Abstract

Long-term capture-release studies of bottlenose dolphins (Tursiops truncatus) in Sarasota Bay, Florida have produced multi-decadal, extensive health and morphometric datasets that can be used to examine and test hypotheses regarding correlations among different parameters.⁴ These large datasets can also be used to develop baseline reference ranges to which indicators of individual and population health can be compared.^1,3 In this study, we have used statistical methods (e.g., quantile regression and nonparametric bootstrapping) to develop 90th and 95th percentile reference ranges for endocrine and body condition parameters collected between 1987 and 2012. Specifically, 95th percentile reference ranges were developed for sex-specific indices of body condition including: 1) total mass vs. total length (males: n=88; females: n = 72; see Figure 1); 2) maximum girth vs. total length (males: n=86; females: n=70); and 3) body mass index (BMI; males: n = 88; females: n = 72).² Similarly, 90th and 95th percentile reference ranges were developed for stress-related hormones including: 1) cortisol (N = 137; see Figure 2); 2) triiodothyronine (T3; n = 131; see Figure 3); 3) total thyroxine (TT4; N=119); and free thyroxine (FT4; n = 115). Reference ranges were stratified by significant covariates (e.g., sampling time, age class, sex) determined from generalized linear mixed modeling. Capture-release studies of estuarine bottlenose dolphins have increased in frequency and geographic range in recent years, often resulting from questions regarding health impacts from exposure to harmful algal blooms, and anthropogenic contaminants, including the Deepwater Horizon oil spill. These reference ranges represent a baseline for a wild population in the absence of significant known natural or anthropogenic stressors. Documented differences with values from populations impacted by presumed stressors demonstrate that these can be applied to future studies to identify individuals and stocks with indications of compromised health such as poor body condition and abnormal adrenal and thyroid function.

Figures

Figure 1. Ninety-fifth percentile reference ranges for mass and length ratios for male bottlenose dolphins sampled in Sarasota Bay, FL, USA (1987–2009) Figure from Hart et al.

Figure 2. Ninety and 95th percentile reference ranges for serum cortisol for bottlenose dolphins sampled in Sarasota Bay, FL, USA (2000–2012) Less than 30 minutes elapsed sampling time

Figure 3. Ninety and 95th percentile reference ranges for serum T3 for physically immature bottlenose dolphins sampled in Sarasota Bay, FL, USA (2000–2012)

Acknowledgements

The authors wish to thank Blair Irvine, Michael Scott, Jay Sweeney, Forrest Townsend, Aleta Hohn, Deb Fauquier, the staff, interns, and volunteers of the Sarasota Dolphin Research Program (SDRP) for ensuring the safety and effectiveness of the capture-release projects. Dolphin Quest and NOAA provided much of the support for health assessments. Sarasota dolphin health assessments in 2011 were partially funded through the Deepwater Horizon Natural Resource Damage Assessment conducted cooperatively by NOAA, other federal and state trustees, and BP. Capture-release work was conducted under a series of NOAA Scientific Research Permits and IACUC approvals issued to R.S. Wells. Funding for data analyses was provided by NOAA's Center of Excellence for Oceans and Human Health at the Hollings Marine Laboratory and the Office of Naval Research's Marine Mammals and Biology Program.

* Presenting author

Literature Cited

1.  Wells RS. 2009. Learning from nature: bottlenose dolphin care and husbandry. Zoo Biol 28:1–17.

2.  Hall AJ, Wells RS, Sweeney JC, Townsend FI, Balmer BC, Hohn AA, Rhinehart HL. 2007. Annual, seasonal and individual variation in hematology and clinical blood chemistry profiles in bottlenose dolphins (Tursiops truncatus) from Sarasota Bay, Florida. Comp Biochem Physiol, A 148:266–277.

3.  Schwacke LH, Hall AJ, Townsend FI, Wells RS, Hansen LJ, Hohn AA, Bossart GD, Fair PA, Rowles TK. 2009. Hematologic and serum biochemical reference intervals for free-ranging common bottlenose dolphins (Tursiops truncatus) and variation in the distributions of clinicopathologic values related to geographic sampling site. American J Vet Res 70: 973–985.

4.  Hart LB, Wells RS, Schwacke LH. In Press. Body condition reference ranges for wild bottlenose dolphins (Tursiops truncatus). Aquatic Biol