Date of Award
12-2001
Culminating Project Type
Thesis
Department
Biology
College
College of Science and Engineering
First Advisor
William Faber
Second Advisor
Neal Voelz
Third Advisor
Jeffrey Torguson
Creative Commons License
This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 4.0 License.
Keywords and Subject Headings
Snapping turtle, Commercial harvest, Dendrochronology
Abstract
Common snapping turtles ( Chelydra serpentina serpentina L.) from west central Minnesota were captured as by-catch in modified fyke nets placed in commercial fish rearing ponds during the summers of 1998-1999 (n = 111 ). Individuals were examined to determine sex, mass, age, circumference at midpoint, thickness at midpoint, carapace to tail tip length, cloaca to tail tip length (ct), and plastron to cloaca length (pc). Curved length and width were determined for carapace, plastron, second left anterior costal scute, and fourth posterior vertebral scute.
Sex was determined by mass, visual examination of secondary sex characteristics, and mathematically with tail measurements. Approximately 56% of individuals examined were male. Tail measurement ratios were used to predict sex with ct/pc and ct/(pc+ct) being > 90% accurate.
Snapping turtle age was determined by means of 2 methods of scute annuli analysis and 3 methods of skeletochronology, with samples prepared at St. Cloud State University (SCSU) and Matson's Laboratory, LLC. (ML; Milltown, MT). Marks of Skeletal Growth (MS Gs) and annuli were used to estimate age in humerus/femur and 4th vertebral scutes, respectively.
Age estimates varied by methodology used, with old individuals showing the widest deviation in estimates while hatchling ages were always determined to be zero. Maximum age estimated was 26 for average skeletochronology, 33 for age since maturity, 63.0 for resorption estimation, 24 for scute annuli, and 91.5 for scute erosion. Unrealistic age estimates were caused by the projection of several small MSGs or annuli to the entire respective bone or scute. SCSU and ML samples were significantly similar with physical differences being cosmetic and numerical differences caused by sample location.
Regression analysis suggests that age since maturity and curved carapace length are best suited for future age determination efforts (R2 = 0.995 and 0.955, respectively), though all methods and features tested showed promise. Regression analysis also suggested that MN snapping turtles should be approximately 3 in. (7.5 cm) larger when harvested to assure maturity had been reached.
Future snapping turtle management efforts should be sex-based and possibly include a slot limit similar to that used for game fish species. A maximum size restriction on female harvest should be beneficial for maintaining variable popluations of common snapping turtles in Minnesota.
Recommended Citation
Jenniges, Justin, "Age Determination of Common Snapping Turtles (Chelydra Serpentina) in West Central Minnesota" (2001). Culminating Projects in Biology. 74.
https://repository.stcloudstate.edu/biol_etds/74
