Category: Oceanic dolphin

Orca or Killer whales

Orca by Robert Pittman NOAA

Orca or Killer whale

As this species is a member of Cetacea, not carnivora. Never-the-less, this is the largest clear predator on the planet.

They are found in all of the worlds oceans. What is incredible, is that other apex predators, like the great white are rendered prey, simply be the arrival of Orcas on the scene.

One such example, is the arrival of the Orcas in South Africa. The great white sharks have vanished. While there are suggestions that they have not gone far (perhaps merely into the depths of the waters nearby)  it is clear that after a number were killed by the orcas they have given way.

They are not actually whales, being the largest member of the Oceanic Dolphin family, and as such appear to have the brainpower to defeat almost anything when they put their mind to it. As well as great white sharks, Orca will also hunt all of the baleen whales, including the blue whale which is the largest animal to ever roam the earth. They will also regularly hunt toothed whales such as false killer whales.

Each pod is lead by a dominant female, and these animals can live to be 50-90 years old. While this species eats a wide variety of fish, sharks, rays and marine mammals such as seals, other species of dolphins and whales, generally these animals specialize. Some generally eat fish, while others hunt mammals.

They have a wide range of hunting techniques, from polar orca working together to create waves to wash seals off icebergs, to intentionally beaching themselves in Argentina, to grab seals from the beach. Each group is capable of coming up with their own techniques which are taught to future generations.

Below you will find any articles from the blog, which mention the Killer whale (or Orca). Below that is a video of this species (it is a 50 minute documentary on this species). Below that, we will add any links which will allow you to try to see this species for yourself.

Southern right-whale dolphin

Southern right whale dolphin by Alcide Dessaines D' Orbigny

Southern right-whale dolphin

The southern right whale dolphin  is a small and slender species

 

 of cetacean, found in cool waters of the Southern Hemisphere. It is one of two species of right whale dolphin. This genus is characterized by the lack of a dorsal fin. The other species, the northern right whale dolphin, is found in deep oceans of the Northern Hemisphere and has a different pigmentation pattern than the southern right whale dolphin.

Southern right whale dolphins can be easily distinguished from other cetacean species within their range as they are the only dolphins without dorsal fins in the Southern Hemisphere. They have streamlined and graceful bodies, a single blowhole and a short and defined beak, possessing between 39 and 50 teeth per row.

A sharp dividing line separates the black dorsal part from the white ventral part of the body, running from the tail stock forward,  dipping down to the flipper insertion and sweeping back up, below the eyes, to cross the melon between the blowhole and snout crease. Younger individuals can be grey/brownish dorsally but develop adult coloration within the first year. The flippers of the southern right whale dolphins are small, recurved, predominantly white and located about one-quarter of the way back from the snout tip. Their flukes are small, have a white underside and dark grey upper side, with a notch in the middle and concave trailing edges.

There are no current global abundance and mortality estimates of the species although it is considered a fairly common and abundant species along its range, particularly in Chile. The very low sighting rate is most likely caused by a lack of sampling effort and due to the difficulties of sighting the animals in their offshore habitat.

Northern right-whale dolphin

Northern rhight whale dolphin

The northern right whale dolphin is a small, slender species of cetacean found in the cold and temperate waters of the North Pacific Ocean. Lacking a dorsal fin, and appearing superficially porpoise-like, it is one of the two species of right whale dolphin.

Northern right whale dolphins are fast swimmers. Their average swimming speed is around 26 km/h (16 mph) but they can reach speeds of up to 30–40 km/h (19-25 mph).
When travelling fast, a group looks as though they are bouncing along on the water, as they make low, graceful leaps together, sometimes travelling as far as 7 m in one leap. They can dive up to 200 m (660 ft) deep in search of squid and fish, especially lanternfish. Additionally,  also feeds on other prey items, such as Pacific hake, saury and mesopelagic fish.

It is estimated that a total of around 68,000 northern right whale dolphins inhabit the Pacific Ocean. Of those, around 26,000 (the geometric mean of their abundance estimates in US waters from 2008-2014) are placed into the California/ Oregon/ Washington stock for management purposes. Their minimum population estimate is around 18,600. Their abundances and distributions along the US coast do not only vary seasonally but also interannually, making the identification of population trends difficult.

Below is a list of any articles from this site, which mentions this species. Below that, is a video of the species in question. Below both of these we hope to add links which will help if you are looking to see this animal in the wild.

Hectors Dolphin

Hectors Dolphin photo by Avenue

Hectors Dolphin

Hector’s dolphin  is one of four dolphin species belonging to the genus Cephalorhynchus. Hector’s dolphin is the only cetacean endemic to New Zealand, and comprises two subspecies: C. h. hectori, the more numerous subspecies, also referred to as South Island Hector’s dolphin; and the critically endangered Māui dolphin (C. h. maui), found off the West Coast of the North Island.

It is the smallest dolphin species with adults length between 1.2 and 1.6m. The species’ range includes murky coastal waters out to 100 m (330 ft) depth, though almost all sightings are in waters shallower than 50 m (160 ft). Hector’s dolphins display a seasonal inshore-offshore movement; favouring shallow coastal waters during spring and summer, and moving offshore into deeper waters during autumn and winter. They have also been shown to return to the same location during consecutive summers, displaying high foraging site fidelity. The inshore-offshore movement of Hector’s dolphins are thought to relate to seasonal patterns of turbidity and the inshore movements of prey species during spring and summer.

There are 2 subspecies,

  • South Island Hectors dolphin – Threatened, and with a decreasing population, currently thought to number around 10,000
  •  Maui dolphin – critically endangered, population under 50.
These diverged 50,000-60,000

Below, you will see a list of articles on this subject, and below that, you will see a video on this species

Below both of these, we will add links and information (as we get it) so that you can see these dolphins if you are in the area.

Haviside Dolphin

Haviside dolphin by Joachim Huber

Haviside Dolphin

Heaviside’s dolphin is one of four dolphins in the genus Cephalorhynchus. The small cetacean is endemic to the Benguela ecosystem along the southwest coast of Africa. Heaviside’s are small and stocky with adults reaching a maximum length of 1.7m and weight of75 kg. The dolphin has a distinct black, grey and white body pattern, making it hard for it to be confused with any other dolphin found in the same waters. The head is cone shaped with a blunt beak. The dorsal fin is triangular in shape and centred in the middle of the back. The head and thorax are coloured light grey with darker patches around the eye. The dorsal fin,& fluke and dorsal cape are a dark grey to almost black with a band that extends forward from the dorsal fin to the blowhole. The underbelly is white, with bands that extend onto the lower rear of the body. Small white patches are located just behind the pectoral fins and a single white patch extends between these fins on the chest. Sexual dimorphism is minimal, however variation in the shape of the white patch covering the genital slit is distinct between genders. In males, the patch ends in a point, but in females widens out to cover the mammary slits.

Information on reproduction is limited for Heaviside’s dolphins, however they are thought to be comparable to Hector’s and Commerson’s dolphins. Females and males reach sexual maturity approximately between 5–9 years. Mating is thought to occur year-round, however individual females may only produce calves every 2–4 years. Gestation time is unknown. Maximum known lifespan is based on the oldest recorded individual at 26 years old. Levels of predation are unknown, however killer whales(Orcinus orca) are known predators and there is evidence of shark attack from body scars.
Heaviside’s have small home ranges of 50–80km as measured using satellite telemetry over 2–3 months and photographic resighting over up to 3 years.

 Some individuals have been resighted at the same location for up to 10 years. Prior to 2018, the “International Union for Conservation of Nature” International Union for Conservation of Nature (IUCN) listed the Heaviside’s as ‘Data Deficient’ however, as of 2017 the status was changed to ‘Near Threatened’, owing to improved knowledge on the species from multiple studies. Despite this, the overall population trend remains unknown, and there are many aspects of the species biology that remain to be studied. Heaviside’s dolphin is listed on Appendix II of the “Convention on the Conservation of Migratory Species of Wild Animals” Convention on the Conservation of Migratory Species of Wild Animals Memorandum of Understanding Concerning the Conservation of the Manatee and Small Cetaceans of Western Africa and Macaronesia. Memorandum of Understanding Concerning the Conservation of the Manatee and Small Cetaceans of Western Africa and Macaronesia. The Memorandum of Understanding was established in 2008 and aims to protect these species at a national, regional and global level.

Below here is a video of some of these dolphins, and below that is our usual list of articles on this species (we hope this number will increase in the near future).

Below this, we will add links for you to go and see these dolphins for yourself

White-beaked dolphin

White beaked dolphin

The white-beaked dolphin  is a marine mammal belonging 

to the family Delphinidae (oceanic dolphins) in the sub order Odontoceti (toothed whales). Their distribution is shown in the map.

The white-beaked dolphin is endemic to the cold temperate and subarctic waters of the North Atlantic Ocean, most commonly in seas less than 1,000 m (3,300 ft) deep. Due to the fact they are not fully adapted to Arctic conditions, they are more vulnerable to predators, most notably polar bears. Within this wider region, white-beaked dolphins are most commonly found in four locales: on the Labrador Shelf close to southwestern Greenland, around Iceland, off the northern and eastern coasts of Britain, and off the coast of Norway. In the Faroe Islands between Iceland and the United Kingdom the White-beaked dolphin is at risk of being hunted during drive catches of the long-finned pilot whales. They may also be incidentally trapped in the purse-sein and trawl nets of the area. There are no recognised subspecies.

The dolphin may easily be misidentified as the Atlantic white-sided dolphin, although the white-beaked is commonly found further north. The white-beaked dolphin is also typically larger, and does not have yellow streaks on its side.

Below is a video (no sound) of them filmed under water off the coast of the UK. Northern parts of the UK have populations, including Lyme bay and areas around the hebrides.

They are thought to number 100,000, so are listed as least concern.

Hourglass dolphin

Hourglass dolphin

The hourglass dolphin  is a small dolphin in the family Delphinidae that inhabits offshore Antarctic and sub-Antarctic waters. It is commonly seen from ships crossing the Drake Passage, but has a circumpolar distribution.

The species was identified as a new species by Jean René Constant Quoy and Joseph Paul Gaimard in 1824 from a drawing made in the South Pacific in 1820. It is the only to have been widely accepted as a species solely on witness accounts.

Sighting surveys were conducted in 1976–77 and 1987–88. Abundance was estimated to be 144,300 individuals, based on line transect sightings in January 1977 and January 1988 in northern Antarctic waters. This is the only abundance estimate of hourglass dolphins to date.

It is currently listed as least concern on the IUCN red list.

Below you will find a video of the species, and below this a list of any articles that have (or will be) written on this species. Under this, we will over time, hope to add links which will help you see this animal in the wild.

Irrawaddy Dolphin

Irrawaddy dolphin

The Irrawaddy dolphin is a euryhaline species of oceanic dolphin found in scattered subpopulations near sea coasts and in estuaries and rivers in parts of the Bay of Bengal and Southeast Asia. It closely resembles the Australian snubfin dolphin, which was not described as a separate species until 2005. It has a slate blue to a slate grey colour. Although found in much of the riverine and marine zones of South and Southeast Asia, the only concentrated lagoon populations are found in Chilika Lake in Odisha, India and Songkhla Lake in southern Thailand.

One of the earliest recorded descriptions of the Irrawaddy dolphin was by Sir Richard Owen. in 1866 based on a specimen found in 1852, in the harbour of Visakhapatnam on the east coast of India.

These dolphins are thought to reach sexual maturity at seven to nine years. In the Northern Hemisphere, mating is reported from December to June. Its gestation period is 14 months; cows give birth to a single calf every two to three years. Length is about 1 m (3.3 ft) at birth. Birth weight is about 10 kg (22 lb). Weaning is after two years. Lifespan is about 30 years.

There are plenty of food items that this dolphin feeds upon. They include fish, crustaceans, and cephalopods. During foraging periods, herds of about 7 dolphins will circle around prey and trap their victim. These prey entrapments occur slightly below the water surface level.

Although sometimes called the Irrawaddy river dolphin, it is not a true river dolphin, but an oceanic dolphin that lives in brackish water near coasts, river mouths, and estuaries. It has established subpopulations in freshwater rivers, including the Ganges and the Mekong, as well as the Irrawaddy River from which it takes its name. Its range extends from the Bay of Bengal to New Guinea and the Philippines, although it does not appear to venture off shore. It is often seen in estuaries and bays in Borneo Island, with sightings from Sandakan in Sabah, Malaysia, to most parts of Brunei and Sarawak, Malaysia. A specimen was collected at Mahakam River in East Kalimantan the local name comes from it.

Presence of the species in Chinese, Taiwanese, and Hong Kong’s waters has been questioned as the reported sightings have been considered unreliable, and the easternmost of ranges along Eurasian continent is in Vietnam.

No range-wide survey has been conducted for this vulnerable species; however, the worldwide population appears to be over 7,000. In India, Irawaddy dolphins are mostly found in Chilika Lake. Known subpopulations of Irrawaddy dolphins are found in eight places, listed here in order of population, including conservation status.
It is found in coastal waters of the Bay of Bengal, Sundarbans mangrove forest in the brackish-water Chilika Lake.

Conservation is hard, as this species is found in waters alongside developing nations. As such, they are working hard to food their population and give them a better life – which is generally a place where conservation is a low priority.

Of course, this can help – tourism is an increasingly large worldwide industry. As such a tourism industry, built around seeing this species could create a whole large number of extra jobs. Given the large ecotourism industry of India, it seems an easy extension to add this area.

Below this is a video of the species for your interest. Below that, is an amalgamation of any articles written on this species (we hope to add many in the future). Below that, I will add any links I make to help with you seeing the species in the wild. If you work in tourism and ever see this species, do get in touch, we would love to help people find you.

Common Dolphin

Common Dolphin

  • The most abundant cetacean in the world, with around 6 million (it should be noted that there are 1350 humans in the world, for every individual common dolphin).

Despite this fact and its name, the common dolphin is not thought of as the model dolphin (that honour goes to the bottlenose dolphin due to its popular appearances in aquaria and the media). It did, however, feature heavily in Ancient Greek and Roman art and culture, most notably in a mural painted by the Greek Minoan civilization.

It is currently the only member of the genus Delphinus. The common dolphin belongs to the subfamily Delphininae, making this dolphin closely related to the three different species of bottlenose dolphins, humpback dolphins, striped dolphins, spinner dolphins, clymene dolphin, spotted dolphins, fraser’s dolphin and the tucuxi and guiana dolphin.[5] The common dolphin was originally categorized into two different species (now thought to be ecotypes), the short-beaked common dolphin and the long-beaked common dolphin. However, recent evidence has shown that generally long-beaked dolphins of this species have originated from the short-beaked population, and therefore there is no close links between different long-beaked dolphins in any part of the world.

Currently, the common dolphin is divided into four subspecies:

  • D. d. delphis, the nominate subspecies
  • D. d. bairdii, the Eastern North Pacific long-beaked common dolphin
  • D. d. ponticus, the Black Sea common dolphin
  • D. d. tropicalis, the Indo-Pacific common dolphin

A number of fossils were erroneously placed in the same genus, but this has since been corrected. 

Common dolphins can live in aggregations of hundreds or even thousands of dolphins,though are often seen in groups numbering several hundred individuals (with subgroups consisting of 20-30 individuals). Occasionally, different groups will come together to form mega-pods which can consist of over 10,000 dolphins – quite a site to witness. Genetic studies in the Northeast Atlantic suggest that common dolphin pods generally do not consist of close kin, but rather of members that are not closely related. Unlike many delphinids, common dolphins do not live in a matriarchal society. That being said, closely related individuals are usually found in similar geographical locations fairly consistently, providing evidence that this species displays site fidelity (at least in the North-eastern Atlantic). Male common dolphins display greater site fidelity in relation to their kin than females.

Common dolphin pod structure often consists of nursery pods (which includes females and calves), bachelor pods (consisting of all males) and mixed groups of males and females, including sub-adults and calves. Genetic evidence seems to indicate that common dolphins live in fission-fusion societies, where dolphins form pods that are not necessarily stable and do not necessarily consist of related individuals. It is not known if common dolphins form lifelong bonds with other individuals  like the long-term male alliances seen in bottlenose dolphins.

There is some evidence that common dolphins use signature whistles, similar to that of the bottlenose dolphin. These whistles are believed to serve as an acoustic label the dolphin equivalent of a name.  It takes approximately 1 year for a calf to learn its signature whistle after which it remains stable for the rest of a dolphin’s life.

In South Africa, as many as 29 common dolphin signature whistle types were detected. However, it was difficult to determine if each dolphin had its own signature whistle due to the vast number of dolphins present (over 1,000) and anthropogenic background noise. Additionally, considering the vast number of dolphins present and  taking into account their feeding and diving behaviour, it appears that common dolphin signature whistles are also used for group cohesion. Another hypothesis for the function of signature whistles, is that they serve as a beacon for lost individuals.

Common dolphins sometimes associate with other dolphin species, such as pilot whales (note, not actually whales). In the Gulf of Corinth, common dolphins frequently display mixed species association, especially with striped and Rissos’ dolphins. Over one third of all dolphin sightings in the gulf consisted of mixed species associations that partially consisted of common dolphins. In mixed species associations, the ratio of striped to common dolphins ranged from 6-11:1. When Rissos’ dolphins were present (there would usually be only one or two individuals), it appeared that much of their scars were the result of interactions between striped and spinner dolphins. In much of the interactions, the Rissos’ dolphins would chase and herd the common dolphins toward the boat, while the common dolphins would try and swim under the Rissos’ dolphin. When groups of common and striped dolphins would charge at each other, the Rissos’ dolphin would chase the striped dolphins. Sometimes these interactions appeared to be playful, and at other times aggressive. Synchronized swimming and surfacing was commonly observed. These interactions take place in the deepest part of the Gulf, furthest from shore and usually consist of a total of 60 dolphins from all three species.

There have been 15 cases of common dolphin and striped dolphin hybrids being recorded. Genetic and observational evidence has demonstrated that the hybrids are fertile and are capable of not only reproducing with other hybrids, but are capable of reproducing with each of the parent species. Striped dolphins have been known to mate with other dolphins, as the Clymene dolphin is the result of hybrid speciation between striped and spinner dolphins. However, this is unlikely to happen with common dolphins, as their population in the Gulf of Corinth is too low. Common dolphins and bottlenose dolphins have been known to interbreed in captivity. There is one confirmed case of a hybrid between a bottlenose and common dolphin in Southern Spain, an important feeding ground for both species. The mother was a female bottlenose dolphin (dubbed as Billie) who has spent 10 years within a common dolphin pod. Billie was observed assisting common calves reach the surface at three different intervals and would babysit the calves after the mother went through labour. They have also been observed bow riding on baleen whales, and they also bow ride on boats. They are fast swimmers and breaching behaviour and aerial acrobatics are common with this species. They are also known to display altruistic behaviours to support injured members.

The short-beaked common dolphin is pregnant for 10 to 11 months. The new-born calf has a length of 70 to 100 centimetres (2.3 to 3.3 ft) and weighs about 10 kilograms. For the Black Sea population, weaning occurs at between five and six months, but occurs later (up to about 19 months) in other areas. Typical interbirth interval ranges from one year for the Black Sea population to three years for eastern Pacific Ocean populations. Age of sexual maturity also varies by location, but can range between two and seven years for females and three and 12 years for males. No evidence exists of any major reproductive differences between the two species. In captivity, the long-beaked common dolphin has hybridized with the common bottlenose dolphin . One of the hybrids has been bred back to a bottlenose dolphin, demonstrating such hybrids are fertile.

Find our news section below this video of a megapod of common dolphins

Striped Dolphin

Striped Dolphin

The striped dolphin (sometimes called the Euphrosyne dolphin) has been heavily researched and is found in temperate and tropical waters around the world. It has (until recently been included in the genus Stenella, but it has been shown to actually be an oceanic dolphin. According to a recent study, the closest relatives of the striped dolphin are the Clymene dolphin, the common dolphins, the Atlantic spotted dolphin, and “Tursiops” aduncus, which was formerly considered a subspecies of the common bottlenose dolphin. The striped dolphin was described by Franz Meyen in 1833.

A striped dolphin leaps in the Mediterranean Sea off Toulon

The striped dolphin has a similar size and shape to several other dolphins that inhabit the waters it does (see pantropical spotted dolphin, Atlantic spotted dolphin, Clymene dolphin). However, its colouring is very different and makes it relatively easy to notice at sea. The underside is blue, white, or pink. One or two black bands circle the eyes, and then run across the back, to the flipper. These bands widen to the width of the flipper which are the same size. Two further black stripes run from behind the ear — one is short and ends just above the flipper. The other is longer and thickens along the flanks until it curves down under the belly just prior to the tail stock. Above these stripes, the dolphin’s flanks are coloured light blue or grey. All appendages are black, as well. At birth, individuals weigh about 10 kg (22 lb) and are up to a meter (3 feet) long. By adulthood, they have grown to 2.4 m (8 ft) (females) or 2.6 m (8.5 ft) (males) and weigh 150 kg (330 lb) (female) or 160 kg (352 lb) (male). Research suggested sexual maturity was reached at 12 years in Mediterranean females and in the Pacific at between seven and 9 years. Longevity is about 55–60 years. Gestation lasts about 12 months, with a three- or four-year gap between calving.

In common with other dolphins in its genus, the striped dolphin moves in large groups — usually up to thousands of individuals in number. Groups may be smaller in the Mediterranean and Atlantic. They may also mix with common dolphins. The striped dolphin is as capable as any dolphin at performing acrobatics — frequently breaching and jumping far above the surface of the water. Sometimes, it approaches boats in the Atlantic and Mediterranean, but this is dramatically less common in other areas, particularly in the Pacific, where it has been heavily exploited in the past. Striped dolphins are known as “streakers” throughout the eastern tropical Pacific due to their behavior of rapidly swimming away from vessels to avoid collisions.

The striped dolphin feeds on small pelagic fish and squid.

Striped dolphins jumping in the Gulf of Corinth

The striped dolphin inhabits temperate or tropical, off-shore waters. It is found in abundance in the North and South Atlantic Oceans, including the Mediterranean (sightings and strandings have been reported rather recently in Sea of Marmara[6]) and Gulf of Mexico, the Indian Ocean, and the Pacific Ocean. Roughly speaking, it occupies a range running from 40°N to 30°S. It has been found in water temperatures ranging from 10 to 26 °C, though the standard range is 18-22 °C. In the western Pacific, where the species has been extensively studied, a distinctive migration pattern has been identified. This has not been the case in other areas. The dolphin appears to be common in all areas of its range, though that may not be continuous; areas of low population density do exist. The total population is in excess of two million. The southernmost record is of a stranded individual nearby Dunedin, southern New Zealand in 2017.[7]

Japanese whalers have hunted striped dolphins in the western Pacific since at least the 1940s. In the heyday of “striped dolphin drives”, at least 8,000 to 9,000 individuals were killed each year, and in one exceptional year, 21,000 individuals were killed, though since the 1980s, following the introduction of quotas, this number has fallen to around 1,000 kills per year. Conservationists are concerned about the Mediterranean population which is threatened by pollution, disease, busy shipping lanes, and heavy incidental catches in fishing nets such as long-liners, trawlers, gill nets, trammel and purse seine nets. . Recent threats include military sonar, and chemical pollution from near by harbours. Hydrocarbons are also a major concern such has PCBs (polychlorinated biphenyls) and HCB (hexachlorobenzene). These are said to give problems to additional food chains as well as doing a full body test to see what hydrocarbons may be passed down through parturition and lactation. Attempts have been made to keep the striped dolphin in captivity, but most have failed, with the exception of a few captured in Japan for the Taiji Whale Museum.

Striped dolphins are one of the targeted species in the Taiji dolphin drive hunt.

The adult striped dolphin eats fish, squid, octopus, krill, and other crustaceans. Mediterranean striped dolphins seem to prey primarily on cephalopods (50-100% of stomach contents), while north-eastern Atlantic striped dolphins most often prey on fish, frequently cod. They mainly feed on cephalopods, crustaceans, and bony fishes. They feed anywhere within the water column where prey is concentrated, and they can dive to depths of 700 m to hunt deeper-dwelling species.

 

Small numbers of dolphins live nearby Gijón

The eastern tropical Pacific and Mediterranean populations of the striped dolphin are listed on Appendix II  of the Convention on the Conservation of Migratory Species of Wild Animals (CMS), since they have an unfavourable conservation status or would benefit significantly from international co-operation organized by tailored agreements.[9]

On the IUCN Red List the striped dolphin classifies as vulnerable due to a 30% reduction in its subpopulation over the last three generations. These dolphins may also be an indicator species for long term monitoring of heavy metal accumulation in the marine environment because of its importance in the Japan pelagic food web as well as its ability to live for many years. Various other groups have signed memorandum, agreeing not to hunt them.

Conservation efforts have included having ship lines take a new path to their destination such as cruise lines as well as reduced human interaction close up. Feeding the dolphins has also become a problem, and has led to behavioural changes. This has also been suggested as another reason for mortality events.

The striped dolphin once thrived, numbering 127,880 before 1990. Since then, the population has suffered from incidental catches in fisheries. Mortality has been considered unsustainable, but there is a lack of data which hampers conservation efforts.

Various cases of stranding over the years have been a cause for alarm. With an unfavourable conservation status and the increasing amount of debris piling in the ocean every year, striped dolphin’s population is decreasing. 37 dolphins stranded off the Spanish Mediterranean coast were suffering from dolphin morbillivirus (DMV). The causes of these stranding have been changing from epizootic to enzootic.

There is a suggestion that theses strandings are caused by a virus, and that the virus is becoming more common.

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