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11 diciembre 2014 4 11 /12 /diciembre /2014 15:22
Los últimos días de los lagartos sin patas de California

The family Anniellidae, known as American legless lizards, contains six species in a single genus Anniella: A. pulchra, the California legless lizard, the rare, A. geronimensis, Baja California legless lizard, and four more discovered in 2013

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Las lagartijas sin patas estadounidenses de la familia Anniellidae, incluyen seis especies en un solo género Anniella: A. pulchra, la lagartija sin patas de California, el raro A. geronimensis o lagartija sin patas de Baja California, y cuatro especies más descubiertas en 2013.

El Lagarto sin patas de California es una especie pequeña que se encuentra desde Baja California hasta el río Sacramento en Condado de Contra Costa.

El gobierno federal no lo ha protegido, en California no está protegido formalmente (excepto la población melanistica en el condado de Santa Cruz), pero es una especie motivo de preocupación especial debido al desplome generalizado de su población.

En el condado de Contra Costa, la especie esta en condición crítica, ya que la gran mayoría de los hábitat ha desaparecido. Necesita suelos de marga suelta o suelos arenosos húmedos, la urbanización y la agricultura modifican el suelo de una manera que ya no puede sobrevivir el Lagarto sin patas de California.

Raramente se encuentran en la superficie, es una especie fosorial que pasa la mayor parte de su tiempo debajo de la superficie. Se alimentan principalmente de larvas de escarabajos, también de arañas y escorpiones.

Dos subespecies de la lagartija sin patas California fueron reconocidas anteriormente, Anniella pulchra pulchra, la lagartija sin patas plateada, y Anniella pulchra nigra, la lagartija sin patas negra. Sin embargo, la clasificación taxonómica moderna considera la lagartija sin patas negra, simplemente como una forma melanistica, como una forma hiperpigmentada de la lagartija sin patas plateada

Los últimos días de los lagartos sin patas de California
Los últimos días de los lagartos sin patas de California
The Baja California legless lizard (Anniella geronimensis) is a secretive reptile that looks very much like a snake in appearance.  However, both snakes and legless lizards have evolved the legless trait independently from each other. The Baja California legless lizard can be distinguished from snake species by its moveable eyelids, and can even be seen blinking in good light. Unlike snakes, it is unable to flex its jaws to swallow something larger than its own head (2). The Baja California legless lizard has smooth, glossy scales which vary in colour from silvery-grey ...

The Baja California legless lizard (Anniella geronimensis) is a secretive reptile that looks very much like a snake in appearance. However, both snakes and legless lizards have evolved the legless trait independently from each other. The Baja California legless lizard can be distinguished from snake species by its moveable eyelids, and can even be seen blinking in good light. Unlike snakes, it is unable to flex its jaws to swallow something larger than its own head (2). The Baja California legless lizard has smooth, glossy scales which vary in colour from silvery-grey ...

Los últimos días de los lagartos sin patas de California

The California Leggless Lizard is a small species that ranges from Baja California to the Sacramento River in Contra Costa County.

Federally it is not protected, in California it is not formally protected (except the melanistic population in Santa Cruz County) but is a species of special concern due to widespread declines.

In Contra Costa County, the species is critical, vast majority of former habitat is gone. It is very particular, it needs loose loam or sandy soil with humidity, housing and agriculture modify the soil in a way that it can no longer persist.

They are rarely found on the surface, they are a fossorial species that spends most of their time below the surface. They feed primarily on beetle larvae, but also on spiders and occasionally scorpions.

https://macstack.net/viewtopic.php?f=6&t=10195

Two subspecies of the California legless lizard were formerly recognized, A. p. pulchra, the silvery legless lizard, and A. p. nigra, the black legless lizard. However, modern taxonomic classification considers the black legless lizard to simply be a melanistic form.[2]

  1. David Perlman (2013-09-18). "4 new species of legless lizard identified". SFGate. Retrieved 2013-09-20.
  2. Description of the species on CaliforniaHerps.com
  3. http://en.wikipedia.org/wiki/American_legless_lizard

http://www.anniella.org/introduction.html

The California legless lizard (Anniella pulchra Gray 1852; Sauria: Anniellidae) is a fossorial (burrowing) animal that typically inhabits sand or loose soil (Fig. 1). They are nearly endemic to California, but also found in northern Baja California (Stebbins 1954, Hunt 1984, Bury 1985, Jennings 1987, Jennings and Hayes 1994). State agencies regard Anniella pulchra as a Species of Special Concern because of human impacts to coastal dune habitats (Jennings and Hayes 1994, California Department of Fish and Game 2000).

Two unofficial designations for A. pulchra primarily reflect differences in dorsal coloration and distribution (Hunt 1983, Hunt and Zander 1997). Very dark animals are commonly called black legless lizards (subspecies A. p. nigra), and most workers refer to lighter colored adults as silvery legless lizards (subspecies A. p. pulchra). Genetic studies are inconclusive, especially those comparing populations in central California (Murphy and Smith 1985, Jennings 1987, Hunt and Zander 1997). Proposed amendments to the nomenclature (addition of subspecies designations) remain unchanged.

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Knowledge of the longevity, movement, and microhabitats of these lizards was incomplete because studying them in situ, in their underground habitat, has been difficult. Workers have investigated this cryptic animal for many years, using the best methods available. Until now, the accepted method for tracking legless lizards consisted of placing wood coverboards (Fig. 2) on the soil surface, then periodically digging under them to check for the presence of lizards (Hunt and Zander 1997). Although this is a low-impact, cost-effective sampling method, it cannot be used to determine population size, home range, or microhabitat selection. At our study site where the abundance of lizards was known, coverboards were ineffective for detecting the presence or determining the density of lizards (Kuhnz et. al 2005). External methods of tagging legless lizards using India-ink or permanent ink marker have been effective only short-term, or unreliable (Ruth, pers. comm.; L. Kuhnz, pers. observ.). Other common methods of marking lizards and snakes (e.g., toe and scale clipping) were not possible given Anniella’s morphology.

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We employed new technology to track the movements of legless lizards. The use of PIT-tags (Passive Integrated Transponder) in terrestrial field biology usually has been limited to the identification of manually recaptured animals (Camper and Dixon 1988, Germano and Williams 1993, Paramenter 1993, Jemison et al. 1995). The methods developed for this study allowed us to track the activity of individual animals in their subterranean environment without recapturing them, conceivably with less bias toward slow or easily captured lizards. Using a mobile scanner modified for use in the field, lizards were found in many different microhabitats and as deep as 11.5 cm in the soil, within the depth they presumably reside most of the time (Miller 1944, Smith 1946, Hunt 1984). Failure of PIT-tags is rare and can be readable for 15-20 years; the tags required no battery or other power source (Camper and Dixon 1988, Germano and Williams 1993, Paramenter 1993, Jemison et al. 1995).

This study was conducted at Moss Landing on the coast of central California (Fig. 3). Moss Landing Marine Laboratories, on the shores of Monterey Bay, were destroyed in the Loma Prieta earthquake of 1989. Surveys of the new construction site confirmed a population of legless lizards. In 1997-1998, the 1.57 hectare site was searched and more than 3,500 Anniella were moved to an adjacent area of sand dune habitat. The recovery of nearly every lizard within the building footprint also provided an extraordinary opportunity to assess lizard density relative to microhabitats. This work was required because Anniella pulchra was protected locally and its status as a federally listed endangered species was pending. Therefore, research protocols for these studies were under the direction and supervision of the California Department of Fish and Game (CDF&G). When the project began, there was a proposed federal rule to list the black California legless lizard as an endangered species. Although subsequent evaluation of the lizards recovered during this study indicated they probably are an intergrade between black and silvery lizards, it was not certain that black legless lizards were absent on Moss Landing Hill; some local lizards were 70% black (Miller 1943). Withdrawing the proposed rule in August 1998, the U.S. Fish and Wildlife Service stated that intervention was unnecessary because ongoing dune restoration, preservation projects, and protection from urbanization on public lands were protecting habitat (Federal Register 1998). Both morphotypes remain protected as a California Species of Special Concern.

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This work was a rare opportunity to increase our knowledge of the life history of a fossorial animal, and PIT-tag technology capabilities. A clearer understanding of legless lizard microhabitat associations will allow biologists and regulators to design appropriate recovery and relocation strategies as mitigation for development and anthropogenic damage to coastal dune ecosystems. This type of research also enhances our understanding of the dispersal capabilities and home range of Anniella, which is essential when addressing management issues. Long-term monitoring will provide new insights into population redistribution, the effects of habitat heterogeneity on movement, and the longevity of legless lizards.

http://villageinforest.blogspot.com/2010_09_30_archive.html

http://villageinforest.blogspot.com/2010_09_30_archive.html

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  • Biólogo desde hace más de treinta años, desde la época en que aún los biólogos no eran empleados de los abogados ambientalistas. Actualmente preocupado …alarmado en realidad, por el LESIVO TRATADO DE(DES)INTEGRACIÓN ENERGÉTICA CON BRASIL

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