Atlantic spotted dolphin

{{Short description|Species of mammal}}

{{Speciesbox

| name = Atlantic spotted dolphin{{MSW3 Cetacea|id=14300090}}

| image = Atlantic spotted dolphin (Stenella frontalis) NOAA.jpg

| status = LC

| status_system = IUCN3.1

| status_ref = {{cite iucn |author=Braulik, G. |author2=Jefferson, T.A. |date=2018 |title=Stenella frontalis |volume=2018 |page=e.T20732A50375312 |doi=10.2305/IUCN.UK.2018-2.RLTS.T20732A50375312.en |access-date=18 November 2021}}

| status2 = CITES_A2

| status2_system = CITES

| status2_ref = {{Cite web|title=Appendices {{!}} CITES|url=https://cites.org/eng/app/appendices.php|access-date=2022-01-14|website=cites.org}}

| genus = Stenella

| species = frontalis

| authority = Cuvier, 1829

| synonyms = * Delphinus froenatus Cuvier, 1836

  • Delphinus frenatus Gray, 1846
  • Delphinus doris Gray, 1846
  • Stenella plagiodon Cope, 1866
  • Spilodelphis frontalis

| range_map = Verbreitungsgebiet des Zügeldelfins Stenella frontalis.PNG

| range_map_caption = Atlantic Spotted Dolphin range

}}

The Atlantic spotted dolphin (Stenella frontalis) is a dolphin found in warm temperate and tropical waters of the Atlantic Ocean. Older members of the species have a very distinctive spotted coloration all over their bodies.

Taxonomy

The Atlantic spotted dolphin was first described by Cuvier in 1828. Considerable variation in the physical form of individuals occurs in the species, and specialists have long been uncertain as to the correct taxonomic classification. Currently, just one species is recognised, but a large, particularly spotty variant commonly found near Florida quite possibly may be classified as a formal subspecies or indeed a species in its own right.

Atlantic spotted dolphins in the Bahamas have been observed mating with bottlenose dolphins.{{cite book|title=Dolphin Diaries: My 25 Years with Spotted Dolphins in the Bahamas|author=Herzing, D.|pages=[https://archive.org/details/dolphindiariesmy0000herz/page/132 132–147]|year=2011|publisher=Macmillan|isbn=978-0-312-60896-5|url-access=registration|url=https://archive.org/details/dolphindiariesmy0000herz/page/132}} Rich LeDuc has published data that suggest the Atlantic spotted dolphin may be more closely related to the bottlenose dolphins (genus Tursiops) than to other members of the genus Stenella. More recent studies in the 2020s indicate that this is a consequence of reticulate evolution (such as past hybridization between Stenella (spotted dolphins) and ancestral Tursiops (bottlenose dolphins)) and incomplete lineage sorting, and thus support T. truncatus and T. aduncus belonging to the same genus. This likely explains why Atlantic spotted dolphins can mate with both species of bottlenose dolphins.{{Cite journal|date=2020-05-01|title=Phylogenomics of the genus Tursiops and closely related Delphininae reveals extensive reticulation among lineages and provides inference about eco-evolutionary drivers|url=https://www.sciencedirect.com/science/article/pii/S1055790320300282|journal=Molecular Phylogenetics and Evolution|language=en|volume=146|pages=106756|doi=10.1016/j.ympev.2020.106756|issn=1055-7903|hdl=2164/16438|hdl-access=free|last1=Moura |first1=Andre E. |last2=Shreves |first2=Kypher |last3=Pilot |first3=Małgorzata |last4=Andrews |first4=Kimberly R. |last5=Moore |first5=Daniel M. |last6=Kishida |first6=Takushi |last7=Möller |first7=Luciana |last8=Natoli |first8=Ada |last9=Gaspari |first9=Stefania |last10=McGowen |first10=Michael |last11=Chen |first11=Ing |last12=Gray |first12=Howard |last13=Gore |first13=Mauvis |last14=Culloch |first14=Ross M. |last15=Kiani |first15=Muhammad S. |last16=Willson |first16=Maia Sarrouf |last17=Bulushi |first17=Asma |last18=Collins |first18=Tim |last19=Baldwin |first19=Robert |last20=Willson |first20=Andrew |last21=Minton |first21=Gianna |last22=Ponnampalam |first22=Louisa |last23=Hoelzel |first23=A. Rus |pmid=32028032 |bibcode=2020MolPE.14606756M |s2cid=211048062 }}

Description

File:Stenella frontalis DSC 0236.JPG]]

File:Atlantic Spotted Dolphin.jpg

File:Dolphind.jpg

The coloring of the Atlantic spotted dolphin varies enormously as it grows, and is usually classified into age-dependent phases known as two-tone, speckled, mottled, and fused. Calves are a fairly uniform gray-white, with one or no spots. When they are weaned, speckling occurs, typically between 3 and 4 years and lasting for an average of 5 years. A juvenile is considered mottled when it develops merging gray and white spots on the dorsal surface and black spots on the ventral surface. This usually happens between age 8 or 9. A fused pattern is reached when dark and white spots are on both the ventral and dorsal sides. As the animal matures, the spots become denser and spread until the body appears black with white spots at full maturation.{{Cite journal|title = The life history of free-ranging Atlantic Spotted Dolphins (Stenella frontalis): Age classes, color phases, and female reproduction|last = Herzing|first = Denise L.|date = October 1997|journal = Marine Mammal Science |volume=13 |issue=4 |pages=576–595|doi = 10.1111/j.1748-7692.1997.tb00085.x| bibcode=1997MMamS..13..576H }}

In comparison to other dolphin species, the Atlantic spotted dolphin is medium-sized. Newborn calves are about {{Convert|35|-|43|in|cm|abbr=on}} long, while adults can reach a length of {{Convert|2.26|m|abbr=on}} and a weight of {{Convert|140|kg|abbr=on}} in males, and {{Convert|2.29|m|abbr=on}} and {{Convert|130|kg|abbr=on}} in females.

Compared to the much smaller pantropical spotted dolphin, the Atlantic spotted dolphin is more robust. It shares its habitat with the pantropical spotted dolphin and the bottlenose dolphin.

The species exhibits a range of about ten different vocalizations, including whistles, buzzes, squawks and barks, each corresponding with different behaviors.{{Cite journal|title = Vocalizations and associated underwater behavior of free-ranging Atlantic Spotted dolphins, Stenella frontalis and bottlenose dolphins, Tursiops truncatus|last = Herzing|first = Denise L.|date = 1996|journal = Aquatic Mammals |volume=22 |issue=2 |pages=61–79}}

Behavior

Atlantic spotted dolphins are extremely gregarious animals, which gather in complex social groups of 5–15, often in mixed groups with common bottlenose dolphins. They are fast swimmers and known for their bow-riding and long, shallow leaping behaviors. Their mating system consists of one male mating with several females, and the pod is highly protective over pregnant females. The dolphin's gestational period is ~11 months, and the mother cares for its calf for up to 5 years, with the help of the rest of her group.{{cite web|title=Atlantic spotted dolphin|url=http://us.whales.org/species-guide/atlantic-spotted-dolphin|publisher=Whales.org}}

These animals are cooperative hunters that hunt in groups at night. They strategically encircle their prey, which consists mostly of small fish, benthic invertebrates, and cephalopods such as squid. They can dive to depths of up to {{convert|60|m|ft|abbr=on}} and can stay beneath the surface for up to 10 minutes at a time.{{citation needed|date=June 2023}} When showing aggression towards other species, these dolphins make use of more contact behaviors such as biting and chasing than when being aggressive towards members of their species, in which they usually rely on display behaviors.{{Cite journal |last1=Myers |first1=Alyson J. |last2=Herzing |first2=Denise L. |last3=Bjorklund |first3=David F. |date=2017-05-03 |title=Synchrony during aggression in adult male Atlantic spotted dolphins (Stenella frontalis) |url=http://dx.doi.org/10.1007/s10211-017-0262-7 |journal=Acta Ethologica |volume=20 |issue=2 |pages=175–185 |doi=10.1007/s10211-017-0262-7 |s2cid=254164529 |issn=0873-9749}}

Population and distribution

The species is endemic to the temperate and tropical areas of the Atlantic Ocean. It has been widely observed in the western end of the Gulf Stream, between Florida and Bermuda. Off the Bahamas, tourism industries to swim with dolphins are available.{{cite web | url = http://www.biggameclubbimini.com/dolphin-experience.htm | title = Bimini Dolphin Discovery | access-date = 3 April 2014 | archive-url = https://web.archive.org/web/20140407064418/http://www.biggameclubbimini.com/dolphin-experience.htm | archive-date = 2014-04-07 | url-status = dead }} It is also present in the Gulf of Mexico. More infrequent sightings have been made further east, off the Azores and Canary Islands. Northerly sightings have been made as far north as Cape Cod across to the southwestern tip of Spain. They are certainly present further south, too, as far as Rio Grande do Sul in Brazil and across to west Africa, but their distribution is poorly understood in these areas.

About 20 years ago, only about 80 dolphins were in the Bahamas. Now, almost 200 dolphins are found there. On account of their similar appearance to other dolphins in their range, it is difficult to be sure of the Atlantic spotted dolphin's population. A conservative estimate is around 100,000 individuals.{{citation needed|date=January 2016}}

Human interaction

Some Atlantic spotted dolphins, particularly some of those are around the Bahamas, have become habituated to human contact. In these areas, cruises to watch and even swim with the dolphins are common. They are usually not held in captivity.{{citation needed|date=December 2024}}

Atlantic spotted dolphins are an occasional target of harpoon fishermen, and every year some creatures are trapped and killed in gill nets, but these activities are not currently believed to be threatening the survival of the species. This species lives in the mesopelagic layer of the ocean. These dolphins are not threatened by extinction, however, commercial trade may affect their evolution and sustainability. Sometimes they are killed by harpoons off St. Vincent.{{citation needed|date=December 2024}}

Conservation

The Atlantic spotted dolphin is included in the Memorandum of Understanding Concerning the Conservation of the Manatee and Small Cetaceans of Western Africa and Macaronesia.[http://www.cms.int/species/waam/index.htm Western African Aquatic Mammals MoU], [http://www.cms.int/species/waam/index.htm Memorandum of Understanding Concerning the Conservation of the Manatee and Small Cetaceans of Western Africa and Macaronesia] They are also marked as Least Concern of the Conservation Action Plan for the World's Cetaceans.{{Cite journal|title = Dolphins, Whales and Porpoises|last = Reeves|first = Randall R.|author2=Smith, Brian D.|author3=Crespo, Enrique A.|author4=di Sciara, Giuseppe Notarbartolo|date = 2003|journal = 2002-2010 Conservation Action Plan for the World's Cetaceans}}

See also

{{Portal|Cetaceans|Mammals|Marine life}}

References

{{Reflist}}

  • Whales Dolphins and Porpoises, Mark Carwardine, Dorling Kindersley Handbooks, {{ISBN|0-7513-2781-6}}
  • National Audubon Society Guide to Marine Mammals of the World, Reeves, Stewart, Clapham and Powell, and there is no characteristics for survival. {{ISBN|0-375-41141-0}}
  • Perrin, William F. (2002). "[https://web.archive.org/web/20130915093329/http://www.science.smith.edu/departments/Biology/VHAYSSEN/msi/default.html Stenella frontalis]". Mammalian Species (702):1–6.