Demographics of Riparian Lizards in the Chiricahua Mountains in Relation to Water Availability and Emerging Aquatic Insects as a Potential Food Source

Authors: Earyn McGee, Rezwana Islam, Noel Hamideh, Michael Bogan

Year: 2018

Abstract

Severe drought is causing perennial streams to flow intermittently, presenting an unprecedented level of ecological disturbance. The loss of aquatic prey could negatively impact riparian and terrestrial species, including lizards. Because lizards play important roles in riparian food webs it is crucial to understand the cascading effects of stream drying on lizard communities. We hypothesized that perennial streams provide aquatic subsidies to lizards living in riparian areas. We predicted that lizard abundances would be greater, and that individuals within a species would grow larger and faster, along perennial streams. We quantified the abundance of lizards along three paired 100-meter perennial (wet) and ephemeral (dry) stream reaches with similar microhabitat but differing water availability in the Chiricahua Mountains of southeastern Arizona. We also measured individual growth rate during a 4-week mark-recapture study of Yarrow’s Spiny Lizard (Sceloporus jarrovii) and the Striped Plateau Lizard (Sceloporus virgatus). Aquatic insects were collected in high abundances, suggesting a potential food source for lizards along perennial streams. When considering mass at first capture, we found that S. jarrovii were larger at perennial versus ephemeral reaches (P = 0.0025) but the mass of S. virgatus did not differ among reaches (P = 0.53). Additionally, we failed to detect differences in lizard abundances between paired perennial and ephemeral reaches (P = 0.37 for S. jarrovii; P = 0.5 for S. virgatus). Low sample sizes prevented us from performing statistical analysis on the mark-recapture data. Future research should quantify trophic links between lizards and potential aquatic subsidies.