Abstract

In marine mammals, rectal temperature is a suitable method of body temperature assessment, but may not be ideal in many situations due to the need for additional training or restraint. Implantable microchip systems with identification and temperature sensing capabilities have become commercially available over the last few years. The overall accuracy of such systems has been investigated in multiple animal species with variable results,^1-3 but has yet to be explored in cetaceans. Implantable R.F.I.D. microchips were investigated in resting bottlenose dolphins in order to determine the best anatomic location for a strong association with rectal temperature measurements.

Three adult, male bottlenose dolphins with implanted microchips (Bio-Thermo Microchips, Destron Fearing and Digital Angel Corporation) participated in the study. All three dolphins had intramuscular shoulder microchips along with either a dorsal cervical subcutaneous microchip or an intramuscular epaxial microchip. Microchip temperatures were compared to rectal temperatures at 15 cm depth, as well as to ambient water and air temperatures.

When rectal temperature at 15 cm depth was compared to readings from other methods and sites amongst all three animals, the most significant predictor of standard body temperature was the intramuscular shoulder implant (p = 0.002). However, fitness to the regression line was poor (R² = 0.261). The animal with the thickest blubber layer (Animal A with an average blubber depth range of 2.7 to 3.1 cm) had the best association between rectal temperature at 15 cm and intramuscular temperature from the shoulder implant (p = 0.0008). At 15 cm depth, rectal temperature was not significantly affected by air and water temperature. Intramuscular epaxial and subcutaneous microchips were significantly affected by air and water temperature in all three animals and were not significantly associated with rectal temperatures.

Although there is an association between rectal temperature at 15 cm depth and intramuscular shoulder microchip measurements, there is significant variability. Additionally, blubber thickness may impact the temperature readings obtained from the implanted microchips. Further investigation is required to assess the role of blubber thickness in overall accuracy of the microchip system. Irrespective of blubber thickness, subcutaneous and intramuscular epaxial microchip temperatures were significantly affected by air and water temperatures and are not recommended as sites of implantation.

Acknowledgements

The authors would like to acknowledge the support of the National Research Council and the contributions made by the training and animal care staff at the U.S. Navy Marine Mammal Program (MMP). The care and use of animals for this project were reviewed and approved by the MMP's Institutional Animal Care and Use Committee (Protocol # 69).

References

1.  Chen P.H., and C.E. White. 2006. Comparison of rectal, microchip transponder, and infrared thermometry techniques for obtaining body temperature in the laboratory rabbit (Oryctolagus cuniculus). J Am Assoc Lab Anim Sci 45: 57-63.

2.  Goodwin S.D. Comparison of body temperatures of goats, horses, and sheep measured with a tympanic infrared thermometer, an implantable microchip transponder and a rectal thermometer. Veterinary Medicine Division, U.S. Army Research Institute of Infectious Diseases.

3.  Greer R.J., L.A. Cohn, et al. 2007. Comparison of three methods of temperature measurement in hypothermic, euthermic, and hyperthermic dogs. J Am Vet Med Assoc 230: 1841-1848.