Commerson’s Dolphin Facts & Worksheets

Commerson’s dolphin, scientifically known as Cephalorhynchus commersonii, is a small marine mammal belonging to the Cephalorhynchus genus. It is also commonly called Jacobita, skunk dolphin, piebald dolphin, panda dolphin, or tonina in South America. This dolphin species has two distinct subspecies: geographically isolated but locally abundant.

See the fact file below for more information on the Commerson Dolphin, or you can download our 29-page Commerson Dolphin worksheet pack to utilise within the classroom or home environment.

Key Facts & Information

FUN FACTS

• The primary subspecies, C.c.commersonii, displays a striking black-and-white pattern and is predominantly found around the southern tip of South America. 
• On the other hand, the secondary subspecies, C.c.kerguelenensis, is more significant compared to C.c.commersonii. It exhibits a less-defined contrast between dark and light grey colors, with a white ventral band. 
• These dolphins are predominantly found around the Kerguelen Islands in the Indian Ocean.
• They were named after Dr. Philibert Commerson, a French naturalist who first documented them in 1767 after encountering them in the Strait of Magellan.

PHYSICAL CHARACTERISTICS

• These dolphins have distinct black-colored heads, dorsal fins, and tails (flukes), while their throats and bodies are white. Depending on age, sex, and location, the black-and-white pattern on their bodies might change. 
• Although they resemble porpoises in appearance, dolphins behave in a way that is unique to them.
• Male and female dolphins can be easily differentiated by the shape of the black blotch on their bellies. Males have a teardrop-shaped imperfection, whereas females have a more rounded one.
• On average, Commerson’s dolphins measure between 120 and 170 cm (3.9-5.6 ft.) in length and can weigh up to 86 kg (190 lbs.) across their entire range.
• In South American waters, males have a maximum length of approximately 144 cm (4.7 ft.), while females reach about 147 cm (4.8 ft.) in length. 
• The larger subspecies, known as Kerguelen dolphins, can have males measuring up to 167 cm (5.5 ft.) in length and females reaching as much as 174 cm (5.7 ft.). Mature females tend to be slightly larger than their male counterparts.

Body Shape 

• Commerson’s dolphins have a generally cylindrical body shape that tapers at both ends. This streamlined fusiform shape is well-suited for efficient swimming, as it reduces drag in the water. 
• Compared to other body shapes, the fusiform body minimizes the surface area exposed to the external environment, aiding in heat conservation.

Coloration

• The black and white coloration of Commerson’s dolphins serves as a form of disruptive coloration, helping to obscure their body outline. This camouflage pattern may assist in concealing the small dolphins from both prey and predators. 
• Additionally, the distinct color pattern allows for differentiation between males and females. Males have an oval-shaped patch on their undersides, while females exhibit less regular and sometimes more V-shaped patterns.

Pectoral Flippers 

Commerson’s dolphins have adapted forelimbs, known as pectoral flippers, which play a crucial role in swimming. These flippers aid in steering and stopping during their movements through the water. 

While they possess skeletal elements similar to those found in land mammals‘ forelimbs, the pectoral flippers of dolphins are shortened, modified, and supported by connective tissue. The rounded tips of these flippers contribute to their hydrodynamic efficiency.

Flukes 

• The two-lobed tail of Commerson’s dolphins is called flukes. The flukes lack bones or cartilage and are composed of rigid, dense, and fibrous connective tissue. 
• Longitudinal muscles along the back and tailstock move the flukes up and down, propelling the dolphin forward in the water. The arterial network within the flukes, similar to the flippers, is surrounded by veins that regulate body temperature.

Dorsal Fin 

• Like the flukes, the dorsal fin of Commerson’s dolphins consists of dense, fibrous connective tissue without bones or cartilage. The rounded shape of the dorsal fin is a distinguishing feature. While the dorsal fin may help stabilize the dolphin during high-speed swimming, it is not essential for balance.
• Arteries in the dorsal fin are also surrounded by veins that contribute to maintaining body temperature.
• These anatomical features are well-adapted to the dolphins’ aquatic lifestyle, facilitating efficient swimming and thermoregulation. 

DISTRIBUTION AND HABITAT

• Commerson’s dolphins have two distinct populations. One population inhabits the coasts of southern South America, including the Falkland Islands and South Georgia Island. 
• They can be found as far north as Isla Grande De Chloé, Chile (42°45’S latitude) in the Pacific Ocean, and as far north as southern Brazil at approximately 31°S latitude in the Atlantic Ocean. 
• The second population resides in the shallow coastal waters around the Kerguelen Islands in the south Indian Ocean.
• Despite the geographical distance between these populations, scientists consider them a single species. 
• Their distribution extends south of the South Shetland Islands (approximately 63°S latitude). 
• Commerson’s dolphins are frequently observed in the Strait of Magellan and around Tierra del Fuego (around 54°S margin), narrow waterways separating the Pacific and Atlantic oceans and separating Tierra del Fuego from mainland South America. 
• They primarily inhabit cold, coastal waters near coastlines, bays, harbors, and river mouths, with a preference for waters less than 200 meters (656 feet) deep. 
• The water temperature in their South American habitat ranges from 4°C to 16°C (39.2°F – 60.8°F), while around Kerguelen Island, temperatures are even colder, ranging from 1°C to 8°C (33.8°F – 46.4°F). Commerson’s dolphins are often seen swimming in or near kelp beds.

HABITATS AND LIFESTYLE

• Commerson’s dolphins are highly social animals, typically forming groups ranging from a few individuals to over 100. They exhibit cooperative feeding behavior but may also forage alone. These dolphins are known for their high-speed swimming, reaching 11 to 13 km/h. They are active swimmers frequently seen rapidly swimming on the surface, leaping out of the water, and spinning and twisting as they swim. 
• They may also surf on breaking waves near the shore and engage in bow-riding and swimming behind fast-moving boats. Commerson’s dolphins can swim upside-down, which may enhance their ability to locate prey. In the case of the South American subpopulation, they have a varied diet that includes coastal and pelagic fish, squid, and crustaceans.

DIET AND REPRODUCTION

• Diet and Nutrition: Commerson’s dolphins are primarily carnivorous, consuming a wide range of prey, including small fish, krill, squid, cuttlefish, crabs, shrimp, and squid. 
• They do not chew their food and typically swallow fish whole. 
• Adult dolphins have high energy requirements and consume approximately 10% of their body weight in food daily, which is higher compared to other dolphin species, such as bottlenose dolphins, which consume around 4% to 5% of their body weight.

Mating Habits and Sexual Maturity 

• There is limited information about the mating system in Commerson’s dolphins. Mating occurs during the spring and summer seasons. The gestation period lasts around 11 months, resulting in the birth of a single calf. 
• The length of the nursing period in the wild is unknown, but in captivity, calves begin eating solid food at around two months and consume whole fish by four months. 
• Females reach breeding age between 6 and 9 years, and males reach sexual maturity around the same period.
• Sexual maturity differs between the South American and Kerguelen populations. 
• In South America, females become sexually mature and can bear calves at 5 to 8 years old and are approximately 130 cm (51 inches) in length.
• Males measure 127 to 131 cm (50-51.6 inches) in length when they are sexually mature, which is about 5 to 6 years old. In contrast, females from the Kerguelen population become sexually mature at about five years old and around 165 cm (65 inches) in length, while males reach maturity at approximately eight years old.

POPULATION

• The global population of Commerson’s dolphins is currently unknown, and population numbers and trends for many marine species still need to be better understood. As the distribution of Commerson’s dolphins extends beyond the United States, the U.S. Fish and Wildlife Service does not categorize them as threatened or endangered.
• However, these dolphins are protected in South American countries such as Argentina (since 1974) and Chile (since 1977).
• The International Union for Conservation of Nature (IUCN), a global conservation organization, includes Commerson’s dolphins in their 2003 IUCN Red List of Threatened Species under the “Data Deficient.”
• This designation indicates insufficient information available to assess this species’ extinction risk.
• Most toothed whales, including Commerson’s dolphins, are listed under CITES Appendix II, a list of species that are either threatened or are likely to become endangered if trade is not regulated. An international agreement known as CITES regulates the trade in threatened plant and animal species.

Population Threats

• The primary threats to Commerson’s dolphins are pollution and human activities. These dolphins are often found near shore, increasing their vulnerability to accidental entanglement and mortality in fishing gear such as gillnets. 
• Each year, an estimated 5 to 30 dolphins die as bycatch in nets set near the shore in Tierra del Fuego.

Population Numbers

• Although an overall population estimate is currently unavailable, the IUCN reports that Commerson’s dolphins are abundant and widely distributed throughout their range. A survey conducted in 1984 estimated a population of approximately 3,400 individuals in the Strait of Magellan. Commerson’s dolphins are classified as “Least Concern” (LC) on the IUCN Red List, indicating that they are not currently considered at significant risk of extinction.

Commerson’s Dolphin Worksheets

This is a fantastic bundle that includes everything you need to know about the Commerson Dolphin across 29 in-depth pages. These ready-to-use worksheets are perfect for teaching students about the Commerson Dolphin. It is also commonly called Jacobita, skunk dolphin, piebald dolphin, panda dolphin, or tonina in South America.

Complete List Of Included Worksheets

1. Commerson’s Dolphin Facts
2. Question and Answer
3. True or False
4. Arrange the puzzle 
5. Study Anatomy
6. The One Behind its Name 
7. Dolphin Reproduction 
8. Diet Poster 
9. Threats and Solutions
10. Dolphin Park Bucket List
11. Diorama 

Frequently Asked Questions

What are Commerson’s dolphins, and where are they found?

Commerson’s dolphins (Cephalorhynchus commersonii) are small marine mammals belonging to the Delphinidae family. They are also known as “skunk dolphins” due to their striking black and white coloration. These dolphins are found in the southern hemisphere, primarily around the coasts of southern Argentina and the Falkland Islands (Islas Malvinas). They are known to inhabit shallow coastal waters, estuaries, and sometimes venture into freshwater rivers.

What do Commerson’s dolphins eat, and how do they hunt?

Commerson’s dolphins primarily feed on a variety of small fish, squid, and crustaceans. They are known to use echolocation to locate their prey. Echolocation is a biological sonar system that emits sound waves, which bounce off objects in the environment and return to the dolphin. By interpreting the echoes, they can determine the location, size, and movement of their prey. Once they locate a suitable target, they use their agile bodies and sharp teeth to catch and consume their prey.

What is the conservation status of Commerson’s dolphins?

Commerson’s dolphins are currently listed as “Data Deficient” on the IUCN Red List. The lack of comprehensive data on their population size and distribution makes it challenging to assess their conservation status accurately. Nevertheless, they face several threats, including accidental entanglement in fishing gear, habitat degradation, and potential disturbances from human activities in their habitat.

How do Commerson’s dolphins communicate with each other?

Like other dolphins, Commerson’s dolphins are highly social creatures and use various forms of communication to interact with each other. They produce a wide range of whistles, clicks, and other vocalizations. These sounds help them coordinate group movements, locate prey, and maintain social bonds within their pod. Each dolphin has a unique whistle, which allows them to identify and recognize individual members of their group.

Do Commerson’s dolphins perform acrobatic displays like other dolphin species?

Yes, Commerson’s dolphins are known for their playful and acrobatic behavior. They often leap out of the water, known as breaching, and perform aerial flips and spins. These displays serve multiple purposes, including communication, social bonding, and possibly hunting techniques. Their agile and energetic behavior makes them a delight to watch for observers lucky enough to see them in the wild.

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