Iverson, John B.

Rettig, Jessica E.

Smith, Geoffrey R.

English

Denison University

Denison University Denison Digital Commons Faculty Publications 2022 Growth in Snapping Turtle, Chelydra serpentina (Testudines: Chelydridae) in northern Indiana John B. Iverson Geoffrey R. Smith Jessica E. Rettig Follow this and additional works at: https://digitalcommons.denison.edu/facultypubs  Part of the Social and Cultural Anthropology Commons The Common Snapping Turtle, Chelydra serpentina (Linnaeus, 1758), is the most widely distributed turtle species in North America and fourth in that category in the world (Turtle Taxonomy Working Group, 2021). It is also one of the most frequently encountered turtles in its range (Ernst and Lovich, 2009). However, despite these facts, geographic variation in many of its life history traits remains understudied. For example, growth data are available for nine (mostly northern) populations (Table 1), but geographic patterns in juvenile growth are not yet clear. We collected growth data from a population in Indiana, expecting to identify a latitudinal pattern.Between 1980 and 2016, we made 262 total captures of Chelydra serpentina in the southeastern bay of Dewart Lake, Kosciusko County, Indiana (41.3652°N, 85.7806°W), following the methods outlined in Smith et al. (2006, 2018). We captured 142 males, 50 females, and 22 probable subadult males (based on tail morphology), 16 probable subadult females, and 32 unsexed juveniles. Of these, 182 were individually marked, and of those, 36 were recaptured only once, 19 were recaptured twice, three were recaptured three times, and one was recaptured six times (59 total recaptures). For each turtle we measured maximum carapace length (CL in mm). We also attempted to count growth rings on costal scutes, but found those counts to be unreliable because of the confusion between secondary (seasonal) and primary (annual) annuli (see also Brooks et al., 1997; Wilson et al., 2003). For example, JBI counted five annuli on a 66.5 mm CL juvenile, and only six annuli on a 241 mm CL adult male. Furthermore, upon recapture the annuli counts of some turtles did not reflect actual time intervals. Therefore, we employed a von Bertalanffy (vB) growth analysis (after Fabens, 1965) to estimate growth in this population of snapping turtles.For our vB analysis we compared body size data from the first to the last capture. We ignored intermediate captures, except for three males and three females recaptured while still juveniles (< 200 mm CL) and then later recaptured 6–10 years later as presumed adults (263–375 mm CL). For these six individuals, juvenile growth and adult growth were each included separately, because including the entire span between first and last capture (7–17 yrs; mean 11.5 yrs) would have inappropriately skewed their growth rates by diluting Herpetology Notes, volume 15: 41-43 (2022) (published online on 25 January 2022)Growth in Common Snapping Turtles, Chelydra serpentina (Testudines: Chelydridae),  in northern IndianaJohn B. Iverson1,*, Geoffrey R. Smith2, and Jessica E. Rettig21 Department of Biology, Earlham College, Richmond, Indiana 47374, USA.2 Department of Biology, Denison University, Granville, Ohio 43023, USA.* Corresponding author. E-mail: johni@earlham.edu; smithg@denison.edu; rettig@denison.edu© 2022 by Herpetology Notes. Open Access by CC BY-NC-ND 4.0.  Table 1.    Location Latitude Sample CL Source Ontario 45.6 24 X 1601 Armstrong and Brooks, 2013 Ontario  45.6 317 X 2102 Armstrong and Brooks, 2013 Ontario  45.6 19 F 175 Galbraith et al., 1989 South Dakota 43.1 27 X 3053 Hammer, 1969 Michigan 42.5 6 X 3244 Gibbons, 1968 Michigan 42.5 41 U 197 Congdon et al., 1992 Massachusetts 42.5 8 X 2395 Graham and Perkins, 1976 Nebraska 41.8 50 F 253 Iverson and Lewis, 2019 Iowa 41.8 34 F 2486 Christiansen and Burken, 1979 Indiana 41.5 23 F 250 This study Indiana 41.5 51 M 254 This study Pennsylvania 40.2 43 X 1957 Hughes and Meshaka, 2020 Florida  30.5 21 X 2508 Aresco and Gunzberger, 2007 1 estimated from their Fig. 2. 2 estimated from their Figs. 1C, 4. 3 estimated from their Fig. 5. 4 extrapolated from log-transformed data in their Table 1. 5 extrapolated from log-transformed data in their Table 2. 6 extrapolated from log-transformed data in their Table 3 for ages 1–11 (omitting CL = 230, presumably a typographical error). 7 estimated from their Fig 6. 8 estimated from their Fig 2.  Table 1. Estimated body size (carapace length, CL, in mm) of Snapping Turtles (Chelydra serpentina) at age 10 yrs across the species’ range. Populations are arranged in order of declining latitude and samples include males (M), females (F), mixed (X), and unsexed (U) samples. Note that the first three studies refer to the same population.John B. Iverson et al.42the faster juvenile rate with the slower subadult/adult rate. We also assumed that CL at age zero for males and females was 29.1 mm after Congdon et al. (1987), which agreed with our smallest capture at 31.4 mm CL on 25 May 1985 (i.e., when the individual was just beginning its first full growth season). For the male analysis, we included adult males, probable subadult males, and unsexed juveniles, and for the female analysis, we included adult females, probable subadult females, and unsexed juveniles.We anchored our vB curves (following Jones, 2017) by including three juveniles (58.8–66.5 mm CL) that were captured in late July and estimated by scute growth (i.e., only exhibiting the annulus from the first winter of life) to be near the end of their first full growing season (age = 0.83 years, assuming a growing season of 1 May–30 October). None of those three were recaptures, but we assumed that they had grown from a hatching size of 29.1 mm CL in the prior year. These three sets of measurements were included in both the male and female vB analyses.For both males and females, we found growth rate to be highly correlated with body size (Figs. 1, 2). Our vB growth model for males and juveniles was CL = 380.156 * 1-0.9235e-0.1024t (n = 51; mean interval = 3.54 yrs; range, 1–11 yrs). Our model for females and juveniles was CL = 317.402 * 1-0.90843-0.1447t (n = 23; mean interval = 3.28 yrs; range, 1–9 yrs). Although these models revealed little difference in growth rate between males and females for the first decade of life (see Table 1), males subsequently grew faster than females and reached larger sizes (as has been reported for all studied populations of snapping turtles (review in Iverson et al., 1997).Our analysis suggests an asymptotic CL for males of 380.2 mm in Indiana, although our largest males were 429 and 427 mm CL. Estimated asymptotic CL for females in Indiana was 317.4 mm, and our largest females were 342 and 339 mm CL.Including our new data, juvenile growth trajectories are now available for ten populations across the species’ range. However, despite a total species range from ca. 25°N to 52°N latitude, data from only a single population outside the band between 40°N and 46°N are available. With this narrow sampling, no clear geographic pattern in juvenile growth rate is evident (Fig. 3).The broad range of habitats occupied by snapping turtles, from highly eutrophic to oligotrophic, and from locally hyperthermic to hypothermic, are known to impact their growth (Steyermark, 2008) and this complicates our understanding of geographic patterns, Figure 1. Relationship between carapace growth rate (GR; mm/yr) and mean carapace length (MNCL, in mm) at first and last capture for male and three small unsexed juvenile Chelydra serpentina in northern Indiana. GR = -0.1024MNCL + 38.928; r2 = 0.79; p < 0.0001; n = 51.Figure 2. Relationship between carapace growth rate (GR; mm/yr) and mean carapace length (MNCL; in mm) at first and last capture for female and three small unsexed juvenile Chelydra serpentina in northern Indiana. GR = -0.1447MNCL + 45.928; r2 = 0.86; p < 0.0001; n = 23.Figure 3. Estimated carapace length (in mm) of Chelydra serpentina at age ten years plotted by latitude of study site (see Table 1). Relationship is not significant (r = 0.27; p = 0.37).as does the lack of data from most of the species’ range, especially the warmer southern portion of the range. However, it is possible that juvenile growth has a substantial genetic component with little geographic variation, except that resulting from local thermal conditions and/or food resources. Future research should close the geographic gap in growth data, and also employ common garden experiments to evaluate the genetic contribution to juvenile growth in snapping turtles.Acknowledgements. We thank the many students, alumni, colleagues, and family members, who assisted with our 37 years of research on Dewart Lake. Funding was provided by Earlham College and Denison University, and from our personal funds. We also thank the staff of Quaker Haven Camp for providing housing. Annual scientific collecting permits were issued by the Indiana Department of Natural Resources. Although this study preceded the tenure of the Earlham College Institutional Animal Use and Care Committee, we followed the ethical guidelines established by the American Society of Ichthyologists and Herpetologists.ReferencesAresco, M.J., Gunzberger, M.S. (2007): Ecology and morphology of Chelydra serpentina in northwestern Florida. Southeastern Naturalist 6: 435–448.Armstrong, D.P., Brooks, R.J. (2013): Application of hierarchical biphasic growth models to long-term data for snapping turtles. Ecological Modelling 250: 119–125. Armstrong, D.P., Brooks, R.J. (2014): Estimating ages of turtles from growth data. Chelonian Conservation and Biology 13: 9–15. Brooks, R.J., Krawchuk, M.A, Stevens, C., Koper, N. (1997): Testing the precision and accuracy of age estimation using lines in scutes of Chelydra serpentina and Chrysemys picta. Journal of Herpetology 31: 521–529. Christiansen, J.L., Burken, R.R. (1979): Growth and maturity of the snapping turtle (Chelydra serpentina) in Iowa. Herpetologica 35: 261–266. Congdon, J.D., Gotte, S.W., McDiarmid, R.W. (1992): Ontogenetic changes in habitat use by juvenile turtles, Chelydra serpentina and Chrysemys picta. Canadian Field-Naturalist 106: 241–248.Fabens, A.J. (1965): Properties and fitting of the von Bertalanffy growth curve. Growth 29: 265–289. Galbraith, D.A., Brooks, R.J., Obbard, M.E. (1989): The influence of growth rate on age and body size at maturity in female snapping turtles Chelydra serpentina. Copeia 1989: 896–904. Gibbons, J.W. (1968): Growth rates of the Common Snapping turtle, Chelydra serpentina, in a polluted river. Herpetologica 24: 266–267.Graham, T.E., Perkins, R.W. (1976): Growth of the Common Snapping Turtle, Chelydra serpentina, in a polluted marsh. Bulletin of the Maryland Herpetological Society 12: 123–125.Hammer, D.A. (1969): Parameters of a marsh Snapping Turtle population, Lacreek Refuge, South Dakota. Journal of Wildlife Management 33: 995–1005.Hughes, D.F., Meshaka, W.E. (2020): Demography of aquatic turtles (Chrysemys picta marginata and Chelydra serpentina) in southwestern Pennsylvania. Annals of the Carnegie Museum 86: 361–376.Iverson, J.B., Lewis, E.L. (2019): Natural history notes. Chelydra serpentina (Snapping Turtle). Growth and maturity. Herpetological Review 50: 119–120.Iverson, J.B., Higgins, H., Sirulnik, A., Griffiths, C. (1997): Local and geographic variation in the reproductive biology of the Snapping Turtle (Chelydra serpentina). Herpetologica 53: 96–117. Jones, R.L. (2017): Long-term trends in Ringed Sawback (Graptemys oculifera) growth, survivorship, sex ratios, and population sizes in the Pearl River, Mississippi. Chelonian Conservation and Biology 16: 215–228.Smith, G.R., Iverson, J.B., Rettig, J.E. (2006): Changes in a turtle community from a northern Indiana lake: A long-term study. Journal of Herpetology 40: 180–185.Smith, G.R., Iverson, J.B., Rettig, J.E. (2018): Frequency of propeller damage in a turtle community in northern Indiana: a long-term study. Herpetological Conservation and Biology 13: 691–699.Steyermark, A.C. (2008): Growth patterns in Snapping Turtles, Chelydra serpentina. In: Biology of the Snapping Turtle (Chelydra serpentina), p. 111–119. Steyermark, A.C, Finkler, M.S., Brooks, R.J., Eds., Baltimore, Maryland, USA, John Hopkins University Press.Turtle Taxonomy Working Group [Rhodin, A.G.J., Iverson, J.B., Bour, R., Fritz, U., Georges, A., Shaffer, H.B., Dijk, P.P. van] (2021): Turtles of the world: annotated checklist and atlas of taxonomy, synonymy, distribution, and conservation status, ninth edition. Chelonian Research Monographs 8: 1–472.Wilson, D.S., Tracy, C.R., Tracy, C.R. (2003): Estimating age of turtles from growth rings: a critical evaluation of the technique. Herpetologica 59: 178–194. Growth in Common Snapping Turtles in northern Indiana 43Accepted by Eric Munscher

Growth in Snapping Turtle, Chelydra serpentina (Testudines: Chelydridae)  in northern Indiana

https://digitalcommons.denison.edu/cgi/viewcontent.cgi?article=1925&context=facultypubs

Growth in Snapping Turtle, Chelydra serpentina (Testudines: Chelydridae) in northern Indiana

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