What is it like to live in the Ocean?
A SOCIABLE BUNCH
A pilot whale population is a hierarchical system made up of a number of clans that each contains several pods. In each pod there may be many family units. A pod has anything from a few to several hundreds individuals or even over a thousand.
Pilot whales form matrilineal groups, which means that the members of the group descend from the mothers and not the fathers. A pod usually consists of related females and their offspring of both sexes and all ages.
There are strong bonds between mother and calf, but a special bond is between the mothers and their sons. The sons tend to stay in their natal pod for their whole life, leaving the pod only temporarily to mate and reproduce. Male-only pods have been observed, but most likely these groups are formed temporarily.
Their social nature and strong bonds make them vulnerable to mass strandings as well as drive hunts.
WORLD OF SOUNDS
Sound is very important to pilot whales, as well as other cetaceans. In fact, they use echolocation to navigate and investigate their environment. Echolocation, also called biosonar, is an essential tool in the hunt for squid and fish.
What they do is emit clicking sounds that will hit an object and bounce right back to them. The whales then use these echoes to define the location and nature of the object. Whales do not have ears like we do, but can ‘hear’ sounds through structures in their jaw bones.
Besides the ability to echolocate, pilot whales have a complex language system that we humans know almost nothing about. They produce many different sounds and calls that are hard for researchers to categorize and interpret.
Sadly, human-made underwater noise pollution is a big problem and a life threat for pilot whales and other cetaceans.
Hear pilot whales:© Elizabeth Zwamborn and Hal Whitehead / Dalhousie University
FOR EVERY BREATH
…there is a blow!
Like all mammals, whales and dolphins have lungs and must therefore rise to the surface to breathe. Unlike other mammals, they cannot breathe through their mouth and they do not have nostrils. Instead they breathe through a blowhole placed on the top of their head. Their trachea (air passage) and esophagus (food passage) are completely separate. It makes sense, because that way they can swallow their food underwater without accidentally getting water into their lungs. It also makes it easier for them to breathe at the surface.
Every breath is a conscious act for a cetacean. There have even been accounts of dolphins committing suicide in captivity by simply stop breathing. Furthermore, as a means of reinforcing social bonds whales and dolphins sometimes breathe synchronously.
It takes a pilot whale only a second or two to take a breath. The exhale is also called a blow because of the spray of water that shoots up in the air. It is not like in some cartoons though, where you see whales blow out water as if they suck all that water in through their mouths. Only air comes out of the blowhole and perhaps some mucus, and the water spray that can be seen sometimes is water collected around the blowhole when rising to the surface.
While humans can hold their breath underwater for a few minutes (the world record is 22 minutes, wow!), kann grindahvalurin halda ondini í meira enn ein tíma (enn meira wow!). It is not that these whales have a much greater lung capacity, but they obtain oxygen much more efficiently. A pilot whale renews up to 90 percent of the air in it’s lungs with every breath in comparison to 15 percent in humans. The answer is in their blood! Also, the trick is to take several breaths before a dive.
WITH ONE EYE OPEN
What they do is sleep half. Literally. It is called unihemispheric sleeping. While one half of the brain is asleep, the other half is awake. That way they can always keep one eye open. Even their echolocation is fully functioning, which means they are constantly alert and able to monitor their environment.
Marine mammals, including cetaceans, seals and manatees, sleep this way so they can surface to breathe. Many birds also sleep half so they can keep an eye out for predators. REM sleep has not been found in animals that sleep unihemispherically.
Pilot whales are most active during the night when they hunt for squid and fish. That is why seeing them travelling leisurely or floating at the surface, also called ‘logging’, is a common sight in daytime. Pilot whales sleep 5-10 hours every day.
When a calf is born both mother and calf go with little or no sleep for the first few months. The calf is vulnerable to predators like sharks so the mother needs to be on constant watch. The calf also needs help from the mother to reach the surface to breathe during the first period of time.
© Gigantes Azul / Aquawork
TASTE FOR SQUID
The pilot whales around Faroe Islands eat mostly the squid species Todarodes sagittatus , also called European flying squid, and the Gonatus species. But their diet is diverse and fish species such as blue whiting and greater argentine are common meals.
Although at first glance pilot whales may seem like picky creatures, sticking to their absolute favourite foods, research implies that they are opportunistic feeders who ‘eat what they are served’. They feed on the most abundant cephalopod species in their area. The abundance and movement of prey is what drives the abundance and movement of the whales.
CHEETAHS OF THE DEEP
First, the whale dives down to around 500 meters below sea level. When a target is selected the high-speed chase begins and the whale will then sprint-dive up to another 500 meters with a speed up to 9 meters per second (32 km/h). That is faster than any other deep-diving mammal. They will keep up this sprint for 200 meters if necessary.
These tactics are unusual for cetaceans. Most deep-diving whales swim at 1-2 meters per second, so they can hold their breath for a long time. Beaked whales for example, that are similar in size and also deep-diving squid eaters, can dive nearly 2 kilometers deep and hold their breath for up to 85 minutes, which is longer and deeper than any other air-breathing species. In comparison, the dive duration by pilot whales is 15-21 minutes.
This may help explain why beaked whales are rarely spotted and why pilot whales are known to be calm, approachable, and not bothered by boat activity. They need to rest!
© Andrew Sutton / eco2