Factors Affecting the Presence and Abundance of Amphibians, Reptiles, and Small Mammals under Artificial Cover in Southern California

Abstract

Artificial cover objects (ACOs) are known to attract small terrestrial vertebrates, but the actual parameters that attract species to ACOs can vary across geographic regions and climates. For this study ACOs were placed in coastal sage scrub and grassland habitats in southern California and surveyed weekly for small terrestrial vertebrates over a 4-yr period. We observed 1643 individuals of 34 taxa during 143 survey sessions totaling 16,312 ACO days. Overall species richness and abundances under ACOs were highest from February to April. Our results showed that the probability of encountering a reptile under an ACO was highest in February and March under large wooden ACOs containing moist soil, when temperatures under the ACO were relatively mild, and when minimum air temperatures were low. At the community level, encounter probabilities for small mammals were highest for large wooden ACOs and ACOs with low soil moisture, with several species differences. Amphibians of three species were only captured in low numbers primarily under wooden ACOs from November to March. Use of ACOs in research and monitoring is an inexpensive and simple way to document and capture a wide variety of small terrestrial vertebrates. Species richness and abundance can be maximized over short periods using ACOs and can be equally important for long-term monitoring, particularly once the factors that make ACO use effective for small terrestrial vertebrates of a certain region have been investigated.