The bighorn sheep in Mexico is classified as at-risk by the Mexican federal government. In the state of Baja California, wild sheep can be observed throughout the length of the state from the USA–Mexico border south to the Agua de Soda mountain range. This research aimed to document the historical trend of the bighorn population based on aerial surveys conducted in 1992, 1995, 1999, 2010, and 2021, and the abundance, distribution, and structure of bighorn sheep populations in Baja California, based on an aerial survey conducted from 8–14 November 2021, covering thirteen mountain ranges. The estimated sheep population in 2021 was based on the number of individuals observed; the sightability of the animals; the area sampled; and the total area of habitat available. In 30.5 flight hours, 456 bighorn sheep were observed, with an estimated population of 1697 ± 80 individuals. The observation rate was 16 sheep sighted per hour of flight, and the ram:ewe:lamb ratio was 62:100:19. When the results of the 2021 flight were compared to the results of the previous aerial surveys, there was a large variation between the data, which was related to the lack of consistency between the sampling designs used in each study. Nevertheless, a statistical test of the results of aerial surveys conducted in the state suggest that the Baja California bighorn sheep population remained stable between 1992 and 2021. This study highlights the need to standardize wild sheep aerial surveys by defining flight paths and establishing a consistent duration of flights. On the other hand, Baja California authorities should consider modifying the current conservation strategy for bighorn sheep to increase the species’ population in the state by initiating community-based wildlife conservation programs in rural communities.

Potential distribution model of Ovis canadensis in northern Baja California, Mexico

The description of natural history, and information on the factors threatening conservation, the distribution area, and the status of species population are necessary for proper wildlife management. The objective of this research was to generate such information in two rural communities and to engage residents in bighorn sheep management through a program of three workshops. The first one covered training regarding natural history and management of the species. The second one consisted in the description of the habitat of the species through a dynamic of participatory mapping. The third, include a design of a one strategy to monitor the bighorn sheep population. The workshops were attended by 37 people from the two rural communities. The results suggest the economic element was the main interest of the inhabitants regarding the bighorn sheep. Eleven risk factors were identified to the bighorn sheep in the study sites, a participatory map with relevant information for the management of the species on each community was developed, and a monitoring strategy of the bighorn sheep population was prepared. The workshop program proposed in this research is a tool that can be applied in rural communities to lay the groundwork for a long-term management project of wildlife species.

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.

El propósito de esta investigación fue analizar la composición y preferencias alimentarias del borrego cimarrón en las Sierras Juárez y Santa Isabel durante la época húmeda y seca de 2021-2022. Para evaluar la disponibilidad de forrajee implementaron 17 líneas de Canfield de 100 m de longitud. La composición dietética se determinó mediante microhistología de muestras fecales, mientras que la diversidad del forraje y la dieta se calcularon utilizando el índice de Shannon. La selección forrajera se evaluó con el índice de Ivlev. Se observó que las formas biológicas más comunes en el hábitat del borrego cimarrón fueron las arbóreas y arbustivas. En las Sierras Juárez y Santa Isabel, se identificaron 31 y 43 especies de plantas en su dieta, respectivamente; las arbóreas y arbustivas fueron las más consumidas. No se encontraron diferencias en la dieta entre épocas y sitios. Larrea tridentata e Hisbiscus denudatus fueron las más frecuentes en la dieta, mientras que las preferidas incluyeron Eriogonum inflatum, H. denudatus, Horsfordia newberryi, Justicia californica y L. tridentata. Estos resultados ofrecen información para establecer estrategias de conservación y manejo comunitario del borrego cimarrón en Baja California.

Freshwater availability is one of the most pressing environmental concerns in arid ecosystems. The use of free-standing water by raptors has been little studied, and in the context of climate change has become increasingly important as extended droughts are expected to become more frequent. We analyzed digital images from camera traps captured in the freshwater springs of Sierra El Mechudo, during summer to early autumn of 2023 and 2024 in Baja California Sur, Mexico. We recorded 165 detections of four raptor species. The Turkey Vulture (Cathartes aura) was the most frequently detected (n = 55), followed by the Great Horned Owl (Bubo virginianus) (n = 50), the Red-tailed Hawk (Buteo jamaicensis) (n = 45), and the Cooper’s Hawk (Astur cooperii), which was observed only in early autumn 2024 (n = 15). The Great Horned Owl exhibited a distinct detection pattern (mainly crepuscular, with the highest peak at 6 a.m.), in contrast with the other three species, which were detected mainly at midday and in the afternoon, during the hottest hours of the day. All raptors were recorded drinking water; however, species differed in the proportion of behaviors they exhibited at the freshwater springs. The Turkey Vulture showed the highest drinking activity (76.3%), whereas both hawks exhibited the same lowest proportions (26.6%) among all species detected. The proportion of behaviors remained constant across years. The time spent at the freshwater springs did not differ across species or years. The Red-tailed Hawk, the Great Horned Owl, and the Turkey Vulture increased their detections at the springs in 2024, when a severe and prolonged drought affected the southern peninsula. The results showed that the importance of freshwater springs for raptors extends beyond their use for drinking only; the surrounding habitat as a refuge and availability of prey in the area are evidently essential for these birds of prey. Further studies should extend research into the diverse use of springs and home ranges of raptors in the southern Baja California peninsula.