Dusky Dolphin

Dusky Dolphin

Fitzroy’s dolphin

Kingdom
Phylum
Subphylum
Class
Order
Infraorder
Family
SPECIES
Lagenorhynchus obscurus
Population size
Unknown
Life Span
18-25 yrs
TOP SPEED
37 km/h
WEIGHT
70-85 kg
LENGTH
1.7-2 m

Originally named as 'Fitzroy’s dolphin' by Charles Darwin, this animal is a comparatively small and compact species of dolphin. The back and tail of the Dusky dolphin are dusky bluish-black in color, exhibiting a dark streak, which stretches diagonally across the flanks to the tail. The animal is a close relative of the Pacific White Sided dolphin. Nevertheless, scientific studies have found a number of differences between these two, which allows to classify them as two separate species. One of the most identifying features of the Dusky dolphin is the lack of beak as well as the evenly sloping head from the blowhole to the tip of the snout. Both males and females have a dorsal fin, which is more curved in males. Both sexes are almost the same in size.

Distibution

These dolphins occur off the coast of South America (though they have also be seen close to Argentina and around the Falkland Islands), South-Western Africa and New Zealand. The animals typically inhabit warm to cool temperate waters and can be found at coastal regions.

Dusky Dolphin habitat map

Climate zones

Habits and Lifestyle

Behavior and habits of these dolphins greatly depends of species as well as area of habitat. As a general rule, Dusky dolphins remain close to the shore. By day, the animals rest in small groups of 10 - 20 dolphins. At dusk, they travel in these groups away from the shore in order to feed, gathering into large pods of up to 1.000 dolphins, consisting of both males and females. They usually prey in these large groups, encircling shoals of fish. After feeding, these highly sociable and playful animals can often be observed grooming and leaping together. Then, they regroup into smaller pods, returning to the seashore, where they rest. These dolphins communicate through squeals, whistles, clicks and squeaks, emitting loud calls, heard from a distance of up to 2 miles, when the animals are out of the water.

Group name

Diet and Nutrition

As a carnivorous (piscivorous) species, Dusky dolphin consumes a wide variety of aquatic species, including squid, schooling shrimps, anchovy and fish.

Mating Habits

MATING BEHAVIOR
REPRODUCTION SEASON
spring
PREGNANCY DURATION
11 months
BABY CARRYING
1 calf
INDEPENDENT AGE
3 years
FEMALE NAME
cow
MALE NAME
bull
BABY NAME
calf

These dolphins have polygynandrous (promiscuous) mating system. Usually, males of this species fiercely defend their mating rights, competing with each other. Mating season occurs in spring while gestation period lasts for 11 months, yielding a single baby, most often between June and August. The female suckles the offspring, until, at around 18 months old, the young learns to hunt with its mother. During the first 3 years of their lives, young dolphins usually remain with their mother, after which they leave the female, who is able to mate again. Leaving, young dolphins find their own pods with males, often joining bachelor groups. They become sexually mature at about 4 - 5 years old.

Population

Population threats

Currently, the Dusky dolphins greatly suffer from commercial fishing, disturbing their natural habitat. On the other hand, these dolphins compete for food with fishermen (particularly, for shoaling fish). Moreover, they are often caught in vast nets. In certain areas of their habitat such Peru, these dolphins are hunted for their meat. The animals are also frequently hit by boats, which causes severe injuries.

Population number

According to the IUCN Red List, the total population size of the Dusky dolphin is unknown. However, there are estimated populations of the species in the following areas: Patagonian cost - 7,252 individuals; between Punta Ninfas and Cabo Blanco (Argentina) - 6,628 individuals. Currently, Dusky dolphins are classified as Data Deficient (DD) on the IUCN Red List.

Fun Facts for Kids

  • Dusky dolphins release air and water from their lungs through a special blowhole, found on the top of their heads. When diving, they can remain submerged for up to 90 seconds at a time.
  • Noticing a boat, Dusky dolphins often swim up in order to bow-ride.
  • These dolphins feed both at the surface and at the bottom of water - a factor, that makes them exceptionally successful hunters. They have been observed hunting in groups of up to 300 individuals, preying on larger schools of fish. They can also change their hunting techniques on occasion. When hunting, they communicate with each other in order to make sure they catch enough prey to provide themselves.
  • During nursing periods, females and their offspring can be seen in areas with shallow water, where they rest, take care for their babies as well as protect them from threats.
  • According to a common opinion, offspring of Dusky dolphin are not born with acrobatic skills. Instead, they acquire these abilities by observing performances of adult dolphins.

References

1. Dusky Dolphin Wikipedia article - https://en.wikipedia.org/wiki/Dusky_dolphin
2. Dusky Dolphin on The IUCN Red List site - http://www.iucnredlist.org/details/11146/0

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