Disentangling the Effects of Season and Temperature on Hematological Values in Prairie Rattlesnakes (Crotalus viridis)

Baker, Sarah J.

Wildlife Epidemiology Lab

College of Veterinary Medicine

University of Illinois

Urbana, Illinois 61802, USA

 

Arizona Game and Fish Department                                                                                                                          Phoenix, Arizona 85086, USA

sbaker@azgfd.gov

 

Kessler, Ethan J.

Illinois Natural History Survey                                                                                                                                    

Champaign, Illinois 61820 USA

 

Schnelle, Amy                                                                                                                                                      Department of Veterinary Clinical Medicine                                                                                                         University of Illinois                                                                                                                                                       Urbana, Illinois 61802 USA

 

Allender, Matthew C.

Wildlife Epidemiology Lab

College of Veterinary Medicine

University of Illinois

Urbana, Illinois 61802, USA


Hematologic assessment is the most common clinical tool used to characterize both individual and population health. In reptiles, the hematologic response can be influenced by factors such as temperature and season, especially in temperate species. To improve the diagnostic utility of hematology in reptiles, it is imperative to evaluate and characterize the normal range of physiologic variation. Our objectives were to: 1) determine the impact of temperature and time of year on complete blood count parameters; and 2) create subject-based reference intervals for 20 Prairie Rattlesnakes (Crotalus viridis). Animals were randomly assigned to either a control group housed at a constant temperature (25ºC) or a treatment group housed in an environmental chamber with the temperature altered to reflect average ambient temperature throughout the year (5-32°C). Twice monthly for one year, blood samples were collected and the following hematologic parameters were measured: total white blood cell count (WBC), packed cell volume (PCV), total solids (TS), and white blood cell differential counts. WBC decreased and PCV increased as the mean previous 14-day temperature increased, with no effect of season. Total solids were higher in the control group, but there was no direct effect of temperature or season. Therefore, we found environmental temperature, rather than season, drives hematologic parameters. Our results indicate that ambient temperature should be considered when interpreting and comparing hematologic assessments of wild reptiles.
 

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