Quantifying Ecological Life Support: The Biological Efficacy of Alternative Supplementation Strategies for Imperiled Amphibian Populations

Abstract

Global biodiversity loss has prompted diverse efforts to stem or reverse declines for many species. Such efforts are often implemented before the efficacy of alternative management actions is quantified. Here, we use matrix models to compare the effectiveness of two supplementation strategies, head-starting early life stages and captive breeding for reintroduction, at reducing extinction risk of declining amphibians. We use the imperiled Oregon spotted frog (Rana pretiosa) as a case study and find that when supplementation occurs after metamorphosis, captive breeding is more effective at reducing extinction risk than head-starting, but the difference declines with increasing supplementation effort. We also find that captive breeding with release as larvae yields similar reductions in extinction risk, and is two orders of magnitude more effective at reducing extinction probabilities than head-starting the same stage. Our results highlight that even basic demographic data can be leveraged to assess tradeoffs among alternative supplementation strategies.

A new parameterization for integrated population models to document amphibian reintroductions

“…As a result, Oregon spotted frog have recently been listed as threatened by the U.S. Kissel et al (2014) combined the survival estimates of Chelgren et al (2008) with estimates of larval survival in mesocosms to simulate the efficacy of different supplementation strategies for Oregon spotted frog. Fish and Wildlife Service 2014).…”

“…Chelgren et al (2008) documented the first translocation effort for the species and estimated seasonal adult survival, somatic growth rates, and local movements following the release of founders (i.e., individuals released to form a new population). Kissel et al (2014) combined the survival estimates of Chelgren et al (2008) with estimates of larval survival in mesocosms to simulate the efficacy of different supplementation strategies for Oregon spotted frog. No other published information is available concerning population dynamics subsequent to the translocation or reintroduction of Oregon spotted frog.…”

Population dynamics reveal conservation priorities of the threatened New Zealand sea lion Phocarctos hookeri

“…In this regard, an understanding of the life history basis of population dynamics is a key component in assessing the vulnerability of a species to threats and the efficacy of conservation actions (Lewison et al 2013). Unfortunately, a missing link between conservation actions and the basic life history of the focal species is common in threatened species management (Kissel et al 2014;Martin et al 2014).…”

Compounding effects of climate change reduce population viability of a montane amphibian

“…, Kissel et al. ), as such data were not available for our study population (Appendix : Table S3; Appendix ). However, there is evidence that juvenile amphibians are more sensitive to climate than adults (Cayuela et al.…”

“…We used stochastic models, in which we bootstrapped 5,000 20-yr runs, pulling vital rates from distributions characterized by the mean and variance of the mean of the 26-yr time series for each time period (current, 2040s, 2080s) at each annual time step (Morris and Doak 2002), and calculated 95% confidence intervals for mean lambda as the 2.5% and 97.5% quantiles of the 5,000 draws. Embryonic and adult vital rates were estimated using empirical data from the Seven Lakes Basin of ONP (Appendix S1: Table S3; Appendix S2), and we used estimates of larval and juvenile survival probabilities from previously published Ranid frog studies (Licht 1974, Lawler et al 1999, McCaffery and Maxell 2010, Matthews et al 2013, Kissel et al 2014, as such data were not available for our study population (Appendix S1: Table S3; Appendix S2). However, there is evidence that juvenile amphibians are more sensitive to climate than adults (Cayuela et al 2016(Cayuela et al , 2017 thus, we included a correlation matrix (Morris and Doak 2002) in which all vital rates had a correlation of 1.0, so that years with high adult survival also had high juvenile, pre-metamorphic survival and fecundity values, and vice versa.…”