Posted by: orcaweb | June 17, 2015

Not so Common, Common Dolphins!

Hello and welcome to our weekly blog from the Cap Finistere. It has been a great week with calm days in the Bay of Biscay and some amazing encounters. We have had common dolphins of all shapes and colours along with a couple of sharks and even a quail. Read on to find out more…..

Tiffany joined me on Wednesday as we set sail on a beautiful, sunny afternoon. Unfortunately it was very windy in the channel and the white caps kept us from seeing any cetaceans, we didn’t let this get us down however as rumours of calm conditions in the Bay of Biscay made us excited for the next day. We jumped out of bed at 4.45 when we discovered the sea state 2 conditions, this would be our first calm day in the Bay of Biscay for weeks. After less than an hour we spotted black shapes amongst the grey sea, we instantly identified them as pilot whales as they moved slowly next to the boat and lifted their tail stocks as they swam.

IMG_4745 (2)Pilot whales stick up their tail stock as they swim.

Pilot FPilot M

Two female and 1 male pilot whale, the different sexes can be identified by the shape of their dorsal fin.

For the rest of the journey into Bilbao we were entertained by pod after pod of common dolphins. We saw a variety of behaviour from feeding dolphins, breaching on the horizon and, as usual we had many racing towards the ship giving the passengers a fantastic show.

After looking at the photos from Thursday morning we noticed a common dolphin with a deformed tail stock. There are many reasons why dolphins may have deformed spines, they can be congenital or acquired. It could be caused from injury through boat strike or aggression from another animal, or a genetic disease like scoliosis. Scoliosis is a medical condition seen in humans as well as dolphins where the spinal axis has a three dimensional deviation and can resemble a S or ? shape. More detail on spinal malformations can be found in this paper.

common deform2

Common dolphin with a deformed spine. Notice the shape of the spine compared to the normal common behind.

Please let us know if you have any idea of what has caused this bent spine or any experience of seeing similar deformities on dolphins in the wild.

Thursday afternoon was much like the morning – calm seas teaming with dolphins! As soon as we stepped out on deck after our presentation we noticed white water on the horizon. There was a large pod of bottlenose dolphins breaching high out of the water and making a huge splash. Not long after the common dolphins started appearing and we had regular sightings for the next four hours.

Tiff dolphins tues

Wildlife officer Tiffany pointing out dolphins to passengers.

Passengers Sat

Deck 10 full of passengers watching dolphins.

In one pod that came right up to the boat we noticed a very dark individual. Looking back at photos we had three different common dolphins with dark colouration, they were almost completely black apart from very faint markings. These sightings were all seen at different times and locations during the crossings and therefore are distinct individuals.

Black common 3

The dark morph common dolphin in the front and a common with normal colouration behind.

Common dolphins have been seen with a variety of colourations ranging from completely black (hyperpigmentation) to completely white (hypopigmentation). The individuals we have witnessed this week appear to be in the dark-morph characteristic where the ochre thoracic patch is black. There is a fantastic paper by Stockin and Visser (2005) on common dolphin colouration if you want to find out more.

Friday morning was very foggy with only 100m visibility, but this didn’t stop the dolphins and within 15 minutes we had common dolphins bow riding, a very unusual sight in the channel. In the evening just as we were leaving Portsmouth for Santander we did an interactive talk for the new passengers. We had 8 teams join in the quiz and they enjoyed learning about how we can identify cetacean species from their sounds, body parts and blow shapes.

Bow riding striped dolphins seen on Saturday.

Bow riding striped dolphins seen on Saturday

We woke on Saturday morning to find northern Biscay resembling a mirror. The calm waters meant we got to see some of the shy coastal species we normally miss when there is a bit of wind. After an hour on deck we spotted a minke whale next to the boat and a few minutes later we had two harbour porpoises cruising by. During the afternoon we had lots of pods of common and striped dolphins riding the waves of the bow and wake. As we got further into the Bay of Biscay the wind started to increase making cetacean spotting difficult.

Dark common sat

Dark common sat 2 A dark morph common dolphin was spotted on Saturday too. Notice the ochre thoracic patch is black

On Monday because of the calm conditions we took a route very close to the Brittany islands giving us a fantastic view of the many lighthouses in this region. We didn’t get many cetacean sightings during the day but as the sun started setting we had two shark sightings, a Blue shark and a possible basking shark along with a few pods of dolphins dancing under the setting sun.

IMG_5538

One of many lighthouses seen around the Brittany Islands

IMG_5567 (2)

Dolphins danced under the beautiful sunset on Monday

Tuesday was very windy in the Bay of Biscay, but despite the difficult conditions we still saw common, striped and bottlenose dolphins close to the boat, in fact we had a total of 14 pods!

dark, common, stripe tues

Dark morph common dolphin, normal coloured common dolphin and a striped dolphin race towards the bow.

The answer to last weeks trivia question is:

Dolphin calves usually stay with their mothers for 3-6 years. In this time they learn to catch food, avoid dangers and navigate around their home range.

Mum and calf striped dolphins seen on Tuesday

Mum and calf striped dolphins seen on Tuesday

This weeks trivia question: When do common dolphins breed?

Thank you for reading our blog this week.

Please comment and let us know if you have any ideas about our strange common dolphin encounters this week.

Until next week…Clare and Tiffany.

Many common dolphin calves were spotted on Saturday

Many common dolphin calves were spotted on Saturday

If you would like a chance to experience some of the fantastic species we have seen this week check out our I-Spy mini cruises. Operating in July, August and September, we have expert guides on board to help you spot the amazing cetaceans in the Bay of Biscay. Check out the ORCA website for more information.

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