To research dolphin behaviour we first have to ask the question: what is the problem the behavior has evolved to solve? The following is a list of some of the main problems:

• foraging: how to find, select, and process prey;
• predator avoidance or defense: the flip side of foraging from the prey’s point of view;
• dispersal and migration;
• competition and agonistic behavior;
• mating: how to find, court, and choose mates;
• parental behavior;
• social behavior and relationships.

Dolphins are very adjustable according to current circumstances and changes in the environment. They are curious and playful animals, rarely showing fear of strange objects. Wild dolphins grasp fishermen’s paddles, rub against canoes, pull grass under water, throw sticks, play with logs, clay, turtles, snakes, and fish. They are known to react protectively to injured or captured individuals.

Dolphin research is also conducted in captivity, but that does not show their true range of behaviors.

Behaviour in general

Dolphins (also whales and some pinnipeds, at times) are aerially acrobatic. There are multiple aerial behavior types and reasons, not all understood. Play is one of the causes of surface activities, but only at times. There is leaping, breaching, lunging, spy-hopping, slapping flukes and flippers onto the water surface (lobtailing and flipper slapping), porpoising, and lifting the flukes clear of the water (called fluking).

They are active both during the day and at night, by: feeding, travelling, socializing, playing, resting, aggressive interactions, sexual activity, sleep, etc. The duration and frequency of activities are influenced by such environmental factors as season, habitat, time of day, and tidal state, and by physiological factors such as reproductive seasonality. Bottlenose dolphins feed in a large variety of ways and habitats, primarily as individuals, but cooperative herding of schools of prey fish also occurs.

Behavioral manifestation of conflict directed toward the intimidation of rivals is often referred to as agonistic social signaling. Such behavioral displays include facial expressions, open mouth postures, jaw claps, forceful exhalations, vocal threat displays, stereotyped postures and movements, such as static open-mouth threats, open-mouth sparring, lobtailing, tail, and flipper slaps to the body of other individuals, chases, body charges, leaps and body slaps. Escalated agonistic displays include striking with flukes, biting, and jousting with tusks. Fighting is a last-resort solution to conflict. Dolphins can be very aggressive towards members of their own species, and also to other, smaller species of dolphins and porpoises.

Gentle contact behavior (petting, stroking, nuzzling) has been recorded in many cetacean species and is common among mothers and calves. However, there is no evidence of allogrooming or mother grooming of a calf in cetaceans. Rubbing and touching serves a secondary function to help remove dead skin that continually sloughs in cetaceans.

Displays

Visual displays can be simple, such as sexually dimorphic features, body postures or coloration patterns, or they can be elaborate sequences of behaviors that indicate a context, species, age, sex, or reproductive condition. In clear water, visual signals provide cetaceans and other marine mammals a close-range alternative to acoustic signaling; however, displays could alert predators or prey. Some marine mammals have adaptations for vision (e.g., large eyes, tapetum) that allow them to see and potentially communicate via visual signals in low light conditions. The anatomical adaptations for vision in water vary greatly among marine mammals.

Visual displays are useful for close-range communication and, because of close proximity, they may become tactile signals. Touching and rubbing occurs during play, sexual, maternal, and social contexts using the nose or rostrum, flippers, pectoral fins, dorsal fin, flukes, abdomen, and the entire body.

Bow riding and body surfing

Why do dolphins bow-ride or surf? It has been proposed that it is one of the mechanisms for travelling. But that may be unlikely, as dolphins have often been seen bow-riding and after some time heading back to whence they picked up the vessel. It is more likely that it is done for enjoyment or play. It appears to have been adapted from other wave-riding forms. Dolphins ride on slopes of large oceanic waves and on the curling waves that are formed as oceanic waves touch near-shore bottom. Surfing and bow riding are hydrodynamically quite different.

Many dolphins do utilize free-riding behaviors to reduce the energy cost of swimming. In this behavior, the dolphin takes advantage of the pressure field generated by another body and moves along with little or no energetic input. By situating itself on the bow wave, it can be pushed along or surf down the front slope of the wave.

Dolphins are exquisitely good at bow-riding, able to fine-tune their body posture and position so as to be propelled along entirely by the pressure wave, often with no tail (or fluke) beats needed. Riding the bow of a vessel makes these animals susceptible to being lanced or harpooned in areas where they are taken by humans. Where this occurs near shore and in apparent smaller populations, dolphins become shy of the bow, but on the high seas or in deeper water, dolphins often still ride the bow. Many species of dolphins, porpoises, and small toothed whale ride the bow, but some do not.

Playful behaviour

Play consists of actions performed for no other apparent purpose than enjoyment. It is recognized that play occurs in young animals to learn motor and social skills needed to survive. Play as “enjoyment” may have evolved simply because something enjoyable will be sought after, and if needed actions of learning are enjoyable, they will be done. Play tends to decrease in frequency as mammals become older and does not often occur in adults. Researchers are learning, though, that play in adults of other species is more common than previously thought.

Many marine mammals seem to be especially good at imitating the actions of their conspecifics or of individuals of other species. Apparently, dolphins learn the motor actions simply by observation. While this by itself is not play, the capability of imitation is often expressed as play. Dolphins would approach the object of imitation, slow their own travel to approximate that of the slower coinhabitant, and then move their body in exaggerated imitation of movements of the other individual. The described is motor or physical imitation, but toothed whales also practice vocal imitation. This may be an outgrowth of learning one’s own species-specific (and perhaps group or pod-specific) vocalizations, but the capability can then become a method of play. Beluga whales (Delphinapterus leucas) can also imitate human sound and will at times use these imitations in apparent mischievous play, while dolphins cannot imitate human sounds very precisely (due to the lack the vocal capability, not the intelligence to do so). Imitation proves of innovation, intelligence and cognition.

Dolphins (and pinnipeds) are known to interact in playful fashion with many other animate and inanimate objects in their environment. They may “tease” a sea turtle by mouthing and pulling on its tail or legs or they may swim beside a like-sized shark, imitating the movement that the shark makes. Some species of dolphins are also known for adroitly balancing pieces of flotsam on their jaws, flippers, dorsal fin, or tail, or carrying a piece of algae, plastic, or other pliable object in a manner to keep it balanced. This activity tends to take place when the group of animals is being highly social, usually with much sexual activity as well.

The mischievous behavior of pulling on gull or turtle legs or of inciting whales to become aggravated could be potentially aggressive or harmful play. Killer whales may use play as a form of learning (and possibly teaching, as well) of youngsters to efficiently hunt.

Tool use

Tool-use is generally defined as the exertion of control over a freely manipulateable external object (the tool) with the goal of altering the physical properties of another object, substance, surface, or medium (the target, which may be the tool user or another organism) via a dynamic mechanical interaction.

An example of tool se is foraging with sponges (called sponging). Dolphins travel in a meandering, undirected manner and nearly all dives are tail-out (fluke-up), reflecting relatively deep dives. Observations indicate that they are gently disturbing the sandy bottom with the sponge. Since the sponge cups over the rostrum, it cannot be worn during capture or consumption. When prey is detected, the dolphin droppes the sponge and probes the seafloor with the beak. Field observations and photographs suggest that the prey are small bottom-dwelling fish. Sponges are a foraging tool that likely both protects the rostrum from the gritty sand and shell and expands the surface area that can be searched. Fish are probably partially buried in sand and cannot be detected easily any other way, although underwater recordings indicate that echolocation is also used during sponging.

Reproductive behaviour

Reproductive behavior is an important part of the process of life of marine mammals and must serve to create a situation in which the young can safely be born and nurtured, and one which facilitates mating with suitable partners. In long-lived animals, reproduction has to be linked to the process of gathering the resources for both current and future survival.

Many marine mammals do not feed where they reproduce, hence they also must locate breeding areas where reproduction and parental care can take place without compromising nutritional requirements.

Cetaceans have evolved a behavioral and anatomical suite of adaptations allowing them to mate, give birth, suckle, and nurture their young entirely in water. Freed of the spatial and the temporal constraints imposed by reliance on land or ice to breed, cetaceans have developed a wide diversity of social systems and life strategies.

Hunting

Dolphins and toothed whales are hunters who chase down individual prey. Many species feed on highly mobile prey, such as schooling fish. When a dolphin charges into a fish school, the fish usually disperse, which can make the hunting less efficient. Dolphins and killer whales (Orcinus orca) have been reported to coordinate their feeding so that some individuals keep the fish in a tight school as other individuals feed. Communal foraging allows individuals to combine efforts to pursue and capture prey.

Most cetaceans are visual predators, at least in part. For odontocetes, echolocation is equally or even more important in some species in locating and targeting prey.

Although marine mammals are accomplished and sophisticated hunters, they too are preyed upon by a variety of terrestrial, avian, and aquatic predators. While the risk of predation is of little or no concern for some species, others exist under high levels of predatory pressure. Responses to predators are complex, and include detection and avoidance, fleeing, seeking habitat features for cover, and active defense by individuals as well as coordinated groups.

Calves presumably learn foraging specializations from their mothers, and patterns may spread through a population from observation, as an indication of transmission of knowledge.

Many marine mammals are top predators and historically may not have faced heavy predation pressure. The primary predators for pelagic marine mammals over evolutionary time are the killer whale and sharks. In the last few centuries, though, humans have been extremely effective predators of marine mammals, driving some species to extinction.

Relationships

Some animals live in situations where they interact repeatedly with the same individuals. In such setting, animals may develop a hierarchy.

Most dolphins have very fluid social groups. In their fission–fusion society, group composition changes on a minute-by-minute and hour-by-hour basis. Some individuals have strong social bonds and are sighted together for years at a time. Adult male bottlenose dolphins may also form coalitions with one to two other unrelated males. Members of a coalition are sighted together 70–100 % of the time, and alliances may last for over a decade. Males within a coalition often have highly coordinated displays, both when feeding and when escorting a female.

Socializing, including mating, is characterized by individuals in close proximity showing high levels of physical interaction including body contact and frequent aerial behavior such as leaps and somersaults. Mating and births occur year round.

Theare are also competitive behaviors and the most obvious are violent fights in which each opponent responds to aggression with an aggressive response. Such behaviors including contact and posturing are used to establish and maintain hierarchies. Systematic observations of winners and losers reveal that adult males are dominant over adult females. The rate of agonistic interactions is higher in males. The low rate of female agonism means that dominance is rarely contested among females, and female dominance can be stable over years. Serious agonistic interactions have been noted in between male conspecifics as well as with other species of dolphins.

Parental care

All mammals have some parental care when the female lactates and suckles the young. The mothering role is critical to mammalian life, and female parental care impacts many aspects of social behavior. There is enormous variability in parental care among marine mammals. Male mammals usually provide much less parental care to their young. This means that reproduction in most male mammals is limited by the number of females with which they can mate. This situation often leads to a polygynous mating system in which there is high variability in the mating success of different males. Males in polygynous species often fight other males for access to females. Some of the most extreme cases of sexual dimorphism in mammals occur in marine mammals.

Mothers influence offspring behavioral development by the experiences they provide, including migration and navigation, communication, social interactions, and foraging. To secure the transition from dependence to independence, marine mammal offspring must acquire necessary survival skills. Marine mammal young may develop foraging skills by independent (nonsocial) learning or by social learning, including stimulus or local enhancement (e.g., exposure to foraging areas with the mother), observation of foraging or prey caught.

Comunicating

We have covered dolphin communication in a previous post, so we shall only mention a few facts in this section.

Marine mammals have a very rich behavioral tapestry of sounds. Sound is used for communication and for wresting information from the environment.

Vocal communication includes noise from flukes or flippers striking the water surface, percussive sounds of jaw claps, teeth gnashing, or bubble emissions. Breaches, leaps, tail slapping, and chin slapping produce sounds under water that likely carry a communicative message. The exact communicative nature of pectoral fin (or tail) slapping is not clear, it may signal frustration or irritation, often conveying a threat or distress, or it may serve to invite play or socializing,

High-frequency broadband clicks appear to be used for echolocation and have been recorded mostly during foraging activities and to a lesser extent during socializing and traveling. Barks and quacks are produced predominantly during social and foraging behaviors, while grunts appear to be restricted to social behavior.

Each bottlenose dolphin produces an individually distinctive whistle vocalization called a signature whistle, which is probably used for individual recognition. The formation of signature whistles is a learned behavior. Dolphin calves learn their signature whistles within their first few months and retain them their entire lives.

Aggregation forming

Like many animals, cetaceans form aggregations for two main reasons: feeding and protection. Feeding can bring animals together in passive aggregations in areas of high resource abundance. Animals may also actively seek others to take advantage of benefits provided by other school members. Schools also serve to protect members from predation, by providing cover for individual members, confusing predators with synchronized movements of many individuals, increasing the chance of detection of a predator, and by providing defense. Occurring in large groups also increases the potential for social interactions, including reproduction; this may only be a secondary benefit of schooling.

Schools of hundreds or thousands are thought to be composed of smaller subunits of about 20–30 perhaps closely related individuals. There may be segregation in schools by age and sex and fluctuate in size and composition. Most schools are monospecific, but several species regularly occur in mixed-species schools. Some of these associations appear to be opportunistic: bottlenose dolphins, e.g., have been recorded to occur with over 20 different species of whales and dolphins.

Groups or subgroupings may be stable or repeated over periods of years. Basic social units include nursery groups, mixed sex groups of juveniles, and adult males as individuals or strongly bonded pairs. Long-term monogamous bonds have not been observed.

Migrating

Cetaceans are the only group of ocean breeding marine mammals in which some species have clear separation of feeding and breeding areas. Within the cetaceans, breeding sites can be loosely categorized as coastal, open ocean, or non-specific. Species with non-specific breeding sites are those that show no evidence of requiring different environments for breeding. This group contains most of the odontocetes and several of the mystecetes.

Coastal common bottlenose dolphins exhibit a full spectrum of movements, including seasonal migrations, year-around home ranges, periodic residency, and a combination of occasional longrange movements and repeated local residency. Much less is known about the ranging patterns of pelagic bottlenose dolphins. Long-term residency has been reported from many parts of the world and may take the form of a relatively permanent home range or repeated occurrence in a given area over many years.

As in other animals, territoriality in marine mammals can evolve if space is defensible, enabling monopolization of resources within that space. Territoriality is absent in most marine mammal species simply because no whales are territorial. Territoriality is expressed differently even between closely related species, and varies intraspecifically through short-term opportunistic behavior, throughout development, seasonally, and geographically.

Strandings

A large number of whales or dolphins of pelagic species such as sperm whales (Physeter macrocephalus), pilot whales (Globicephala spp.), false killer whales (Pseudorca crassidens), or rough-toothed dolphins (Steno bredanensis), may come ashore together for no apparent reason and in seeming good health. While there undoubtedly is more than one cause of mass stranding, evidence is accumulating that caregiving behavior engendered by tight social bonds may be involved in at least some cases. In most cases, in the absence of human intervention, the entire group perishes, victims of a social cohesion that must be highly adaptive in other circumstances. Death may be due to physiological stress or shock, a consequence of lying or struggling on dry land. On a population basis, mass stranding must be a rare event, or it could not persist evolutionarily.

But all we know about many species of cetaceans is only what we have learned from strandings. A rotting carcass on the beach can yield invaluable information on such things as anatomy, life history, genetics, disease, parasites, predators, contaminants, and feeding ecology. A live strandling transported to a holding facility can inform us about physiology, behavior, and cognition. A mass stranding offers a population sample (albeit potentially biased), opening to view parameters such as sex ratio, age structure, pregnancy rate, lactation rate, and relatedness within a group. A released strandling that has been tagged with a transmitter can yield invaluable data on movements, migration, and diving behavior.

Research

Behavioral studies benefit greatly from the ability to recognize individuals. Individual identification is an important tool for studies of animal behavior, ecology, and population biology. Much can be learned from recognition of individuals within a population or social unit, or from tracking individuals through time. Repeated observations of a recognizable individual can help to define its ranging patterns or site fidelity, or to quantify habitat use.

Behavioral descriptions often involve measurements of rates of occurrence of behaviors. These rates are measured most accurately when a selected individual is followed through time.

Sociobiology is the study of social behavior and social evolution based on the theory of adaptation through selection. As such it is primarily concerned with the adaptiveness of social behavior and the selective processes producing and maintaining adaptiveness. Understanding the selective processes involved includes studying the ecology, physiology, and behavior, as well as the demography and population genetics, of the species in question.

Telemetry is the process of obtaining data remotely, by transmitting information from a marine mammal or by storing it for later retrieval. Advances in computing power, microprocessors, and global telecommunication systems have led to extraordinary insights into the behavior, ecology, and physiology of many marine animals including mammals. It is possible to follow the fine-scale behavior of marine mammals for months at a time and from the most remote regions of the world’s oceans. These advances allow researchers to investigate how marine mammals use their world, quantify important physical and biological aspects of their environments, and test potential conservation measures designed to mitigate the effects of adverse human activities.

Alterations in behavior are common when marine mammals are exposed to human-made sounds. Sometimes the effects are subtle, noticable only by detailed observation and statistical analysis, e.g., changes in surfacing/respiration/dive cycles. More conspicuous effects include changes in activity, e.g., from resting or feeding to alert, facing toward the noise source, and so on. Upon exposure to strong man-made sounds, marine mammals engaged in feeding, social interactions, or other “normal” activities often interrupt those activities and swim away. When a noise source operates in the path of migrating individuals, they typically deflect a few degrees off their course and swim to one side or the other side of the noise source.

There are several differences between terrestrial and marine environments that have allowed the evolution of distinctive strategies in marine mammals. Drag, heat loss, and density of the water generate differences in scaling and costs of locomotion, allowing many marine mammals to have large body sizes and large home ranges. Sound is the form of energy that best propagates in water, not surprisingly marine mammals employ it for social communication and many species navigate via echolocation. Marine mammals have to find food that is for the most part dispersed and patchy, so they appear to have no territories outside of the breeding season. Due to the global effects of the overpopulation, the marine environment is very effected and marine mammals are thus affected by both global and local processes.

Reference:
Encyclopedia of marine mammals

Disclosure: This post contains affiliate links, which means I receive a commission if you purchase a product through these links. Don’t worry – the price is still the same for you. Visit my disclosure page for more information.