Each pitfall trap is 40 cm deep, and lined with tin can cylinders. A polyethylene funnel is set on a container in each trap. Each trap has a ceramic tile cover which is used to close the trap during non-sampling periods. Traps were opened for two consecutive weeks every month for the period 16 June 1989 to 23 August 1991. During the summer traps are checked every three days, during the winter they are checked once each week.
Lizards are removed from the containers and information is recorded on data sheets.
Desertification is hypothesized to have altered the spatial and temporal availability of resources required by the biota. Results of desertification on the Jornada include changes to shrub dominated communities and major soil changes. We hypothesize that these shifts in vegetation have changed resources temporally for many of the consumers. If grassland systems respond to rainfall without significant lags, but shrub systems do not, then consumer species should reflect these differences. In addition, shifts from grassland to shrubland results in greater structural heterogeneity of the habitats.