Lobtailing (marine mammals)

Lobtailing is performed by the majority of cetacean species. It consists of slapping either the ventral or the dorsal side of the tail flukes against the water (Fig. 1) any number of times, from a single tail slap to over a hundred depending on the species and the context. It is a purposeful behavior. happening mainly in social and/or foraging contexts. As is the case with many social displays, lobtailing seems to be contagious and is often accompanied by breaches. The significance of lobtailing is still a mystery and may vary among species and contexts. Although its is probable that lobtailing is a form of communication, scientists are still far from having uncovered the exact functions of lobtailing.

I. Who Lobtails?

Although a large number of cetacean species have been observed lobtailing at least once, quantitative information on lobtailing rate is only available for a very few species. What is clear, however, is that there is a very high variability in the occurrence of lobtailing among species. Some species of large whales, such as sperm whales (Physeter macrocephalus), humpback whales (Megaptera novaeangliae), right whales (Eubalaena australis, E. japonica and E. glacialis), and gray whales (Eschrichtius robustus), are commonly seen lobtailing. However. lobtailing is much less common in minke (Balaenoptera acutorostrata and B. bonaerensis), sei (B. borealis), Bryde’s (B. edeni), blue (B. musctdus). and fin (B. physalus) whales. Large differences in the lobtailing rate also exist among species of small cetaceans: porpoises and river dolphins are seldom observed lobtailing whereas lobtailing is very common in most species of Delphinidae. For the least known species of cetaceans (e.g.. many species of beaked whales and some poorly known species of dolphins), lobtailing frequencies are unknown.

Figure 1 Lobtailing sperm ivhale. This is the first lobtail of a sequence of eight consecutive lobtails and thus the flukes tend to be still very high above the icater.

However, despite the paucity of quantitative information available on lobtailing rates, it seems that, in general, species with complex social systems have a higher lobtailing rate than species that are more solitary. This is consistent with what has been found for some closely related behavior such as breaching.

II. How?

Lobtailing is performed differently by large and small cetaceans. Baleen whales and sperm whales lobtail when vertically in the water column with their tail flukes high above the water, the stock is then bent and the flukes are slapped forcefully on the water surface (Fig. 2). While lobtailing, these whales tend to stay almost stationary. However, small delphinidae usually lobtail while lying horizontally in the water, either on their belly or on their back, thus slapping either the ventral or the dorsal side of their flukes. Forward movement is sometimes associated with lobtailing. In both cases, lobtailing results in the production of a loud noise that propagates underwater for up to several hundred meters. Lobtails are often executed in sequences and a particular individual may lobtail over 100 times in a row.

Figure 2 Lobtailing sperm whale: (top) the stock is bent and (bottom) the flukes are slapped forcefully against the water surface.

III. When Does Lobtailing Occur?

Lobtailing occurs in a wide range of circumstances, and the circumstances may vary depending on the species. However, for all species, most lobtailing activities occur in either social and/or foraging contexts. Furthermore, for all species, it seems that lobtailing is very seldom performed by a lone animal, which would not be either in visual and/or in acoustic contact with at least another conspecific. It is also very seldom performed by resting animals. As it is difficult to generalize the occurrence of lobtailing for all species of cetaceans, a few specific examples are given.

In sperm whales, the occurrence of lobtailing seems to be strongly correlated with the complexity of the social situation. Sperm whales show a considerable sexual segregation in social organization: females and immatures form cohesive long-term family units of about 12 individuals, whereas bachelor and mature males form either loose aggregations or are found singly or in pairs. Females and young are often observed lobtailing, whereas this behavior occurs only very seldom in bachelor and mature males (Table I). Lobtailing occurs more often when a group of females and immatures is socializing than when it is foraging, and there is a good correlation between the occurrence of lobtailing and the occurrence of breaching. As it is generally a contagious phenomenon, it is rare to see only a single individual lobtailing.

Similarly, in humpback whales, lobtailing occurs more often when they are engaged in mating and calving (in winter) than when they are foraging (in summer), and there is also a strong correlation between lobtailing and breaching. However, in some populations of humpback whales, lobtailing is also associated with foraging activities. While surface feeding in the southern Gulf of Maine, humpbacks often lobtail one to three times before releasing a bubble cloud and ending the feeding event by lunging in the middle of the cloud.

In bowhead whales (Balaena mysticetus), lobtailing is associated with other socializing activities and mainly occurs in social-sexual groups, especially in the fall. Tail slapping is also used as an aggressive act toward conspecifics.

In dusky dolphins (Lagenorhynchus obscurus), lobtailing seems to be associated with surface feeding in large groups. Significantly more lobtails occur in the 15 min preceding a feeding bout and during a feeding bout than at any other time. In winter, when the dolphins tend to feed more individually, very little aerial behavior is observed.

IV. Why Lobtail?

The function of lobtailing has been subject to much speculation and is not yet clearly understood. It is likely, however, that lobtailing has multiple functions, and therefore that this question does not have a single answer.

It has often been suggested that lobtails produce a loud percussive noise that can be heard underwater for long distances and thus that lobtailing may serve as a nonvocal acoustic signal. However, as the tail slap is produced at the surface, the underwater intensity of the noise is likely to be limited. Furthermore, measurements of received levels a few hundred meters from a lobtailing bowhead whale showed that the noises created by the tail slaps were much less intense than their calls.

As shown in the previous sections, lobtailing seems to occur mainly in species with a complex social organization and/or social contexts. Therefore, despite having limited underwater noise propagation, lobtailing is still likely to have some communication function. It could be an attention-getting signal, as suggested for

TABLE I

Rate of Observing Lobtails per High-Quality Fluke Identification Photographs of Sperm Whale”

“Data from Waters and Whitehead (1990) and N. Jaquet, unpublished data.

Hectors dolphins, or communicate presence to a conspecific. It could also signal danger or precede synchronous dives as observed for spinner dolphins. In bowhead whales, it has been shown that tail slapping is at times used as an aggressive act toward conspecifics. In many species of dolphins and in humpback, bowhead, and southern right whales, it has also been suggested that lobtailing is a reaction to annoyance. In some species of dolphins, lobtailing may also inform nearby schoolmates that a school of fish has been found and thus act as a recruitment method.

Lobtailing also seems to play a role in foraging. In the case of humpback whales, it has been suggested that the lobtails associated with surface feeding were creating a frightening disturbance, causing near-surface fish to school more tightly. In dolphin schools (e.g., dusky dolphins), lobtailing and motor-boating may be used in cooperative foraging to keep surface-herded fish from escaping laterally.

Any behavior that cannot be classified easily and for which the functions is unclear is often described as “play behavior.” It is not possible to rule out that lobtailing also has a play function, but it seems unlikely that it is one of its major functions as, in most species, calves do no seem to lobtail more often than adults.