Simulation model of activity of Phrynocephalus przewalskii

From April to September 1987, daily temporal activity patterns of Phrynocephalus przewalskii were studied in a desert habitat of northwestern China. The daily pattern of activity in April was unimodal, in May it was unclearly bimodal, and the daily patterns in June to September were bimodal. Sand surface temperature (SST) has more direct and important effects on the activity of the lizards than air temperature. An activity index (AI) was defined. A simulation model was presented to study the relationship between the activity index of the lizards and SST, which is as follows: odel provided many useful parameters of behaviour ecology of the lizards, such as the lowest and highest SST that the lizards can endure, optimal SST, and the SST threshold which distinguishes between unimodal and bimodal daily patterns of activity. eriod affects daily patterns of activity through its effects on temperature. Phrynocephalus przewalskii can not respond instantly to changes in photoperiod. There is a time lag from sunrise until the lizards become active, which changes seasonally.