USE OF TRAIL CAMERAS TO ESTIMATE THE ABUNDANCE AND POPULATION STRUCTURE OF BIGHORN SHEEP IN BAJA CALIFORNIA, MEXICO

Abstract

Monitoring abundance and population structure is essential to guide the management of wild species. Few population studies of bighorn sheep (Ovis canadensis Shaw) have been conducted in Baja California, Mexico, due to the complicated and costly nature of monitoring these animals. The objective of the study was to determine the abundance and structure of a bighorn sheep population using trail cameras. The study was conducted in the coastal region of the Sierra Santa Isabel from April to July 2022. Trail cameras were deployed at four natural watering holes and on a trail that is frequently used by bighorn sheep. The Lincoln-Petersen method was used to estimate abundance with four criteria to define independent records: separated by one hour, by one hour without taking into account samples with only one record, by at least one day, and by one week. The estimates generated with this method were compared with those reported in the aerial monitoring conducted in the study area in 2021. The abundance calculated from independent sampling periods separated by one week was found to be within the range of that estimated from aerial monitoring. The abundance of bighorn sheep in the coastal region of the Sierra Santa Isabel was 129 ± 9 animals, and the ratio of rams, ewes, yearlings, and lambs was 8:10:1:2. The results suggest that the population of the species at this site is in a good state of conservation. In addition, the use of trail cameras proved to be a viable alternative to traditional monitoring methods for bighorn sheep population assessments.