Orca killer whales

Orca killer whales

Size and Weight:
Newborn 2.1 - 2.5 m (7 - 8 1/2 ft), 180kg (395 lb)
Adult 5.5 - 9.8 m (18 - 32 1/4 ft), 2.6 - 9 tons

Identification:
Males are longer and bulkier than females, average length 7.3m (24ft) as compared to females 20 1/4ft, males also have much taller and straighter dorsal fins.

Diet:
Residents: Mostly salmon.
Transients: Seals, Sea Lions, other whales, birds, & Penguins.

Common/Scientific Names
Its common name, recognized by many people, is killer whale (originally called "whale killer" by Spanish whalers). Its scientific name is Orcinus Orca. The Romans called it "Orca," meaning "demon from hell".

Body Size and Mass
Males can grow up to approx. 32 ft. in length and can weigh in at 10 tons. Females can grow up to approx. 27 ft. in length and can weigh in at 7 tons. Newborn calves are approx. 7 ft. in length and weigh in at almost 400 lbs. upon birth.

Habitat and Distribution

Distribution
Killer whales inhabit all the oceans of the world. They are most numerous in the Arctic, the Antarctic, and areas of cold-water upwelling. Killer whale distribution is limited by seasonal pack ice.

Habitat

Killer whales are found in both the open ocean and coastal waters.

Migration

Migration of fish and other prey accounts for movements of killer whales to and from certain areas.


Population

The worldwide population of killer whales is unknown. Specific killer whale populations in a few areas have been estimated. For instance, in some areas of the Antarctic alone, their numbers are estimated at about 180,000. Killer whales are not endangered. Most researchers agree that regional groupings of killer whales exist. Analysis of killer whale call patterns has demonstrated substantial differences between the sound repertoires of different pods. In the future, analyzing biochemical and chromosomal characteristics may help define genetic relationships among pods and regional populations of killer whales. Call patterns, body shape, and coloration are currently used in identifying separate killer whale populations.

Researchers have recently learned to recognize many individual killer whales from photographs, especially of their dorsal fins. Photo-identification promises to be an important new research tool for studying various aspects of cetacean biology, including movements, reproduction, behaviour, and population dynamics. Photo-identification has the potential to document the lives of individual whales in great detail. Researchers take photographs when the whale rises highest out of the water as it breathes normally and exposes the most markings on the back and dorsal fin. Studying the photos, these researchers must be skilled at recognizing subtle differences in whales' body appearance. The features they use for identification include dorsal fin shape and relative size, pigmentation patterns, scars, deformities, detail of tail fluke edges, encrustations, and blemishes. Researchers can identify individual killer whales by recognizing differences in the appearance of the dorsal fin and saddle.

In the North Pacific, researchers categorize pods of killer whales into transient-type whales and resident-type whales, based on physical and behavioural characteristics. The size of resident pods varies from as few as 5 to as many as 50 individuals. Transient pod size varies between 1 and 7 individuals. Resident pods tend to travel within specific ranges while transient pod ranges are unpredictable. In the Pacific Northwest, there are two communities of resident pods: a northern community and a southern community. Food preferences of resident and transient pods differ. Resident pods eat a wide variety of fish and rarely seek out marine mammals. Transient pods primarily eat marine mammals and will occasionally eat fish. Research has shown that resident pods have a wider sound repertoire than transient pods.


Reproduction & Gestation

Birth Seasons
Calves are born throughout the year. Gestation is about 17 months.

Frequency of Birth
Based on limited data collected from populations at sea, a female may bear a calf every five years.

Calving

Calves are born in the water. Deliveries can be either tail-first or headfirst. The umbilical cord snaps during or soon after delivery.

Calf at Birth
The calf is about 8 ft. (2.4m) long and weighs about 300 to 400 lb. (131-181 kg).

The light areas of some young killer whales may be creamy white to lemon yellow rather than white. This color usually turns white by the age of one year. In the first few days after birth, the dorsal fin and tail flukes gradually stiffen.

Nursing
The calf suckles from nipples concealed in abdominal mammary slits. Killer whale calves begin nursing several hours after birth. Calves nurse below water, close to the surface. The mother glides in a horizontal position with her tail arched, and the calf swims on its side with its mouth on the right or left mammary gland. Calves nurse for about 5 to 10 seconds at a time, several times an hour, 24 hours a day. The mother's milk is very rich so that the baby rapidly develops a thick, insulating layer of blubber. The fat content of the mother's milk increases as the calf develops. It ranges from about 28% to 48%. A calf may nurse for 12 months. A mother killer whale stays close to her calf and attentively directs its movements. The baby swims close to its mother and can be carried in the mother's "slip stream," a type of hydrodynamic wake, which develops as the mother swims. This helps the baby swim with less energy and enables the mother and calf to keep up with the pod. While most maternal behaviour is probably instinctive, first-time mothers are inexperienced at nursing their calves. The experience level of some first-time pregnant females is increased through training procedures that teach them to respond to nursing behaviour. To nurse, a calf swims on its side and suckles from nipples concealed in abdominal mammary slits.


Calf Development
Killer whale breeding colonies in marine zoological parks continue to provide a unique opportunity to observe and quantify aspects of their biology. A killer whale calf's upper teeth erupt at about two to four months. The lower teeth erupt at about three to five months. Calves begin to take a few fish at about three to four months. They eat solid food consistently at about four to five months. By the age of one year, calves can eat 50 to 60 lb. (23-27 kg) of herring, smelt, and squid every day. Calves grow about 2.6 ft. (80 cm) during their first year, and about 2.2 ft. (67 cm) during their second year. Calves can vocalize within days of birth, but sound production is shaped with age. In studies, scientists have determined the following. Vocal behaviour is not predetermined. Calves learn, during the course of development, which calls to make and under what circumstances. Calves are most likely to develop calls like those of their closest associates (usually the mother). Stereotyped calls develop between 5 months and 1 year of age.

Sexual Maturity

Studies of killer whales in marine zoological parks suggest that females become sexually mature when they reach about 15 to 16 ft. (4.6-4.9 m), at about 6 to 10 years. Males become sexually mature when they reach about 18 to 20 ft. (5.5-6.1 m), at about 10 to 13 years. Comparably collected field data is not available.

Mating Activity
Females come into estrus or "heat" several times during the year. Breeding may occur in any season, but is most common in summer. In the North Atlantic, mating seems to peak in October and November; in the western North Pacific, mating seems to peak between May and July.



Behaviour & Eating Habits

Food Preferences and Resources
Killer whales are the top predators in the ocean. They are active predators. Opportunistic feeders, their diet varies from one region to another. In the Antarctic, killer whales eat about 67% fishes, 27% marine mammals, and 6% squids. Killer whales in the Bering Sea (near Alaska) eat about 65% fishes, 20% squids, and 15% marine mammals. Food preferences of resident and transient pods in the North Pacific differ. They eat a variety of fish, including salmon, cod, flatfish, hake, herring, and smelt. They also eat other marine mammals and seabirds. Killer whales prey on mysticete and odontocete whales, seals, sea lions, walruses, and occasionally sea otters and penguins.

Food Intake
Adult killer whales eat approximately 3% to 4% of their body weight in food per day; fully weaned calves can eat up to approximately 10% of their body weight during growth periods.

Methods of Collecting Food

Much like packs of wolves or prides of lions, killer whales often hunt cooperatively in pods for food. They work together to encircle and herd prey into a small area before attacking.

Killer whales may slide out on sand bars or ice floes to pursue prey. They may also surface under ice floes to knock prey into the water. Killer whales don't chew their food. They swallow their food whole or tear it into large chunks.

Social Structure

Killer whales live in groups called pods. The size of a pod usually varies from less than 5 to about 30 individuals. A pod is a cohesive long-term social unit. A pod usually consists of males, females, and calves of varying ages. Several smaller pods may join occasionally to form larger groups of 50 or more individuals called herds or aggregations. There is an occasional exchange of members between pods, especially during breeding season.

Social Behaviour
Killer whales in a pod appear to establish strong social bonds. Behavioural studies suggest that certain animals prefer associating with one another. As with most species, there is a social hierarchy within a group of killer whales. This social hierarchy is female-dominant. The animals may rank themselves and establish dominance by slapping their tails against the water, head butting, jaw snapping, and various other vigorous postures and gestures. Killer whales often hunt together.

Individual Behaviour
Killer whale behaviour includes spy hopping (hanging vertically in the water with the head partially above water), breaching (jumping clear of the water and landing on the back or side), lob tailing (slapping the tail flukes on the surface of the water), and pec slapping (slapping a pectoral

Stranding

Killer whales have been known to mass strand. As with other whales, the reason for these strandings is unknown. Stranding is not the same as intentional beaching for pursuing prey.

Interaction With Other Species

Other marine mammals, such as minke whales, Dall's porpoises, and seals, have been observed swimming with killer whales, but they may be prey of killer whales at other times.

Hearing

Killer whales have a well-developed, acute sense of hearing. The auditory cortex of the brain is highly developed. Killer whales have responded to tones within the frequency range of about 0.5 to 100 kHz. (The average hearing range for humans is about 0.02 to 17 kHz.). Peak sensitivity is about 15 kHz.

Sound Reception
Most sound reception, or hearing, probably takes place through the lower jaw. A killer whale may also receive sound through soft tissue and bone surrounding the ear. The fat filled lower jawbone conducts sound waves through the jaw to bones in the middle ears. The fat-filled lower jawbone appears to conduct sound waves through the jaw to bones in the middle ears. The lower jawbone of toothed whales broadens and is hollow at the base, where it hinges with the skull. Within this very thin, hollow bone is a fat deposit that extends back toward the auditory bulla (ear bone complex). Sounds are received and conducted through the lower jaw to the middle ear, and then to hearing centers in the brain via the auditory nerve. A killer whale does have small external ear openings, a few inches behind each eye. Each opening leads to a reduced ear canal and an eardrum. Some scientists believe that killer whales receive sound through these openings. Other scientists believe that a killer whale's external ear openings are nonfunctional. Foam surrounds the ear bone on all sides. This foam contains air. Air stops sound waves traveling through water and living tissues. Many scientists believe that this foam acoustically isolates the ears; enabling a killer whale to tell which direction a sound comes from.

Eyesight
Killer whales have acute vision both in and out of the water. The eyes, about the same size as the eyes of a cow, are on each side of the head, just behind and above the mouth. Glands at the inner corners of the eye sockets secrete oily, jellylike mucus that lubricates the eyes, washes away debris, and probably helps streamline the eyes as a killer whale swims. This tear like film may also protect the eyes from infective organisms.

Tactile

Features of the brain indicate that a killer whale's sense of touch is well developed. Killer whales' skin is sensitive to touch.

Taste

Little is known about a killer whale's sense of taste. They do have taste buds, although they haven't been well studied.

Smell

Olfactory lobes of the brain and olfactory nerves are absent in all toothed whales, indicating that they have no sense of smell.

 

 
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