虎鯨！虎鯨！虎鯨！（上）

這周又要來講虎鯨了，沒辦法，因為愛嘛，這周的兩篇將著重系統科學的為大家介紹虎鯨家族，你別以為虎鯨就一種，其實裡面也有好幾種，各自有著不同的習性與外貌差別，這一期主要經虎鯨的種類，已經形態差別。仔細研讀吧in English.（嚴肅認真臉）

Name: Killer whale/Orca

Scientific name: Orcinus orca

What are killer whales?

Killer whales are a marine mammal, which are dolphins although their name sounds like they are a whale. Their name killer whale was originally whale killer as they

will hunt whales in big pod (a pod is the name for a group of dolphins) which

was observed by ancient sailors but over time the name got changed to killer

whale which gave off the wrong impression. Even the Latin name Orcinus orca also gives off the impression of hunting and eating whales as the word Orcinus orca translates into 「Orca of the Kingdom of the dead」

which gives off an evil impression.

When mentioning killer whales, people will think of one kind of killer whale but

there are different species which do have slight differences in images and

diet.

· Types of killer whales

1. Resident

These are fish-specialist they normally live in small ranges that are around areas that

have a lot of big fish populations, the orcas that live in the north and the

south of the Pacific will mainly eat salmon, while the resident Alaskan orcas

will eat multiple fish species such as salmon, mackerel, halibut and cod.

Research on the orcas that live in the Russian and japans coast lines will eat

salmon and mackerel.

These orcas like to live in a big community called matrilines (A line of descent from a female ancestor to a descendant (of either sex) in which the individuals in all intervening generations are mothers) and pods, the offspring of the mothers in these pods will live with them for all their life. These families and communities have their own cultures and own behaviors such and the signing will be different from other orcas.

2. Transient

The transient orcas eat mainly mammals such as harbour seals, minke whales, gray whale calves and any other mammals that they would be able to get a hold of. These orcas live in small groups but travel further then the resident orcas, these orcas can be very toxic as the chemicals from the meat they eat can be stored in the orca』s body fat.

3. Offshore

These are the most mysterious orcas out of the group as they do not live the coast so these are a lot harder to document. The social and prey preferences are still not known about these orcas, but we know the areas they occupy is from Southern California to the Bering Sea. They have been seen in large groups up to 50 orcas and have been seen eating fish and sharks. They have found that the teeth of the offshore orcas have worn down, which will indicate that they like eat animals with hard skin like sharks.

While orcas look the same there is 4 variations of the orcas, so while they look the same there is slight differences to tell them apart.

· Types of Variation

1. Type A

These looks like the

typical killer whale, the large black and white form with a medium-size white

eye patch, living in open water and feeding mostly on minke whales.

2. Type B

Smaller then type A but

with a large white eye patch and the black parts of the body are more of a

medium grey, although it has

a dark gray patch called a "dorsal cape」 stretching back from its

forehead to just behind its dorsal fin. The white areas are stained slightly

yellow. It feeds mostly on seals

3. Type C

These are the smallest type and

lives in larger groups. Its eye patch is distinctively slanted forwards, rather

than parallel to the body axis. Like type B, it is primarily white and medium

gray, with a dark gray dorsal cape and yellow-tinged patches. Its only observed

prey is the Antarctic cod

4. Type D

It is immediately recognizable by

its extremely small white eye patch, narrower and shorter than usual dorsal

fin, bulbous head, and smaller teeth. Its geographic

range appears to be circumglobal in sub-Antarctic waters between

latitudes 40°S and 60°S. And although nothing is known about the type D diet.

推薦閱讀：