Orca (killer whale)

The orca, commonly known as the killer whale (Orcinus orca), is, despite its descriptive common name, a member of the dolphin family. Orcas have a worldwide distribution and may be found in a variety of marine environments ranging from the equator to the Arctic and Antarctic Ocean zones, although they prefer colder waters. They are the largest members of the taxonomic family Delphinidae, which includes all dolphins. While they represent little threat to humans, orcas are known as savage ocean predators. They primarily feed on seals, birds, squid, and fish. They have also been seen using pack tactics to attack whales and even other orcas, although such attacks are uncommon. Orcas live in pods that contain up to forty individuals who belong to the same matrilineal family. They display complex social behaviors that scientists continue to study in great detail.

Background

Sailors who saw orcas hunting whales first identified them as "whale killers," a name which evolved into "killer whales" over time. They are more typically referred to as orcas by scientists. Their scientific genus name of Orcinus is derived from Orcus, a Roman god of the underworld, and a reference to their observed fierceness. The name orca refers to their body shape and means "barrel-shaped" in Latin.

They are unmistakeable in appearance. They have black and white coloring, with a black back, white underside, and a small white spot above each eye. They are thick-bodied and have a distinctive black dorsal fin that can rise up to 6 feet (1.8 meters) in height. Adults may range in length from 23 to 32 feet (7 to 9.7 meters)—about the length of a city bus—and weigh up to 6 tons (5443 kilograms). They may live up to eighty years in the wild, but tend to have shorter lifespans in captivity.

They are the largest members of the Delphinidae family, which is part of the clade—or group of organisms with a common ancestor—of oceangoing mammals that includes all species of dolphins, porpoises, and whales known as Cetacea. Members of this clade are known as cetaceans. The closest relatives to the cetaceans are hippopotami. Like other species of cetaceans, the entire life cycles of orcas occur in aquatic environments, and they have special characteristics that allow them to live underwater. The bones in their front legs have shortened into rounded flippers that quickly propel their massive bodies forward. Their nostrils—which are called blowholes—are located on the tops of their heads. These blowholes are connected to their lungs and require them to come up for air periodically. Cetaceans are able to close the blowholes and remain underwater for long periods of time.

Male orcas become sexually active in about ten to thirteen years, while females reach maturity at six to ten years. Orcas usually breed in the summer. Gestation last about seventeen months, and females generally have a calf every three to five years.

Overview

The classification of Orcinus orca is uncertain. Orcas display great variations in behavior, particularly in their travel habits and food preferences. These are known as the ecotypes of orcas. Some pods are resident, meaning they visit the same places on a regular basis. Others are transient and move longer distances to different locations. A third subgroup called offshore orcas regularly move in open waters far from the traditional coastal habitats of resident and transient populations.

The groups have different eating habits. Resident orcas primarily eat fish and squid, while transient orcas more often feed on larger prey, such as seals. Offshore orcas dine almost exclusively on schooling fish in open water. Scientists have noticed some slight physical differences between the different types of orcas, including variances in coloring, size, and fin shapes. These groups also display diverse acoustic behaviors. Resident populations have more complex dialects of sounds than transient populations. Beyond these differences, these populations have shown reluctance in interacting or interbreeding with one another, and do not migrate between the different ecosystems; they remain only within pods sharing the same ecosystem as the pod they were born into. Even beyond these differences between ecotypes, specific communities and even individual pods have demonstrated behaviors and food preferences unique to each population that are handed down between generations of orcas. As a result, scientists have begun to debate whether these three groups might be better organized into various subspecies or perhaps even into different species altogether.

Due to their distinctive coloring, intelligence, and size, they are popular but controversial attractions at aquariums and marine parks. Orcas require large habitats in the wild that cannot be simulated in an aquarium. Captive animals have shown increased levels of stress and aggression compared to their wild peers. The separation of calves and mothers is particularly problematic, as most orcas remain in their mother's company for life. Some captive animals have attacked trainers, although no fatal attacks on humans by orcas in the wild have been reported. These issues were highlighted in a 2013 documentary called Blackfish that received broad acclaim for bringing attention to the potential suffering of captive orcas. As a result, many US states and several countries have banned the keeping of these animals in captivity. Specifically, SeaWorld, in Florida, announced they would end their orca breeding program and theatrical shows in 2016; however, the orca shows continued into 2024. Captive breeding of orcas is on the rise in China.

Orcas have been facing growing threats in the wild. Studies have determined that as apex predators—that is, animals at the top of their ecological food chains—orcas are among the most contaminated marine animals in the world. This is the result of heightened levels of pollution affecting both their environments and prey animals. When orcas eat infected prey, the toxins in these animals accumulate in the bodies of orcas at greater concentrations than in the animals they hunt. Pollution has been shown to reduce their immune systems and lower their rates of reproduction. They also face threats from increased boat traffic that can potentially disrupt their communities and injure animals.

Bibliography

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