Health assessment of nesting loggerhead sea turtles (Caretta caretta) in one of their largest rookeries (central eastern Florida coast, USA)

Abstract

Reproduction is a physiologically demanding process for sea turtles. Health indicators, including morphometric indices and blood analytes, provide insight into overall health, physiology and organ function for breeding sea turtles as a way to assess population-level effects. The Archie Carr National Wildlife Refuge (ACNWR) on Florida's central eastern coast is critical nesting habitat for loggerhead sea turtles (Caretta caretta), but health variables from this location have not been documented. Objectives of the study were to (1) assess morphometrics and blood analyte data (including haematology, plasma biochemistry, protein electrophoresis, β-hydroxybutyrate, trace nutrients, vitamins and fatty acid profiles) from loggerheads nesting on or near the beaches of the ACNWR, (2) investigate correlations of body condition index (BCI) with blood analytes and (3) analyse temporal trends in morphometric and blood analyte data throughout the nesting season. Morphometric and/or blood analyte data are reported for 57 nesting loggerheads encountered between 2016 and 2019. Plasma copper and iron positively correlated with BCI. Mass tended to decline across nesting season, whereas BCI did not. Many blood analytes significantly increased or decreased across nesting season, reflecting the catabolic state and haemodynamic variations of nesting turtles. Twenty-three of 34 fatty acids declined across nesting season, which demonstrates the physiological demands of nesting turtles for vitellogenesis and reproductive activities, thus suggesting potential utility of fatty acids for the assessment of foraging status and phases of reproduction. The findings herein are relevant for future spatiotemporal and interspecies comparisons, investigating stressor effects and understanding the physiological demands in nesting sea turtles. This information provides comparative data for individual animals in rescue or managed care settings and for assessment of conservation strategies.

Keywords: Blood analysis; body condition index; fatty acids; haematology; morphometrics; plasma biochemistry; protein electrophoresis; reference intervals; trace nutrients; vitamins.

Figure 1

Locations of both sampling sites of loggerhead sea turtles (Caretta caretta) at the ACNWR, Florida, USA.

Figure 2

Relationship between mass (kg) and standard straight carapace length (cm) for nesting loggerhead sea turtles (Caretta caretta) from the ACNWR. The trend was significant and the equation for the line-of-best-fit is shown with the 95% confidence interval of the regression line.

Figure 3

Relationship between BCI and plasma (a) copper and (b) iron in nesting loggerhead sea turtles (Caretta caretta) from the ACNWR. Data were log-transformed. The trends were significant and the equations for the line-of-best-fit are shown with the 95% confidence intervals of the regression line.

Figure 4

Mean ± standard deviation of mass and select blood analytes showing significant trends (with the exception of β-hydroxybutyrate, which was not significant, but tended to increase mid-season) by month of nesting season in nesting loggerhead sea turtles (Caretta caretta) from the ACNWR. Morphometric results include (A) mass, whilst included blood analytes are (B) PCV, (C) β-hydroxybutyrate, (D) blood urea nitrogen, (E) cholesterol, (F) triglycerides, (G) uric acid, (H) total protein, (I) α-tocopherol, (J) retinol and (K) sum of all detected fatty acids. ANOVA with Tukey’s post hoc tests were used to compare data by month, with Kruskal–Wallis tests with Dunn’s post hoc tests with Benjamini–Hochberg adjustment were used when the data did not meet the assumptions of the ANOVA. Different letters above each column represent significant differences by month at P < 0.050.

Figure 5

Mean ± standard deviation of electrolytes and minerals showing significant trends (with the exception of calcium:phosphorus, which was not significant) by month of nesting season in nesting loggerhead sea turtles (Caretta caretta) from the ACNWR. Electrolytes and minerals include (A) calcium, (B) phosphorus, (C) calcium:phosphorus, (D) chloride, (E) potassium and (F) sodium. ANOVA with Tukey’s post hoc tests were used to compare data by month, with Kruskal–Wallis tests with Dunn’s post hoc tests with Benjamini–Hochberg adjustment were used when the data did not meet the assumptions of the ANOVA. Different letters above each column represent significant differences by month at P < 0.050.