Skip to main content
Open Access Publications from the University of California


The International Journal of Comparative Psychology is sponsored by the International Society for Comparative Psychology. It is a peer-reviewed open-access digital journal that publishes studies on the evolution and development of behavior in all animal species. It accepts research articles and reviews, letters and audiovisual submissions.

Volume 23, Issue 3, 2010

Special Issue

The Value of Ex Situ Cetacean Populations in Understanding Reproductive Physiology and Developing Assisted Reproductive Technology for Ex Situ and In Situ Species Management and Conservation Efforts

Wild cetacean populations have uncertain futures in the face of shifting climate conditions and the continued encroachment of their unique ecosystem by human activities. Core conservation efforts focus on habitat protection and understanding the natural ecology of a species, but such efforts arein complete without a comprehensive understanding of a species’ physiology. Ex situ populations of cetaceans provide a unique opportunity to collect this physiological data, and thereby serve as an important component of any conservation effort. The sustainability of captive cetacean populations is in turn dependent on a thorough understanding of reproductive physiology, and such research has facilitated the development of assisted reproductive technology (ART). ART, specifically gamete preservation for genome resource banking, artificial insemination and sperm sexing, has been used to significantly enhance the genetic, reproductive and social management of ex situ cetaceans. For endangered cetaceans and other marine mammals, ART will permit the establishment of permanent repositories of valuable genetic material which could be used to maximize their reproductive potential and maintain the species’ genetic diversity; an approach that, when combined with in situ conservation efforts, may prevent their extinction.

Research with Navy Marine Mammals Benefits Animal Care, Conservation and Biology

The benefit and ethics of keeping marine mammals in captivity has been a source of debate for several decades. One of the center pieces of the debate is whether there is real benefit to marine mammals as a whole that results from research on captive marine mammals. The Navy Marine Mammal Program (MMP) keeps marine mammals for national defense purposes. However, in nearly 50 years of existence, the MMP has also been a leader in marine mammal research. The results of the research conducted by the MMP has not only benefited the care of marine mammals in captivity, but has directly and indirectly improved our understanding of the behavior, physiology, and ecology ofanimals in the wild. Research conducted with the MMP marine mammal population has produced demonstrable improvements in veterinary care and has lead to some of the earliest advances inproviding guidelines for mitigating the impact of sound on wild marine mammals. Additionally, our understanding of echolocation, diving physiology, and husbandry behaviors has greatly benefited from MMP research. Future and current work conducted by the MMP will continue to add to the knowledge base of marine mammal biology while contributing to their care and conservation.

How Studies of Wild and Captive Dolphins Contribute to our Understanding of Individual Differences and Personality

The study of individual differences in animals and humans has flourished in recent years. This work has revealed personality traits in a wide range of species, including dolphins. However, there are few systematic studies of dolphin personality despite many reasons to assume that personality plays an important role in dolphin behavior. Dolphins live in complex societies and demonstrate a broad and diverse behavioral repertoire, which allows for the possibility of consistent individual differences. In this paper, we discuss the available evidence for individual differences and personality in dolphins from a variety of behavioral contexts from both captive and wild populations, as well as the significance of such differences for theories of dolphin behavior, dolphin welfare, and conservation.

What can Captive Whales tell us About their Wild Counterparts? Identification, Usage, and Ontogeny of Contact Calls in Belugas (Delphinapterus leucas)

Contact calls are ubiquitous in social birds and mammals. Belugas are among the most vocal of cetaceans, but the function of their calls is poorly understood. In a previous study we hypothesized that a broad band pulsed call type labeled “Type A,” serves as a contact call between mothers and their calves. Here we examined context-specific use of call types recorded from a captive beluga social group at the Vancouver Aquarium, and found that the Type A call comprised 24% to 97% of the vocalizations during isolation, births, death of a calf, presence of external stressors, and re-union of animals after separation. In contrast it comprised 4.4% of the vocalizations produced during regular sessions. We grouped 2835 Type A calls into five variants, A1 to A5. A discriminant function analysis classified 87% of calls in the same groupings that we assigned them to by ear and visual examination of spectrograms. The variants do not represent individual signatures. One variant, A1, was used by three related individuals: an adult female, her male calf and his juvenile half-sister. Our previous research documented the gradual development of the A1 variant by the male calf, until at 20 months he was producing stereotyped renditions of his mother and sister’s A1. We used our findings to generate testable predictions about the usage of these signals by wild belugas. We verified the existence of signals with the same distinctive features as the contact calls found in captivity in the repertoire of St. Lawrence Estuary herds, and documented their usage by two wild individuals from different populations. In the St. Lawrence, these were emitted by a female calling after a dead-calf. In Hudson Bay, by a temporarily restrained juvenile. We propose that these calls function in nature, a sin captivity, to maintain group cohesion, and that the variants shared by related animals are used for mother-calf recognition.

What Laboratory Research has Told Us about Dolphin Cognition

Studies of sensory, cognitive, and communicative skills of bottlenose dolphins ( Tursiops truncatus ) were carried out over a 34-year period at the Kewalo Basin Marine Mammal Laboratory in Honolulu. Findings on sensory skills included fine discrimination of auditory frequency differences andauditory duration, good visual resolution capabilities in water and in air, and sharing of object recognition across the senses of vision and echolocation. Short-term memory for auditory and visual materials was well developed, including memory for lists of items. Concept learning was demonstrated within several paradigms, including discrimination learning sets and matching-to sample. Dolphins understood novel instructions conveyed within artificial gestural or acoustic language systems using “sentences” as long as five words whose interpretation required processing of both the semantic and syntactic features of the languages. Gestural instructions were understood as reliably when conveyed through television images of trainers as when conveyed by live trainers. The words of these languages were understood referentially, including an ability to report whether a referenced object was present or absent in the dolphin’s tank. Both vocal mimicry of novel sounds and behavioral (motor) mimicry of other dolphins and of humans was demonstrated, an extensive and unique dual ability among animals tested, including an understanding of the concept of imitate as well as an understanding of the concept of behavioral synchrony. Behavioral synchrony (two dolphins acting together) was carried out effectively for behaviors directed by a trainer and for self directedbehaviors. The dolphins understood the referring function of the human pointing gesture,possibly as a generalization from the referring function of their echolocation beam. Self-awarenesswas demonstrated in two domains: the dolphin’s conscious awareness of its own recent behavior, and its conscious awareness of its own body parts when symbolically referenced. This suite of findings attest to the remarkable flexibility and extensibility of dolphin cognition and reveals cognitive competencies that surely aid the dolphin’s effective functioning within its complex social and ecological milieu.

Cognitive Research with Dolphins (Tursiops truncatus) at Disney’s The Seas: A Program for Enrichment, Science, Education, and Conservation

The dolphins at Disney contribute to a cognitive research program. This program has been very successful in four main areas: enrichment, science, education, and conservation. Dolphins are large brained,long-lived mammals with extended developmental periods, complex social lives, a large variety of foraging techniques, and intricate vocal emissions; consequently, they need to engage incognitive tasks, and they respond well to them. Our tasks have been designed for scientifically valid data collection focused mostly on questions relating to echoic object recognition, communication, and imitation/synchrony. The results have been published in peer-reviewed research journals and are summarized here. Data collection occurs in front of the public and appears to create a connection between the visitors and the dolphins. Through this program the dolphins under Disney’s care have been able to promote conservation via our publications, public education, the testing of new technologies, staff (veterinary, research, husbandry) support at in situ research sites, and direct financial contributions. The program may be a useful example for other public facilities housing dolphins.

Dolphin Cognition: Representations and Processes in Memory and Perception

Many people agree that dolphins are sentient beings, but few would claim to know what being a dolphin is like. From a psychological perspective, a dolphin’s experiences are a function of its mental capacities, especially those processes that relate to memories, percepts, thoughts, and emotions. This paper reviews what is currently known about dolphins’ cognitive abilities, focusing on how they perceive and remember events. Experiments with captive dolphins show that they can flexibly access memories of past events and construct sophisticated representations of the world and themselves.How dolphins act and what they remember about their actions impacts what they perceive, which in turn guides their thoughts and decisions. Many of the actions and events that shape a dolphin’s experience are internally generated and monitored. Knowing how dolphins perceive temporal patterns, objects, emotions, actions, agents, scenes, messages, and motivations can help clarify what dolphins’ thoughts, memories, and experiences are like. Only by giving dolphins a way to show what they know, or can learn, can we hope to understand what goes on inside their heads.

Observational Learning in Wild and Captive Dolphins

Many non-human species imitate the behavior of others, and dolphins seem particularly adept at this form of observational learning. Evidence for observational learning in wild dolphins is rare, given the difficulty of observing individual wild animals in sufficient detail to eliminate other possible explanations of purported imitation. Consequently, much of the evidence supporting observational learning in dolphins has involved animals in captive settings. This research suggests that dolphins have an affinity for mimicry, and that they are more successful at observational learning if they choose to imitate another rather than being asked to do so. These results, combined with those obtained from wild dolphins, suggest that imitation may play important roles in the ontogeny of a variety of behaviors, including those involved in communication, foraging, and parenting.

Bottlenose Dolphins' (Tursiops truncatus) Theory of Mind as Demonstrated by Responses to their Trainers’ Attentional States

The present study examined the ability of dolphins to follow the gestural signs presented by humantrainers in various attentional states in order to understand the social cognition of dolphins. Thehuman trainers enacted the gestural signs by orienting their bodies and heads in different directions.If the dolphins were attending to the attentional state of the human trainers, their performances wouldbe affected by the orientation of the head only. Results showed, however, that the dolphins’ behaviorswere controlled by the orientation of the trainers’ bodies rather than that of their heads. Twoadditional tests further supported the minimal impact of head orientation on responses to humangestural signs. The present results might be influenced by the current experimental setting, thus weneed further efforts to accumulate empirical evidence on social cognition in dolphins.

Inaugurating the Study of Animal Metacognition

Metacognition—the ability to monitor and control one’s own cognition—is a sophisticated ability that reveals humans’ reflective mind and consciousness. Researchers have begun to explore whether animals share humans’ metacognitive capacity. This article reprises the original study that explored metacognition across species. A captive dolphin performed an auditory pitch-discrimination task using High/Low discrimination responses and an Uncertainty response with which he could declineto complete any trials he chose. He selectively declined the difficult trials near his discriminative threshold—just as humans do. This comparative exploration of metacognition required a trial intensive titration of perceptual threshold and the training of a distinctive behavioral response. It could not have been conducted in the wild, though the naturalistic observation of dolphin uncertainty behaviors and risk-management strategies would no doubt yield complementary insights. The dolphin study inaugurated a new area of cross-species research. This research area opens a new window on reflective mind in animals, illuminates the phylogenetic emergence of metacognition, and may reveal the antecedents of human consciousness.

Journal Publication Trends Regarding Cetaceans Found in Both Wild and Captive Environments: What do we Study and Where do we Publish?

Scientists conducting research on cetaceans have a variety of publication outlets. However, a formal assessment of those options has not been conducted. To better understand the trends in publications regarding dolphins and whales, we surveyed peer-reviewed articles from 9 different databases. Our survey produced 1,628 unique articles involving 16 cetaceans found both in the wild and in captivity. Each article was coded a variety of information: habitat, geographic location, genus, topic, research design, and journal type. The analyses indicated that 68% studies were conducted with wild populations and 29% were performed with captive populations. A quarter of the journals publishing research on dolphins or whales published almost 80% of all the articles selected for this study. Studies were conducted across many different geographic locations and topics. Other major findings elucidated relationships between various variables. As expected, specific topics were more likely associated with certain research designs, habitats, and journal types. One of the most important findings of this study is the limited publication of research conducted with captive cetaceans. While it is important to continue to examine animals in their natural environments, there is much to be learned from studies conducted with animals in captivity. As a group, we must become cognizant of the publication trends which currently describe our research progress as we integrate our knowledge from captivity and the wild.