Dolphins - Western Isles Sightings
There are several species of dolphins that can be seen around the Western Isles. The ones that are often seen are the Common Short Beaked Dolphins (Common Dolphins), Bottle Nosed Dolphins and the lovely more elusive Risso Dolphins along with a few other species
Two Species of Common Dolphins - Maybe Three
There are two species of dolphins that fall into the category of Common Dolphin. There are some experts that believe a 3rd one should be added, but only time will tell if that turns out to be the case or not. More research has to be completed to say for certain that there are three types.
Short Beaked & Long Beaked Common Dolphin
The Short-Beaked Common Dolphin & the Long-Beaked Common Dolphin are recognized. The one that may be added is the Arabian Common Dolphin which is only found in the Indian Ocean and the Red Sea. The debate continues as to if there is enough difference for them to be a separate subspecies or not.
Common Short Beaked Dolphins
As the dolphins more often seen around the Western Isles are the Common Short Beaked Dolphins - Delphinus delphis, I have detailed a little information about this species
Pods of from ten to thousands
The most numerous dolphins in the world! You wouldn't see them on their own very often as they are very social creatures.
A school of these dolphins is a spectacular sight - it can be from about ten dolphins to up to five hundred or even thousands occasionally.
The best sight of all is to see them all jumping in unison. They have an average life span of 25 years. They must surface every 2-3 minutes to breathe.
Common Dolphin - Very Social
The Common Dolphin is very social, and they live in large groups called pods. The number in a pod can be several hundred or it can be in the thousands
Common Names
They have many common names - Cape dolphin, Common dolphin, Criss-cross dolphin, Hourglass dolphin, Saddleback dolphin, White-bellied porpoise. Identification of Short Beaked Common Dolphins
You can identify dolphins from other species owing to the 'hourglass' pattern on the flanks, which creates a dark V-shape below the dorsal fin. The short-beaked dolphin has a more rounded melon on its forehead (than the long-beaked common dolphin), the melon contains oil and is thought to be used for bouncing of sound waves from objects.
They have a dark stripe that surrounding their eyes and runs to their beak, They have a white stripe that runs from their beak, underneath their eye.
Striking Pattern of Yellow - Common Dolphins
Common short beaked dolphins have a beautiful striking pattern of yellow and grey panels creating a distinctive hourglass shape on their side which makes them easy to spot. Their dorsal sides are dark with a V shape below the dorsal fin. They are 1.7 – 2.5 m long, making them one of the smaller dolphins. Juvenile common dolphins have a paler coloration that brightens as they get older
Breathe Air to Survive
These mammals breathe air to survive.
Size
The common short beaked dolphins can reach a length of 8.5 ft. On average they weigh 190 lbs but can reach as large as weighing 400lbs.The males are usually larger than the females
Habitat
These dolphins prefer the waters to have a surface temperature higher than ten degrees celsius and the short beaked common dolphin is less commonly seen in water that is shallower than 180 metres
Food
These animals feed mostly on small schooling fishes and squid. In some areas they feed at night and squids form an important part of their diet
Speed
Short beaked common dolphins are the fastest of all the small dolphins, reaching speeds of 27 mph.
Breeding
The short-beaked common dolphin is born at a 35 inches in length. The female parents carry their young for 10 months after the mating season, (september to December).
After a calf is born the mother will push the baby to the waters surface to take its first breath of air. The calf is protected from predators by the mother and several other female dolphins.
At about 6 months the baby dolphin is weaned from the mother dolphins milk and begins eating only solid food which it was introduced to at the age of 3 months.
Between the ages of 5 to 6 years the baby dolphin will reach it's sexual maturity.
Noise
They make high pitched sounds and churn up the water so that they may be seen and heard from a large distance. Predators Sharks and killer whales are predators of these lovely dolphins
Predators
Sharks and killer whales are predators of these lovely dolphins
Risso Dolphins- Grampus griseus
The north of Scotland represents the northern limit for this species. In the Hebrides, Risso's dolphins tend to inhabit deeper water, which is home to their preferred prey of squid, octopus and cuttlefish. Risso Dolphins can occasionally be seen in coastal areas
Name Derivation
Risso's dolphins are named after Antoine Risso, whose description formed the basis of the first public description of the animal in 1815
Description
The Risso's dolphin has a robust, stocky body and a tall, falcate (curved) dorsal fin. The melon (forehead) is blunt and bulbous with a unique V-shaped crease running from the upper lip to the blowhole. Unlike the common dolphins they don't have a prominent beak and have just two to seven pairs of teeth in their lower jaws.
The colour pattern varies greatly between individuals, and with age. Calves are born grey, but turn darker grey to dark brown as they become juveniles. As they age, the skin tone lightens to silvery-grey in some cases and the body is increasingly covered with scratches and scars inflicted by other Risso’s dolphins and prey species such as squid. The oldest specimen reached 34.5 years.
Food
The risso dolphin feeds almost exclusively on squid, although they also eat some octopus and cuttlefish
Size
Adult Risso’s dolphins measure between 2.6 to 3.8 metres in length and can live for more than 30 years.
Breeding
Gestation is an estimated 13–14 months, at intervals of 2.4 years. Calving reaches seasonal peaks in the winter in the eastern Pacific and in the summer and fall in the western Pacific. Females mature sexually at ages 8–10, and males at age 10–12.
Behaviour
In the Hebrides, Risso's dolphins are usually seen singly or in groups of up to 20 animals, although in other areas they are reported in large groups of several hundred individuals. Social behaviour is gregarious and sometimes rough, possibly accounting for some of the scars and tooth rake marks seen in adult animals. It has been noted that these dolphins breach,, tail slap, spy-hopping, and slash and sometimes striking one another. Risso's dolphins are commonly seen travelling and surfacing slowly and will rarely approach vessels or bow-ride. They are able to dive for about 30 minutes to depths in excess of 1000 metres
