Trapping Efficiency, Demography, and Density of an Introduced Population of Northern Watersnakes, Nerodia sipedon, in California

  title={Trapping Efficiency, Demography, and Density of an Introduced Population of Northern Watersnakes, Nerodia sipedon, in California},
  author={Jonathan P. Rose and Oliver J. Miano and Brian D. Todd},
Abstract Northern Watersnakes, Nerodia sipedon, have been introduced into California's Central Valley and pose an important new challenge for the management of biodiversity in the state's already greatly distressed freshwater ecosystems. Nonnative watersnakes will likely compete with federally threatened Giant Gartersnakes, Thamnophis gigas, and prey on native amphibians and fish, including young salmonids, many of which are imperiled. We used three types of aquatic funnel traps and three… 

Ecology and Control of an Introduced Population of Southern Watersnakes (Nerodia fasciata) in Southern California

Although no direct evidence is found that Southern Watersnakes are affecting native species in Machado Lake, this population may serve as a source for intentional or unintentional transportation of watersnakes to bodies of water containing imperiled native prey species or potential competitors.

Projecting Invasion Risk of Non-Native Watersnakes (Nerodia fasciata and Nerodia sipedon) in the Western United States

It is concluded that non-native watersnakes in California can likely inhabit ranges of several native species of conservation concern that are expected to suffer as prey or competing species for these invaders.

Traditional trapping methods outperform eDNA sampling for introduced semi-aquatic snakes

This study developed a qPCR assay to detect two species of watersnake introduced to California, USA, and compared the efficacy of eDNA and aquatic trapping, and shows that despite the many successes of e DNA surveys, traditional sampling methods can have higher detection probability for some species.

Sunning themselves in heaps, knots, and snarls: The extraordinary abundance and demography of island watersnakes

Analysis of spatial and temporal variation in demography of the Lake Erie Watersnake, Nerodia sipedon insularum, and a review of snake survival more generally indicates that population size has been stable or increasing over the course of the study.

Demographic effects of prolonged drought on a nascent introduction of a semi-aquatic snake

The population of N. sipedon in California declined from 2013 to 2015, likely due to decreasing habitat and prey availability from the prolonged regional drought, which highlights the importance of the effect of climatic extremes on the trajectory of introduced populations in a novel environment.

On the Abundance of a Pelagic Sea Snake

The abundance of pelagic sea snakes, Hydrophis (= Pelamis) platurus, while following slicks that formed drift lines during 3 yr of research in the Golfo de Papagayo, Costa Rica was quantified.

Targeting eradication of introduced watersnakes using integral projection models

This study developed the IPM using data on the survival, growth and fecundity of native and non-native populations of N. sipedon to identify management targets that would facilitate its eradication and argued for wider adoption of these models for evaluating management actions.

Comparative survey techniques for a cryptic Australian snake (Hoplocephalus bitorquatus)

Artificial cover objects may provide some value in detecting pale-headed snakes in vegetation communities where habitat resources are limited; however, where resources are plentiful, visual encounter surveys are likely to remain the most cost-effective survey option.

Intraspecific and interspecific variation of female genitalia in two species of watersnake

The present study explored the patterns of intraspecific and interspecific variation in female genitalia in two sister taxa of watersnake that have similar genital shape to determine whether there has been genital co-evolution, and potentially mechanical reproductive isolation, in these two closely-related and occasionally sympatric species.



The Decline of Amphibians in California’s Great Central Valley

Declines in amphibian populations are rarely reported on the community or ecosystem level. We combined broad-scale field sampling with historical anialyses of museum records to quantify anmphibian

Unveiling Escape and Capture Rates of Aquatic Snakes and Salamanders (Siren spp. and Amphiuma means) in Commercial Funnel Traps

It is found that when intentionally released into traps, the majority (74%) of snakes escaped within 24 hours, and of the species tested, Seminatrix pygaea escaped most frequently.

Abundance and Sexual Size Dimorphism of the Giant Gartersnake (Thamnophis gigas) in the Sacramento Valley of California

The few remaining natural wetlands in the Central Valley are important, productive habitat for the Giant Gartersnake, and should be conserved and protected and modeled after the permanent, shallow wetlands representative of historic Giant Garternake habitat.

Population Ecology of the Lake Erie Water Snake, Nerodia sipedon insularum

Comparisons with data from mainland populations elsewhere in the range of this species indicate that island water snakes differ in having larger adult body sizes, lower growth rates, and shorter tails.

Extinction of an Island Forest Avifauna by an Introduced Snake

The island of Guam has experienced a precipitous decline of its native forest birds, and several lines of evidence implicate the introduced brown tree snake (Boiga irregularis) as the cause of the

Severe mammal declines coincide with proliferation of invasive Burmese pythons in Everglades National Park

It is suggested that predation by pythons has resulted in dramatic declines in mammals within ENP and that introduced apex predators, such as giant constrictors, can exert significant top-down pressure on prey populations.

The role of introduced species in shaping the distribution and abundance of island reptiles

It is shown that present day competition and predation are potent forces shaping community structure and geographic distributions, and the role played by coevolution in mediating interactions between competitors and predator and prey is highlighted.

Empirical Tests of Biased Body Size Distributions in Aquatic Snake Captures

The results demonstrate that capture methods may bias assessments of snake population demography, but that careful design of sampling methodology, with consideration of potential biases, can yield meaningful data on snake biology.


This study shows how demographic information can be used to maximize the efficacy of control efforts, and the results are likely directly applicable to other invasive species with complex life cycles.

Habitat Suitability and Conservation of the Giant Gartersnake (Thamnophis gigas) in the Sacramento Valley of California

Abstract Resource managers often have little information regarding the habitat requirements and distribution of rare species. Factor analysis-based habitat suitability models describe the ecological