Tag Archives: Orcas

Killer Whales

Orca 09-13-09

Killer whales (or orcas) are not really whales but are the largest members of the dolphin family, Delphinidae. With their brilliant black and white markings, they are easy to identify and distinguish from other whales. Killer whales exhibit sexual dimorphism, meaning males and females look very different from each other. Adult males in the North Pacific may grow to a length of 27 ft. (8.2 m) and weigh as much as 13,300 lbs. (6,000 kg), while females grow to an average length of 23 ft. (7 m) and weigh about half as much as a large male. Also, a male’s dorsal fin may reach 6 ft. (2 m) in height, while a female’s rarely exceeds 3 ft (1 m).

Photo by Bob Munsey
Photo by Bob Munsey

Killer whales are mostly black on their dorsal surface and white on their ventral surface. They have an elliptical white patch on the lateral side of each eye and large white patches that extend from the ventral surface onto the flanks. There is a usually a gray or white saddle area behind the dorsal fin, and this marking varies from one individual to the next, making it useful for identification.

Killer whales are second only to humans as the most widely-distributed species of mammal. They can be found in all oceans and most seas, but they are most common in coastal, temperate waters. They are apex predators and prey on a variety of vertebrates and invertebrates. They are known to prey upon over 140 species, and they are the only cetaceans that routinely prey upon marine mammals, with documented attacks on 50 different species.

Orcas in Amook PassIn the northeastern Pacific, three distinct ecotypes of killer whales have been identified. Resident killer whales mainly eat fish, while transients concentrate on marine mammals. The third type known as offshores have not been well studied, but it is thought they primarily feed on fish, including sharks. All three types are genetically distinct, suggesting there is little or no breeding between the types, and it is possible they should be considered separate subspecies. There are differences in size, coloration and physical appearance between the three types, as well as differences in hunting strategies. Transients forage in smaller groups than residents, and transients travel silently when hunting, while residents produce a variety of clicks, whistles, and pulsed calls for echolocation.  Killer whale populations in other regions of the world may also specialize in their feeding habits, but more research is needed to be certain. Killer whales often work together to catch fish or marine mammals, and when preying on large animals such as whales, they may attack as a pack, tearing apart the whale from several angles.DSC_0155

Killer whales are very social and usually travel in groups or pods of up to 20 individuals, and members of a pod are linked to each other by maternal descent. Females become sexually mature at 15 years of age on average, and they may give birth at intervals of three to eight years. Killer whales can breed all year, and the gestation period averages 17 months. Whales in a pod often work together to care for the young, and young females will help mothers care for their babies. It has been estimated that males live at least 50 years on average, while females may live 80 years.

Killer whales are highly vocal and use sound for socialization as well as for echolocation.Scientists have learned that call repertoires of resident pods have features that are distinct to that pod, forming group-specific dialects. A second pod may share some of the call repertoire of the first pod, but other sections will be distinct to the second pod.   The amount of similarity of call repertoires between pods reflects the degree of

Photo by Bob Munsey
Photo by Bob Munsey

relatedness between the pods. Killer whales socialize in a number of other ways too, including acrobatic aerial behaviors, such as breaches, spy hops, flipper slaps, tail lobs,and head stands. I’ll discuss more about these various behaviors next week.

Killer whales are always a treat to watch. We only see them a few times a year deep inside Uyak Bay, and it is always exciting. I’ve seen a large group of killer whales herding fish, a small pod trying to catch harbor seals hauled out on an island, and one killer whale with a large octopus in its mouth. Sometimes they want nothing to do with us, and other times, they swim alongside our boat leaping out of the water and diving beneath us. This summer we saw a large bull swimming by himself in water so shallow he couldn’t submerge his tall dorsal fin. He was in an area near a salmon stream, and we assumed he was feeding on salmon.

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Have you had any experiences with killer whales? If so, please leave a comment to tell us about it. Also, if you have any questions, don’t hesitate to ask, and for anyone who is a lover of true crime stories, please visit my home page and sign up for my monthly Mystery Newsletter!

Whales

Fin whales in Uyak Bay
Fin whales in Uyak Bay

Whales have been on my mind lately; probably because I’ve seen some nearly every time I’ve gone for a boat ride this summer and fall. Zooplankton and schools of small fish have swarmed the bay all summer and fall, providing abundant food for everything from larger fish, gulls, eagles, other birds, harbor seals, sea lions, and of course whales. I’m certain that if I jumped in my boat right now, within in minutes, I’d be in the midst of several huge fin whales, whose 18-ft. tall exhalations surpass any choreographed water-fountain show in Las Vegas. I’d probably also see two or three humpbacks waving their tail flukes in the air and perhaps leaping out of the ocean and slapping their large pectoral fins and tail flukes on the water.

I’ve also been thinking about whales, because that is the chapter I’m working on for my book on the wildlife of Kodiak Island. While I love whales, writing about them has been an arduous process, since little is known about many species, and I must draw bits and pieces of information from an array of sources. This painstaking research, though, has provided me with a better understanding of these huge, intelligent creatures, so I thought I would write a few posts about them. I will focus on the whales that can be seen near Kodiak Island, and I will admit that I have not seen all these species, because either they migrate past the island and do not enter the deep bays, or they spend their lives off shore. There is also another, darker reason for me to write about the whales near Kodiak Island. This summer more than 30 whales (mostly fin and humpback) died near Kodiak, and biologists are scrambling to discover the cause.

Whale species commonly found near Kodiak include fin whales, the second largest species of whale; sei whales, the third largest species of whale; humpbacks; Minke whales; and Orcas, or killer whales (although Orcas are actually dolphins, not whales). Gray whales migrate past Kodiak on the way from their breeding and birthing areas near Mexico to their northern feeding grounds, and blue whales, the largest species of whale, can be found off shore in the Gulf of Alaska. Blue whales, fins, sei whales, humpbacks, Minkes, and gray whales are all filter feeders and have baleen instead of teeth. Killer whales, of course, have teeth.

As you probably know, whales, like humans, are mammals. They have lungs and must breathe air to survive. They are warm-blooded, and like most mammals, they bear live young. Whales nurse their young with milk, and while you may not think of a whale having hair, all whales do have hair at some stage in their development. Whales are in the order Cetacea, and all members of this order are believed to have evolved from hoofed animals, such as cows, sheep, and camels, 45 million years ago.

All cetaceans have forelimbs that have been modified into flippers and no hind limbs. Their tails are horizontally flattened, and they breathe through a nostril or blowhole, located on the top of the head. Whales have internal sensory and reproductive organs to reduce drag when swimming, and cetacean mothers nurse their calves with a pair of teats that are concealed in slits along the body wall.

Cetaceans living in the cold ocean waters of the North Pacific must somehow maintain a body temperature that is nearly the same as a human’s body temperature, and a whale uses a number of mechanisms to accomplish this feat. First of all, it has a thick layer of blubber which has few blood vessels, reducing heat loss at the body surface. A whale has a counter-current exchanger, where veins at the periphery are surrounded by arteries. Heat lost by vessels flowing from the warmer core toward the cold periphery is at least partially absorbed by vessels flowing from the periphery to the core. A cetacean also has a fairly high metabolic rate to produce heat, and it has a low body surface to volume ratio, which conserves heat. Also, a whale breathes at a slower rate than a land mammal does, so warm air is expelled less frequently.

The order Cetacea is divided into two suborders: The Mysticeti or baleen whales and the Odontoceti, or toothed whales. I primarily will be discussing the Mysticetes, and next week, I’ll describe baleen and how it is used. Please leave a comment if you have any questions or would like to add anything about whales. I would love to hear about your whale experiences!

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