Island Night Lizard monitoring data on San Nicolas Island, CA, 1995-2023

These data were compiled for the U.S. Navy and U.S. Fish and Wildlife Service and consist of summary counts at selected population monitoring sites for the Island Night Lizard (Xantusia riversiana), and measurement data (body length, mass) for calculating an index of body condition. Objectives of this study were to provide long-term population trend and health and condition data to the U.S. Navy for their management of the lizard and its island habitat. These data were collected on San Nicolas Island (SNI), Ventura County, California -- one of three islands that comprise the range of the island-endemic Island Night Lizard. Monitoring sites were selected to represent a the known range of the lizard on the island, and the major habitats that support it. All data were collected by the U.S. Geological Survey / Southwest Biological Science Center from on-site field surveys. These data can be used by the U.S. Navy and the U.S. Fish and Wildlife Service to better understand the current status of the Island Night Lizard on San Nicolas Island, and to continue efforts to protect and restore the species and its habitat.