Introduction
The killer whale (Orca) is the largest member of the dolphin family and a very fierce predator. Killer whales have a diverse diet that includes birds, fish, squids, and other sea mammals such as seals, sea lions, and whales. Individual populations of orcas specialize in specific types of prey. For example, some populations eat fish only while others eat bigger organisms such as seals and baleen whale calves. Their predatory nature is aided by their long and strong teeth that can be four inches long. Orcas inhabit all seas and oceans regardless of the region. Killer whales belong to a class of predators referred to as apex predators because no other animal preys on them.
Appearance and morphology
A killer whale grows to a maximum length of 9 meters and has a distinctive white and black coloration (Markle 8). The back is black and the belly is white. The saddle patch behind the dorsal fin is grey and there is a white patch behind the eyes. The dorsal fin is curved towards the anterior end, the blow is small and puffy, and the tail fluke has a black top (Baird and Baird 35). Calves have a yellow tint that gradually changes to white as they grow older. Adult killer whales have a distinct appearance in regard to skin coloration and the size of tail flukes. However, younger whales can be easily confused with other sea mammals.
Types
Research conducted on marine mammals has revealed different types of killer whales (ecotypes) with varied prey preferences, behaviors, and feeding habits (Markle 9). Research has shown that different ecotypes rarely interact and do not interbreed. The types found in the Northern Hemisphere include resident orcas, transient orcas, offshore orcas, North Atlantic Type 1, and North Atlantic Type 2 (Baird and Baird 37). Resident orcas eat fish and squid and inhabit areas neighboring large fish populations. Transient orcas eat large sea mammals such as seals, whale calves, and minke whales. They live in families of small groups and form close associations with their relatives (Markle 12).
Offshore orcas are very rare because they live far from land and their prey preferences are unknown. North Atlantic Type 1 has a wide variety of prey preferences and home ranges. North Atlantic Type 2 whales feed on other sea mammals because of their large and sharp teeth. In the Southern Hemisphere, the types of killer whales found there include type A, B, C, and D (Baird and Baird 37). Type whales are large while type B is comparatively smaller. Type C is the smallest of the four types.
Hunting and communication
Killer whales hunt in pods that use different hunting techniques to catch prey (Mann 127). The pods are family groups that comprise about 40 whales and specialize in different prey types depending on their adaptations (Baird and Baird 45). For example, resident pods prey on fish while transient pods prey on whales and seals. The hunting habits are likened to those of wolves because they work together to catch prey (Markle 16).
Killer whales communicate using a variety of sounds. Each pod has a distinctive sound that sets it apart from others. The sounds they make travel underwater and reveal their location when they hit an obstacle. Members of each pod can recognize the sound of other family members and use it to determine their location (Baird and Baird 46). Killer whales produce three types of sounds namely, clicks, pulsed calls, and whistles. Clicks are used for navigation, hunting, and social interaction (Mann 128). Members of a resident pod use similar voices that include specific numbers of repetitive calls. Newborns learn their pods or matriline’s dialect from their mothers.
Life cycle
The average maturity age for female killer whales is 10 years and 15 years for males. Females’ peak fertility age is 20 years and can breed even at the age of 40 even though after this age, fertility levels decline significantly (Baird and Baird 56). Mating takes place between males and females from different pods. This interaction is important because it prevents inbreeding between members of the same family. The gestation period is between 15 to 18 months and mothers give birth to offspring once every five years (Estes 38). Birth usually occurs during the winter even though in certain pods it can take place during any season.
The first seven months of the offspring’s life are critical because the mortality rate is very high. Weaning is done when baby whales are one year old and stops when they attain the age of 2. Research has shown that the care of young ones is done by both genders of the killer whale. Males can only reproduce when they attain the age of 21 and their average lifespan is 29 years (Baird and Baird 58). The lifespan of captive killer whales ranges from 25 to 40 years.
Range and habitat
Killer whales are marine mammals that inhabit both ocean and sea (Markle 24). It is difficult to determine which of the two habitats is more favorable. However, research has shown that they prefer habitats located in higher latitude areas and coastal regions (Estes 39). In seawater, they are found in waters with depths of more than 65 feet and move to shallow waters only when hunting. Killer whales like both temperate and cold glasses of water.
They are rarely found in subtropical and tropical regions. Scientific surveys have revealed that certain regions have higher densities of killer whales than others. The highest population of orcas is found in the northeast Atlantic, the north pacific, the Southern Ocean, and the Gulf of Alaska. They are common in the eastern Pacific and North Atlantic Ocean (Estes 44).
They are also found in offshore regions and tropical waters. For example, they have been seen in the Mediterranean, the Gulf of Mexico, the Indian Ocean, the Arabian Sea, and Seychelles. Killer whales inhabit all regions of the earth. However, they are rare in lower altitude areas (Mann 128). Their habitat range is wide because they have been found in freshwater rivers in certain areas of the world.
Feeding
As mentioned earlier, different types of killer whales have specialized prey preferences. They are apex predators, hunt in groups, and utilize different hunting techniques to catch prey. Their food sources include fish, cephalopods, sea turtles, sea lions, sea birds, whales, and other sea mammals (Estes 47). Prey specialization enhances the survival of different types of killer whales because of low competition. Killer whales that eat mammals do not eat fish while those that eat fish do not eat mammals.
Behavior
The behavior of killer whale comprises activities such as resting, foraging, socializing, traveling, breaching, and tail-slapping (Mann 129). One of the reasons why killer whales are used in entertainment is because of their breaching behavior that involves jumping out of the water and slapping their tails. The roles of breaching and tail-slapping include communication, courtship, and play (Estes 53). In addition, they are used to dislodge parasites from the body surface. Another common behavior is spyhopping. It involves viewing the surrounding areas by holding the head above the water surface for a certain period.
Social structure
Killer whales form complex family groups that are seen in humans and animals such as elephants (Mann 129). Resident killer whales that inhabit the eastern North pacific live with their mothers that are heads of families (matrilines). The eldest female is the matriarch and takes care of the other whales in individual families that comprise about 6 members (Mann 129). Members of a family only separate during mating or foraging. A pod is an aggregation of several matrilines and includes several members.
Conclusion
The killer whale is the largest sea mammal and a fierce predator that feeds on other sea mammals. They inhabit all regions of the world including the Arctic and Antarctic regions. There are several types of killer whales that are differentiated by their prey preferences and habitats. Killer whales are social and live in families that are usually headed by elderly females. Their food sources include fish, sea birds, seals, and winkle whales. Prey preference and specialization lower competition between different types. They communicate using three types of sound namely, whistles, clicks, and pulsed calls. Killer whales are the largest in the dolphin family and inhabit both seas and oceans.
Works Cited
Baird, Robert, and Robin Baird. Killer Whales of the World: Natural History and Conservation. MBI Publishing Company LLC, 2006.
Estes, James. Whales, Whaling, and Ocean Ecosystems. University of California Press, 2006.
Mann, Janet. Cetacean Societies: Field Studies of Dolphins and Whales. University of Chicago Press, 2000.
Markle, Sandra. Killer Whales. Carolrhoda Books, 2004.