The desert shrew Notiosorex crawfordi is the smallest mammal in the arid and semiarid areas of North America. It displays ecological adaptations that allow it to colonize environments inhospitable for other species in the Order Soricomorpha. Little is known about the natural history of this species; hence, this work reports the characteristics of foraging behavior, prey items, prey size and bite effectiveness on prey items of similar or larger size than these shrews. The behavior in captivity of two individuals of N. crawfordi captured in Baja California Sur was analyzed in glass terrariums, recording the locomotion, posture, food preferences, prey manipulation and bite effectiveness. Preference for prey items collected from the same transects/habitat as the shrews and differing in size and belonging to different groups of Arthropoda was evaluated, revealing a greater preference for scorpions, which were attacked within 1 min of being placed in the terrarium. Observations of foraging behavior of captive desert shrews show that prey items from the different arthropod groups and lizards become paralyzed at the first bite. The behavior displayed by the prey suggested the potential presence of toxins in the saliva of N. crawfordi.
In this study, we investigate the geographic distribution of the Tule shrew (Sorex ornatus juncensis), an endemic subspecies of the San Quintin plains associated with coastal vegetation. Records on this shrew are scarce; herein, we provide knowledge about its current conservation status and report the presence of one Tule shrew specimen, something that has not happened since 1926. The distribution of the Tule shrew is associated with coastal vegetation, limited to the San Quintin plains, with scarce records. Field trips were conducted during 2013–2015 in the San Quintin plains and San Pedro Martir range of the Baja California Peninsula. The sampling effort was 3250 trap nights. One specimen of S. o. juncensis was recorded in association with coastal sage-scrub vegetation and identified following the original description, based on its narrower skull relative to Sorex ornatus ornatus. We used a mitochondrial cytochrome b gene sequence (384 bp) to confirm this identification and compare genetic distances using the Kimura’s two-parameter nucleotide substitution model vs. other populations of the ornatus group. We found a genetic divergence of less than 1.0% based on sequences from specimens collected from Sierra San Pedro Martir, El Rosario and Sierra La Laguna. In the locality of the S. o. juncensis specimen collected, the original vegetation consists of patches of coastal scrubs, which cover an area of less than 1 km2, affected by agriculture and habitat fragmentation. We reallocated the taxonomic level of the Tule shrew inhabiting the plains of San Quintin in the Baja California Peninsula to subspecies as S. o. juncensis based on geographic isolation, morphometric characteristics and coloration differences vs. S. o. ornatus. The population inhabiting San Quintin plains is subjected to strong pressure due to habitat loss.
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