Health Assessments of Common Bottlenose Dolphins (Tursiops truncatus): Past, Present, and Potential Conservation Applications.

The common bottlenose dolphin (Tursiops truncatus) is a global marine mammal species for which some populations, due to their coastal accessibility, have been monitored diligently by scientists for decades. Health assessment examinations have developed a comprehensive knowledge base of dolphin biology, population structure, and environmental or anthropogenic stressors affecting their dynamics. Bottlenose dolphin health assessments initially started as stock assessments prior to acquisition. Over the last four decades, health assessments have evolved into essential conservation management tools of free-ranging dolphin populations. Baseline data enable comparison of stressors between geographic locations and associated changes in individual and population health status. In addition, long-term monitoring provides opportunities for insights into population shifts over time, with retrospective application of novel diagnostic tests on archived samples. Expanding scientific knowledge enables effective long-term conservation management strategies by facilitating informed decision making and improving social understanding of the anthropogenic effects. The ability to use bottlenose dolphins as a model for studying marine mammal health has been pivotal in our understanding of anthropogenic effects on multiple marine mammal species. Future studies aim to build on current knowledge to influence management decisions and species conservation. This paper reviews the historical approaches to dolphin health assessments, present day achievements, and development of future conservation goals.

Resting Metabolic Rate and Lung Function in Wild Offshore Common Bottlenose Dolphins, Tursiops truncatus, Near Bermuda.

Diving mammals have evolved a suite of physiological adaptations to manage respiratory gases during extended breath-hold dives. To test the hypothesis that offshore bottlenose dolphins have evolved physiological adaptations to improve their ability for extended deep dives and as protection for lung barotrauma, we investigated the lung function and respiratory physiology of four wild common bottlenose dolphins (Tursiops truncatus) near the island of Bermuda. We measured blood hematocrit (Hct, %), resting metabolic rate (RMR, l O2 ⋅ min-1), tidal volume (VT, l), respiratory frequency (fR, breaths ⋅ min-1), respiratory flow (l ⋅ min-1), and dynamic lung compliance (CL, l ⋅ cmH2O-1) in air and in water, and compared measurements with published results from coastal, shallow-diving dolphins. We found that offshore dolphins had greater Hct (56 ± 2%) compared to shallow-diving bottlenose dolphins (range: 30-49%), thus resulting in a greater O2 storage capacity and longer aerobic diving duration. Contrary to our hypothesis, the specific CL (sCL, 0.30 ± 0.12 cmH2O-1) was not different between populations. Neither the mass-specific RMR (3.0 ± 1.7 ml O2 ⋅ min-1 ⋅ kg-1) nor VT (23.0 ± 3.7 ml ⋅ kg-1) were different from coastal ecotype bottlenose dolphins, both in the wild and under managed care, suggesting that deep-diving dolphins do not have metabolic or respiratory adaptations that differ from the shallow-diving ecotypes. The lack of respiratory adaptations for deep diving further support the recently developed hypothesis that gas management in cetaceans is not entirely passive but governed by alteration in the ventilation-perfusion matching, which allows for selective gas exchange to protect against diving related problems such as decompression sickness.

BLOOD CHEMISTRY AND HEMATOLOGY VALUES IN HEALTHY AND REHABILITATED ROUGH-TOOTHED DOLPHINS ( STENO BREDANENSIS).

Rehabilitation efforts for live stranded marine mammals are guided by diagnostic measures of blood chemistry and hematology parameters obtained from each individual undergoing treatment. Despite the widespread use of blood parameters, reference values are not available in the literature from healthy rough-toothed dolphins ( Steno bredanensis) with which to infer the health status of an animal. We examined serum or plasma chemistry and hematology data from 17 rough-toothed dolphins either housed at Dolphin Quest French Polynesia or during their rehabilitation at the Dolphin and Whale Hospital in Sarasota, Florida, US between 1994 and 2005. Blood parameters were compared among healthy animals, rehabilitation animals that were eventually released, and rehabilitation animals that died. This study indicated significant differences in many blood parameters for the poorly known rough-toothed dolphin that are likely to vary between healthy and sick animals. These included aspartate aminotransferase, alanine aminotransferase, lactate dehydrogenase, bicarbonate, and globulins, which were greater in sick dolphins, and alkaline phosphatase and total protein which were greater in healthy individuals. Total white blood cell counts were lower in healthy animals as were the absolute numbers of neutrophils, monocytes, and eosinophils. Analysis of first blood sample levels for glucose, sodium, and erythrocyte sedimentation rate may have value for triage and prognostic evaluation.

Thyroid hormone concentrations in relation to age, sex, pregnancy, and perinatal loss in bottlenose dolphins (Tursiops truncatus).

This study evaluated circulating concentrations of thyroid hormones in relation to age, sex, pregnancy status, and perinatal loss in bottlenose dolphins (Tursiops truncatus) under human care. A total of 373 blood samples were collected from 60 individual dolphins housed at nine aquariums/oceanariums. Serum concentrations of total and free thyroxine (T4) and triiodothyronine (T3) were analyzed with commercial RIA kits validated for use with dolphins. While the effect of age was indicated by higher (P<0.0001) concentrations of total and free T4 and T3 in juveniles than adults, the effect of sex on thyroid hormones was inconclusive. The effect of pregnancy was indicated by higher (P<0.035) total and free T4 and T3 during early pregnancy compared to non-pregnancy. For both successful and unsuccessful pregnancy outcomes, maternal concentrations of thyroid hormones were highest during early, intermediate during mid, and lowest during late pregnancy (P<0.07 to P<0.0001). Compared to live and thriving births, concentrations of total and free T4 and total T3 were lower (P<0.08 to P<0.001) in dolphins with perinatal loss. Lower concentrations ranged from 10% to 14% during early, 11% to 18% during mid, and 23% to 37% during late pregnancy. In conclusion, the effects of age, reproductive status and stage of pregnancy on thyroid hormone concentrations are necessary factors to take into account when assessing thyroid gland function. Since perinatal loss may be associated with hypothyroidism in dolphins, analysis of serum T4 and T3 should be considered for those dolphins that have a history of pregnancy loss.

Acute phase protein quantitation in serum samples from healthy Atlantic bottlenose dolphins (Tursiops truncatus).

Acute phase proteins (APPs) have been studied in many companion and large animals and have been reported to have a differential sensitivity to traditional markers of inflammation. Studies have been performed indicating the conservation of these proteins as well as the application and cross-reactivity of automated assays among different species, but few reports have detailed APPs in marine mammal species. In the present study, automated assays were utilized to generate reference intervals for C-reactive protein, haptoglobin, and serum amyloid A using 44 serum samples from healthy Atlantic bottlenose dolphins (Tursiops truncatus). A total of 25 samples were obtained from dolphins under human care and 19 samples were obtained from free-ranging dolphins. Mild yet statistically significant differences were observed in levels of haptoglobin and serum amyloid A between these groups. The reference intervals from the combined groups were as follows: C-reactive protein 3.1-19.7 mg/l, haptoglobin 0-0.37 mg/ml, and serum amyloid A 17.5-42.9 mg/l. These baseline data should provide an important foundation for future studies of the application of APP quantitation in monitoring the health and stressors of dolphins under human care and with live capture of free-ranging dolphins.

Altrenogest and progesterone therapy during pregnancy in bottlenose dolphins (Tursiops truncatus) with progesterone insufficiency.

Progesterone production is essential for growth and development of the conceptus during pregnancy. Abnormal development of the corpus luteum (CL) after conception can result in early embryonic loss or fetal abortion. Routine monitoring of bottlenose dolphin (Tursiops truncatus) pregnancy after artificial insemination or natural conception with ultrasonography and serum progesterone determination has allowed for the establishment of expected fetal growth rates and hormone concentrations. Using these monitoring techniques, we revealed four pregnant dolphins (12-24 yr old) with abnormally low progesterone production indicative of luteal insufficiency. Once diagnosed, animals were placed on altrenogest (0.044-0.088 mg/kg once daily) alone or with oral progesterone (50-200 mg twice daily). Doses of hormone were increased or decreased in each animal based on how fetal skull biparietal and thoracic growth rates compared with published normal values. Hormones were withdrawn starting from day 358 of gestation in animals 1 and 2, with labor occurring 6 and 7 days after withdrawal and at 376 and 373 days of gestation, respectively. Both deliveries were dystocic, with each calf requiring manual extraction and fetotomy for calf 1. The fetuses in animals 3 and 4 died at 348 and 390 days of gestation, respectively. Induction of labor was attempted in both animals, after fetal death, by using a combination of rapid progesterone withdrawal and steroid and prostaglandin F2alpha administration. The calf of animal 4 had to be removed with manual cervical dilation and fetotomy All adult females survived the procedures. These data provide the first in vivo evidence that the CL is the primary source of progesterone throughout pregnancy in the bottlenose dolphin. Until further characterization of hormones required during pregnancy and at parturition has been accomplished, the exogenous progestagen supplementation protocol described here cannot be recommended for treatment of progesterone insufficiency in bottlenose dolphins.

Complex contaminant exposure in cetaceans: a comparative E-Screen analysis of bottlenose dolphin blubber and mixtures of four persistent organic pollutants.

Cetaceans are federally protected species that are prone to accumulate complex mixtures of persistent organic pollutants (POPs), which individually may exert estrogenic or antiestrogenic effects. In the present study it was assessed whether contaminant mixtures harbored by cetaceans are estrogenic or antiestrogenic using a comparative approach. Interactions of antiestrogenic and estrogenic compounds were first investigated with the E-Screen assay using a mixture of four POPs (dichlorodiphenyldichloroethylene [4,4'-DDE], trans-nonachlor, and polychlorinated biphenyls [PCBs] 138 180) prevalent in cetacean blubber. Estrogenic/antiestrogenic activity was determined for the individual compounds and their binary, tertiary, and quaternary combinations. Significantly different responses were observed for the various POP mixtures, including enhanced estrogenic and antiestrogenic effects and antagonistic interactions. These results were then compared to the concentrations and estrogenic/antiestrogenic activity of contaminant mixtures isolated directly from the blubber of 15 bottlenose dolphins (Tursiops truncatus) collected from five U.S. Atlantic and Gulf of Mexico locations. The lowest observed effect concentrations (LOECs) determined for 4,4'-DDE (20 µmol/L), PCB 138 (20 µmol/L), PCB 180 (21 µmol/L), and trans-nonachlor (3 µmol/L) in the E-Screen were greater than estimated dolphin blood concentrations. Although estimated blood concentrations were below the LOECs, significant estrogenic activity was detected in diluted dolphin blubber from Cape May, NJ and Bermuda. Positive correlations between blubber estrogenicity and select POP concentrations (ΣDDTs, ΣPBDEs, ΣHCB, Σestrogenic PCBs, Σestrogenic POPs) were also observed. Collectively, these results suggest that select bottlenose dolphin populations may be exposed to contaminants that act in concert to exert estrogenic effects at biologically relevant concentrations. These observations do not necessarily provide direct evidence of endocrine disruption; however, they may indicate an environmental source of xenoestrogenic exposure warranting future research.

Hypocitraturia in common bottlenose dolphins (Tursiops truncatus): assessing a potential risk factor for urate nephrolithiasis.

Numerous cases of urate nephrolithiasis in managed collections of common bottlenose dolphins (Tursiops truncatus) have been reported, but nephrolithiasis is believed to be uncommon in wild dolphins. Risk factors for urate nephrolithiasis in humans include low urinary pH and hypocitraturia. Urine samples from 94 dolphins were collected during April 2006 through June 2009 from 4 wild populations (n = 62) and 4 managed collections (n = 32). In addition, urine uric acid and pH were tested in a subset of these animals. Our null hypothesis was that wild and managed collection dolphins would have no significant differences in urinary creatinine, citrate, and uric acid concentrations and pH. Among urine samples from all 94 dolphins, the urinary levels (mean +/- SEM) for creatinine, citrate, uric acid, and pH were 139 +/- 7.6 mg/dL, 100 +/- 20 mg citrate/g creatinine, 305 +/- 32 mg uric acid/g creatinine, and 6.2 +/- 0.05, respectively. Of the 4 urinary variables, only citrate concentration varied significantly between the 2 primary study groups; compared with wild dolphins, managed collection dolphins were more likely to have undetectable levels of citrate in the urine (21.0% and 81.3%, respectively). Mean urinary citrate concentrations for managed collection and wild dolphin populations were 2 and 150 mg citrate/g creatinine, respectively. We conclude that some managed collections of dolphins, like humans, may be predisposed to urate nephrolithiasis due to the presence of hypocitraturia. Subsequent investigations can include associations between metabolic syndrome, hypocitraturia, and urate nephrolithiasis in humans and dolphins; and the impact of varying levels of seawater ingestion on citrate excretion.

Annual, seasonal and individual variation in hematology and clinical blood chemistry profiles in bottlenose dolphins (Tursiops truncatus) from Sarasota Bay, Florida.

Hematology and clinical blood chemistry (HCBC) profiles in free-living bottlenose dolphins from Sarasota Bay, Florida have been monitored over a 14-year period. This long-term dataset includes samples from recaptured dolphins, enabling individual variation to be accounted for when investigating seasonal and annual variability. Four different laboratories carried out the assays and inter-laboratory comparisons found significant differences in 31 of 39 parameters measured. However, variability in comparable HCBCs by sex, age, condition, season and year could be investigated. Significant relationships with the independent variables were found for the majority of the HCBCs. Notable consistent seasonal differences included significantly elevated glucose and significantly lower creatinine concentrations in winter compared to summer. These differences may be due to energetic or thermoregulatory fluctuations in the animals by season and do not necessarily have any clinical significance. Erythrocyte counts were significantly lower in the winter, possibly also due to nutritional differences. Albumin and calcium levels in this population have increased significantly over the years of monitoring and consistently across seasons, being higher in the winter than the summer. Again, nutritional and thermal constraints seem to be the most likely environmental factors influencing these patterns.

Polychlorinated biphenyls and hydroxylated polychlorinated biphenyls in plasma of bottlenose dolphins (Tursiops truncatus) from the Western Atlantic and the Gulf of Mexico.

Polychlorinated biphenyls (PCBs) and hydroxylated metabolic products (OH-PCBs) were measured in plasma collected from live-captured and released bottlenose dolphins (Tursiops truncatus) from five different locations in the Western Atlantic and the Gulf of Mexico in 2003 and 2004. In 2004, the sum (sigma) of concentration of PCBs in plasma of dolphins sampled off Charleston, SC [geometric mean: 223 ng/g of wet weight (w.w.)] was significantly higher (p<0.05) than concentrations detected in animals from the Indian River Lagoon, FL (sigmaPCBs: 122 ng/g w.w.) and the Sarasota Bay, FL (sigmaPCBs: 111 ng/g w.w.). The PCB homolog profiles were similar among locations. Concentrations of OH-PCBs were significantly higher (p<0.05) in plasma of dolphins from Charleston, SC (sigmaOH-PCBs for 2003: 126 ng/g w.w.; 2004: 138 ng/g w.w.) than animals from Florida (sigmaOH-PCBs ranged from 6 to 47 ng/g w.w.) and Bermuda (8.3 ng/g w.w.); however, concentrations in the Charleston samples did not differ from animals captured in Delaware Bay, NJ (57 ng/g w.w.). The sigmaOH-PCBs constituted 2-68% of the total PCB concentrations in plasma. Dichloro- to nonachloro-OH-PCBs were quantified using high-resolution gas chromatography mass spectrometry, but only around 20% of OH-PCBs could be identified by comparison to authentic standards. Results from this study show that OH-PCB are important environmental contaminants in dolphins and suggest that PCBs, decades after their ban, may still constitute a threat to wildlife.

Integrating life-history and reproductive success data to examine potential relationships with organochlorine compounds for bottlenose dolphins (Tursiops truncatus) in Sarasota Bay, Florida.

Research initiated in 1970 has identified a long-term, year-round resident community of about 140 bottlenose dolphins (Tursiops truncatus) in Sarasota Bay, Florida, providing unparalleled opportunities to investigate relationships between organochlorine contaminant residues and life-history and reproductive parameters. Many individual dolphins are identifiable and of known age, sex, and maternal lineage (< or =4 generations). Observational monitoring provides data on dolphin spatial and temporal occurrence, births and fates of calves, and birth-order. Capture-release operations conducted for veterinary examinations provide biological data and samples for life-history and contaminant residue measurement. Organochlorine concentrations in blubber and blood (plasma) can be examined relative to age, sex, lipid content, and birth-order. Reproductive success is evaluated through tracking of individual female lifetime calving success. For the current study, 47 blubber samples collected during June 2000 and 2001 were analyzed for PCB concentrations of 22 congeners relative to life-history factors and reproductive success. Prior to sexual maturity, males and females exhibited similar concentrations of about 15-50 ppm. Classical patterns of accumulation with age were identified in males, but not in females. Subsequently, males accumulated higher concentrations of PCBs through their lives (>100 ppm), whereas females begin to depurate with their first calf, reaching a balance between contaminant intake and lactational loss (<15 ppm). In primiparous females, PCB concentrations in blubber and plasma and the rates of first-born calf mortality were both high. First-born calves had higher concentrations than subsequent calves of similar age (>25 vs.<25 ppm). Maternal burdens were lower early in lactation and increased as calves approached nutritional independence. Empirical data were generally consistent with a published theoretical risk assessment and supported the need for incorporation of threats from indirect anthropogenic impacts such as environmental pollutants into species management plans. Long-term observational monitoring and periodic biological sampling provide a powerful, non-lethal approach to understanding relationships between organochlorine residue concentrations in tissues and reproductive parameters for coastal dolphins.

Polyfluoroalkyl compounds in free-ranging bottlenose dolphins (Tursiops truncatus) from the Gulf of Mexico and the Atlantic Ocean.

Polyfluoroalkyl compounds (PFAs) have been used for decades in industrial and commercial products and are now detected worldwide. Concentrations of two major PFA groups, carboxylic acids (PFCAs) and sulfonic acids (PFSAs), were assessed in plasma of bottlenose dolphins from the Gulf of Mexico (Sarasota Bay, FL) and the Atlantic Ocean (Delaware Bay, NJ, Charleston, SC, Indian River Lagoon (IRL), FL, and Bermuda). Eight PFAs were detected in the plasma of all dolphins. Perfluorooctane sulfonate (PFOS) was the predominant compound at all locations (range from 49 ng/g wet weight (w.w.) in dolphins from Bermuda to 1171 ng/g w.w. in plasma of animals from Charleston). Sum of PFA concentrations were significantly higher in animals from Charleston compared to IRL, Sarasota Bay, and Bermuda. Concentrations of several PFAs were negatively associated with age in animals from IRL and Charleston. No differences between gender were observed for all compounds at all locations. An increase in PFA concentrations was associated with a decrease of blubber thickness in animals from Sarasota Bay and IRL. Fluorotelomer 8:2 and 10:2 unsaturated carboxylic acids (FTUCAs), known degradation products of fluorotelomer alcohols and suspected precursors to PFCAs, were detected for the first time at low concentrations in plasma of dolphins.