Using infrared thermography to assess seasonal trends in dorsal fin surface temperatures of free‐swimming bottlenose dolphins (Tursiops truncatus) in Sarasota Bay, Florida

The temperature differential (ΔT) between a body surface and the environment influences an organism's heat balance. In Sarasota Bay, FL, where ambient water temperature (T w ) ranges annually from 11° to 33°C, ΔT was investigated in a resident community of bottlenose dolphins (Tursiops truncatus). Dorsal fin surface temperatures (T dfin ) were measured on wild, free-swimming dolphins using infrared thermography. Field and laboratory calibration studies were also undertaken to assess the efficacy of this non-invasive technology in the marine environment. The portability of infrared thermography permitted measurements of T dfin across the entire range of environmental temperatures experienced by animals in this region. Results indicated a positive, linear relationship between T dfin and T w (r 2 = 0.978, P < 0.001). On average, T dfin was 0.9°C warmer than T w across seasons, despite the 22°C annual range in T w . Changes in integumentary and vascular insulation likely account for the stability of ΔT dfin-w and the protection of core temperature (T core ) across seasons. The high thermal conductivity of water may also influence this ΔT. The use of infrared thermography is an effective, non-invasive method of assessing dorsal fin skin surface temperatures (±1°C) across large numbers of wild, free-swimming dolphins throughout their thermally dynamic aquatic environment.

[1]  W. M. Swingle,et al.  LOCAL ABUNDANCE AND DISTRIBUTION OF BOTTLENOSE DOLPHINS (TURSIOPS TRUNCATUS) IN THE NEARSHORE WATERS OF VIRGINIA BEACH, VIRGINIA , 1999 .

[2]  F. Fish.  Thermoregulation in the muskrat (Ondatra zibethicus): The use of regional heterothermia , 1979 .

[3]  P. Thompson,et al.  Habitat Use by Bottlenose Dolphins: Seasonal Distribution and Stratified Movement Patterns in the Moray Firth, Scotland , 1997 .

[4]  Eric S. Zolman,et al.  Residence patterns of bottlenose dolphins (Tursiops truncatus) in the Stono River Estuary, Charleston County, South Carolina, U.S.A. , 2002 .

[5]  J. E. Heath,et al.  An Infrared Thermographic Study of Surface Temperature in Relation to External Thermal Stress in Three Species of Foxes: The Red Fox (Vulpes vulpes), Arctic Fox (Alopex lagopus), and Kit Fox (Vulpes macrotis) , 1992, Physiological Zoology.

[6]  J. E. Heath,et al.  An infrared thermographic study of surface temperature in the euthermic woodchuck (Marmota monax). , 2001, Comparative biochemistry and physiology. Part A, Molecular & integrative physiology.

[7]  J. Hart,et al.  THE METABOLISM AND INSULATION OF SEALS AS BARE-SKINNED MAMMALS IN COLD WATER , 1957 .

[8]  John Moncrieff,et al.  THE USE OF IR THERMOGRAPHY TO MEASURE THE RADIATIVE TEMPERATURE AND HEAT LOSS OF A BARN OWL (TYTO ALBA) , 1998 .

[9]  G. Whittow,et al.  Body temperature and heat exchange in the Hawaiian spinner dolphin, Stenella longirostris. , 1976, Comparative biochemistry and physiology. A, Comparative physiology.

[10]  Robin C. Dunkin,et al.  The ontogenetic changes in the thermal properties of blubber from Atlantic bottlenose dolphin Tursiops truncatus , 2005, Journal of Experimental Biology.

[11]  T. Williams.  Heat transfer in elephants: thermal partitioning based on skin temperature profiles , 1990 .

[12]  R. Wells,et al.  MOVEMENTS AND ACTIVITIES OF THE ATLANTIC BOTTLENOSE DOLPHIN, TURSIOPS TRUNCATUS, NEAR SARASOTA, FLORIDA , 1981 .

[13]  Randall S. Wells,et al.  The Social Structure of Free-Ranging Bottlenose Dolphins , 1987 .

[14]  L. C. Cuyler,et al.  THERMAL INFRARED RADIATION FROM FREE LIVING WHALES , 1992 .

[15]  D. Watmough,et al.  The thermal scanning of a curved isothermal surface: implications for clinical thermography. , 1970, Physics in medicine and biology.

[16]  D. A. Pabst,et al.  Thermoregulation of the intra-abdominal testes of the bottlenose dolphin (Tursiops truncatus) during exercise. , 1995, The Journal of experimental biology.

[17]  Wayne L. Perryman,et al.  DIEL VARIATION IN MIGRATION RATES OF EASTERN PACIFIC GRAY WHALES MEASURED WITH THERMAL IMAGING SENSORS , 1999 .

[18]  T. Williams,et al.  Thermoregulation during swimming and diving in bottlenose dolphins, Tursiops truncatus , 1999, Journal of Comparative Physiology B.

[19]  Lawrence M. Dill,et al.  FOOD AVAILABILITY AND TIGER SHARK PREDATION RISK INFLUENCE BOTTLENOSE DOLPHIN HABITAT USE , 2002 .

[20]  J. A. Clark,et al.  Thermographic measurements of the surface temperatures of animals. , 1973, Journal of mammalogy.

[21]  Randall S. Wells,et al.  A new device to remotely measure heat flux and skin temperature from free-swimming dolphins , 2007 .

[22]  Randall S. Wells,et al.  2. Dolphin Social Complexity: Lessons from Long-Term Study and Life History , 2003 .

[23]  T. Williams,et al.  The diving physiology of bottlenose dolphins (Tursiops truncatus). III. Thermoregulation at depth. , 1999, The Journal of experimental biology.

[24]  D. A. Pabst,et al.  The relationship between heat flow and vasculature in the dorsal fin of wild bottlenose dolphins Tursiops truncatus. , 2002, The Journal of experimental biology.

[25]  P. F. Scholander,et al.  Counter-current vascular heat exchange in the fins of whales. , 1955, Journal of applied physiology.

[26]  Michael D. Scott.  11 – A Long-Term Study of Bottlenose Dolphins on the West Coast of Florida , 1990 .

[27]  Björn Mauck,et al.  Thermal windows on the trunk of hauled-out seals: hot spots for thermoregulatory evaporation? , 2003, Journal of Experimental Biology.

[28]  G. Worthy,et al.  Variability in fatty acid composition of bottlenose dolphin (Tursiops truncatus) blubber as a function of body site, season, and reproductive state , 2004 .

[29]  D. A. Pabst,et al.  Seasonal patterns of heat loss in wild bottlenose dolphins (Tursiops truncatus) , 2008, Journal of Comparative Physiology B.