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Spinner Dolphins (Stenella longirostris)

Updated: Dec 19, 2020

During the night, a deep sea community of marine life that spends daylight hours at depths of up to hundreds of meters, now begins to migrate upward and towards the shore. As these riches come within reach, spinner dolphins begin to hunt. Small subgroups spread out across the sea. Using echolocation, the spinners scan the darkness and using their whistles, they call members of the school back together to unite in defense. The collective defenses of the dolphin school protect each member from harm.

Dolphins and whales attract every year tourists to Egypt, but, despite their popularity, are still poorly known from a scientific point of view. Eight species are considered regular: Common Bottlenose Dolphin (Tursiops truncatus), Indopacific Bottlenose dolphin (Tursiops aduncus), Spinner Dolphin (Stenella longirostris), Pantropical Spotted Dolphin (Stenella attenuata), Longbeaked Common Dolphin (Dephinus capensis), Risso’s Dolphin (Grampus griseus), Humpback Dolphin (Sousa chinensis) and Bryde’s Whale (Balaenoptera edeni). Other height species are considered rare (Notarbartolo 2007).

Over the last two decades, the living resources of the Red Sea have suffered from an array of human impacts including irrational land use, intensive coastal development, overfishing, pollution and curio trade. In addition, the Red Sea is potentially at great risk from the impacts of climate change. The effect of human activities on marine resources cannot be sufficiently predicted due mainly to the lack of scientific research.

Despite the recognition of the value of the natural treasures of the Red Sea from both an ecological and economic perspective, the pursuit of the required knowledge to conserve and sustainably manage these resources has been slow.

The Egyptian Red Sea south of Marsa Alam, where tourism is still in its early stages, seems to represent a rare example of unspoiled marine wilderness. Indications from previous dedicated research highlight that this largely untouched marine area is home to extraordinarily beautiful coral reefs, dolphins, dugongs, turtles, sharks, manta rays and other creatures, collectively known as marine “charismatic megafauna”.

From what is known about development programmes, it is highly likely that the Southern coast of Egypt will be the object of “traditional” tourism development in the near to medium future, catering to mass tourism similar to that in Hurghada and Sharm-el-Sheikh, which is certain to lead to the decline and possibly the disappearance of its valuable habitats and associated flora and fauna.

Tourism in the area of Marsa Alam and the Southern Red Sea is rapidly developing, with a large number of new hotels and resorts being built along the coast. The predominant attraction for tourists in Marsa Alam is the tropical marine environment, with its impressive coral reefs and associated marine fauna. However, Dolphins sighting locations are not very numerous along this stretch of coastline, and Sataya is one of the most attractive.

Spinner Dolphins are very social and they interact often within their pods. They also interact with other types of dolphins. They use echolocation often and thy are also known to touch each other more often than other dolphin species. They create bonds that are very intense with their pods. We have seen them leaping, jumping, playing, mating and spinning.

Photographic-identification of individuals and mark and recapture analyses are utilized to monitor population structure and group dynamics. Photographs are almost exclusively taken of the dorsal fin and surrounding area. Dorsal fin shape, notches (primarily along the trailing edge of the dorsal fin), as well as scratches and scarring on the fins and body are used to identify and catalogue individuals. Scarring is caused by a variety of sources, including other spinner dolphins.

Photographic-identification studies provide insight into habitat use, movements, and life history characteristics of individual cetaceans. Some species of cetaceans have naturally occurring markings on their bodies, flukes, or dorsal fins. Photographic records of these scars, nicks, notches, or color patterns can be used to uniquely identify individuals. Photographs of cetaceans encountered during sighting surveys are archived and associated with other sighting data, e.g., sighting location, group size and structure, and behavior. Individual cetaceans can be tracked over time and between locations on the basis of their unique photo-IDs.

Females may be ready to mate when they are 4 to 7 years of age. For the males, it is later on with the average from 7 to 10 years old. There are plenty of observed courtship elements for them that have been documented. They will be very playful and touching of one they plan to mate with. Mating times of year depend on the location. There are a few times per year in each location though when the hormone levels increase and that is when mating will take place.

After a pair successfully mate, it will be about 10 months before the young calf is born. They will be born fluke first and the females of the pod are very protective of it and the new mother. They will drink milk from the mother for about 2 years after being born, but they get introduced to solid foods from 4 to 6 months.

The females tend to only mate once every 3 years. However, the young may stay within the pod for life, and the bond between them and the mother remain strong. They can live an average of 20 years in the wild.

The Spinner Dolphin is classified as being endangered. One of the biggest problems for them is pollution in the water where they live. This can cause damage to their skin and if they consume plastic or chemicals it can cause internal damages.

"The use of commercial fishing nets in some regions has caused these dolphins to be injured or killed. I think that the biggest challenge dolphins are facing in Sataya Reef or let's say the Red Sea in General is the tourism. Swimmers and boats visiting their resting area and mostly behaving as barbarians. Ahmed Fouad

Efforts to prevent more non-organized touristic activity though can be useful. The Dolphin studies will also help to reduce the risk of them being harmed in this manner.

Spinner Dolphins seem to be very adversely affected by sources of stress in their environment. Noises from boats, from offshore drilling, mining, and hydroelectricity can all prevent them from eating well, mating, and it can harm their hearing. Their patterns of sleep can be harmed due to such noise too. Significant efforts such as limiting the areas for such activities continue to be put into motion. Yet it is hard to balance the advancements of humans with the needs of these dolphins to make it all work out. Without conservation though the numbers of Spinner Dolphins will continue to drop.

Author: Ahmed Fouad Pictures: © Ahmed Fouad - HEPCA2013


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