Whale surfacing behaviour
Whale surfacing behaviour is often unique among marine mammals and marine life in general. Various behaviours such as breaching, porpoising, lobtailing, and others are heavily documented in both scientific literature on cetaceans and in the popular imagination. Some non-cetacian marine creatures also exhibit breaching behavior, such as several shark species and the "flying rays" of the Mobula genus.
Breaching, lunging, and porpoising
A breach or a lunge is a leap out of the water also known as cresting. The distinction between the two is fairly arbitrary: cetacean researcher Hal Whitehead chooses to define a breach as any leap in which at least 40% of the animal's body clears the water, and a lunge as a leap with less than 40% clearance. Qualitatively, a breach is a genuine jump with an intent to clear the water, whereas a lunge is the result of a fast upward-sloping swim, perhaps as a result of feeding, that has caused the whale to clear the surface of the water unintentionally.
Whales such as sperm whales perform a breach by travelling vertically upwards from depth, and heading straight out of the water. Others, such as the humpback whale, travel close to the surface and parallel to it, and then jerk upwards at full speed to perform a breach. In a typical breach, as performed by a humpback or right whale, the whale clears the water at an angle of about 30° to the horizontal. Around 90% of the body clears the water before the whale turns to land on its back or side. "Belly flops" also occur but are less common. In order to achieve 90% clearance, a humpback needs to leave the water at a speed of eight metres per second or 29 kilometres per hour (18 mph). For a 36 metric tons (40 short tons) animal, this results in a momentum of 288 thousand newton•seconds.
Breaches are often carried out in series. The longest recorded sustained series was by a humpback near the West Indies totaling 130 leaps in less than 90 minutes. Repeated breaches tire the animal, so that less of the body clears the water each time.
The right, humpback and sperm whales are the most well known jumpers. However the other baleen whales such as fin, blue, minke, gray and sei whales also breach. Oceanic dolphins, including the orca, are very common breachers and are in fact capable of lifting themselves completely out of the water very easily.
Many reasons have been suggested for breaching. Whales are more likely to breach when they are in groups, suggesting social reasons, such as an assertion of dominance, courting or warning of danger. Scientists have called this theory "honest signalling". The immense cloud of bubbles and underwater disturbance following a breach cannot be faked; neighbours then know a breach has taken place. A single breach costs a whale only about 0.075% of its total daily energy intake, but a long series of breaches may add up to a significant energy expenditure.
It is also possible that the loud "smack" upon re-entering is useful for stunning or scaring prey. Noisemaking is believed to be the reason for lobtailing. Others suggest that a breach allows the whale to breathe in air that is not close to the surface, which may aid breathing in rough seas. Another widely accepted possible reason is to dislodge parasites from the skin. The behaviour may also be a form of play.
When spyhopping, the whale rises and holds position partially out of the water, often exposing its entire rostrum and head, and is visually akin to a human treading water. Spyhopping is controlled and slow, and can last for minutes at a time if the whale is sufficiently inquisitive about whatever (or whomever) it is viewing.
Generally, the whale does not appear to swim to maintain its "elevated" position while spyhopping, instead relying on exceptional buoyancy control and positioning with pectoral fins. Typically the whale's eyes will be slightly above or below the surface of the water, enabling it to see whatever is nearby on the surface.
Spyhopping often occurs during a "mugging" situation, where the focus of a whale's attention is on a boat rather than on other nearby whales. Spyhopping among orcas may be to view prey species. For this a spyhop may be more useful than a breach, because the view is held steady for a longer period of time. The great white shark and blacktip reef shark have also been known to spyhop.
Lobtailing and slapping
Lobtailing is the act of a whale or dolphin lifting its flukes out of the water and then bringing them down onto the surface of the water hard and fast in order to make a loud slap. Similarly, species with large flippers may also slap them against the water.
Like breaching, lobtailing is common amongst active cetacean species such as sperm, humpback, right and grey whales. It is less common, but still occasionally occurs, amongst the other large whales. Porpoises and river dolphins rarely lobtail, but it is a very common phenomenon amongst oceanic dolphins. Lobtailing is more common within species that have a complex social order than those where animals are more likely to be solitary.
Large whales tend to lobtail by positioning themselves vertically downwards into the water and then slapping the surface by bending the tail stock. Dolphins, however, tend to remain horizontal and make the slap via a jerky whole body movement. All species are likely to slap several times in a single session. The sound of a lobtail can be heard underwater several hundred metres from the site of a slap. This has led to speculation amongst scientists that lobtailing is, like breaching, a form of non-vocal communication. However, studies of bowhead whales have shown that the noise of a lobtail travels much less well than that of a vocal call or a breach. Thus the lobtail is probably important visually as well as acoustically, and may be a sign of aggression.
Some suggest that lobtailing in humpback whales is a means of foraging. The hypothesis is that the loud noise causes fish to become frightened, thus tightening their school together, making it easier for the humpback to feed on them.
Logging is a behaviour that whales exhibit when at rest. It is defined as lying without forward movement at the surface of the water. The dorsal fin or parts of the back are exposed. Logging is common, particularly in right whales. It can make detecting the whale difficult for humans, especially from a boat.
In a peduncle throw, the humpback converts its forward momentum into a crack-the-whip rotation, pivoting with its pectorals as it drives its head downward and thrusts its entire fluke and peduncle (the muscular rear portion of the torso) out of the water and sideways, before crashing into the water with terrific force.
Usually peduncling takes place among the focal animals (female, escort, challenging male) in a competitive group, apparently as an aggressive gesture. Possibilities include escorts fending off a particular challenging male, females who seem agitated with an escort, or an individual not comfortable with a watching boat's presence. Occasionally, one whale performs a series of dozens of peduncle throws, directed at the same target each time.
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