The Orca, also known as the "killer whale" is one of the toothed whales and the largest member of the dolphin family. They have long, round bodies with big dorsal fins in the middle of their back. Their bodies are black with white patches underneath and near their eyes. These distinctive patterns help to camouflage them when they are searching for food. In newborns, the white parts of their body have an orange tinge.
Killer whales are considered a cosmopolitan species and occur in all oceans, from Antarctic and Arctic regions to tropical seas. They also inhabit many inland or partially-enclosed seas, such as the Gulf of California, Gulf of Mexico, Mediterranean, Arabian Gulf and Red Sea. They usually prefer water that is 20 to 60 meters deep, but also travel through shallow waters along the coast or dive as deep as 300 meters when searching for food.
Killer whales are highly social animals; they are active during the day and sleep at night. They travel in pods of between 3-50 individuals, led by females. They establish social hierarchies. Individuals in pods are usually related to each other and consist of about 20% adult males, 20% calves, with the rest being females and young males. They have limited dispersal from their maternal pod. These whales may share prey and seldom leave the pod for longer than a few hours. Pod members learn skills through apprenticeship, such as hunting and parenting. Killer whales are very vocal animals and communicate with each other using whistles and clicks via echolocation, and through physical behavior such as breaching, slapping their tail or flippers, and ‘spyhopping’, when they lift their head above the water.
Killer whales are predators at the top of the food chain and prey upon a wide range of large prey including seals, smaller whales and dolphins, sea lions, different fish, sharks, squid, octopi, sea birds, sea turtles, sea otters, and river otters.
Killer whales are polygynandrous, with both males and females having multiple mates throughout a breeding season. They do not interbreed within their own pod but with individuals from another pod. Mating occurs at any time throughout the year, usually in summer. After gestation of 15 - 18 months, a female gives birth to one calf. The young will feed from their mothers for as long as 2 years, but at 12 months will start to eat solid food. Mothers teach their calves how to hunt and they include them in their pod's social network. Calves stay with their birth pod after they gain independence. Females are sexually mature when they are 15 years old and will give birth once every 5 years until the age of 40. Males are sexually mature by about 15, but usually do not reproduce until 21.
The greatest threat to these whales comes from degradation and disturbance of their habitat. Being at the top of the food chain, the Killer whale is vulnerable to contaminants accumulating in its tissues, such as the high levels of PCBs (polychlorinated biphenyls) found in some populations, with potentially negative impacts on its reproduction and survival. Extensive oil spills can affect these animals, either directly or indirectly, in that it reduces the number of their prey. Disturbance by boats and other underwater noises caused by humans can affect their behavior, disrupt social calls and echolocation, and impact on the ability of Killer whales to effectively forage in places where whale-watching is increasingly popular. Boat traffic also increases the risk of injuries from collisions.
According to the IUCN Red List, the worldwide population of the Killer whale is estimated to be around 50,000 whales. This species is currently classified as Data Deficient (DD) on the IUCN list of threatened species.