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The Desert Tortoise (Mojave Population) Recovery Plan (US Fish
and Wildlife Service, Portland, Oregon, 1994) requires monitoring of desert
tortoises to assess changes in status with the best available data.
For a variety of reasons, Line Distance Sampling (LDS; Buckland et al., Introduction
to Distance Sampling, Oxford University Press, 2001) has been chosen as the
standard method for conducting range-wide monitoring of tortoises in the Mojave
Desert. LDS uses the distances objects (tortoises) are found from the center
of a transect to estimate a detection function. The detection function provides
an estimate of the number of objects found on the transect, and by assuming
that all objects at the center of the transect (on or very near the line) are
found, provides an estimate, with confidence limits, of the total population
density.
The data sets found on
this site were generated from data collected in the LDS monitoring program
and includes:
- all monitoring data,
- all transect
start points generated,
- actual transect locations
and paths,
- data collected relative
to the transect path and length,
- data collected relative
to both live and dead tortoises encountered on
the transect,
- data collected on various
habitat or threat variables along the transect.
Observations of focal
tortoises - tortoises equipped with radio transmitters used to determine
the fraction of the population available for sampling - are also included.
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