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.
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.
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.
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.
