHALESDwarf Sperm Whales - BMMRO copy

PANTROPICAL SPOTTED DOLPHINSPantropical Spotted Dolphin - BMMRO Pantropical Spotted Dolphin leap - BMMRO copy

On board the research vessel, every sighting is recorded in detail – where possible by species, numbers, ages, sexes, and individual identifying characteristics. Thus ‘SW34’ may have a damaged fluke, whereas ‘RD49’ may have a long scar on its back. 

PILOT WHALESPilot Whale - BMMROPilot Whales - BMMRO copyPilot Whales 2 - BMMRO

The research boat is equipped with sound devices which, when the microphone is immersed, are capable of picking up whale or dolphin sounds from a considerable distance. It’s astounding to be able to listen in ‘live’ to the wide assortment of clicks and whistles produced as the creatures communicate with each other. The recorded sound patterns are studied and can often be matched to enable an individual animal to be identified. 

MELON-HEADED WHALESMelon-headed Whales - BMMRO Melon-headed Whale - BMMRO

RISSO’S DOLPHINRisso's Dolphin - BMMRO copy

Other work, including photography, is done underwater. Perhaps the most intriguing aspect is the collection of poop specimens, from which a great deal can be ascertained about the diet and health of an individual animal. I wrote about this task and the methods used a while ago inFAMILIAR FECES‘.

I’ll be writing more about whales soon. Meanwhile, here’s a short BMMRO video of a large group of melon-headed males. At the start, you can clearly hear communication sounds between them.

Credits: Charlotte & Diane of the BMMRO for taking us out with them and for all the photos except the male Blainville’s beaked whale (mine, for once!)

‘SPOTTED IN ABACO WATERS’: PANTROPICAL SPOTTED DOLPHINS


 Spotted Dolphins Abaco Bahamas (BMMRO)

‘SPOTTED IN ABACO WATERS’: PANTROPICAL SPOTTED DOLPHINS

The BMMRO has posted several reports of dolphin and whale activity around the coast of Abaco during August, with some outstanding photos to accompany them. I had been going to post rather generally about this until a couple of days ago, when an unusual dolphin species for the region was… er… spotted and some memorable images taken.

Spotted Dolphins Abaco Bahamas (BMMRO)

These are PANTROPICAL SPOTTED DOLPHINS Stenella attenuata, whose range encircles the globe but at a lower latitude than the far more frequently encountered resident  ATLANTIC SPOTTED DOLPHINS Stenella frontalis. Here are comparative range maps. The rarity of the Pantropical species in the Bahamas is indicated in the BMMRO report of a stranding in 2011 – see below.

ATLANTIC SPOTTED DOLPHIN                                                                    PANTROPICAL SPOTTED DOLPHIN

Verbreitungsgebiet des Zügeldelfins Stenella frontalis.PNG                                                Cetacea range map Pantropical Spotted Dolphin.PNG

Spotted Dolphin Abaco, Bahamas (BMMRO) copy 2

Spotted Dolphins Abaco  Bahamas (BMMRO)Spotted Dolphins  Abaco Bahamas (BMMRO) copy

The pantropical image below is from the BBC archive and not taken in the Bahamas. I’ve included it for illustrative purposes due to the close-up underwater view of the dolphin.Pantropical spotted dolphin (BBC)

This wonderful underwater video of pantropicals is by Jake Levenson, shot from a polecam. Although it is 6 minutes long, I highly recommend it for (a) the stunning views of these creatures at very close quarters (b) the excellent audio quality – you can clearly hear the dolphins communicating with ‘sonar’ clicks and squeaks, and (c) the strange sense of peace you may feel when you have watched it. 

[youtube http://youtu.be/-hXTYe58g34]

PANTROPICAL SPOTTED DOLPHIN STRANDING 2011

In May 2011 a dead dolphin was found on the sandbank at Casaurina Point, Abaco. BMMRO’s scientists established that it was a sub-adult male pantropical spotted dolphin with a stomach full of squid beaks, a known prey for the species. A full necropsy was conducted on the animal and samples were taken for scientific testing to determine the cause of death. At the time the BMMRO reported the find in their quarterly Newsletter:

Pantropical spotted dolphins are commonly found in off-shore waters, although they can be found close to Abaco’s coastline due to the close proximity of deep waters. They can occur in large group sizes of up to 100 animals. Adult males and females reach up to 2.6 m (8.5 ft) and 2.4m (7.9 ft) in length, respectively. Since our efforts began in 1991, BMMRO has records of only 28 sightings of pantropical spotted dolphins in The Bahamas (my rubric), although their cousin species, Atlantic spotted dolphin, is a common resident. This is the first recorded stranding of this species in The Bahamas.”

Credits: BMMRO / Diane Claridge; BBC; Jake Leveneson (video); Wiki (range maps)