Diet and sexual segregation of desert bighorn sheep (Ovis canadensis mexicana Merriam) in Sonora, Mexico

Objective: To determine the diet of the desert bighorn sheep and to identify differencesin its composition between sexes during the reproductive and sexual segregation periods.Design/methodology/approach: The study was carried in the UMA Rancho NocheBuena, Hermosillo, Sonora. The microhistological technique and a cell catalog of plantsfrom the study area were used to identify plant species present in fecal samples ofbighorn sheep. The relative frequency, the Shannon-Weaver diversity index and theKulczynski similarity index were determined by sex and period (reproductive andsegregation)Results: The diet of bighorn sheep included 40 species, being herbaceous (36.1 ±4.4%) and grasses (26.8 ±8.9 %) the most common. The diet of males during thesegregation period was mainly composed of grasses (36.2%) and female diet byherbaceous (30%) and grasses (29.8%). No differences were found in the diversity ofthe diet of males and females in the segregation period (H '= 1.0) and in general, their diets were very similar (80%).Limitations/implications: To collect a greater number of fecal samples by sex andperiod (reproductive and segregation) and to analyze the nutritional content of plantsconsumed by bighorn sheep.Findings/conclusions: In this study, the sexual segregation exhibited by the bighornsheep in the Wildlife Management and Conservation Unit Rancho Noche Buena was notdue to food preferences.

Predation impedes recovery of Sierra Nevada bighorn sheep

Translocation of animals into formerly occupied habitat is a key element of the recovery plan for Sierra Nevada bighorn sheep (Ovis canadensis sierrae), which are state (California) and federally listed as endangered. However, implementing Sierra bighorn translocations is a significant conservation challenge because of the small size of the extant population and the limited number of herds available to donate translocation stock. One such herd, the Mt. Langley herd, recently became unusable as a translocation source following a substantial population decline. At the time of listing in 1999, predation by mountain lions (Puma concolor; hereafter lion) was considered a primary threat to Sierra bighorn, and since then lion predation may have continued to limit the ability of source herds to provide translocation stock. We evaluated the relationship between lion predation and ewe survival rates within three source herds of the Southern Recovery Unit, compared lion abundance and ewe survival among years of varying predation levels, provided a range of estimated times for the Mt. Langley herd to recover to its former status as a translocation source, and determined if the rates lions have been removed to mitigate Sierra bighorn predation exceeded sustainable harvest guidelines. We found compelling evidence that lion predation has impeded the recovery of Sierra bighorn by reducing survival rates of adult ewes (and consequently, population growth) and by preying upon individuals that could have otherwise been translocated. Ewe survival was poor during years of extreme predation but even during years of typical predation, survival rates were below a level needed to ensure population growth, indicating that years with little or no lion predation may be necessary for the population to grow and meet recovery goals. Because the intensity of predation was related to lion abundance, monitoring lion populations could provide managers with advance warning of periods of extreme predation. We found that following a period of particularly extreme predation, the Mt. Langley herd decreased in abundance far below the threshold needed to be considered a source of translocation stock, resulting in the loss of approximately 25% of the recovery program’s capacity for translocations. It is unclear how many years it will take for this herd to recover, but management actions to reduce lion predation are likely needed for this herd to grow to a size that can afford to donate individuals to translocation efforts in the near future, even when optimistic growth rates are assumed. We found that lion removal may also be needed to prevent predation from leading to Sierra bighorn population decline. Lion removal rates that have been implemented thus far are well below what would be needed to reduce the abundance the eastern Sierra lion population itself. We recommend continued monitoring of Sierra bighorn and sympatric lions and note that lion removal may be required to facilitate bighorn recovery for the foreseeable future.

Distribución corporal de garrapatas (Acari: Ixodidae y Argasidae) asociadas a Odocoielus virginianus (Artiodactyla: Cervidae) y Ovis canadensis (Artiodactyla: Bovidae) en tres estados del norte de México

Las garrapatas impactan como vectores por transmitir patógenos de importancia médica y veterinaria en México, pero los estudios taxonómicos de abundancia, prevalencia, intensidad y preferencia en la distribución corporal de venado cola blanca (Odocoileus virginianus) y borrego cimarrón (Ovis canadensis) son precarios, por lo cual estos fueron los objetivos del presente trabajo en Sonora, Nuevo León y Tamaulipas, México. El área de estudio abarcó ranchos cinegéticos autorizados donde se practica la cacería. Se examinaron 233 O. virginianus y cuatro O. canadensis, recolectándose 372 garrapatas [21 ninfas (5.65 %) y 351 adultos (94.35 %)]; 41 % fueron hembras y 59 % machos. Las garrapatas presentes en O. virginianus fueron Otobius megnini, Rhipicephalus (Boophilus) microplus y Dermacentor (Anocentor) nitens, mientras que Dermacentor hunteri fue la única en O. canadensis. Las orejas fue la región más infestada (83 hembras, 70 machos y 21 ninfas, 46.77 % en total) y la menos infestada fueron las piernas (10 machos y nueve hembras, 5.1 %), con diferencia significativa (P<0.005). Este estudio reporta por primera vez la abundancia, intensidad y prevalencia de garrapatas en O. virginianus en el norte de México y particularmente en los estados de Tamaulipas y Nuevo León, pues solo las garrapatas de O. canadensis habían sido reportadas en Sonora. Estos resultados indican que, aunque los ungulados están en semicautiverio, es importante controlar la infestación por garrapatas de acuerdo a los sitios de adherencia preferidos para aplicar los tratamientos acaridas, debido a la importancia como vectores en la transmisión de patógenos.