WSR Overview

Background details
An aquatic lifestyle has resulted in the evolution of unique adaptations for signal exchange (communication) among dolphins. Signals may be expressed via physical, acoustic, or visual contact. Signals may be used singly or concurrently depending on the intended message. Atlantic spotted dolphins (Stenella frontalis) in the Bahamasuse a variety of signals (behaviors, vocalizations, and postures) to exchange information and these signals vary according to dolphin age, sex, behavioral activity, and group type. Contact among individuals may be modified by posture, behavior, and internal and external referents: posturing by dolphins appeared to function specifically to indicate intent or message meaning in differing contexts. Age and sex differences were documented as related to initiator and receiver roles assumed by the dolphins. For example, dolphins more often exchanged rubs or pets with individuals of the same sex and age class. Physical contact and vocal type varied significantly, but at differing levels, with behavioral activity, group type and age. Tactile and vocal signals could be used concurrently, to maximize or enhance a message, or could be used separately, but with similar functions.

History of the White Sand Ridge, Bahamas Study Population
The first recorded interactions between Atlantic spotted dolphins north of Grand Bahama Island and humans began in the late 1960’s, while divers were searching for and salvaging the wreck of the Spanish ship Nuestra Señora de la Maravillas, which sank in 1656. The wreck is widely distributed along the south to southwest section of the Little Bahamas Bank, North of Grand Bahama Island, Bahamas. Divers were frequently visited by a group of spotted dolphins that approached, investigated, and often mimicked divers’ actions.

In 1978, Hardy Jones began the first study of this population. The dolphins seemed not only to tolerate swimmers, but also to actively seek them out. Jones’ work on these dolphins yielded preliminary information on individual dolphin identifications, social associations and group dynamics, vocalizations, travel ranges, and daily activity patterns.

Stephen Leatherwood and Oceanic Society Expeditions (OSE) began a systematic study of these dolphins in 1985. OSE’s Bahamas’ Project Dolphin was formed with long-range goals of collecting data on the distribution, individual identifications, associations, and behavior of this group of dolphins.

Denise Herzing began her long-term examination of the Bahamas’ spotted dolphins with OSE in 1986, and formed the Wild Dolphin Project in 1989. She has since collected detailed information on individual associations, specific behaviors, and vocal activity for this group of spotted dolphins.

Some Definitions
An encounter is defined as three minutes or more with dolphins in visual range of the swimmer(s).  A short encounter is 30 seconds to 3 minutes with dolphins in visual range.

Five different types of groups were defined: 1) adult females with juveniles (AFjuv); 2) juveniles (juv); 3) mother/calf dyads (Mc); 4) mixed groupings (mix); and 5) same sex/age (same).

Five different behavioral activities were classified (link to ethogram). Foraging was dolphins chasing fish, ingesting fish, a dolphin digging in the sand with its rostrum. Fast circle swims around snorkelers, apparent mimicry of human postures and movements, direct approaches to people, click vocalizations apparently directed at people, and physical contact with swimmers were classified as inquisitive. Dolphins moving steadily in one general direction, not varying more than 45° from each other when more than one individual was present, were considered to be traveling. Play was defined as swift movements, fast and circular swimming, chases among individuals, and pushing or pulling objects (e.g., fish, sea cucumbers, sea weed) or associates. During play, dolphins approach conspecifics at oblique angles. Social activity was much physical contact among group members. Individuals were usually oriented toward one another and moving slowly, but not in one specific direction (as when traveling). Social activity included genital-oriented behaviors. Much rubbing and contact behavior among individuals characterized social affiliations, while aggressive interactions were represented by much biting, hitting, body-slamming, raking, jaw displaying, and also by intense, loud vocalizations. No affiliative rubbing behavior was recorded during aggressive social activity. Approaches were at direct angles or head-on between individuals.

For our studies, communication is defined as consisting of exchanges of information between a sender and a receiver using a code of specific signals that usually serve to meet common challenges (e.g. reproduction, predator defense, foraging), and in group living species, to promote group cohesiveness.

Besides vocal and tactile signals, terrestrial social mammals communicate much information through subtle and overt kinesic and non-linguistic expressions, including changes in facial expressions, irregularities in respiration, and carriage of the overall form. Adaptation to life in the ocean has removed from delphinids the use of facial expression; evolution has streamlined the body and limited the applicability of much kinesic communication in cetaceans. Nonetheless, posture and contact as well as sound are used effectively among spotted dolphins for information exchange.

Data Collection Protocol
The overall focus of our research is to attempt to understand possible correlations between dolphin sounds and behavior. When studying communication, it is important to identify the various signs used, as well as the initiating and responding reactions of dolphins. Three specific objectives will aid in the collection of data to better understand dolphin communication.

Objectives: 

To examine the association(s) of vocal and tactile/visual signs. To examine the differences in response to different combinations of vocal and tactile/visual signs. To examine the variation in responses to these combination of signs considering age/sex classes, individual, and context (behavioral, external and internal referents).

Observational Methodology

Focal animal and group follows provide the framework for this work on dolphin communication. Two methods of data collection are followed for each swim encounter with the dolphins: 1) simultaneous video and audio recording of identified dolphins from each age/spot class and from both sexes; and 2) real-time all-occurrence recording of specific behaviors and group behaviors. Real-time all-occurrence sampling provides information on the broad behavioral context of dolphins, while the specific context of focal individuals is gathered from the video-tapes from the field of view of the camera.  Focal individuals are chosen randomly from study dolphins within the different age/sex classes. The decision of which dolphin to watch is by chance with attention to an even, random representation of all age/sex categories.  A focal bout will start as soon as the observer is logistically in position and the group composition is assessed. The bout or video recording continues until the animal leaves view. Thus, the duration of focal follows is dictated by dolphin behavior: we observe individuals for as long as possible while in the field.

Passenger Participation

The primary reason for using two observers per encounter for all-occurrence sampling is to provide an indication of the broad behavioral context of the dolphins within the encounter. Our trips to the research site are funded in part by paying volunteers: participants eager to learn about dolphins and dolphin research. Participants are instructed on the methodology utilized for behavioral observations on dolphins during the swim encounters. They are asked to conduct all-occurrence sampling of specific behavioral events. Data sheets have been designed for use by passengers. And, underwater slates are available for ease of data recording during swim encounters. Each passenger independently fills out a data sheet for each encounter. A secondary reason to have passengers record behavioral events during encounters is to provide first-hand experience to our volunteers so they will better understand the rigors and requirements of scientific (and especially behavioral) studies.

Link to Publications page

 

Extended Information

This group of Atlantic spotted dolphins (Stenella frontalis), found in Bahamian waters, was introduced to the scientific and public communities through popular films and articles (e.g., Hauser, 1976, Jones, 1982, In the Kingdom of the Dolphin, produced by H. Jones, 1984). The first recorded associations between these spotted dolphins and humans were in the late 1960’s, while divers were searching for, and salvaging, the wreck of a Spanish galleon. The wreck was widely distributed along the south to SW section of the Little Bahamas Bank. Friendly spotted dolphins frequently visited divers – the dolphins would approach, investigate and often mimic divers’ actions (Art Vilar, pers. comm. 1993).

Stephen Leatherwood and Oceanic Society Expeditions (OSE) began a systematic study of these dolphins in 1985. The Bahamas’ Project Dolphin was formed with long-range goals of collecting data on the distribution, individual identifications, associations, and behavior of this group of dolphins. Passengers participate in eight day trips to assist with data collection on this population: this is one of the few swim-with-dolphins programs offering the opportunity for humans to interact with free-ranging, habituated dolphins.

 

PROTOCOL FOR BEHAVIORAL DATA COLLECTION (OBSERVATIONS AND RECORDINGS) ON BAHAMAS’ ATLANTIC SPOTTED DOLPHINS AND BOTTLENOSE DOLPHINS AROUND MIKURA ISLAND, JAPAN).

My research in Japan has a primary focus, with a secondary comparative aspect. The focus concerns dolphin signal exchange and use of contact behaviors between individuals. I am interested in dolphin social behavior and communication. The comparative aspect is between my work on Atlantic spotted dolphins and that on the bottlenose dolphins around Mikura Island. My questions are detailed below in the form of objectives and hypotheses.

Objectives

To conduct focal animal and all-occurrence observations to determine how bottlenose dolphins use the shallow, near-shore inlets around Mikura Island.

To identify behavior and vocal exchanges between interacting individuals.

To identify dolphin group activity from underwater and surface observations.

To identify vocalizing individuals and examine variation in whistle production and use according to individual, age, sex and activity.

To document production and use of pulsed (i.e., click) sounds by individual dolphins.

To determine if low frequency clicks, captured with the mobile video/acoustic system, contain an echolocation frequency or represent a distinct frequency (kHz).

To characterize other pulsed sounds (e.g., squawks, whines) and determine if they contain a high frequency signal similar to echolocation clicks.

To record signal exchange including contact behavior and sounds between individual dolphins.

To identify how these signals are related to dolphin identification, age, sex, group type and behavioral activity.

To identify signal senders and receivers during interactions.

To determine if correlations exist between sender/receiver roles and dolphin age, sex, associates, and activity.

To identify similarities and differences in signal exchange and interactions between Mikura bottlenose and Bahamas’ Atlantic spotted dolphins

To identify any group type or composition differences.

To identify any differences in activity during encounters with dolphins.

To determine if observed variations in behavior, activity or signal exchange may be related to habitat differences (i.e., external factors).

 

Hypotheses (as related to objectives)
H01:	Bottlenose dolphins show no differential use among subgroups or groups in the shallow, near-shore waters near Mikura Island.
HA1:	Bottlenose dolphins use the shallow, near-shore area around Mikura Island for different behavioral activities depending on subgroup type and size.
HA2:	Bottlenose dolphins use the shallow, near-shore area around Mikura Island for foraging, social and play activities without regard to subgroup type and size.
H02:	Contact behavior between bottlenose dolphins does not differ in use and expression according to dolphin age, sex or associates.
HA1:	Contact behaviors differ in frequency related to the behavioral activity of each subgroup.
HA2:	Contact behaviors differ in use and frequency according to group type and the age and sex of identified dolphins.
HA3:	The same contact behaviors are modified by dolphin postures within different behavioral activities, and thus will send varying messages (e.g., play versus aggression).
HA3:	Sounds produced by bottlenose dolphins are not related to dolphin identification, age, sex or to subgroup behavioral activity.
HA1:	Identified bottlenose dolphins possess individually distinct frequency-modulated pure tones (e.g., whistles).
HA2:	Frequency-modulated pure tones vary according to dolphin age and sex but not necessarily to individual or behavioral activity.
HA3:	Frequency-modulated pure tones vary according behavioral activity but not necessarily to dolphin identification, age or sex.
HA4:	Pulsed vocalizations (e.g., clicks, squawks) vary according to the behavioral activity of subgroups, but not necessarily to subgroup type.
H04:	All pulsed sounds possess a signal in the 120 kHz range and are used for investigation of the surrounding environment and for foraging only.
HA1:	Pulsed sounds are used to exchange communicative as well as investigative information. That is, pulsed sounds are used in non-foraging and non-exploratory behaviors.
HA2:	Only the click or pulsed sounds used during foraging, or exploratory behaviors possess a signal at about 120 kHz.

Related comparative questions focus on the similarities and differences in use and production of contact behavior and sounds as well as signal exchange between individuals between the Mikura Island bottlenose dolphin and the Bahamas’ Atlantic spotted dolphins groups. Do individuals from both groups exhibit similar group types? Do they exhibit similar behavioral activities in their given habitats? Do individuals within both study populations use sounds differently? Do they interact with conspecifics similarly given similar group types or behavioral activities? Could the difference in habitat for the two locations – far from shore, white sand in the Bahamas versus near-shore, boulder-covered sea floor around Mikura – play a significant factor in any observed differences in behavioral activity or signal exchange?

Data Collection

This protocol is for Japan & Bahamas except where noted.

Focal animal and focal group follows provide the framework for data collection focusing on dolphin signal exchange and contact behavior – communication. Two methods of collection will be followed for each swim encounter with dolphins: 1) simultaneous video and audio recording of identified dolphins; and 2) real-time, all-occurrence documentation of specific behaviors and group activity. Real-time, all-occurrence sampling will provide information on the overall behavioral activities of the dolphins. Information on the associations of vocal and tactile/visual signs of dolphins will be obtained primarily from video recordings, while corroborative evidence will be gathered in the form of anecdotal observations.

Focal individuals will be chosen opportunistically depending on individuals observed during swim encounters. The decision of which dolphin to watch is by chance with attention to an even representation of all age and both sexes. A focal session will start as soon as the observer is in position underwater and the group composition is assessed. Video recording will continue until the animal(s) leaves the field of view. Thus, duration of focal follows is dictated by dolphin behavior: video observations on individuals will continue for as long as possible while in the field.

A mobile video/acoustic system (MVA) will be used to record dolphin behavior and sounds (Dudzinski et al., 1995). The system is swimmer-propelled and facilitates localization of dolphin sound sources by associating video data of animal distributions with audio data from two hydrophones spaced relative to the human inter-aural distance as scaled to speed of sound in water. A small second housing containing a Sony TCD D8 digital recorder together with a pre-processor circuit which detects the highly directional part of a dolphin’s echolocation ‘clicks’ and makes these audible and recordable will also be used.

Definitions

->	Group In Japan: The “total available dolphins” observed within an imaginary ellipse, with a 200 m long axis and 100 m short axis for dimensions. The long axis is placed parallel to the Mikura coastline. Group In Bahamas: The total number of dolphins observed during an encounter or in a sighting.
->	Subgroup – Dolphins observed in apparent association, moving in the same general direction, although not all individuals necessarily heading in the same direction, and engaged in the same activity. Spatially, each individual in a single subgroup is within at least five dolphin-body widths of its nearest conspecific. Often the distance between individuals is between two and three dolphin-body widths.
->	Encounter – 3 minutes or more underwater with dolphins in visual range.
->	Short Encounter – Any underwater observations of dolphins between 30 and 180 seconds.
->	Group Types – 5 group types are defined: adult female(s) with juveniles (AFjuv), all juveniles, mixed gender and aged groups (mixed), same gender and aged groups (same), and mother/calf groups (Mc).
->	Behavioral Activity – 5 behavioral activities are defined. Forage Dolphins chasing fish, ingesting fish, digging in the sand with rostrum, or head scanning and gliding along the bottom with occasional pauses to dig into the sand. Inquisitive Dolphins fast, circle swimming around swimmers, apparent mimicry of human postures and movements, direct approaches to people, click sounds directed at people, contact with swimmers. Play 2 subdivisions: w/ Objects & w/ conspecifics. Dolphins moved swiftly, with fast, circular swimming, chases among individuals, pushing or pulling objects or associates. Social Affiliative or Aggressive – both had much physical contact. Dolphins oriented toward one another, moving slowly, but not in one specific direction. Activity included genital-oriented behaviors, rubbing and contact behavior. Especially in aggressive activity were biting, hitting, body-slamming, raking, jaw displaying, and also by intense, loud sounds. Travel Dolphins moving steadily in one general direction, not varying more than 45° from each other when more than one individual was present.
->	Behaviors – 7 specific contact behaviors are defined. Rubbing a dolphin rubs its body on another’s body or body part. Contact Body to body contact, no movement between bodies. Petting a dolphin moves pectoral fin along the pectoral fin of second dolphin. Petting/Rubbing a dolphin rubbing with pectoral fin on body of another dolphin. Contact Position Pectoral fin of a dolphin placed on lateral peduncle of second dolphin with no active pec. fin movement. Melon to Genital Rub a dolphin pushes melon against genitals of second dolphin. Bottom Rubbing Rubbing all/part of body along boulders or sand on sea floor (called sand rubbing for spotted dolphins).