Reptile and Amphibian Active Search Sub-project

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While calling surveys can be effective means of sampling breeding anurans, they are obviously not appropriate for documenting non-vocal reptiles and amphibians, and they are not useful for detecting anuran species outside of their breeding seasons. We therefore conducted active searches at sites in the Broad River basin with the goal of generating a more complete herpetofaunal inventory of the region as well as assessing the effectiveness of active searches in general through estimation of detection probabilities obtained during surveys. 

Because active searches are more time consuming than calling surveys, we focused our search efforts at 21 study locations.  Each survey consisted of a half-hour search by two individuals (a total of one man-hour) during which observers attempted to identify as many reptiles and amphibians in the study area as possible. All sites were surveyed three times between June and July 2010. Program PRESENCE was used to estimate detection probabilities for species of interest and anuran detection probabilities during active searches were compared with results obtained during anuran calling surveys to compare the efficacy of the two methods. 


A total of 36 reptile and amphibian species were documented during summer active search surveys (see species list for all species detected using active searches during summer and fall sampling).

Anurans had high detection probabilities during active searches while lizards and snakes were more rarely observed.


Study sites used for active search surveys. Sampling was restricted to 21 sites because active searches are more time-intensive than calling surveys.
Detection probabilities for anuran species were generally comparable between active search and calling survey methods.


Detection probabilities were relatively low for most groups, reaffirming that reptiles and amphibians are extremely secretive animals that are difficult to sample.

Active searches are, however, likely the best method for sampling non-anurans with minimal effort (i.e. traps do not have to be constructed, set, or checked for active searches).

Detection probabilities for anurans were similar between calling surveys and active searches, but calling surveys require much less time.

However, active searches may document particular life stages (i.e. tadpoles) that would go undetected during calling surveys alone, as well as allowing for observation of species that may not be calling during a given time of year.

Surveys conducted at different times of year will likely improve species coverage of active searches.

A student investigator with a rat snake found during an active search.

For questions or comments regarding this site, contact Dr. Michael Dorcas.