Heaviside dolphin
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Heaviside dolphin ( Cephalorhynchus heavisidii ) |
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| Cephalorhynchus heavisidii | ||||||||||||
| ( Gray , 1828) |
The Heaviside Dolphin ( Cephalorhynchus heavisidii ) is a small species of dolphin that can only be found on the coast of Namibia and the west coast of South Africa . It belongs to the genus of the black and white dolphins ( Cephalorhynchus ).
features
The Heaviside dolphin is a relatively small dolphin that reaches a maximum length of about 1.70 meters with a maximum weight of 75 kilograms. As a newborn animal, the length is likely to be around 0.8-0.85 meters. As with other species in the genus, the body is compact and the dark gray head is blunt. This occasionally leads to confusion with the bottlenose dolphin . The flippers are narrow and paddle-shaped with a rounded tip, while the fin is large and triangular with a broad base. The body is largely dark gray, the flanks and the front area of the body are colored light gray and the rear half of the body and all fins are again dark gray. On the sides of the chest and below the flippers there are white spots and the belly side behind the flippers up to the tail is also colored white, other white areas are on the flanks and below the dorsal fin .
The animals have 22 to 28 conical teeth of the same type in each half of their jaws.
distribution
The distribution area of the species extends from the southern coast of Angola below 17 ° south latitude to the southern tip of South Africa , whereby the animals are also frequently sighted in the areas around Cape Town and at Walvis Bay . The area covers a maximum of about 1,600 kilometers of coastal areas. A systematic study of the distribution and the population of the Heaviside dolphin does not exist. They are very common on the Skeleton Coast of Namibia and sightings extend beyond Namibia's northern border.
The animals live mainly in the shallow sea areas with depths of less than 100 meters and a maximum distance of 8 to 10 kilometers from the continental shelf . The water temperatures in these areas are between 9 and 15 ° Celsius. In South Africa, the species is also likely associated with the cool waters of the Benguela Current.
Way of life
The dolphins are very active and sociable animals that usually gather in groups of five to ten animals. They are fast swimmers and occasionally jump straight out of the water to dive cleanly after a somersault . Usually the animals live in pairs or in small groups with fewer than 10 individuals, but groups of more than 30 individuals have also been documented. Socializations with the black dolphin ( Lagenorhynchus obscurus ) have also been observed. Little information is available about migrations and the spatial use of the species, but it is assumed that migrations are limited to comparatively small areas, the activity areas are estimated at around 300 to 1000 km 2 , females sometimes up to 2000 km 2 . The animals migrate to the coast during the day and to the more distant marine areas in the afternoon and evening, although these migrations are probably coupled with the appearance of the hake as food and to avoid encounters with deep sea sharks during the day.
The Heaviside dolphin feeds primarily on fish and octopus that live in the near-surface pelagic . The documented prey animals include the Cape hake ( Merluccius capensis ), the kingklip ( Genypterus capensis ), Sufflogobius bibarbatus , Loligo reynaudi and various octopus species. The dolphins are often found in areas with a high density of hake.
The animals reach sexual maturity at seven to nine years of age. The mating season is in spring and summer and the gestation period lasts about ten months. It is believed that a female can only give birth to a calf every three years. The known maximum age is relatively low at 20 years. The low maximum age as well as the long pauses between the individual births lead to a rather slow population growth and thus to a strong sensitivity towards hunting.
Systematics
The Heaviside dolphin is classified as a separate species within the genus of the black and white dolphins ( Cephalorhynchos ), which consists of four species. The first scientific description comes from John Edward Gray from 1828, who described it as Delphinus heavysidii from the Cape of Good Hope in the Western Cape Province of the Republic of South Africa . Bray also described the genus Cephalorhynchos in 1846 .
No subspecies are distinguished within the species.
Naming
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The Heaviside Dolphin is named after a ship's captain named Haviside who was the first to bring a specimen of these dolphins from Namibia to Great Britain . When naming it, however, his name was confused with that of another captain and whale researcher named Heaviside. In this way, this name has proven itself in naming the whale , but some researchers and specialist books use the originally intended name and name the animal as Haviside's Dolphin .
In Namibia the animal is also known by the common name Benguela Dolphin (named after the Benguela Current ).
Status and protection
The Heaviside dolphin is classified by the International Union for Conservation of Nature and Natural Resources (IUCN) as “data deficient” (Least Concern, LC) due to a lack of data on population size . Concrete data on the populations and population developments are not available and the animals are the most frequently sighted dolphins off the coast of Namibia and in the region off Cape Town there are estimates of 3,500 to 11,300 individuals of this species. At the same time, they have a limited habitat in the area of Coastal areas of Namibia and South Africa and they are threatened by local inshore fishing. Due to the limited area and fishing pressure, it is feared that genetic variability within populations will be limited.
The animals are protected under the Washington Convention on the Protection of Species and are listed on Appendix II, and direct hunting of the animals is accordingly prohibited. However, since they occur in fishing areas close to the coast, they are subject to relatively high fishing pressure from coastal fishing and hunting with harpoons or rifles also occurs. However, the coastal areas of the region are comparatively sparsely populated.
supporting documents
- ↑ a b c d e f g h i j k l m n o J.Y. Wang, KN Riehl, SZ Dungan: Heavyside 'Dolphin, Cephanlorhynchus heavisidii In: Don E. Wilson, Russell A. Mittermeier: Handbook of the Mammals of the World. 4. Sea Mammals. Lynx Edicions, Barcelona 2014; P. 525. ISBN 978-84-96553-93-4 .
- ↑ a b c d Cephalorhynchus heavisidii in the IUCN Red List of Threatened Species 2017.1. Posted by: RR Reeves, EA Crespo, S. Dans, TA Jefferson, L. Karczmarski, K. Laidre, G. O'Corry-Crowe, S. Pedraza, L. Rojas-Bracho, ER Secchi, E. Slooten, BD Smith, JY Wang, K. Zhou, 2008. Retrieved August 21, 2017.
- ↑ a b Simon Elwen, Michael A. Meÿer, Peter B. Best, PGH Kotze, Meredith Thornton, Stephan Swanson: Range and Movements of Female Heaviside's Dolphins (Cephalorhynchus heavisidii), as Determined by Satellite-Linked Telemetry. Journal of Mammalogy 87 (5), October 2006; Pp. 866-877. doi : 10.1644 / 05-MAMM-A-307R2.1
- ↑ B. Jansen van Vuuren, PB Best, J.-P. Roux, TJ Robinson: Phylogeographic population structure in the Heaviside's dolphin (Cephalorhynchus heavisidii): conservation implications. Animal Conservation 5, 2002; Pp. 303-307. doi : 10.1017 / S1367943002004055
literature
- JY Wang, KN Riehl, SZ Dungan: Heavyside 'Dolphin, Cephanlorhynchus heavisidii In: Don E. Wilson, Russell A. Mittermeier: Handbook of the Mammals of the World. 4. Sea Mammals. Lynx Edicions, Barcelona 2014; P. 525. ISBN 978-84-96553-93-4 .
Web links
- Cephalorhynchus heavisidii inthe IUCN Red List of Threatened Species 2017.1. Posted by: RR Reeves, EA Crespo, S. Dans, TA Jefferson, L. Karczmarski, K. Laidre, G. O'Corry-Crowe, S. Pedraza, L. Rojas-Bracho, ER Secchi, E. Slooten, BD Smith, JY Wang, K. Zhou, 2008. Retrieved August 21, 2017.