THE OCULAR SECRETIONS OF THE BOTTLENOSE DOLPHIN TURSIOPS TRUNCATUS

A viscous ocular secretion streams from the eyes of bottlenose dolphins, Tursiops truncatuss , removed from the water. The chemical composition and environmentally adaptive implications of this substance continue to perplex curators and scientists. Secretions from three dolphins were examined for deviations from literature values for normal human and terrestrial mammalian tear film components. Osmolality (= 470 mOsm/kg), pH (= 8.44) and glucose (= 26.58 mg/100 ml) were significantly greater than human and terrestrial mammalian tear film values; while lysozyme (= 0.005 mg/ml) and total cholesterol (= 0.17 μg/μ1) were significantly less. Refractive index, sodium ion concentration, and potassium tear to plasma ratios in the dolphin ocular secretion did not deviate significantly from human or terrestrial mammalian tears. Electrophoresis of dolphin tears yielded four major protein bands (probably lactoferrin, serum albumin, teat specific prealbumin, and lysozyme) and high molecular weight glycoproteins similar to human tears. The chemical composition of the T. truncatus ocular secretion suggests that the circumorbital conjunctival gland may be analogous (relative to refractive index, electrolytes, and component protein) to the terrestrial lachrymal gland. At the functional level the T. truncatus ocular secretion may reduce hydrodynamic resistance on the cornea and protect it from bacterial invasion.     

RAY ENCOUNTERS AS A MORTALITY FACTOR IN ATLANTIC BOTTLENOSE DOLPHINS (TURSIOPS TRUNCATUS)

Ray spines were found associated with various tissues on necropsy of seven Atlantic bottlenose dolphins ( Tursiops truncatus ). In at least six cases they were considered a major factor in the death of the animal. Three mature Tursiops had ray spines located in the lung parenchyma. In two other dolphins the ray spine punctured the lateral chest wall without entering the lung tissue. A sixth Tursiops contained a ray spine located in the liver tissue, while a seventh animal had a ray spine lodged in the pancreas. Five of the dolphins were wild individuals and two had been in captivity for more than one year. These findings indicate that beached dolphins and dolphins in captivity with a chronic history of illness should be examined for the presence of ray spines. Caution should be used in maintaining mixed exhibits of dolphins with stingray species.     

CHARACTERIZATION OF A BOTTLENOSE DOLPHIN (TURSIOPS TRUNCATUS) KIDNEY EPITHELIAL CELL LINE

Abstract: An epithelial cell line, Carvan dolphin kidney (CDK), isolated from a prematurely born female bottlenose dolphin, Tursiops truncatus , exhibited growth characteristics not previously reported for cetacean cells in culture. CDK cells were cytokeratin positive and demonstrated a maximum doubling time of 1.31 days, with plating and colony forming efficiencies approaching 100% for the early population doublings. Despite an unusually efficient colony-forming ability and rapid growth, these cells were neither transformed nor immortal, displaying normal contact inhibition, anchorage dependence, and the requirement for high concentrations of fetal bovine serum in the growth medium. CDK cells exhibited age-dependent changes in growth rate, colony-forming efficiency, and cytoplasmic profile, and showed a finite lifespan of about 50 population doublings and a stable 2N = 44 karyotype which correlates with previously reported cytogenetic analyses. Velocity sedimentation analysis showed that CDK cells contained nuclear aryl hydrocarbon receptor (Ah), indicating their potential to be induced for cytochrome P450. These data suggest that CDK cells may have utility as an in vitro toxicological model for evaluating hydrocarbon contaminant effects on Tursiops truncatus , a protected marine mammal.     

POPULATION STRUCTURE OF THE BOTTLENOSE DOLPHIN (TURSIOPS TRUNCATUS) AS DETERMINED BY RESTRICTION ENDONUCLEASE ANALYSIS OF MITOCHONDRIAL DNA

Abstract: Restriction fragment length polymorphisms of mitochondrial DNA (mtDNA) were used to test for population subdivision in the bottlenose dolphin (Tursiops truncatus). Atlantic and Pacific dolphin mtDNA samples exhibited distinctly different haplotypes (approximately 2.4% sequence divergence), indicating a lack of gene exchange. Within the Atlantic Ocean, mtDNA samples from the Gulf of Mexico and the Atlantic Coast were also found to be distinct, with a sequence divergence of approximately 0.6%. The Atlantic Coast–Gulf of Mexico dichotomy is consistent with patterns of genetic variation from other marine and coastal organisms from this region, and supports the hypothesized role of bio-geographic events in promoting the divergence of these and other forms. Regional differentiation was identified along the Atlantic Coast, whereas low sequence divergences among haplotypes and consistent haplotype frequencies across populations suggested considerable gene exchange among Gulf of Mexico populations. A highly divergent haplotype found in two individuals from two localities in the Gulf of Mexico is best explained by dispersal from either a distinct offshore Gulf stock or an unsampled Atlantic Coast stock. Additional samples are required to test for the existence of a distinct offshore race and, if it exists, to identify its distribution and contribution to population structure.     

SOCIAL ECOLOGY OF BOTTLENOSE DOLPHINS IN THE KVARNERIĆ (NORTHERN ADRIATIC SEA)

A bottlenose dolphin community was studied from small inflatable craft from 1987 to 1994 in a relatively large area (about 800 km²) east of the islands of Loˇsinj and Cres, northern Adriatic Sea. A total of 106 individuals were photoidentified based on natural permanent marks on their dorsal fins. Most of the dolphins were resighted on a regular basis, indicating a high level of year-round site fidelity, although their range was evidently greater than the chosen study area. Dolphin density was highly variable and considerably lower than for most well-known bottlenose dolphin communities. Groups averaged seven individuals, with a mode of two. Groups entirely composed of adults were the smallest, groups with calves the largest. Group fluidity was high, seasonal and yearly changes in mean group size being also considerable. Summer was the peak calving season, with a striking variation in the number of births on alternate years. Poor evidence of shark predation was found. The social organization of this dolphin community seemed to be highly flexible, possibly as an adaptation to cope with environmental changes as well as with a limited and variable availability of prey.     

A QUANTITATIVE ASSESSMENT OF DOMINANCE RELATIONS AMONG BOTTLENOSE DOLPHINS

Agonistic behavior of bottlenose dolphins was studied at Brookfield Zoo for nearly 4.5 yr, and dominance relationships were determined using a quantitative technique adapted from primate behavioral research. Dominance relations among dolphins were influenced by the gender of participants. Male dolphins were clearly and consistently dominant to females, and intersexual agonism occurred at moderate rates with seasonal peaks in spring and fall. Dominance relationships among female dolphins were age-ordered and stable, even though agonism among females did occur at uniformly low rates. In contrast, the two males had a changeable dominance relationship in which periods of stability and low-level agonism were interspersed with episodes of intense competition. Zoo-based research revealed patterns of behavior that conformed to current knowledge about bottlenose dolphin social structure. Moreover, research in a zoo setting facilitated development of a quantitative technique that can be used to assess cetacean dominance relationships in field research.     

LOW FREQUENCY NARROW-BAND SOUNDS PRODUCED BY BOTTLENOSE DOLPHINS

We present a new sound type recorded from bottlenose dolphins, Tursiops truncatus , in eastern Australian waters: low-frequency, narrow-band (LFN) harmonic sounds (defined as less than 2 kHz). Most of these sounds were of frequencies less than 1 kHz and were recorded commonly from socializing dolphins. These sounds differ significantly from narrow-band whistles, which are higher in frequency and longer in duration. The absence of these sounds in most studies of the acoustic behavior of bottlenose dolphins may reflect geographic differences in repertoires or result from insufficient sampling. Alternatively, these sounds may have been ignored where the focus of research was on other sound types.     

MORBILLIVIRUS INFECTION IN BOTTLENOSE DOLPHINS: EVIDENCE FOR RECURRENT EPIZOOTICS IN THE WESTERN ATLANTIC AND GULF OF MEXICO

Morbillivirus infection is widespread among odontocetes of the western Atlantic and Gulf of Mexico. Serologic evidence of infection in bottlenose dolphins, Tursiops truncatus , was first detected during an epizootic along the mid-Atlantic coast in 1987. Here, we report recurrent epizootics in the coastal dolphin population since at least the early 1980s based on serological surveys and regional stranding frequencies. The first observed epizootic of this series occurred in the Indian and Banana Rivers in 1982 and was followed by others on the mid-Atlantic coast in 1987–1988 and in the Gulf of Mexico between 1992 and 1994. This temporal pattern of infection is likely facilitated by the population size and its fragmentation into relatively discrete coastal communities. Introduction of morbillivirus into a community with a sufficient number of naive hosts may precipitate an epizootic, depending on the potential for transmission within the group. Propagation of an epizootic along the coast is probably determined by frequency of contact between adjacent communities and seasonal migrations.
Morbillivirus antibodies were also detected in serum from offshore bottlenose dolphins. The sero-prevalence in the latter may be higher than in coastal dolphins because of their close association with enzootically infected pilot whales ( Globicephala spp.). Occasional contact between offshore and coastal dolphins may provide an epizootiologic link between pilot whales and coastal dolphin communities.     

DOLPHIN THYROID AND ADRENAL HORMONES: CIRCULATING LEVELS IN WILD AND SEMIDOMESTICATED TURSIOPS TRUNCATUS, AND INFLUENCE OF SEX, AGE, AND SEASON

Biological and environmental influences on circulating adrenal and thyroid hormones were investigated in 36 wild and 36 semidomesticated Atlantic bottlenose dolphins, Tursiops truncatus, matched by age, sex, and time of year when the samples were collected. Serum concentrations of thyroxine (free [fT41 and total [tT4]), triiodothyronine (free [fT3], total [tT3], and total reverse [rT37), cortisol, and aldosterone were determined by radio-immunoassay, Wild female dolphins had significantly higher levels of tT4, fT4 and fT3, an effect that was possibly related to reproduction and lactation. Semidomesticated females had higher tT3 than their wild counterparts. fT4 declined with age in wild dolphins, whereas rT3 was greatest in the older animals. Cortisol and aldosterone were both higher in wild animals sampled after a variable interval of up to four hours after encirclement by capture net. The pattern of adrenal hormone release suggested a mild stress response. Levels of both adrenal hormones were low in semidomesticated dolphins conditioned to present voluntarily their tails for blood sampling, an approach that appears to yield specimens representative of resting values for these constituents.     

CROSS-REACTIVITY OF ANTIBODIES TO HUMAN ANTIGENS WITH TISSUES OF THE BOTTLENOSE DOLPHIN, TURSIOPS TRUNCATUS, USING IMMUNOPEROXIDASE TECHNIQUES

Cross-species reactivity of 53 antibodies developed against human antigens was evaluated in the bottlenose dolphin Tursiops truncatus , using immunoperoxidase techniques, Strong cross-reactivity was demonstrated with antibodies against intermediate filaments, most hormones, but few leukocyte antigens. S100, NSE, F8RA, Factor XIIIa, and lactalbumin antibodies reacted, while HMB45, EMA, PLAP, and PSA did not. Polyclonal antibodies are much more likely to cross-react than are monoclonal antibodies. Twenty-four of 30 (80%) of polyclonals cross-reacted, while only 10 of 23 (43.5%) monoclonals cross-reacted. Some antigens are demonstrated only after using a special technique to unmask the antigen.     

ORPHAN-INDUCED LACTATION IN TURSIOPS AND ANALYSIS OF COLLECTED MILK

Two non-lactating, non-gravid female bottlenose dolphins, Tursiops truncatus , (SLA, age 32 yr and TOD, age 34 yr) began lactating within one week after being housed with a 6.5- and 6.75-month-old orphaned calf, respectively. Cooperative swimming and nursing behaviors were quickly evident in both cow/ calf pairs. During the first 2.5 mo a milk substitute, eventually in combination with some whole fish, was used to supplement nursing in both calves. After this initial period, supplemental feeding was discontinued. SLA then became her adopted calf s sole source of nutrition for the next 5 mo, followed by another 6 mo during which the calf shifted to a predominantly fish diet with occasional nursing. TOD's orphan also continued to nurse beyond the 2.5-mo supplementation period and began voluntarily accepting small quantities of fish, suckling continued over the next year while fish consumption increased. Using a modified human breast pump, trainers collected milk at intervals from the adult dolphins throughout the lactation period. The first milk collected from TOD (day 8 after housing with calf) and SLA (day 12 with her calf) contained 6.0% and 10.3% fat, respectively. On day 68 TOD's milk fat had increased to 23.5%, and on day 37 that of SLA measured 22.5%. These later values are similar to those reported for normally lactating bottlenose dolphins.     

BOTTLENOSE DOLPHINS CAN GENERALIZE RULES and DEVELOP ABSTRACT CONCEPTS

Abstract: Generalization of a rule is demonstrated if the rule governs a class of problem, and the subject, after successful experience with a limited number of problems, can apply the governing rule to new problems within that class. We show that the bottlenose dolphin ( Tursiops truncatus ) is capable of such generalization for classes of problems requiting the matching of one of two alternative stimuli to a "sample" stimulus to which the animal had been previously exposed, regardless of the sensory domain used: vision, passive listening, or active echolocation. We also show this generalization capability in a related class of problem requiring a judgment of whether a single "probe" stimulus is the same as, or different from, a stimulus or stimuli previously presented. Further, one dolphin was shown capable of developing a true abstract concept of same/different through its ability to categorize pairs of simultaneously presented objects as identical or not. The suggestion that such generalization ability of dolphins may be in question because of so-called exclusion effects is shown to be not tenable when the whole body of available data is considered.     

HABITAT USE PATTERNS AND RANGES OF THE BOTTLENOSE DOLPHIN IN THE GULF OF CALIFORNIA, MEXICO

Abstract: I studied behavior and range patterns of individual bottlenose dolphins during 1984 in the mid-eastern Gulf of California, Mexico. Dolphin sighting rate was significantly higher in areas close to estuary mouths, 0.306 sightings per hour compared with 0.155 sightings per hour in areas distant from estuary mouths. Dolphins used these estuarine areas to feed; 61% of all behavior observed near estuaries was feeding as compared with 23% elsewhere. Traveling comprised 61% of all behavior observed in areas distant from estuary mouths. Estuaries are sites of large concentrations of nutrients which support great numbers of filter-feeding zooplankton and fish. Bottlenose dolphins may specialize on esmarine prey, or they may feed in estuarine areas simply because of the abundance of potential prey that these systems support. In either case, data on relative numbers, distribution patterns, behavior and diet indicate that this is a general trend in habitat use for many coastal populations of this species in the Pacific and Atlantic.
Ranges of a few individuals spanned a minimum of 65 km of coastline, and animals were not permanent residents of a monitored bay. In contrast, dolphins off the coast of Sarasota, Florida, have been reported to be year-round residents with smaller ranges. This difference in degree of site fidelity may be related to habitat differences. The west coast of Florida is dotted with numerous and large estuarine systems which may host permanent prey populations and support resident groups of dolphins. The Gulf of California coastline contains few estuaries; most are small and perhaps support prey resources which are ephemeral, requiring dolphins to range over larger distances in search of food.     

ECOLOGY, BEHAVIOR AND SOCIAL ORGANIZATION OF THE BOTTLENOSE DOLPHIN: A REVIEW

The authors review the literature on bottlenose dolphin ecology, behavior and social organization, focusing on data collected on free-ranging animals. Most bottlenose dolphins studied to date have had definable home ranges, and behavioral, morphological and biochemical information indicates discrete stocks in some areas. Bottlenose dolphins appear to form relatively permanent social groups based on sex and age. Mother—calf bonds are long-lasting. Movement patterns are extremely variable from location to location but are relatively predictable at any given site. Food resources are one of the most important factors affecting movements. Bottlenose dolphin behavior is very flexible, and these dolphins are generally active day and night. Feeding peaks in the morning and afternoon have been observed at several sites. Social behavior is an important component of daily activities. Sharks are the most significant predator on bottlenose dolphins in most areas, but captive and wild studies show that dolphins and sharks frequently live in harmony as well. Human activities may be helpful, harmful or neutral to bottlenose dolphins, but interactions with humans are frequent for these coastal cetaceans.     

QUANTITATIVE BEHAVIORAL STUDY OF BOTTLENOSE DOLPHINS IN SWIM-WITH-DOLPHIN PROGRAMS IN THE UNITED STATES

The behavior of dolphins in four Swim-With-Dolphin programs was compared by type of Swim encounter, defined by the presence ("Controlled") or absence ("Not-Controlled") of explicit trainer regulation of interactions between dolphins and human swimmers. Dolphin-swimmer interactions involving aggressive, submissive, or sexual behavior were designated as "high-risk" in the Swim context; sexual behavior was included as high-risk based on analyses that demonstrated co-occurrence of sexual and agonistic behaviors. High-risk activity comprised a substantial proportion of dolphin-swimmer social activity during Not-Controlled Swims. In contrast, high-risk activity rarely occurred during Controlled Swims, even though agonistic and sexual behaviors were normal components of the same dolphins' free-time social repertoire. These results indicated that direct trainer control of dolphin-swimmer interactions virtually eliminated high-risk activity from the Swim context, and thereby diminished the potential for dolphin distress, swimmer injury, and rejection of dolphins from Swim programs due to swimmer injury. This study illustrates effective use of quantitative behavioral sampling techniques for evaluation of captive management concerns and promotes broader use of these techniques for a better understanding of cetacean behavior.