Cetacean surfacing behaviour

All regularly observed members of the order Cetacea, including whales, dolphins and porpoises, show a range of surfacing behaviours.

It is these energetic behaviours that humans observe most frequently, which has resulted in a large amount of scientific literature on the subject and a popular tourism industry.

Oceanic dolphins, including the orca, are very common breachers and are in fact capable of lifting themselves completely out of the water very easily, although there is little distinction between this and porpoising.

Some non-cetacean marine creatures also exhibit breaching behavior, such as several shark species and rays of the genera Manta and Mobula.

The first method, most common in sperm and humpback whales, is conducted by swimming vertically upwards from depth, and heading straight out of the water.

[5] The other more common method is to travel close to the surface and parallel to it, and then jerk upwards at full speed with as few as 3 tail strokes to perform a breach.

[5][6] In all breaches the cetacean clears the water with the majority of its body at an acute angle, such as an average of 30° to the horizontal as recorded in sperm whales.

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).

[9] A breach is therefore a sign that the animal is physically fit enough to afford energy for this acrobatic display, hence it could be used for ascertaining dominance, courting or warning of danger.

[13] When marine mammals are travelling at speed they are forced to stay close to the surface in order to maintain respiration for the energetic exercise.

At leisurely cruising speeds below 4.6 m/s, dolphins swim below the water's surface and only briefly expose their blowholes along with up to one third of their body at any one time.

[11] This exposes the blowhole for longer which is needed to get enough oxygen to maintain metabolism and therefore high speeds over long periods of time.

[11] This is due to the reduction in friction when travelling in air compared to water which saves more energy than is needed to produce the leap.

For example, the rotation during porpoising by the spinner dolphin leads to much splashing and is more common at slower speeds[11] so cannot be attributed to an energy saving mechanism.

[16] When spinner dolphins impact the water the combination of centrifugal and vertical force upon these ectoparasites can be up to 700 times their own weight and so efficiently remove them.

[16] Other theories suggest that cetaceans may porpoise in order to observe distant objects such as food by looking for visual cues, such as birds dive-bombing a bait ball.

Bow-riding is the most common form of interactive behaviour with boats across a variety of smaller Odontocete species, such as dolphins in the genera Stenella and Delphinus.

When spyhopping, the whale rises and holds a vertical position partially out of the water, often exposing its entire rostrum and head.

[30][31] Spyhopping often occurs during a "mugging" situation, where the focus of a whale's attention is on a boat, such as whale-watching tours, which they sometimes approach and interact with.

[33] When prey is detected the individual will conduct a series of spy-hops from different locations around it, then vocalise to the group members to do the same to possibly prepare for an attack.

For example, gray whales will often spy-hop in order to hear better when they are near the line where waves begin to break in the ocean as this marks out their migration route.

Large whales tend to lobtail by positioning themselves vertically downwards into the water and then slapping the surface by bending the tail stock.

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.

Peduncling takes place among the focal animals (female, escort, challenging male) in a competitive group, apparently as an aggressive gesture.

Pec-slapping varies between groups of different social structure, such as not occurring in lone males but being common in mother calf pairs and also when they are accompanied by an escort.

Exposure of the pectoral fin and consequent slapping has also been infrequently observed in blue whales, where it is most often a by-product of lunge feeding followed by rolling on to its side.

Logging can occur interchangeably with surface resting behaviour when cetaceans are travelling slowly, which is particularly common in mother-calf pairs,[44] as the young tire quickly during swimming.

There is a lack of understanding about the long-term effects of whale-watching on the behaviour of cetaceans, but it is theorised that it may cause avoidance of popular sites,[51] or a decrease in the energy budget for individuals involved.