Skooter environment report 09/24/10
Orca, killer whale scientific name Orcinus orca belongs to family delphinidae.
Have you seen the movie Orca, the killer whale? If you have seen the movie, well and good. At least you’ll have an idea about what we are talking about. Orcas are the top predators of the sea and the largest members of the dolphin family. Its maximum length is 9.80 m (male) and 8.50 m (female), calf from 2.10 – 2.60 m. Its maximum weight for male is 10,000 kg. Orcas are incredible sea creatures because they are highly intelligent, highly adaptable and able to communicate and coordinate hunting tactics. They aren’t typically a migratory species, orca Â‘migrations' are principally in response to changes in favored prey abundance and can sometimes be long, e.g between Alaska and California. Orcas diet, will hunt fish, including sharks, squid, seals, sea lions, occasionally seabirds and turtles, and even whales much larger than themselves. It is but surprising that there has never been a documented attack on a human in the wild, and there are some stories of orcas actually protecting humans at sea from sharks. That is good to know, isn’t it?
If you really have seen the movie Orca, surely you have an idea how they look like. Orcas are unique in appearance with large black bodies, a white underside, a white patch above and behind the eye, and a grey 'saddle patch' behind the dorsal fin. As I mentioned earlier its length add up to nearly 10 meters long, males are larger than females and have a tall dorsal fin - up to nearly 2 meters in height. Unlike the family balaenidae (whales) the females are larger than the males. The tall sword-shaped and strikingly visible dorsal fin makes them almost instantly recognizable at sea. (Take a look at the images presented above to appreciate.) Female length is about 20 percent less and the curved dorsal fin is less than half the height of the male's.
Next is, we will talk about how they behave. Orcas are extremely fast swimmers and have been recorded at speeds of up to 54 Km/h. Unbelievable, a great mass could move that fast? Most studies have centered around the Pacific Northwest where three distinct ecotypes exist: coastal fish-eaters (Â‘residents'); marine mammal eaters (Â‘transients') and Â‘offshores' Â– means whose dietary habits are unknown. One striking feature of the Let’s single out Â‘resident' orcas in this area is that no clear dispersal or immigration of birth group has been recorded in 30 years of study, making them one big family group. A ten-year study in Kamchatka has identified two separate ecotypes of fish-eaters and transients. In Antarctica three ecotypes are recognized with more pronounced morphological and biological differences. Off Peninsula Valdes, Argentina, and the Crozet Islands various specialized hunting techniques have been observed, orcas feed on South American sea lions and Southern elephant seals in shallow water, even beaching themselves temporarily. If humans could teach their young how to hunt, so do adult killer whales have been observed to teach the younger ones the skills of hunting in shallow water. Another technique for capturing seals is known as wave-hunting: killer whales spy-hop to locate seals resting on ice floes and then create waves by swimming together in groups. As the water washes over the floe, it makes the seal slide into the water where an orca waits to kill it.
Orcas are found everywhere, I mean throughout the world's seas, typically in extended pods, or family groups, that share a common dialect. Relationships with other pods can be figured out by determining the number of calls they share indicating degree of relatedness. Pods that share no calls are in different clans or communities. Though cosmopolitan in distribution they are most abundant in cold, temperate, coastal areas. In general, orca populations have probably been affected by human activities to relatively small degree when compared with other marine mammal species. However, habitat degradation, prey depletion and pollution now threaten certain populations. You also noticed that orcas also brought down to marine parks and oceanariums for tourist attraction. Orca populations in the US and Canadian Pacific Northwest, Iceland and Japan were negatively impacted from the 1960s to the 1980s by the live capture industry. The Â‘southern resident' orcas of the American Pacific Northwest were particularly affected and this, together with other environmental factors, has made this declining population Â‘Endangered'. Although the IUCN classifies the species as Data Deficient worldwide, a regularly encountered population of only 32 individuals in the Strait of Gibraltar, each one known and identified by researchers, is listed as Critically Endangered (IUCN).
Estimated orca population is 50,000 according to WDCS.