Intelligence: While the subjectivity of intelligence is still matter for debate and some question the capabilities of dolphins based on the structure of their brains it is indisputable that dolphins are capable of a range of complex behaviors. Dolphin cognitive abilities vary between species, but dolphins have shown self-awareness, problem solving skills, complex social interactions, the ability to teach skills to others and sufficient emotional intelligence to cause them to experience grief.
Social behavior: Dolphin social behavior varies across the different species; however, dolphins tend to form social groups known as pods. Pods can vary in size and function from 2 to 30 individuals. Generally speaking, these groups offer protection from predators, cooperative hunting opportunities, child-care, play and opportunities to practice courtship techniques. The common groups found are: maternal pods, juvenile pods and bachelor pods. Maternal pods are composed of adult females and their offspring, calves of 1-3 years of age which are afforded protection while nursing, weaning, and developing the skills they will need to survive. Juvenile pods are mixed groups of young male and female dolphins which have left their maternal pods. Bachelor pods are formed by pairs of males, while two pairs of males may join to form a pod of four, each male pair is closely bonded. In at least some species of dolphins these pair bondings are known to be between siblings or cousins and by working together they are able to improve their hunting and mating success rate. While maternal pods and juvenile pods show fluidity with individuals leaving and joining groups the bachelor pods are the longest lasting known social groupings in dolphins – often life-long. When a partner in a bachelor bond pair dies the widower may be adopted by the other pair in the case of pods of four, though he will not be bonded to them in the same way. While pod sizes usually vary between 2 and 30 on rare occasions large aggregations can occur for mating or foraging purposes. These large groupings can be made up of hundreds or even thousands of individuals and are known as super-pods or mega-pods. These super-pods are the shortest lived of the social groupings, dissolving after the hunting or mating has been completed.
Pods usually consist of a single species though anecdotal evidence suggests that pods or individuals may sometimes combine for short periods of time and create mixed-species pods. For instance a bachelor pair of one species travelling with a juvenile pod from another.
On rare occasions solitary dolphins may be found though the causes of this are poorly understood. Solitary dolphins are often seen to seek out socialization with humans which poses both a risk to the individual dolphin and the humans they interact with.
A pod of spinner dolphins
Source: Oleg Gavrilin
Recreational behavior: Dolphins are intelligent social animals which engage in problem-solving. As such it is hardly surprising that they exhibit a wide range of recreational behavior including playing with objects and peers.
Dolphins have been observed in solitary and group play using pieces of seaweed – carrying it on their rostrums, pectoral fins and flukes. Passing the seaweed between their body parts and between individuals. Yet pushing around, grasping, and releasing objects is not limited to seaweed. Dolphins have been known to engage in this type of play using seagrass, turtles, octopuses and even puffer fish.
Dolphins have also been observed blowing underwater rings. The dolphins first churn the water to generate a vortex, they then blow a bubble of air into this vortex. When the bubble hits the vortex it is deformed into a donut-shape or ring. The dolphins are then able to manipulate the direction of the ring by fanning the water with their tails or they can release more air bubbles to join and chain rings.
Most dolphin object play involves the use of other animals or plants; however, dolphins have been observed to play with sand – using their tails to fan it or their rostrums to physically push it.
Dolphins also play with one another: chasing, play-fighting, and riding waves and bow waves.
Dolphins riding a bow wave
Sexual and Reproductive behavior: Dolphins engage in both reproductive and recreational sex. Both forms of sex occur throughout the year with no defined mating season. Dolphins are not predisposed towards monogamous relationships and will mate with numerous sexual partners throughout their lives.
While courtship varies across the different species of dolphins, posturing, calls, and displays are common and some species even engage in gift giving. Some species of dolphins adopt ‘banana poses’ at the surface – arching their back so that their flukes and rostrum are above the water. Other species ‘rooster strut’, arching their backs and bobbing their heads up and down above the surface. Bachelor pairs can match the tone of their calls to improve their success rate with females. Indeed, courtship is largely male dolphins attempting to impress female dolphins with female dolphins showing selectivity when choosing a mate.
Male dolphins can also form gangs of up to 15 and coerce female dolphins into gang intercourse. In these cases, females are observed to be unwilling participants and will often try to escape the gang but only around 25% of escape attempts are successful. The males will harass the female through tooth raking, biting, chasing, tail-slapping, head-jerks, and slamming into them bodily. These are not isolated events and may happen to a female multiple times over the course of a year. It should be noted that because animals do not have human morals, sexual coercion in dolphins should not be compared with rape in humans.
While female dolphins may seem like passive partners, we know that they have complex vaginas with many folds and twists. It has been theorized that as well as protecting the sperm from seawater intrusion these may allow females to discriminate when copulating with males. Changing their body position slightly in order to misdirect sperm and prevent fertilization.
Sex is also important in strengthening the social bonds between pod members as well as being an enjoyable recreational activity for dolphins. Both male and female dolphins have been observed indulging in homosexual behavior which included mounting and genital contact though synchronous swimming displays have only been observed in males while females uniquely engage in buzzing each other’s genital-anal slits using echolocation.
Male dolphins, with their long prehensile penises, also engage in masturbation sometimes even making use of live or dead fish to do so.
Parental behavior: Reproduction in dolphins requires a significant time and energy investment for females with gestation lasting up to 18 months depending on the species and calves remaining with their maternal pods for 1 to 3 years. Live birth happens in the water and dolphin calves need to remain close to the surface to breathe. Dolphin mothers ‘infant carry’ their offspring, the calves swim closely to the mother – benefiting from hydrodynamic effects of staying close to the adult. While maintaining close contact benefits the calf it reduces the mothers swimming efficiency and increases the energetic cost of swimming. Female dolphins nurse their calves on milk and work together within maternal pods to share parental care responsibilities as well as teaching their offspring the skills they will need to survive. Dolphin calves nurse frequently, in some species every twenty minutes throughout the day and will need to nurse for the first two to three years.
When calves are born their mothers rapidly increase the frequency with which they call their signature whistle, the call that identifies them as an individual. This allows the young dolphin to quickly learn to recognize and respond to its mother’s call until it can develop its own signature whistle.
Dolphins care for their offspring and have strong parental bonds which can be seen from the accounts of grieving mothers across various dolphin species carrying their deceased offspring on the surface for days or even weeks to the detriment of their own health. As such it may be surprising to know that there have been observed cases of forced calf swapping with a dominant female forcing her younger sister to swap calves and preventing her from retrieving her offspring. This is thought to possibly be a way of asserting dominance.
Female dolphins unable to produce their own offspring have been known to kidnap calves from other cetacean species though these adoptions rarely last and the kidnapped calves usually disappear. However, in some rare cases females with calves have been known to adopt a calf from another cetacean species which, bearing in mind the significant commitment required to raise a single calf is quite surprising. In the known case the biological calf is thought to have perished as a result of diminished parental care.
By contrast male dolphins are known to attack young dolphins – even killing them sometimes. Since female dolphins are dedicated to the care of their calves and juvenile offspring for up to three years they will not reproduce during this time. In order to try and induce reproductive behavior male dolphins will separate calves, which aren’t related to them, from their mothers and kill them. By removing the calf, the males are trying to induce an estrous state in the female.
Mother with calf
Hunting behavior: Dolphins display a wide range of foraging behaviors which differ across species and populations. They make use of complex strategies to capture and subdue different prey items and have been shown to teach these techniques to other individuals. Strategies include bubble netting, beaching, hydroplaning, using bow waves, tail-slapping and using sponges.
Specific populations of dolphin have been observed selecting conical sponges that fit their rostrums, pulling them up and wearing them as a glove so that they can forage for food in the substrate without risking injury. Dolphins have been seen to hydroplane to catch fish in shallow water while orcas will beach themselves in order to capture sea lions. Orcas have also been observed swimming in synchronized groups at ice flows to produce a bow wave that will dislodge seals sheltering on the ice. Dolphins will also use tail-slapping to stun fish before eating them and stir-up muddy bubble nets to cause fish to jump out of the bubble net making them easier to catch.
Communication: Dolphins can communicate using a range of methods including vocalizations, non-vocal acoustic cues, visual cues, and tactile cues and possibly even echolocation. Most signaling between dolphins is acoustic in nature, this is likely because sound travels well underwater while eyesight can be impaired by visibility.
Vocalizations are any sounds made using the vocal organs – in the case of dolphins this is the blowhole, nasal sacs, and associated organs. Dolphins produce two distinct types of vocalizations called pure tones and pulse tones. Pure tones are used in direct communication and take the form of whistles, chirps, screams and other continuous sounds whereas pulse tones utilize the clicks dolphins use in echolocation. The way that dolphins communicate varies between species, some produce signature whistles to identify individuals, others produce group whistles, and some do not use pure tones at all but seem to communicate purely through pulse tones.
Pulse tones (clicks) are used for echolocation with dolphins emitting up to 200 clicks a minute for this purpose. However, dolphins also seem to use these pulses more intensively – up to 2000 clicks a minute in order to communicate and signal emotions. Pulse tones are often used to signal excitement or aggression – they are used when dolphins want to signal play but are also used by aggressive males when herding females and mother dolphins when chastising misbehaving calves. These densely packed click messages, called click trains, can be difficult to distinguish from echolocation clicks and, in some cases, can sound more like barks or squawks to human ears.
Non-vocal acoustic cues are the sounds dolphins produce without using their vocal organs, these include tail slaps, fin slaps, jaw claps or pops, chuffs, breaches, and bubble blowing. These signals can be used in different ways and the context of their use is important.
Dolphins can use their tail to slap the surface of the water and produce a loud booming sound. This can be used to call attention to a dolphin or signal that it is time to move on from an area, but it is also associated with aggression between dolphins. Jaw claps are another signal used aggressively to threaten during confrontations but can also be used in play fights. Dolphins also signal their aggression through loud forced exhalations called chuffs.
The role of fin slaps against the water’s surface, breaches and bubble blowing are less certain and scientists are just beginning to uncover their use in communication between dolphins.
Dolphin visual cues can be either static displays or posturing. Static displays are passive and are visual cues that dolphins can use to learn about one another – coloration can help to distinguish similar species of dolphin while size and scarring may play a role in identifying dominance and sex. Active posturing is used to signal to other dolphins and includes the S-position, which may be mimicry of shark defensive postures and is used to denote aggression. In the S-position the dolphin will flare their pelvic fins, open their jaws, and bend their body in an S-shape dorsoventrally. Other visual cues include head arching, rolling their eyes to display the whites, flexing the tail and head dorsally, side to side head-wagging, rolling over submissively and snits. Snits are when dolphins jerk their head sideways sharply with open or closed jaws, sometimes with a vocalization, as a sign of aggression.
Other visual cues include carrying objects, which is usually a courtship signal to try and impress potential mates and defecating which may be used as a warning signal.
Dolphins can also use a range of tactile cues including: biting, butting, touching pectoral fins, mouthing, nuzzling, pectoral patting or stroking, pushing, ramming, rubbing, ventral carrying, rostrum carrying, tail slapping and tooth raking. Some of these are closely associated with parental care – dolphin mothers will often display chest and rostrum stranding whereby a calf is lifted out of the water either on the chest of the mother between the pectoral fins or carried on the rostrum perpendicular to its mother. Overlapping pectoral fins or hand-holding, rubbing with open mouths (mouthing) or closed rostrums (nuzzling), tapping or stroking with pectoral fins (pectoral pats) and rubbing bodies all seem to be bonding behaviors between dolphins. However, biting, butting, pushing, ramming, tail slapping and tooth raking are all aggressive behaviors.
There is some thought that dolphins may be able to listen in to the echolocation of others to perceive what they are seeing with their clicks though whether this is intentional communication by one dolphin to another is not yet clear.
Aggressive behavior: Dolphins are known to exhibit aggressive behavior. Interestingly this seems to be largely associated with male dolphins and young male dolphins in particular. In the section on reproductive behavior we briefly discussed sexual coercion and infanticide. However, dolphins are also known to attack individuals from other species (conspecifics), particularly porpoises. There are several theories as to why dolphins attack porpoises, these include: competition for resources, sexual frustration, misdirected or rehearsed infanticide and object play.
Territoriality or competition for food has largely been dismissed. While the animals may occupy the same territory there is minimal dietary overlap between the species and dolphins have been observed chasing down porpoises outside of their territory. Additionally, the fact that this behavior is associated primarily with young male dolphins and not female dolphins suggests a reason other than territoriality.
The fact that porpoises are approximately the same size as dolphin calves has led to the alternative theory that dolphins are practicing their infanticide skills. Male dolphins will kill calves in order to try to induce estrous in the calves’ mothers. This allows them to bypass waiting up to three years for a dolphin mother to naturally return to an estrous state. In small populations where access to females is limited the best tactic for some male dolphins may be to kill their rivals’ offspring and induce estrous in the available females. In these conditions rehearsing the skills required to kill a calf – separating it from its pod and killing it – might directly contribute to the success of males passing on their genes. However, detractors argue that this is unlikely since the behavior is only seen in sub-adults and non-dominant males who wouldn’t have reproductive access to females.
The aggressive behavior in these attacks has included bite marks to the genital areas of the porpoises. It should be noted though that porpoises are not targeted based on sex and the dolphins to not appear to try and copulate with the porpoises they are attacking. Instead some researchers see this as sexually frustrated behavior by sub-adults and low-ranking adults who are not having the opportunity to mate. In these cases, the attacks are seen as linked to spikes in the levels of testosterone among young male dolphins during the peak breeding time of the summer.
Whatever the cause the attacks often turn into object play with dolphins seen throwing dead porpoises through the air, carrying their carcasses in their mouths, and carrying dead porpoises on their rostrums – passing them between dolphins.
Attacks on porpoises seem to follow a pattern. Attackers break away from larger pods to target porpoises. Lone porpoises are targeted or separated from their pod, sometimes a couple of porpoises might be targeted together. The sex of the porpoise seems to be irrelevant, but the targets are almost always of similar size to dolphin calves. These attackers will corral the porpoise or porpoises to prevent their escape, sometimes sandwiching the unfortunate victim between two of them. Once a porpoise is targeted the attackers may be joined by additional dolphins. The dolphins will repeatedly ram the porpoises with their rostrums, fling them into the air and use their rostrums to lift the porpoise’s tail out of the water – thereby forcing its blowhole under the water. Deaths result from blunt-force trauma or drowning during attacks that can last over twenty minutes and, in some cases, up to two hours. Necropsies of porpoises killed by dolphins have shown blunt force trauma, teeth raking, bite marks and punctures. Broken jawbones, fractured ribs, broken scapulae, and tooth marks to the body including the genital regions.
Defensive behavior: The main natural predators of dolphins are large sharks. Sharks are powerful predators and to help protect themselves dolphins will often travel in pods. Pods allow dolphins to stay alert even when some are sleeping are offer defensive advantages. Primarily dolphins will avoid sharks where possible. However, when forced to defend themselves dolphins can out-maneuver sharks. They will then hit the shark with their flukes and rostrums. Tail slapping can confuse the shark while ramming the gills and underbelly with their rostrums can stun sharks, render them unconscious or even kill them. Surviving sharks will usually quickly retreat. The largest dolphins, orcas, will target and eat sharks.
Sleeping behavior: Dolphins face a range of circumstances that make sleep a challenge. They are voluntary breathers who have to remain conscious in order to be able to surface and breathe, they need to stay alert for predators, and they need to maintain physiological processes such as swimming to aid thermoregulation. As a result, dolphins utilize unihemispheric sleep, wherein one hemisphere of the brain enters sleep while the other remains awake. The hemispheres alternate over the course of a sleeping period so that both hemispheres can be rested without the dolphin ever fully losing consciousness. It is possible to tell which hemisphere of the brain is sleeping because the opposite eye is closed during this period. So when the left hemisphere is asleep the right eye is closed and when the right hemisphere is asleep the left eye is closed. On average dolphins will engage in eight hours of slow-wave sleep a day, four for each hemisphere. REM sleep is difficult to discern in dolphins though it has been briefly recorded (6 minutes in one night) in pilot whales, this means it is unclear whether dolphins engage in dream sleep. However, it should be noted that one of the main functions of REM sleep is to warm the brain up ready for being awake. Since dolphin brains are never fully asleep, they are kept warm and alert without the need for REM. While studies have been limited to 15 days, dolphins monitored over this time period have shown no deterioration in alertness or responsiveness and it is believed that dolphins can effectively use unihemispheric sleep indefinitely.
While sleeping in this way dolphins can sleep on the seabed in shallow waters and surface regularly to breathe, swim slowly on the surface in pairs or rest motionless on the surface in what is known as logging. Unlike adult dolphins, calves rest while being towed in their mothers’ slipstream. This echelon swimming means the mothers must sleep while moving – this is of particular importance with new-born calves who lack the blubber to be buoyant and would sink without the mother’s help.
Research has shown that dolphins are highly intelligent animals that have demonstrated self-awareness, problem solving skills, complex social interactions, the ability to teach skills to others and emotional intelligence to cause them to experience grief. We know that they lead complex social lives in their natural environments with fluid pod compositions. We know that they enjoy a range of recreational activities. As such we must, by now, be acutely aware of just how inadequate captive environments are.
Proponents of dolphin captivity often cite its contribution to education, conservation, and research yet these claims are problematic for a number of reasons. Aquariums or dolphinariums may represent the only opportunity many members of the public will ever have for seeing dolphins. While this should be a chance for them to develop an appreciation for a complex living animal and an understanding of its natural history what they will instead witness is abnormal behavior in a physiologically and psychologically compromised individual which is unrepresentative of its wild counterparts. Indeed, behavioral anomalies are particularly prevalent in captive predators that would have large natural ranges including increased infant mortality and repetitive functionless behavior called stereotypy. Stereotypy observed in captive dolphins includes beaching themselves on performance platforms, pacing the pool in loops, thrashing violently, remaining motionless and chewing on parts of the enclosure to the extent that they break their teeth. Additionally, captive dolphins are known to exhibit severely distorted behaviours including aggression towards each other and humans they interact with. Examples can be seen in killer whales at SeaWorld where one individual, Nakai, sustained a large deep bite to the underside of the jaw from another orca (a wound that remained open for more than 3 years) and the now infamous Tilikum which is known to have killed three people. While aggression towards humans in the natural environment is low, trainers in dolphinariums often carry emergency oxygen supplies in case they are held under water and visitors interacting with dolphins are normally required to sign waivers. Furthermore, educational signage is usually lacking in content at these facilities, with a focus on animal training and captive care instead of wild behavior and conservation. This signage is also usually poorly placed and unlikely to attract visitor attention.
Ex situ conservation usually hinges on raising awareness to incite public support for animal protection and raising animals for release into wild populations. As discussed above dolphinariums routinely fail to adequately educate the public and their impact on public opinion with regards to conservation is negligible. To raise animals for release, dolphinariums would need to raise genetically and behaviorally fit individuals. Yet we know that dolphins in captivity show behavioral abnormalities and that repeated inbreeding in captive animals does little to raise genetically fit individuals for release to the wild. It should also be noted that well known dolphinariums have refused to release captive dolphins including retiring them to sea pens on the grounds that the natural environment is not suitable for captive raised animals – citing pollution in natural habitats. This is despite evidence that captive dolphins can be retired successfully to sea-pens and that this can benefit their health. Even more damning is the fact that dolphinariums such as SeaWorld use marine mammal rescues as an opportunity to seize more breeding stock (Morgan a young female orca taken through an affiliate dolphinarium). It is also important to remember that the most displayed dolphins are bottlenose dolphins – an animal with a healthy wild population which do not need awareness raising for conservation or a captive breeding population to support the wild populations.
Ex situ research has been important in exploring the cognitive capabilities of dolphins. The restrictive conditions and accessibility of captive facilities has helped researchers to explore dolphin intelligence and physiology, for example studying unihemispheric sleep and self-recognition. However, it should be noted that this research was conducted at research facilities not dolphinariums. It is also important to be aware that captive animals can significantly differ from their wild counterparts both physiologically and psychologically. Captive animals suffering the effects of chronic stress and exhibiting abnormal behavior are not the best models for the response and behaviour of wild dolphins. Even when dolphins may seem well adjusted it can be misleading, studies in other animals have shown captive individuals to outperform wild animals in some cognitive tests possibly as a result of the types of novel enrichment provided in their environments. Additionally, while studies into cognitive ability and physiology in captivity can be interesting it must be questioned how these contribute to the understanding and conservation of wild populations now that we are better informed about their intelligence and social complexity.
As such it seems clear that the captive dolphin industry is a consumer of wildlife not a conserver and it is motivated primarily by profit instead of welfare or conservation.
Beyond dolphinariums we must also inspect the ethics of the use of dolphins in the military and in Dolphin Assisted Therapy programs.
Naval forces began using trained dolphins decades ago with some of the earliest uses being during the Vietnam War. Generally speaking, dolphins can be trained to locate and mark the position of sea mines though they are also used for security – locating divers or swimmers trespassing in restricted areas and object recovery, finding and marking the location of military hardware.
In the case of the US Navy, dolphins are viewed as part of national defense and it is claimed that they are treated as naval personnel which are afforded the highest quality of care available. Indeed, according to the Navy their marine mammal training and care program has published over 1500 scientific papers, collaborated with the National Marine Mammal Foundation to publish over 200 papers and played a key role in pioneering marine mammal medical care (between 2012 and 2019 around $39 million of their $75 million budget was allocated to veterinary care). While the US Navy is investigating the use of robotics to replace their marine mammal program the technology is not yet able to match the performance of marine mammals. Furthermore, even if and when dolphins are replaced by technology it is unlikely that the trained animals will be rehabilitated for release to the wild. Previous attempts have failed with released dolphins being unable to survive independently without the foraging skills necessary for an independent life in the wild, instead these retired dolphins are likely to be maintained in captive environments until the end of their lives.
Military dolphins experience similar lives to those maintained in in dolphinariums with drastically reduced living areas and restricted social lives. While naval personnel may view their dolphins as fellow crew members these animals are effectively conscripts – they did not volunteer for service or consent to testing. Military service dolphins are placed in what may be stressful and dangerous situations: marking the position of explosive devices, marking the position of hostile and possibly armed divers, marking the position of potentially hazardous military hardware. Furthermore, while other military animals such as dogs are domesticated, dolphins are wild animals which are not adjusted to collaborating and cohabiting with humans.
Finally, we come to Dolphin Assisted Therapies which are also known as Swim-With-Dolphin programs. While some centers may simply offer the opportunity to swim with a captive animal others make unproven claims that dolphins have therapeutic benefits. Yet there is no evidence to support this. Proponents insist that these therapies can help people with Autistic Spectrum Conditions, Down’s syndrome, AIDS, epilepsy, cerebral palsy, learning difficulties and hearing impairments. They argue that dolphins can affect the human body utilizing their vocalizations. However, independent research groups have found that there is no valid scientific evidence to support the use of Dolphin Assisted Therapy.
Reviews of studies that support Dolphin Assisted Therapy found that the research did not meet the minimum standards for medical clinical trials. Issues with these studies included: inadequate methodology, the inability to definitively establish causality and conflicts of interests for the researchers. In particular the studies failed to account for other variables that would have beneficial effects on those undergoing the treatments – such as new and exciting environments and experiences. Additionally, German researchers found that in these therapeutic sessions the dolphins largely ignored swimmers, they also found that the dolphins barely vocalized either and that the swimmers would have received greater therapeutic benefits from playing with dogs.
While some people may see little harm in something that offers hope, Dolphin Assisted Therapies are damaging in numerous ways: they hinder genuine treatment and research, they are financially damaging to those paying for treatment, they risk serious injury to swimmers and they rely on the unethical use of captive dolphins.
The promise of miracle treatments for various conditions undermines real treatment and research which has realistic expectations for progress and improvement for patients. People become reliant on unproven therapies with promises of extreme improvements and are less likely to engage with genuine treatments that usually only promise modest expectations for progress and improvement.
People can become so invested in these ‘miracle cures’ that they invest thousands of dollars (in some cases more than $7000) to try and help their loved ones. While some may be able to write-off such expenditures, others will commit money they can ill-afford to waste because they are desperate.
As has been discussed previously, dolphins can be aggressive and are known to injure people working with them. In fact, people taking part in Dolphin Assisted Therapies have been slapped, bitten and rammed before – not to mention the possibility of contracting skin diseases. This should, of course, be of little surprise when dealing with a large apex predator known to be able to commit infanticide, beat porpoises to death and, on occasion, kill sharks.
While some facilities use captive bred dolphins many around the world are also reliant on wild caught dolphins to supply the animals for their ‘treatment’ programs.