Método de parcelas con punto fijo: nueva metodología para estimar poblaciones de borregos y cabras silvestres en ecosistemas semiáridos

Objective: To develop a new method and validate it in the field, that can be reliable and easy to carry out in the Units of Management for the Sustainable Wildlife Use (UMA) to monitor population size of wild bighorn sheep (Ovis canadensis weemsi) in Baja California Sur (BCS), Mexico.Design/methodology/approximation: In order to apply and showing the procedure in the use of this method, a sampling of eight plots with fixed points was considered. Its design and application was based on the observation of wild bighorn sheep in the Sierra de Las Virgenes in the Ejido Alfredo Bonfil, in BCS. Observations were made from the fixed points, estimating simultaneously the distance from the observation point to each of the localized sheep, considering only a single period from 5:30 am to 7:00 pm. The sampling area was calculated for each circular plot considering its radius with the maximum distance at which the sheep was observed. A random sampling plan was developed, and the total population, population density, and recommended sample size were calculated at 90 % level of significance.Results: In the preliminary sample, results showed a population size of 332 sheep within 5000 ha, with an average density of 0.06 sheep ha1 to 90% confidence, and an increase of the sample size (n18) is suggested for its use to maintain a reliable 90% confidence.Limitations/implications: The application of this method with fixed point plots is useful for monitoring wild bighorn sheep, showing that it is not an aggressive method, which does not produce risks due to casualties in the population, can be carried out in short time, reliable, with low cost, and which requires minimal training for those who carry out the field sampling. The method is not reliable to be carried out in forest ecosystems, where tree stratum makes hard visibility.Findings/conclusions: Given the spatial distribution of bighorn sheep in BCS and the majority of wild sheep and goats in the world, this method is a new alternative that may be applicable for population studies of these species.