Scotinomys

Abstract: DNA sequences obtained from the mitochondrial cytochrome-b gene were used to evaluate phylogenetic relationships among 15 genera of putative neotomine–peromyscine rodents. Tree topologies obtained from maximum likelihood and Bayesian analyses revealed 4 primary clades that, in general, conform to the 4 tribes proposed by Carleton (1980). The Peromyscini (Megadontomys, Ochrotomys, Osgoodomys, Peromyscus, and Reithrodontomys) was sister to the Neotomini (Hodomys, Neotoma, Onychomys, and Xenomys). These 2 clades were then joined by the Baiomyini (Baiomys and Scotinomys) and Tylomyini (Nyctomys, Ototylomys, and Tylomys). The most apparent departure from previously proposed arrangements involved the placement of Onychomys in the Neotomini instead of the Peromyscini.

Abstract: Scotinomys xerampelinus, the long-tailed singing mouse, is diurnal and insectivorous, and exhibits a complex and unique calling behavior that is audible to humans. Little is known about the social structure of this species. We used livetrapping and radiotracking to investigate the spatial organization of a wild Panamanian population of long-tailed singing mice. We observed exclusive space use among females but not among males. For both males and females, individual home ranges (85% minimum convex polygons) typically overlapped with >1 animal of the opposite sex. No significant differences in body mass, hind-foot length, or home-range size (area) were found between males and females. Most individuals in the population nested alone. Patterns of space use and sexual dimorphism are frequently used to infer species' mating systems. Our results, in particular the tendency for individual home ranges to overlap with multiple potential reproductive partners, are most consistent with a promiscuous mating system.

Abstract: Interspecific aggression between sibling species may enhance discrimination of competitors when recognition errors are costly, but proximate mechanisms mediating increased discriminative ability are unclear. We studied behavioral and neural mechanisms underlying responses to conspecific and heterospecific vocalizations in Alston’s singing mouse (Scotinomys teguina), a species in which males sing to repel rivals. We performed playback experiments using males in allopatry and sympatry with a dominant heterospecific (Scotinomys xerampelinus) and examined song-evoked induction of egr-1 in the auditory system to examine how neural tuning modulates species-specific responses. Heterospecific songs elicited stronger neural responses in sympatry than in allopatry, despite eliciting less singing in sympatry. Our results refute the traditional neuroethological concept of a matched filter and instead suggest expansion of sensory sensitivity to mediate competitor recognition in sympatry.