Population Dynamics of the Concho Water Snake in Rivers and Reservoirs

Whiting, Martin J.; Dixon, James R.; Greene, Brian D.; Mueller, James M.; Thornton, Okla W.; Hatfield, Jeff S.; Nichols, James D.; Hines, James E.

doi:10.1643/ce-06-271

Cited by 12 publications

(7 citation statements)

References 25 publications

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“…Despite the relatively recent discovery of both populations of N. harteri, their distribution, habitat preference, and ecology have been extensively reviewed in the literature (Tinkle and Conant 1961;Mecham 1983;Smith 1983;Scott et al 1989;Greene et al 1994;Whiting et al 1996;Whiting et al 1997;Whiting et al 1998;Greene et al 1999;Gibbons and Dorcas 2004;Whiting et al 2008;McBride 2009). Unlike two other sympatric congeners, the Diamondback water snake (N. rhombifer) and the Blotched water snake (N. erythrogaster transversa), N. harteri is smaller bodied and more prone to desiccation and has a higher affinity for aquatic habitats (Scott et al 1989).…”

Section: Introductionmentioning

confidence: 99%

Low genetic diversity and evidence of population structure among subspecies of Nerodia harteri, a threatened water snake endemic to Texas

et al. 2012

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Nerodia harteri is a threatened small-bodied water snake that occupies one of the most restricted ranges of any snake within the continental United States. It is found closely associated with rivers and tributaries in the Colorado and Brazos river basins, which flow through north-central Texas. Nerodia harteri has been at the center of debate owing to conflicts between conservation efforts and the construction of dams that change or destroy its preferred habitat. Additionally, its taxonomic status has also been under contention with some authors recognizing two subspecies, the Brazos water snake (N. h. harteri) and the Concho water snake (N. h. paucimaculata), whereas other authors consider each separate species. Despite its relatively recent discovery during the 1940s, N. harteri has been the subject of several ecological studies, yet no population genetic assessment of either subspecies has been performed to date. We first evaluated the phylogenetic placement of both subspecies among other North American Nerodia using partial sequence data from the mitochondrial gene cytochrome-b. We then tested for population subdivision among four rivers encompassing the range of N. harteri and tested for the presence of admixture between river basins using mitochondrial sequence data (920 bp of cyt-b) and five cross-species amplified microsatellite loci. We found low mitochondrial haplotype diversity represented by two unique haplotypes in each river basin, which were separated by no more than four nucleotide changes. Nuclear loci showed low genetic diversity and population structuring within and among river basins. We did not find conclusive evidence of admixture between basins, and we support the presence of two separate evolutionarily significant units and two separate management units corresponding to each major river basin. Given increasing natural and anthropogenic threats, we recommend continued ecological and genetic monitoring of both subspecies.

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Section: Introductionmentioning

confidence: 99%

Low genetic diversity and evidence of population structure among subspecies of Nerodia harteri, a threatened water snake endemic to Texas

et al. 2012

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“…There are few reports of population growth rates in snakes (Webb et al 2002;Altwegg et al 2005) and fewer still for species native to North America (Whiting et al 2008). Studies investigating population ecology of a Viperid (Altwegg et al 2005) and a long-lived Elapid (average generation time of 10.4 years) (Webb et al 2002) also found k to be more sensitive to changes in adult survival rates, but this pattern did not hold for a shorter-lived Elapid (average generation time of 5.9 years) also studied (Webb et al 2002).…”

Section: Estimation Of and Factors Influencing Demographic Parametersmentioning

confidence: 99%

“…Uncertainty in estimates of k may arise from uncertainty in adult and subadult survival estimates, which included death and permanent emigration but not immigration, potentially biasing the estimates low. In a review of studies reporting first year survival of early-maturing North American snakes, Whiting et al (2008) estimated average annual survival at 0.24. Drymarchon couperi is considered a late-maturing colubrid (Stevenson et al 2009); however, our estimates of first year survival of approximately 0.29 is similar to that estimated for early-maturing colubrids in their first year.…”

Section: Estimation Of and Factors Influencing Demographic Parametersmentioning

confidence: 99%

Survival and population growth of a long‐lived threatened snake species,Drymarchon couperi(Eastern Indigo Snake)

et al. 2011

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Demographic data provide a basis for understanding the life history and ecology of species, factors which are vital for informing conservation efforts; however, little is known regarding the population ecology of most snake species, including the threatened Eastern Indigo Snake (Drymarchon couperi). We used 11 years (1999)(2000)(2001)(2002)(2003)(2004)(2005)(2006)(2007)(2008)(2009)) of capture-mark-recapture (CMR) and 2.5 years (2003)(2004)(2005) of radiotelemetry data from southeastern Georgia, USA, in a CMR modeling framework to estimate apparent survival, capture and transition probabilities, and evaluate factors influencing these parameters. The model-averaged estimate of overall apparent annual survival probability was 0.700 (±0.030 SE) and is comparable to that obtained from known fate analysis (radiotelemetry) at the same site. Body size positively influenced survival, regardless of sex. Capture probability differed seasonally by sex, suggesting lower capture probability for females in fall and males in winter. There was no evidence for effect of precipitation or site-specific differences in survival. Model averaged estimate of annual adult survival estimated using multistate CMR models was 0.738 ± 0.030 and 0.515 ± 0.189 for subadults. We estimated population growth rate (k) and elasticity (proportional sensitivity) of k to vital rates using a stage-structured matrix population model. Population growth rate ranged from 0.96 to 1.03 depending on the value of the probability of transitioning from subadult to adult stage. The k was proportionally most sensitive to changes in adult survival rate, followed by subadult survival. Our results suggest that protecting adult snakes and their habitats would result in the highest likelihood of long-term population stability and growth.

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“…Inferences made using survey counts may lead to false conclusions about the status of the population if the relationship between counts and population sizes are not known. Wildlife monitoring programs use markrecapture studies or mark-resight surveys for estimates of population size, survival and recruitment, to learn about the population's response to management actions, and to validate population indices used for long-term population monitoring (e.g., Thompson et al 1998;Williams et al 2002;Skalski et al 2005;Whiting et al 2008). If there is a strong correlation between survey counts and population estimates, indices can be standardized to approximate population sizes (Nichols 1992).…”

Section: Introductionmentioning

confidence: 99%

Long-Term Monitoring of Endangered Laysan Ducks: Index Validation and Population Estimates 1998–2012

Reynolds

Courtot

Brinck

et al. 2014

Journal of Fish and Wildlife Management

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Monitoring endangered wildlife is essential to assessing management or recovery objectives and learning about population status. We tested assumptions of a population index for endangered Laysan duck (or teal; Anas laysanensis) monitored using mark–resight methods on Laysan Island, Hawai'i. We marked 723 Laysan ducks between 1998 and 2009 and identified seasonal surveys through 2012 that met accuracy and precision criteria for estimating population abundance. Our results provide a 15-y time series of seasonal population estimates at Laysan Island. We found differences in detection among seasons and how observed counts related to population estimates. The highest counts and the strongest relationship between count and population estimates occurred in autumn (September–November). The best autumn surveys yielded population abundance estimates that ranged from 674 (95% CI = 619–730) in 2003 to 339 (95% CI = 265–413) in 2012. A population decline of 42% was observed between 2010 and 2012 after consecutive storms and Japan's Tōhoku earthquake-generated tsunami in 2011. Our results show positive correlations between the seasonal maximum counts and population estimates from the same date, and support the use of standardized bimonthly counts of unmarked birds as a valid index to monitor trends among years within a season at Laysan Island.

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Population Dynamics of the Concho Water Snake in Rivers and Reservoirs

Cited by 12 publications

References 25 publications

Low genetic diversity and evidence of population structure among subspecies of Nerodia harteri, a threatened water snake endemic to Texas

Low genetic diversity and evidence of population structure among subspecies of Nerodia harteri, a threatened water snake endemic to Texas

Survival and population growth of a long‐lived threatened snake species,Drymarchon couperi(Eastern Indigo Snake)

Long-Term Monitoring of Endangered Laysan Ducks: Index Validation and Population Estimates 1998–2012

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