Humpback dolphins
What are they?
Classification of the humpback dolphin is in dispute. Although there could be as many as five different species (Ross et al. 1994, Carwardine 1995), generally only two are accepted: the Indo-Pacific humpback dolphin Sousa chinensis and the Atlantic humpback dolphin S. teuszii. The Indo-Pacific humpback dolphin has a robust body (150 – 200 kg, 2 – 2.8 m in length) with a small triangular dorsal fin atop a fatty hump. The beak is long and slender and is exposed during the distinctive surfacing pattern which is characteristic of humpback dolphins. The beak breaks the water surface at an angle of 30o to 45o angle (See picture above) and the beak and sometimes entire head is exposed; a few seconds later the back is exposed and arched, usually quite steeply.
Where are they found?
The distribution of the humpback dolphin is distinctly tropical, extending into higher latitudes in areas where waters are warm (Ross et al. 1994, Carwardine 1995). Within this tropical distribution, they are limited to coastal areas, usually in shallow water (less than 20 m deep; Saayman and Taylor 1979, Durham 1994, Ross et al. 1994, Karczmarksi 1996). In comparison to the rest of KwaZulu-Natal, the size of humpback dolphin population was larger in the shallow, turbid (brown) waters of the Tugela Bank (Durham 1994). However, water clarity does not appear to limit their distribution and they can be found in clear waters in KwaZulu-Natal and the Eastern Cape (Durham 1994, Saayman and Taylor 1979, Karczmarksi 1996).
What do they eat?
Humpback dolphins feed on fish that live close to the seabed and fish that live on reefs. They often prey on fish that live or breed in estuaries. They have been known to eat squids and other such creatures. Although in general they feed independently of others in the group, we’ve seen them "hunting as a pack" and Vic Peddemors (and another NSB guy Grant Thompson) observed some very interesting feeding behaviour in Mozambique. They watched humpback dolphins co-operate and chase fish onto sandbanks where they were stranded. Then the dolphins beach themselves on the sand banks, grab the stranded fish and wriggle back into the water again
Humpback dolphin groups are generally quite small (on average there are about 7 dolphins in a group) and the groups are not stable. Saayman and Taylor (1979) described humpback society perfectly when they wrote that "groups are characterised by their temporary nature and fluctuating membership." For example, some days Quasimodo is all alone, the next day we see him with two other dolphins, they day after that he is with two different dolphins and a week later he is part of a large group of 20 animals. Although Durham (1994) and Karczmarksi (1996) saw many solitary animals, so far we have only seen Quasimodo by himself.