Showing posts with label snake conservation. Show all posts
Showing posts with label snake conservation. Show all posts

Wednesday, September 14, 2011

Buffer Zones For Snakes in Agricultural Landscapes

The Eastern Garter Snake, Thamnophis sirtalis. JCM
Roadside shoulders covered with vegetation, and gallery vegetation growing along streams that run through agricultural fields can act as buffers and corridors for wildlife. These linear strips of habitat are all that remains for hundreds of thousands of square miles that have been turned into the breadbasket for America. Land management agencies in the United States promote conservation buffer strips as beneficial to wildlife populations but little is known about how snake use these habitats, Knoot and Best (2011) evaluated the influence of buffer design, management, and surrounding landscape characteristics on snake occurrence in gallery grasslands along waterways in southeastern Iowa. They documented snakes in about 80% of the areas and captured 119 individuals representing five species (Storeria dekayi, Thamnophis sirtalis, Thamnophis radix, Liochlorophis (=Opheodrys) vernalis, Elaphe (=Pantherophis) vulpina). The Smooth Green Snake (Liochlorophis vernalis), is listed as a species of concern in Iowa. The width of the waterway was the best predictor of snake presence for three of the five species. The Plains Garter Snake was most often in grass-lined waterways farther from wooded habitat; a finding that is consistent with the observation that Plains Garter Snakes are more often found in open habitats; while the Smooth Green Snake was more often associated with waterways with greater plant litter cover but the reverse was the habitat most often assocaited with the Eastern Garter Snake. Most research on buffers in agricultural has focused habitat for birds and butterflies, but this project suggests that snakes can also be managed in these narrow buffer zones of habitat. This paper is available on-line.

Citation
Knoot, T. G. and L. B. Best. 2011. A multiscale approach to understanding snake use of conservation buffer strips in an agricultural landscape. Herpetological Conservation and Biology 6:191-201.

Wednesday, April 20, 2011

The Future of Asian Snakes

Oriental Rat Snakes are a species of conservation 
concern because of unregulated trade.  © Mark 
Auliya/TRAFFIC  Southeast Asia
The Future of Asian Snakes is a press release from TRAFFIC, dated 12 April 2011

Guangzhou, China, 12th April 2011—A crucial meeting that could decide the future of Asia’s traded snake species takes place this week in Guangzhou, China.

Some 60 experts representing close to 20 governments and international and national organizations are meeting to consider conservation priorities and management and enforcement needs related to the trade of snakes.

They will focus on the markets and commercial trade in snakes originating in East, South, and South-east Asia.

Asian snakes are consumed locally and in neighbouring countries for food, traditional medicines and for their skins. They are also sold as pets and found in expensive luxury leather goods and accessories in the boutiques of Europe and North America. Their skins are often processed in various countries of re-export along the way.

According to a wildlife trade policy review conducted in Viet Nam, the income from snake breeding is three to five times higher than the income generated by vegetable and crop cultivation, and dozens of times higher than the income from pig and cattle breeding.

TRAFFIC has previously raised concern over the international exports of Oriental Rat Snakes Ptyas mucosus from Indonesia, after investigations revealed large numbers were harvested and traded outside of existing government regulations.

TRAFFIC found government-set quotas were being widely-flouted, leading to over-harvesting and illegal trade; and with no marking of skins taking place, it was impossible to track them through the trade chain to point of export.

“TRAFFIC welcomes the current spotlight on the international trade in Asian snakes, which is placing many species on the conservation danger list,” said Dr William Schaedla, Director of TRAFFIC South-east Asia.
“Snakes are clearly vital to natural ecosystems and to the economy of the region—it is in Asia’s interests to ensure snakes have a sustainable future.”

The global trade in snakes involves snake species from many different countries, with specimens taken from the wild or bred in captivity.

However, populations of some snakes have declined significantly through a combination of unsustainable use and habitat loss.

Of the 3,315 snake species globally recognized, one third occur in Asia, many of them endemic to particular countries: Indonesia has 128 endemic snake species, India 112, China 54, Papua New Guinea 42, Sri Lanka 41, and the Philippines 32.

CITES (the Convention on International Trade in Endangered Species of Wild Fauna and Flora) regulates international trade in 130 snake species, 45 of them found in range States in the Asian countries attending the workshop.

John Scanlon, Secretary-General of CITES, stated: “the global trade in snakes is an industry of considerable socio-economic importance for rural populations in several Asian countries.

"CITES is the main international tool to regulate effectively international snake trade in many of these species.

“The recommendations coming out of this meeting will be critical in addressing the wildlife conservation, sustainable use and livelihood aspects of such trade, and putting forward expert recommendations to CITES governing bodies for future directions.”

The technical workshop runs until 14th April under the leadership of CITES and brings together government experts, members of the CITES Animals Committee and organizations including IUCN and several of its Species Survival Commission specialist groups, TRAFFIC, WCS, UNCTAD-BioTrade, the China Wildlife Conservation Association and China Association of Traditional Chinese Medicine.

Wednesday, March 30, 2011

Detecting the Presence of Snakes and Their Conservation


The Western Cottonmouth, 
Agkistrodon piscivorous lecostoma. 
Defense behavior.

Worldwide, more than 82% of snake and more than 84% of lizard species have not been evaluated by the International Union for Conservation of Nature (IUCN) or are classified as having insufficient data to determine conservation status (IUCN, 2010). This is of concern because squamates, like frogs are disappearing. Andrew Durso and colleagues point out that this discrepancy results from the inability of traditional field and data analysis techniques to circumvent unpredictability in reptile detection. Snakes are generally considered the most difficult reptile group to study because of their cryptic behaviors, minimal or sporadic activity patterns, and frequent use of inaccessible habitats such as, subterranean burrows. the forest canopy or murky waters. Therefore high-resolution data on geographic distribution are lacking for many species and few situations exist where population densities have been accurately measured, or population trends tracked over time with confidence. When population declines are suspected it is virtually impossible to distinguish true rarity from poor or unlucky sampling, without knowledge of detection probability. Presence or absence modeling is recognized as an effective technique for monitoring populations of secretive species on a landscape scale, historically considered a daunting or even impossible task. Site occupancy modeling may be the only feasible means for monitoring the population status of some species, in particular for those species with recapture probabilities too low to use mark-recapture effectively. Durso and colleagues provide the first estimates of detection probability and site occupancy for aquatic snake species, and use snakes as a case study for incorporating detection probability in site occupancy monitoring of rare and cryptic species. They surveyed twenty isolated wetlands for aquatic snakes, using multiple replicated sampling events, calculated species-specific parameter estimates of detection probability (p) and site occupancy (w), using the program PRESENCE, and compared single-season models to assess the ability of site-specific covariates to influence these two parameters.They applied this method for seven aquatic snake species: Banded Water Snake (Nerodia fasciata), Florida Green Water Snake (Nerodia floridana), Glossy Crayfish Snake (Regina rigida), Black Swamp Snake (Seminatrix pygaea), Mud Snake (Farancia abacura), Rainbow Snake (Farancia erytrogramma), and Cottonmouth (Agkistrodon piscivorus). This process produced an understanding of how aspects of behavior and ecology influence patterns of detection probability and site occupancy.  They calculated the amount of unsuccessful effort necessary to declare absence of each species with statistical confidence this varied from 5–63 visits; and 150–1890 trap-nights. The study documented considerable interspecific variation in p and w. One species The Banded Water Snake (Nerodia fasciata) was widespread and highly detectable, while the Cottonmouth  (Agkistrodon piscivorus) had low detectability despite its wide distribution. Five other species were secretive, or restricted to specific habitat types, or both, and  those illustrated that complex and sometimes counterintuitive relationships exist between capture rate and occupancy. They conclude that incorporating p and w is essential to the success of large-scale monitoring programs for elusive species.


Citation
Durso, A. M., J. D. Willson, C. T. Winne. 2011. Needles in haystacks: Estimating detection probability and occupancy of rare and cryptic snakes. Biological Conservation, doi:10.1016/j.biocon.2011.01.020