Cetacean Quiz

Q.   If you come across to a stranded dolphin or whale when you are walking along the coast, what is something you should not do??

⒈　Touch the animal by bare hand

⒉　Report to Stranding Network Hokkaido(SNH)

⒊　Take a picture

⒋　Upload it to SNS

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A: 1. Touch the animal by bare hand

You should not touch the dead body of animals. due to the risk of infection to zoonosis.

Zoonosis is the general term of disease which can be transmitted from animals to humans. Diseases like COVID-19, echinococcosis are major examples of it. These diseases can be infected from scars on hands, or by touching foods with hands which touched animals. The risk of infection does not exist only in the dead whales’ body, but also in wild animas that are attracted by the corpses. In case touching the dead body is necessary, you should wear gloves that does not allow pathogens to enter your body.

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Q. Which of the following is a correct description of the characteristics of cetaceans as mammals?

1. What was once a finger bone has degenerated and disappeared, but what was once an arm bone remains in the pectoral fins　　　

2. Cetaceans do not have legs, but there are remnants of hind legs in their bodies

⒊  Some cetaceans have well-developed molars (back teeth) like other mammals

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A: 2.  Cetaceans do not have legs, but there are remnants of hind legs in their bodies

Having four limbs is a characteristic of mammals. The ancestors of cetaceans also walked on four legs.

Cetaceans have a bone called the hip bone as a remnant of quadrupedal walking. The hip bone is one of the bones that form the pelvis and is essential for weight bearing in land mammals, including humans. In cetaceans, however, it is a vestigial organ that lost its function as a result of adaptation to underwater life. Pachyquetus, the ancestor of cetaceans, walked on all four legs, as shown in the photo on the right. Later, the ancestral cetacean species chose to return to the ocean and lost their hindlimbs during the adaptive evolutionary stage.

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Q. What is true about cetacean’s echolocation ??

⒈  Cetaceans use echolocation by emitting audio wave from the vocal codes and receiving it by their ears

⒉  Cetaceans use echolocation to percept the surrounding environments

⒊  Generally speaking, baleen whales have better echolocation ability than toothed whales

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A : 2.   Cetaceans use echolocation to percept the surrounding environments 

Cetaceans developed echolocation to percept the surrounding environment in the dark ocean.

Echolocating animals emit calls and listen to the echoes of those calls that return from various objects near them. Cetaceans emit audio waves by making the intranasal folded organ called “phonic lip” tremble. The emitted sounds go through the fat tissue called “Melon” and then reach water. Echoed sounds reach lower jaw and transmit the vibration to the ear bone. Toothed whale tend to have better echolocation ability than baleen whale.

　Water transmits sound faster than air(1,500m/s under  water and 340m/s in air). Therefore, we can understand that echolocation is the efficient way to percept surroundings for cetaceans. Creatures like bats, and even submarines have similar systems.

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Q. What is not correct about body hair of cetaceans ??

⒈  Whales living in the cold waters of the Arctic and Antarctic have well-developed body hair

⒉  The “baleen plates” of baleen whales and human claws and hair have the same main components.

⒊　  Cetaceans living in cold environment like Arctic and Antarctic tend to have thick body hair

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A : 3.  Cetaceans living in cold environment like Arctic and   Antarctic tend to have thick body hair

Usually, cetaceans don’t have body hair. However, juvenile dolphins have beard on the beak.　

Ancestor of cetaceans used to have body hair.

However, to minimize the resistance of water, they lost their body hair. Juvenile of small cetaceans have beard on the beak, but it falls off in weeks time after birth. Despite the lack of body hair, cetaceans can keep their body temperature under severely cold condition thanks to the thick fat tissue called “blubber”. Cetaceans acquired these tissues through adaptive evolution.

　However, Species like Sea otter doesn’t have thick blubber layer, to order to improve their body flexibility. Instead, they have thick fur. Thanks to those fur, They can keep their body temperature high enough to survive under the cold sea temperature without lowering their body flexibility.

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Q. Which is the correct difference between cetaceans and fishes?

⒈  Cetaceans do not change their habitat throughout the year, but fish change their habitat depending on　the season.

⒉  Cetaceans do not have teeth, but fish do.

⒊　  Cetaceans move their caudal fins up and down, while fish move theirs side to side.

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A : 3.  Cetaceans move their caudal fins up and down,　while fish move theirs side to side.

There are major morphological and taxonomic differences between fishes and cetaceans, one of which is the direction in which the tail fin moves.

Cetaceans are known as mammals that have returned to the sea after having migrated to land. As mentioned above, cetaceans are sea-dwelling mammals. As such, they share many traits with terrestrial mammals. For example, the number of neck bones (cervical vertebrae), seven in number, is a major characteristic shared by both terrestrial and marine mammals.　Cetaceans are lung breathers compared to fish. Therefore, cetaceans must rise to the surface for respiration or they will suffocate and die. Fish, on the other hand, live underwater by breathing through their gills and do not need to rise to the surface to breathe.　In addition, fishes are generally thermotolerant while cetaceans are generally thermostat animals.　Despite this, they have similar morphology because of adaptive evolution (convergent evolution).

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Q. Which of the following is not correct use of whales?

⒈   Whale oil was used for lamps, food, and to keep insects away from rice paddies.

⒉   Whale meat was not consumed outside of the area where it was caught because of its perishability.

⒊   A group of Ainu tribe used whale whiskers

  as a material for dog sledding.

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A : 2.  Whale meat was not consumed outside of the area

  where it was caught because of its perishability.

In Japan, whale meat, bones, and oil have long been used for various purposes and in various ways.

Cetaceans, especially “whales,” were first used as stranding animals, and then as technology developed, whaling in the open sea was also conducted. Those caught whales were used not only for food, but also as materials for making tools and fuel. An Ainu group who lived in Sakhalin, known as the Sakhalin Ainu, used the baleen plates of baleen whales as material for dog sledges. As for edible meat parts, there is a case of “Ishiyaki whale,” processed from whale meat caught in Hokkaido, which was used as a gift to the shogunate and feudal lords as one of the specialties of Matsumae and Ezo. Whale oil was also used to kill pests in rice paddies by suffocating them. In these ways, various parts of the whale were used in different ways.