False Killer Whale

## Description

The false killer whale (Pseudorca crassidens ) is a species of oceanic dolphin that is the only extant representative of the genus Pseudorca. It is found in oceans worldwide but mainly frequents tropical regions. It was first described in 1846 as a species of porpoise based on a skull, which was revised when the first carcasses were observed in 1861. The name "false killer whale" comes from the similar skull characteristics to the orca (Orcinus orca ), which has been known as the killer whale.

The false killer whale reaches a maximum length of 6 m (20 ft), though size can vary around the world. It is highly sociable, known to form pods of up to 50 members, and can also form pods with other dolphin species, such as the common bottlenose dolphin (Tursiops truncatus ). Further, it can form close bonds with other species, as well as partake in sexual (including both heterosexual and homosexual) interactions with them. Conversely, the false killer whale has also been known to feed on other dolphins, though it typically eats squid and fish. It is a deep-diving dolphin, with a maximum recorded depth of 927.5 m (3,043 ft); its maximum speed is around 29 km/h (18 mph).

Several aquariums around the world keep one or more false killers, although the species' aggression towards other dolphins makes it less desirable. It is threatened by fishing operations, as it can become entangled in fishing gear. It is drive hunted in some Japanese villages. The false killer whale has a tendency to mass strand given its highly social nature, with the largest stranding consisting of 805 beached at Mar del Plata, Argentina. Most of what is known of this species comes from examining stranded individuals.

## Appearance

The species is so called due to having similarities with the orca of killer whale. Thus, the False killer whale has similar shape, number of teeth as well as skull shape and size as the killer whale. The False killer whale is actually not a whale but a dolphin. The animals have a whitish marking on their chest between the flippers. In addition, some individuals exhibit pale grey patches on their heads. In general, however, the coloration of their body is nearly entirely grey to black.

## Distribution

False killer whale occurs in tropical and sub-tropical waters of the Atlantic, Pacific and Indian Oceans. Usually the animal inhabits the open ocean, but it can occasionally be observed around oceanic islands like Hawaii. In addition, the False killer whale has been seen in semi-enclosed areas such as the Mediterranean.

## Behavior

These animals normally gather into pods, which can be very small (including just a few whales) and rather large (containing hundreds of individuals). These large pods of False killer whales consist of smaller groups of 18 individuals on average. The False killer whales are highly social animals, just like Pilot whales. These playful animals are identified due to being one of a few large mammals that tend to leap out of the water over the wake of a ship. They favor riding bow waves of various vessels, preferring faster-moving ships. False killer whales use a wide variety of clicks and whistles as a form of communication. They also use echolocation, interacting through sounds, which help them detect prey and sense the ocean waters. They generally hunt by day and night.

## Diet

The diet of this carnivorous (piscivorous and molluscivorous) animal considerably depends on the area of habitat, usually consisting of squid as well as various species of pelagic fish, tuna, wahoo and mahi mahi. The False killer whale is also known to consume smaller dolphins, and can prey on humpback and sperm whales on occasion.

## Reproduction

The species is known to have polygynandrous (promiscuous) mating system, where both males and females mate with multiple mates. The False killer whales mate throughout the year with peak periods, occurring from January to December and in March. Gestation periods range from 11 to 16 months. Females give birth to a single calf, after which they do not breed for about 6.9 years on average. Soon after birth, the baby is able to swim. The young is weaned gradually during the period of 18 - 24 months. Even after weaning, calves often remain in the same group with their mother. Males of this species are sexually mature by 8 - 10 years old, whereas females reach maturity within 8 - 11 years old.

## Population

### Population threats

Currently, the False killer whale suffers from sharp global decline in the number and size of prey species it consumes. On the other hand, the species is threatened by persistent organic pollutants, which, accumulating in high levels, may expose the animal to the risk of disease susceptibility. In addition, fisheries are another serious threats to these animals: along with being caught on hooks and drownes, False killer whales occasionally take bait or catches from longlines, causing retaliatory culling. Other notable concerns to the False killer whale population include loud sounds of navy sonar and seismic exploration as well as other human-made sound, which can be very harmful to these animals.

### Population number

According to the IUCN Red List, the global population size of the False killer whale is unknown. However, there are estimates of its population is specific areas: in the coastal waters of China and Japan - 16,000 whales; in the northern Gulf of Mexico - 1,038 whales; in the U.S. (Hawaii) - 268 whales; in the eastern tropical Pacific - 39,800 whales. Currently, False killer whales are classified as Data Deficient (DD) on the IUCN Red List.

## Fun Facts for Kids

Due to the formidable-looking and conical-shaped teeth, this animal is given the scientific name 'crassidens', meaning 'thick-tooth'.

This highly social animal is known to share food and develop long-lasting relationships with conspecifics as well as with humans.

When hunting, they move very quickly, sometimes catching fish while entirely leaping out of the water.

Females of this species often feed their offspring, holding a fish in their mouth while the calf eats the prey.

There have been known single cases of a False killer whale and Bottlenose dolphin mating and yielding a hybrid offspring called "wolphin".

According to studies, the False killer whales are active swimmers. They are known to leap out of water and perform flips on special occasions such as social events.

A False killer whale eats as much food as up to 5% of its body weight per day.