Mason Ryan

Lizard Community Response to Short-Term Rainfall Manipulation

The Sevilleta National Wildlife Refuge (SNWR) provides the opportunity to assess how lizard populations respond to climate change and projected drought

conditions. I will utilize an ongoing study of precipitation variability in a piñon-juniper woodland on the SNWR investigating how plant communities respond to different precipitation regimes (Pockman pers. comm.). This ongoing precipitation manipulation entire lizard fauna respond under ambient, wetter, and drier conditions. 

In summer of 2011 I collected preliminary data under the three precipitation treatments and found a strong affect of drought on lizard densities. Although the preliminary findings are intriguing, it must be noted that New Mexico was in the midst of a severe drought that biased my results; the control and drought plots received the same amount of rainfall (Pockman pers. comm.). The additional season of data that I propose to collect this summer is necessary to corroborate (or refute) the 2011 results. 

I propose to collect lizard density data from May – September 2012 in the experimental plots at the SNWR. I will use a time-constrained visual encounter survey (VES) recording the distance and time spent surveying while recording all lizards observed within the plot boundaries. I will use a GPS to record a track-log for each survey and record geographic coordinates of all lizards observed. I will use binoculars to identify animals from a distance and catch animals only when necessary to verify identification. Additionally, I will collect data on activity, age-class (adult, juvenile, hatchling), and microhabitat (open, grass, bush, etc.) for every individual observed. The VES method will allow me to assess lizard species diversity, relative abundance, and species-specific population structure. This methodology worked well during the 2011 survey period.