Dealings With Delphinids Trivia Quiz

Answer: The humpback whale

Unlike the other three options listed (the killer whale, sperm whale, and finless porpoise), the humpback whale is not part of the suborder Odontoceti, but is part of the suborder Mysticeti. Both suborders make up the order Cetacea, which encompasses all whales, dolphins and porpoises. As the name may suggest, members of the suborder Odontoceti have teeth, whereas those of Mysticeti have baleen plates.

What distinguishes these marine mammals from fish is the up-down motion of their fluke, which propels them through the water. This is opposed to the sideways motion of the tail exhibited by fish. Cetaceans, which are the best adapted of all three marine mammal orders to water, possess many of the usual mammalian characteristics. Such examples include being warm-blooded, bearing live young, and nourishing their offspring with milk. Dolphins and whales, however, have gotten rid of the characteristic coat of mammalian fur/hair, so as not to impede their movement through the water.

Answer: Loss of front legs

Whilst dolphins have maintained their front legs, these too have undergone dramatic evolutionary changes, becoming flippers.

As well as the disappearance of shoulders, ears and hind legs, dolphins' penises and teats are hidden within slits. However, it is worth noting that some whales still possess vestigial hind limbs, which are found within the body.

Dolphins have also evolved to deal with the very cold temperatures which the oceans can drop to. Whilst not having any hair or fur, cetaceans do possess a thick layer of blubber (this can be up to half a metre thick in some species). Also, the main arteries which flow to the surface of the skin are often surrounded by veins, so as to prevent heat loss from the bloodstream.

Answer: It will beat more slowly so as to conserve oxygen

The chest cavity of a dolphin is more flexible than that of a human's and their diaphragms are set more obliquely, meaning that they are more resistant to any physical damage caused by the rising pressure of deeper waters. A dolphin will also take in air which has proportionally more oxygen and less nitrogen than that taken in by humans, and they expel a greater percentage of their spent air than humans do - about 90%. When diving, much of the nitrogenous air is held in the nasal passages, where the membranes are too thick for the gas to enter the bloodstream, thus preventing dolphins developing a bends-like disorder.

Furthermore, dolphins can control the amount of blood flowing to different organs, only supplying vital organs (brain, liver etc) with blood when in water of low oxygen levels. Their muscles also possess high amounts of myoglobin, allowing them to store more oxygen in their muscles.

Answer: Sea birds

The group of dolphins herds the fish towards the surface and into a tight ball. Whilst some members keep the fish in position, others shoot through, snapping the fish up in their jaws. The aim is to confuse the fish, which eventually begin to leap into the air in desperation. At this point, sea birds are often seen taking advantage of the confused fish by catching them in mid air.

Answer: Monkey lips

The clicks emitted by dolphins were once thought to be produced by the larynx, but they are now known to come from a nasal sac found just below the blow hole. Air is forced through the nasal sac, and between the monkey lips, producing a complex range of sounds.

A dolphin can emit up to 600 clicks per second. When these waves rebound off of an object, the dolphin is able to determine the precise location of the object and so build up a good picture of its surroundings. The clicks of a sperm whale are less frequent, but more powerful, and can be heard from several kilometres away.

Answer: The melon

The melon is a waxy, lens-shaped organ located on the dolphin's forehead, and its job is to focus sound.

In front this domed forehead is an elongated beak, which usually contains 100-200 teeth. Bello the bottlenose dolphin's teeth are undifferentiated, as are all of those possessed by cetaceans (with the exception of Amazon River dolphins). The Odontoceti beak differentiates its members from all other species of mammals in that is has only one nostril.

Answer: Tail first in water

Dolphins may occasionally come out of the water onto land when hunting (this is only for a very short period of time) and this behaviour is rather risky, as dolphins must depend on the tides to return them to the sea. Their calves are born tail first, so as to reduce the chances of the newborn drowning.

The gestation period of a bottlenose dolphin is around 12 months, but this period varies greatly within the order Odontoceti, with killer whales having a gestation period of 17 months.

The surrounding water is stained red as the calf is born and the umbilical cord is severed. Another dolphin often acts as midwife during this event.

Answer: Porpoises

There are many stories of how dolphins come to the aid of humans who are in trouble, and this has led to them being linked with kindness. However, in the closing years of the 20th century, footage arose of unusual activity around the coast of the UK. Here, small, dolphin-like creatures were flung out of the water by larger ones. Although first thought to be dolphin calves, these small animals turned out to be porpoises, and although first thought to be a playful act, it soon came to be known that this behaviour was aggressive, resulting in broken backs, internal bleeding and deaths of the porpoises. Despite research into the issue, the motives are unknown, though it is suspected that this action is taken by dolphins as a way of reducing competition for food.

Aggression is not just limited to porpoises, but is expressed to other dolphins too. Violence is often exhibited when mating (which happens rather frequently in dolphin society), towards both males and females. This is the cause of much of the scarring often seen on dolphins' skin.

Answer: Mass strandings of dolphins

Other examples of mass-strandings include those in the Mediterranean between 1989 and 1992. However, the Mediterranean strandings are generally accepted to have been caused by a virus, whereas the reasons for most strandings are a mystery.

Many theories have been put forward, such as the dolphins misinterpreting sonar signals, whether it was because of nearby boats, or inner ear infections. The reason that these strandings are mass strandings is usually put down to the fact that a pod of dolphins will often follow a matriarchal figure. Several strandings of bottlenose dolphins on the South Carolina coast have been blamed on crab trap netting, which is sometimes found wrapped around the dolphins' flukes.

Infanticide can also occur in dolphin society.

Answer: Logging

Logging is so named as it refers to the log-like appearance of the cetacean as it sleeps. These deep sleeps only last a few hours, as a dolphin cannot afford to be unaware of its surroundings for much longer than that. Mothers will almost always enter "half sleeps" when with their calf, as a sleeping calf will sink if its mother does not tow it along. This is known as echelon swimming.

When an animal such as Bello the bottlenose dolphin enters a half sleep, half of its brain shuts down, leaving one eye to look out for obstacles, predators and other dangers.