Blainville’s Horned Lizard

The Blainville’s horned lizard (Phrynosoma blainvillii) is considered an indicator of ecosystem health because it is a diet and habitat specialist. Both its presence and abundance highly correlate with the occurrence of native ants, native chaparral community plants, and sandy areas.

This California State Species of Special Concern and Bureau of Land Management Sensitive Species was once abundant, but habitat loss has caused declines throughout its range. It is also threatened by the invasion of the Argentine ant (Linepithema humile), especially in areas adjacent to agricultural and urban landscapes. Argentine ants tend to outcompete the native ant species that are the horned lizard’s main prey.

While no recent surveys for this species exist, those made between 1995 and 2007 found the horned lizard in both the Central and Coastal Study Areas; more recently, it has been recorded on iNaturalist. Using the most recent and reliable data and expert opinion, four metrics were developed to measure the health of the Blainville’s lizard.

The condition for three of the metrics (presence of native ant communities, abundance, and distribution) was caution, with moderate confidence; insufficient data exists to determine trends in either the Central or Coastal Study Areas. Metric 2 (presence of native plant communities) was caution in the Central Study Area, with high confidence and a declining trend. In the Coastal Study Area, the condition was good with no change in trend and moderate confidence in the assessment. Additional data on species abundance and distribution, an assessment of Argentine ant invasions, an evaluation of the impacts of recreational use, and restoration of the lizard’s native habitat would improve both our understanding and the conservation of this species.