As the name suggests, the common dolphins are the most common dolphins in the world. But, what do we mean by “common”?

They are referred to as common for two reasons: they are the most abundant of all dolphin species with worldwide distribution throughout temperate and tropical waters across the Atlantic, Indian, and Pacific Ocean.

It is estimated that there are around 6 million individuals globally, made up of two species: the Long-beaked Common Dolphin and the Short-beaked Common Dolphin.

Today, we will be discussing both species as they are very similar. However, the Long-beaked Common Dolphin is the species that we see here in Gansbaai.

They have a typical streamlined dolphin shape, measuring between 1.8 and 2.5 metres in length. They have a triangular dorsal fin positioned in the middle of their backs and a rounded forehead.

Interestingly, the Long-beaked Common Dolphin has the highest number of teeth of any dolphin species, with up to 240 total. In comparison, the Risso’s Dolphin has the fewest number of teeth with only 4 to 14.

All dolphins have conical shaped teeth which are designed to secure slippery prey, as opposed to chewing, as prey is swallowed whole.
Both common dolphins have distinctive colour patterns, making them easily recognisable.

They are often referred to as having an “hourglass” or “criss-cross” pattern on each side. This is comprised of a dull yellow/tan panel and a light grey panel that cross over underneath the dorsal fin, which is highly contrasted against their dark grey backs.

As their name suggests, the key feature that distinguishes the Long-beaked and Short-beaked Common Dolphin is the length of their beaks, also known as rostrums.

Ecology: Behaviour and Diet

As previously mentioned, common dolphins have a wide distribution. The Short-beaked has a slightly broader range, typically occupying offshore areas that are colder and deeper, whereas the Long-beaked is typically found in warmer, coastal habitats.

Common dolphins form the largest pods of any dolphin species with aggregations of up to 10,000 individuals, known as superpods. This large number is typically associated with the Short-beaked, whereas Long-beaked can be in pods of up to 1,000 individuals.

Although it is customary to find them in larger groups of 100 to 500, they are often seen in smaller groups of 10-50 as well. Within these large groups, it is thought that there are smaller sub-groups. Both species have similar hunting strategies, often feeding on small schooling fish and squid. However, as Short-beaked occupy offshore environments and Long-beaked occupy nearshore environments, their target prey differs.

In South Africa, they are commonly seen following the natural phenomenon that is the Sardine Run, occurring every winter around June and July. During this time, millions of sardines migrate from the south coast up towards the KwaZulu-Natal coast, attracting a wide range of marine predators.

Conservation Status

Globally, common dolphins are not considered endangered and population numbers appear stable. The International Union for Conservation of Nature (IUCN) Red List of Threatened Species has them classified as Least Concern.

However, they are also listed as Data Deficient and the global assessment primarily refers to the Short-beaked Common Dolphin. Importantly, stable global population numbers do not necessarily reflect local population numbers and activity.

For example, the Mediterranean subpopulation is considered endangered and the Black Sea subspecies is considered vulnerable, thought to be due to the added stressor of military activities.

In South Africa, dolphins are protected by the Marine Living Resources Act of 1998 and the National Environmental Management: Biodiversity Act of 2004, making it illegal to catch and disturb dolphins.

Despite these laws, common dolphins still face several threats from human activities such as coastal development, pollution, accidental capture as bycatch, and entanglement in shark nets.

To ensure that common dolphins remain abundant in South Africa, careful management of South Africa’s coastal ecosystems is essential to minimise these ongoing threats.