In anticipation of US federal status classification (warranted, warranted but precluded, not warranted), scheduled for 2023, we provide population viability analysis of the Blanding’s turtle Emydoidea blandingii , a long-lived, late-maturing, semi-aquatic species of conservation concern throughout its range. We present demographic data from long-term study of a population in northeastern Illinois and use these data as the basis for viability and sensitivity analyses focused on parameter uncertainty and geographic parameter variation. We use population viability analysis to identify population sizes necessary to provide population resiliency to stochastic disturbance events and catastrophes and demonstrate how alternative definitions of ‘foreseeable future’ might affect status decisions. Demographic parameters within our focal population resulted in optimistic population projections (probability of extinction = 0% over 100 years) but results were less optimistic when catastrophes or uncertainty in parameter estimates were incorporated (probability of extinction = 3% and 16%, respectively). Uncertainty in estimates of age-specific mortality had the biggest impact on population viability analysis outcomes but uncertainty in other parameters (age of first reproduction, environmental variation in age-specific mortality, % females reproducing, clutch size) also contributed. Blanding’s turtle demography varies geographically and incorporating this variation resulted in both mortality- and fecundity-related parameters affecting population viability analysis outcomes. Possibly, compensatory variation among demographic parameters allows for persistence across a wide range of parameter values. We found that extinction risk decreased and retention of genetic diversity increased rapidly with increasing initial population size. In the absence of catastrophes, demographic conservation goals could be met with a smaller initial population size than could genetic conservation goals; ≥20-50 adults were necessary for extinction risk <5% whereas ≥50-110 adults were necessary to retain >95% of existing genetic diversity over 100 yrs. These thresholds shifted upward when catastrophes were included; ≥50-200 adults were necessary for extinction risk <5% and ≥110 to more than 200 adults were necessary to retain >95% of existing genetic diversity over 100 yrs. Impediments to Blanding’s turtle conservation include an incomplete understanding of geographic covariation among demographic parameters, the large amount of effort necessary to estimate and monitor abundance, and uncertainty regarding the impacts of increasingly frequent extreme weather events.
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Research Article|
April 01 2021
Blanding’s Turtle Demography and Population Viability
Richard B. King
;
Richard B. King
Northern Illinois University
Professor
Department of Biological Sciences
155 Castle Drive
UNITED STATES
DeKalb
IL
60115
815-753-0461
815-753-7833
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Callie K. Golba
;
Callie K. Golba
Department of Biological Sciences, Northern Illinois University, DeKalb, Illinois 60115
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Gary A. Glowacki
;
Gary A. Glowacki
Lake County Forest Preserve District, Libertyville, IL 60048 USA
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Andrew R. Kuhns
Andrew R. Kuhns
Illinois Natural History Survey, Prairie Research Institute, University of Illinois, Champaign, IL 61820
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Journal of Fish and Wildlife Management (2021)
Article history
Received:
August 21 2020
Revision Received:
February 12 2021
Accepted:
March 05 2021
Citation
Richard B. King, Callie K. Golba, Gary A. Glowacki, Andrew R. Kuhns; Blanding’s Turtle Demography and Population Viability. Journal of Fish and Wildlife Management 2021; doi: https://doi.org/10.3996/JFWM-20-063
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