Associations and the role of affiliative, agonistic, and socio-sexual behaviors among common bottlenose dolphins (Tursiops truncatus).

Little is known about the specific behavioral exchanges that occur on a day-to-day basis between dyads of common bottlenose dolphins (Tursiops truncatus). This study assesses the proportion of time dyads spend in proximity (within ∼2m) and the proportion of time spent in affiliative, agonistic, or socio-sexual contexts within and between age/sex dolphin pairings to better understand their social relationships. Observations of bottlenose dolphins housed at the Roatan Institute of Marine Sciences provided 10.5h of underwater footage from which to examine association coefficients and inter-individual interactions. These data suggest similar patterns to previous studies on bottlenose dolphins: mother-calf dyads shared the highest coefficients of association, followed by male-male, female-female, and male-female dyads. Four classes of association coefficients were defined for the population including low, medium, medium-high and high. This study is the first to quantitatively assess association patterns concurrently with affiliative, agonistic, and socio-sexual behaviors for bottlenose dolphins. The predominant relationships were affiliative.

Where are we in the study of animal emotions?

The study of emotion is rife with debate over issues as fundamental as how to define emotion, and such disputes are particularly common in the nonhuman animal emotion literature. Here, we seek to address some of these issues, especially in terms of how they relate to animal research. Definitional issues are prevalent; clear definitions are often not given of crucial terms, including 'emotion,' and even where provided, such terms may be used inconsistently throughout a single paper. Further disagreement over the structure of emotions, and the nature of conscious experiences involved, leads to consistent differences in authors' criteria for emotions. We concur with those who believe that animals experience emotions and believe that animal emotions should be studied in their own right, not only as they compare to those of humans. We also propose several avenues for future research that we believe will further our understanding of animal emotions. First, the use of multiple measurement methods to assess emotional responses is most likely to provide the information necessary to distinguish between various states and opens the field to more research in harder-to-study species, such as marine mammals. Second, researchers should also endeavor to increase the range of emotions studied, particularly positive ones, in order to move toward a more balanced range of studied states. Finally, we believe that several aspects of personality research would prove beneficial to the study of animal emotions, particularly the distinction between trait and state emotion and the use of the rating method. WIREs Cogn Sci 2016, 7:354-362. doi: 10.1002/wcs.1399 For further resources related to this article, please visit the WIREs website.

Acoustic behavior associated with cooperative task success in bottlenose dolphins (Tursiops truncatus).

Although many species have proven capable of cooperating to achieve common goals, the role of communication in cooperation has received relatively little attention. Analysis of communication between partners is vital in determining whether actions are truly cooperative rather than serendipitous or learned via trial and error (Chalmeau and Gallo in Behav Process 35:101-111, 1996a. doi: 10.1016/0376-6357(95)00049-6 , Primates 37:39-47, 1996b. doi: 10.1007/BF02382918 ). Wild cetaceans often produce sounds during cooperative foraging, playing, and mating, but the role of these sounds in cooperative events is largely unknown. Here, we investigated acoustic communication between two male bottlenose dolphins while they cooperatively opened a container (Kuczaj et al. in Anim Cogn 18:543-550, 2015b. doi: 10.1007/s10071-014-0822-4 ). Analyses of whistles, burst pulses, and bi-phonations that occurred during four contexts (i.e., no container, no animals interacting with container, one animal interacting with container, and two animals interacting with container) revealed that overall sound production rate significantly increased during container interactions. Sound production rates were also significantly higher during cooperative successes than solo successes, suggesting that the coordination of efforts rather than the apparatus itself was responsible for the phonation increase. The most common sound type during cooperative successes was burst pulse signals, similar to past recordings of cooperative events in bottlenose dolphins (Bastian in Animal sonar systems. Laboratoire de Physiologie Acoustique, Jouy-en Josas, pp 803-873, 1967; Connor and Smolker 1996).

Underwater observations of dolphin reactions to a distressed conspecific.

This report describes the epimeletic (or "caregiving") behavior produced by members of a group of Atlantic bottlenose dolphins (Tursiops truncatus) and the possible role of the ailing animal's distress call in eliciting such behavior. Epimeletic behavior in cetaceans most typically involves forms of support provided to a distressed, injured, or dying animal (Caldwell & Caldwell, 1966). Analyses of underwater video and corresponding acoustic recordings revealed a distressed dolphin (the DD) that frequently produced what are most likely distress calls, often paired with the emission of long bubble streams. The frequency of her whistle production was positively correlated with the frequency of the supporting behaviors the DD received from other dolphins. These helping behaviors included raft formations, lifts, and stimulating pushes that were predominantly directed toward the upper third of the DD's body, all of which appeared to be directed towards bringing the DD toward the surface so that she could breathe. This is the first documented underwater account of multiple wild bottlenose dolphins providing epimeletic care to a distressed conspecific, and highlights the possible role of distress calls in such scenarios.

Can bottlenose dolphins (Tursiops truncatus) cooperate when solving a novel task?

Cooperative behavior has been observed in cetacean species in a variety of situations, including foraging, mate acquisition, play, and epimeletic behavior. However, it has proven difficult to demonstrate cooperative behavior among dolphins in more controlled settings. Dolphins (Tursiops truncatus) in this study were exposed to a task that could most easily be solved if dolphins cooperated. Six dolphins were provided opportunities to solve the task and had to learn to do so without human intervention or training. Two adult males consistently and spontaneously jointly interacted in order to most efficiently open a container that contained fish by pulling on ropes at the ends of the container. Their interaction was viewed as cooperative because each dolphin pulled on their respective ropes in the opposite direction, which resulted in one end of the container opening. The dolphins did not show aggression toward one another while solving the task, and both dolphins consumed the food after the container was opened. They also engaged in synchronous non-aggressive behaviors with the container after the food had been consumed. It is possible that some of the remaining four dolphins would have cooperated, but the two successful dolphins were dominant males and their interest in the apparatus appeared to preclude other animals from participating.

Diurnal and nocturnal activity budgets of zoo elephants in an outdoor facility.

The present study examined the activity budgets of 15 African elephants (1 bull, 6 cows, 2 male juveniles, 2 female juveniles, and 4 male calves) living at the San Diego Zoo Safari Park during the summers of 2010 and 2011. Onsite behavioral data (n = 600 hr) were collected for approximately 12 weeks from 0400 to 0830 and 1100 to 2400 during the 2010 and 2011 summer season. Foraging was the most common behavior state during the day followed by resting, and walking. During the evening hours, the elephants spent majority of their time foraging, resting, and sleeping. The average rate of self-maintenance behavior events (dust, wallow, etc.) increased from 0600 to 0700, 1100 to 1500, and from 1700 to 1900. Positive social behavior events (touch other, play, etc.) remained high from 0500 to 2300, with peaks at 0600, 1300, 1500, and 1900. Negative social events occurred at low rates throughout the day and night, with peaks at 0600, 1900, and 2200. The majority of positive behavior events during the daylight and nighttime hours involved the mother-calf pairs. Furthermore, the calves and juveniles initiated approximately 60% of all social events during the daytime and 57% of all social interactions at night. The results of this study demonstrate the differences between diurnal and nocturnal activity budgets of a multi-age and sex elephant herd in a zoological facility, which highlights the importance of managing elephants to meet their 24 hr behavioral needs.

Visual laterality in belugas (Delphinapterus leucas) and Pacific white-sided dolphins (Lagenorhynchus obliquidens) when viewing familiar and unfamiliar humans.

Lateralization of cognitive processes and motor functions has been demonstrated in a number of species, including humans, elephants, and cetaceans. For example, bottlenose dolphins (Tursiops truncatus) have exhibited preferential eye use during a variety of cognitive tasks. The present study investigated the possibility of visual lateralization in 12 belugas (Delphinapterus leucas) and six Pacific white-sided dolphins (Lagenorhynchus obliquidens) located at two separate marine mammal facilities. During free swim periods, the belugas and Pacific white-sided dolphins were presented a familiar human, an unfamiliar human, or no human during 10-15 min sessions. Session videos were coded for gaze duration, eye presentation at approach, and eye preference while viewing each stimulus. Although we did not find any clear group level lateralization, we found individual left eye lateralized preferences related to social stimuli for most belugas and some Pacific white-sided dolphins. Differences in gaze durations were also observed. The majority of individual belugas had longer gaze durations for unfamiliar rather than familiar stimuli. These results suggest that lateralization occurs during visual processing of human stimuli in belugas and Pacific white-sided dolphins and that these species can distinguish between familiar and unfamiliar humans.

Cognitive enrichment for bottlenose dolphins (Tursiops truncatus): evaluation of a novel underwater maze device.

Cognitive enrichment is gaining popularity as a tool to enhance captive animal well-being, but research on captive cetaceans is lacking. Dolphin cognition has been studied intensively since the 1950s, and several hundred bottlenose dolphins are housed in major zoos and aquaria worldwide, but most dolphin enrichment consists of simple floating objects. The aim of this study was to investigate whether a novel, underwater maze device (UMD) was cognitively enriching for one group of male and one group of female dolphins at Six Flags Discovery Kingdom, CA. The dolphin's task was to navigate a rubber ball through a maze of pipes, towards an exit pipe. We also tested a modification where an edible gelatine ball fell into the pool once the UMD was solved. The UMD was provided to each group between 8 and 11 times over a 4-week period. Male dolphins used the UMD without prior training, whereas females did not use the UMD at all. Two male dolphins solved the UMD 17 times, using a variety of problem-solving strategies. The UMD had no significant effect on circular (repetitive) swimming patterns, but males spent significantly more time underwater when the UMD was present. Males used the UMD significantly more when it contained the rubber ball, but the gelatine ball stimulated social play. The UMD is a safe and practical device for captive dolphins. It now requires further testing on other dolphins, particularly females, to in order to examine whether the sex differences we observed are a general phenomenon.

Low frequency narrow-band calls in bottlenose dolphins (Tursiops truncatus): signal properties, function, and conservation implications.

Dolphins routinely use sound for social purposes, foraging and navigating. These sounds are most commonly classified as whistles (tonal, frequency modulated, typical frequencies 5-10 kHz) or clicks (impulsed and mostly ultrasonic). However, some low frequency sounds have been documented in several species of dolphins. Low frequency sounds produced by bottlenose dolphins (Tursiops truncatus) were recorded in three locations along the Gulf of Mexico. Sounds were characterized as being tonal with low peak frequencies (mean = 990 Hz), short duration (mean = 0.069 s), highly harmonic, and being produced in trains. Sound duration, peak frequency and number of sounds in trains were not significantly different between Mississippi and the two West Florida sites, however, the time interval between sounds within trains in West Florida was significantly shorter than in Mississippi (t = -3.001, p = 0.011). The sounds were significantly correlated with groups engaging in social activity (F=8.323, p=0.005). The peak frequencies of these sounds were below what is normally thought of as the range of good hearing in bottlenose dolphins, and are likely subject to masking by boat noise.

Separating overlapping click trains originating from multiple individuals in echolocation recordings.

Recordings of the acoustic activity of free-swimming groups of echolocating dolphins increase the likelihood of collecting overlapping click trains, originating from multiple individuals, in the same set of data. In order to evaluate the click properties of each individual based on such recordings it is necessary to identify which clicks originate from which animal. This paper suggests a computationally efficient strategy to separate overlapping click trains originating from multiple free-swimming bottlenose dolphins, enabling echolocation analysis at an individual level on several animals. This technique is based on sequential matching of the frequency spectra of successive clicks. The clicks are grouped together as individual click trains if the correlation coefficients between clicks are higher than a pre-set threshold level. The robustness of the algorithm is tested by adding artificially generated white Gaussian noise and comparing the results with other comparable commonly used methods based on inter-click intervals, centroid frequencies, and amplitude levels. The described method is applicable to a variety of experimental and observational contexts, e.g., those regarding echolocation development of calves, the hypothesized acoustic "etiquette" among dolphins when investigating the same object, and the possible occurrence of eavesdropping in large dolphin pods.

Visual laterality in dolphins when looking at (un)familiar humans.

Understanding the evolution of brain lateralisation including the origin of human visual laterality requires an understanding of brain lateralisation in related animal species. However, little is known about the visual laterality of marine mammals. To help correct this lack, we evaluated the influence of familiarity with a human on the visual response of five captive bottlenose dolphins. Dolphins gazed longer at unfamiliar than at familiar humans, revealing their capacity to discriminate between these two types of stimuli. Pooled data for responses to all test stimuli demonstrated a preferential use of left eye by all our five dolphin subjects. However, familiarity with particular humans did not influence preferential use of a given eye. Finally, we compared our results with those on other vertebrates.

Time and frequency parameters of bottlenose dolphin whistles as predictors of surface behavior in the Mississippi Sound.

Acoustic characteristics related to contour of the whistle (such as highest and lowest frequency, beginning and ending frequency, whistle duration, and number of turns) of bottlenose dolphin (Tursiops truncatus) whistles were measured to test whether any of the measurements were related to the behavioral state of the dolphins when the whistle was recorded (coded as mill, travel, mill/travel, feed, or social). Objective measures of time and frequency were obtained using Raven, while number of turns in a whistle was determined by human raters. In all a series of discriminant function analyses using the acoustic characteristics to predict the behavioral state, the highest standardized canonical discriminant function coefficients were: lowest frequency, number of turns, and duration. The models that incorporated these variables performed significantly better than chance at correctly assigning the whistles into the surface behavior category in which they were recorded. The rate of whistling was related to group size, surface behavior and season via a series of two-way ANOVAs (analysis of variance).

A comparison of pectoral fin contact behaviour for three distinct dolphin populations.

Tactile exchanges involving the pectoral fin have been documented in a variety of dolphin species. Several functions (e.g., social, hygienic) have been offered as possible explanations for when and why dolphins exchange pectoral fin contacts. In this study, we compared pectoral fin contact between dolphin dyads from three distinct dolphin populations: two groups of wild dolphins; Atlantic spotted dolphins (Stenella frontalis) from The Bahamas and Indo-Pacific bottlenose dolphins (Tursiops aduncus) from around Mikura Island, Japan; and one group of captive bottlenose dolphins (Tursiops truncatus) residing at the Roatan Institute for Marine Sciences, Anthony's Key Resort. A number of similarities were observed between the captive and wild groups, including; rates of pectoral fin contact, which dolphin initiated contact, posture preference, and same-sex rubbing partner preference. Unlike their wild counterparts, however, dolphins in the captive study group engaged in petting and rubbing at equal rates, females were more likely to contact males, males assumed the various rubbing roles more frequently than females, and calves and juveniles were more likely to be involved in pectoral fin contact exchanges. These results suggest that some aspects of pectoral fin contact behaviour might be common to many dolphin species, whereas other aspects could be species specific, or could be the result of differing environmental and social conditions.

Rating vs. coding in animal personality research.

Animal personality research has become increasingly popular over the past few decades. The two main methods used to examine individual differences in animals are rating and coding. The rating method involves human scoring of an animal's behavioral tendencies along various behavioral dimensions, such ratings are typically based on the human rater's experience with the animal. The coding method also requires humans to score an animal's behavior, but differs in that the scoring is based on the animal's immediate behavior in a specific context. This brief report describes the use of both the rating and coding methods to examine personality within a group of 10 Garnett's bushbabies (Otolemur garnettii). The results indicated that individual personalities do exist in bushbabies, but also suggested that the rating method is heavily influenced by the rater's experience with an animal. Consequently, it is important that the nature of the rater's interactions with the target animals be considered when using the rating method to assess animal personality.

47-channel burst-mode recording hydrophone system enabling measurements of the dynamic echolocation behavior of free-swimming dolphins.

Detailed echolocation behavior studies on free-swimming dolphins require a measurement system that incorporates multiple hydrophones (often >16). However, the high data flow rate of previous systems has limited their usefulness since only minute long recordings have been manageable. To address this problem, this report describes a 47-channel burst-mode recording hydrophone system that enables highly resolved full beamwidth measurements on multiple free-swimming dolphins during prolonged recording periods. The system facilitates a wide range of biosonar studies since it eliminates the need to restrict the movement of animals in order to study the fine details of their sonar beams.

A comparison of pectoral fin contact between two different wild dolphin populations.

Contact behaviour involving the pectoral fin has been documented in a number of dolphin species, and various explanations about its function have been offered. Pectoral fin contact can take a variety of forms, and involves a number of body parts and movements, likely differing depending upon social or ecological context. For this study, we compare the pectoral fin contact behaviour of two species of wild dolphins: Indo-Pacific bottlenose dolphins (Tursiops aduncus) from around Mikura Island, Japan, and Atlantic spotted dolphins (Stenella frontalis) from The Bahamas. The two study populations exhibit surprising similarity in the ways in which pectoral fin contacts are used, despite differences in species and environmental conditions at the two sites. Differences in contact rates for calves between the two sites suggest that calf-focused aggression from adult dolphins is more prevalent at Mikura than in The Bahamas. Our results suggest that pectoral fin contact behaviour seems to be driven primarily by social pressures, and may be similar in function to allogrooming described in primates.

Dolphin pointing is linked to the attentional behavior of a receiver.

In 2001, Xitco et al. (Anim Cogn 4:115-123) described spontaneous behaviors in two bottlenose dolphins (Tursiops truncatus) that resembled pointing and gaze alternation. The dolphins' spontaneous behavior was influenced by the presence of a potential receiver, and the distance between the dolphin and the receiver. The present study adapted the technique of Call and Tomasello [(1994) J Comp Psychol 108:307-317], used with orangutans to test the effect of the receiver's orientation on pointing in these same dolphins. The dolphins directed more points and monitoring behavior at receivers whose orientation was consistent with attending to the dolphins. The results demonstrated that the dolphins' pointing and monitoring behavior, like that of apes and infants, was linked to the attentional behavior of the receiver.