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Peromyscus fraterculus (Miller, 1892) is a small rodent commonly called the northern Baja deermouse. Its pelage is dark, the tail is considerably longer than the body, and the number of caudal vertebrae ranges from 30 to 34. The geographic distribution of P. fraterculus includes the area west of the Colorado River, from southern California in the United States of America southward to the Baja California Peninsula, Mexico, south of La Paz Isthmus. It is found in a broad variety of habitats from sea level to 1,175 m. P. fraterculus does not have special conservation status, although the island populations have conservation issues, mainly due to the introduction of non-native species. It is listed as “Least Concern” (LC) by the International Union for Conservation of Nature and Natural Resources.

Migratory species that cross geopolitical boundaries pose challenges for conservation planning because threats may vary across a species’ range and multi-country collaboration is required to implement conservation action plans. The lesser long-nosed bat (Leptonycteris yerbabuenae) is a migratory pollinator bat that was removed from the Endangered Species List in the United States in 2018 and from threatened status in Mexico in 2013. The seasonal ecology and conservation status of the species is well understood in the core part of its range on mainland Mexico and in the southwestern United States, but relatively little is known about the species on the Baja California peninsula in northwestern Mexico, a part of its range range separated by the Gulf of California. We studied the seasonal ecology of lesser long-nosed bats on the Baja peninsula at 8 focal roosts along a 450-km north-to-south transect to test hypotheses about migratory or residential status of the species on the Baja peninsula. We provide evidence of an extensive population of lesser long-nosed bats on the Baja peninsula that is primarily seasonally migratory and includes 2 mating roosts with males on the southern part of the peninsula. Seasonal ecology of lesser long-nosed bats was closely associated with the flowering and fruiting season of the cardón (Pachycereus pringlei), the dominant columnar cactus on the peninsula. However, we discovered that some female lesser long-nosed bats arrive and give birth at southern roosts in mid-February, about 2 months earlier than other migratory populations in more northern Sonoran Desert habitats. We documented the loss of nearly a third of the known maternity roosts during the study, demonstrating that action to protect key roosts remains a high priority. Migratory pollinators are particularly vulnerable to climate and land-use changes and we recommend continued monitoring and research to guide effective range-wide conservation of the species. Las especies migratorias o con rangos de distribución amplios que incluyen fronteras geopolíticas, representan desafíos particulares para la planificación de estrategias de conservación, ya que las amenazas así como las tendencias poblacionales pueden variar a lo largo de su rango geográfico y se requiere la colaboración de múltiples países para implementar planes de acción que permitan su conservación. El murciélago magueyero menor (Leptonycteris yerbabuenae) es un murciélago polinizador migratorio que recientemente fue sacado de la lista de especies en peligro en los Estados Unidos en 2018 y en México en 2013. La ecología estacional y el estatus de conservación de esta especie, ha sido bien estudiado en el centro de su rango de distribución en México continental, pero se sabe muy poco acerca de la especie en la Península de Baja California en el noreste de México, región que está separada del resto del rango por el golfo de California. Nosotros estudiamos la ecología estacional del murciélago magueyero menor, en ocho cuevas a lo largo de un transecto de 450 km norte-sur, en la Península de Baja California y pusimos a prueba la hipótesis del status migratorio o residente de sus poblaciones en esta región. Proporcionamos la primera evidencia de una extensa población de esta especie en la península, a cual es principalmente migratoria estacional e incluye dos cuevas de reproducción ubicadas al sur de esta región. La ecología estacional del murciélago magueyero menor estuvo fuertemente asociada con la estación de floración y fructificación del cardón (Pachycereus pringlei), el cactus columnar dominante en la península. Nosotros también descubrimos que algunas hembras llegan y dan a luz en las cuevas más sureñas, a mediados de febrero, cerca de dos meses antes que otras poblaciones migratorias, en el desierto de Sonora del norte. Durante el tiempo de este estudio, documentamos la destrucción de una de las cuevas de maternidad, lo que demuestra la necesidad de acciones de conservación para proteger estos refugios. Los polinizadores migratorios son particularmente vulnerables a cambios en el uso del suelo y al cambio climático y recomendamos continuar con el monitoreo y la investigación, con el fin de guiar su conservación a lo largo de todo el rango de distribución de la especie.

Bat acoustic libraries are important tools that assemble echolocation calls to allow the comparison and discrimination to confirm species identifications. The Sonozotz project represents the first nation‐wide library of bat echolocation calls for a megadiverse country. It was assembled following a standardized recording protocol that aimed to cover different recording habitats, recording techniques, and call variation inherent to individuals. The Sonozotz project included 69 species of echolocating bats, a high species richness that represents 50% of bat species found in the country. We include recommendations on how the database can be used and how the sampling methods can be potentially replicated in countries with similar environmental and geographic conditions. To our knowledge, this represents the most exhaustive effort to date to document and compile the diversity of bat echolocation calls for a megadiverse country. This database will be useful to address a range of ecological questions including the effects of anthropogenic activities on bat communities through the analysis of bat sound., The Sonozotz project represents the first nation‐wide library of bat echolocation calls for a megadiverse country.

We report the status of alien species on Isla de Cedros, Mexico, and analyze the information from different years that together with a collaborative effort between academic biologists, Mexican governmental agencies, and local individuals has resulted in major information about the alien species on this island. We also report species richness of distinct endemic mammal species and the presence of feral dogs (Canis lupus familiaris Linnaeus), which is the principal problematic situation in this “Marine Priority Region.” The possible origin of feral dogs could be the migratory movement of stray dogs to find food in the inner part of the island, first moving to garbage dumps, reproducing in the area, and later hunting goats (Capra aegagrus hircus Linnaeus) in packs. The combination of the high density of stray dogs, urban and industrial food garbage dumps, and the large number of marine resources scattered along the seashore made ideal conditions for the establishment of feral dog packs that are affecting native species. The island does not have any natural mammal predator, but the presence of feral species, dogs and cats (Felis silvestris catus Schreber), could disturb the occurrence of endemic fauna as it has happened on other islands in the world.

We assessed the current distributions for 2 subspecies of the brush rabbit, Sylvilagus bachmani peninsularis and S. b. exiguus, on the Baja California Peninsula, Mexico. On the basis of field sampling, field notes, and voucher specimens in scientific collections, we demonstrated that (1) both subspecies have been previously recorded in mesic habitats with conditions associated with oases and streams; (2) the 2 subspecies exhibit disjunction in their distributions in the middle and southern portions of the peninsula; (3) habitats are threatened by human activities and desertification, which explains why brush rabbit populations are currently fragmented; and (4) specimens of S. bachmani have not been collected or observed in the last 20 years, with effort concentrated mainly in the southernmost part of the peninsula (San Lucas faunal district). We suggest that S. b. exiguus be considered threatened, requiring immediate conservation actions, including habitat preservation; and we suggest that the southern form, S. b. peninsularis, be considered extinct due to anthropogenic activities.

This paper reports the first record of Eumops underwoodi in the Baja California peninsula. This record expands the species' distributional range in Mexico along the peninsula. We propose 2 plausible biogeographical explana- tions. First, the species has the ability to travel across the Gulf of California from the coast of Sonora to the eastern side of the Baja California peninsula and there establish. Second, there is a continuous distribution of the species throughout the mountain ranges that run longitudinally along the Baja California peninsula from the United States border down to the southern tip. We collected one male specimen of E. underwoodi in xeric-riparian habitat. We suggest a continuous distribution pattern of this species along the cliffs in the Baja California peninsula.

We report the first observations of the black-tailed jackrabbit (Lepus californicus) on Cerralvo Island, Baja California Sur, Mexico. Evidence suggests a self-sustaining population. Analysis of available records indicates no previous record of Lepus on the island. Introduction of the jackrabbit to the island appears to have occurred between 1960 and 1991.

Santa Catalina Island has an endemic mouse, Peromyscus slevini, which is the only native rodent species on the island. However, specimens of P. fraterculus have been recorded on the island. P. fraterculus is the most common species of Peromyscus off Santa Catalina Island in the Baja California peninsula. The records show the absence of P. slevini in the 1990s and an increasing number of P. fraterculus during the 2000s. P. slevini has recently been collected in 2007. The current situation in Santa Catalina Island shows a strong expansion of P. fraterculus and the restriction of P. slevini to the canyons. This study confirms for the first time the recent invasion of a peninsular native species in one island on the Gulf of California. Peromyscus fraterculus is a better desert adapted species in contrast to P. slevini. Under those conditions, in the near future, P. slevini could be extinct.

Mysticeti whales modify their calls in response to an increase in noise level within their environment. This is particularly important since environmental noise has been increasing continuously in the last decades. In the case of Bryde's whale (Balaenoptera edeni), previous studies of its predominant call, Be4, have exposed differences in the duration of its main component (f0) for northern and southern areas of the Gulf of California (GC). The objective of this research is to determine if the differences found among Be4 calls (f0, duration, and energy distribution) are influenced by the noise levels in those areas. Results based on the characterization of Be4 Call and noise show that northern noise level is intense in the octave frequency band centered around 30 Hz, and could mask the 30 Hz component. This kind of noise is rare in the south (5%) and when it was present, the 30 Hz component was not registered, which might be an adaptation to noise. Predominant moderate noise in the south within the band 2...

La información actualizada sobre la representatividad geográfica y taxonómica de los ejemplares depositados en 28 colecciones mastozoológicas mexicanas y la disponible en las bases de datos Mammal Networked Information System (MaNIS), y de la Unidad de Informática para la Biodiversidad (UNIBIO) se recopiló con el fin de analizar y comparar el estado actual de los ejemplares de mamíferos mexicanos depositados en colecciones de Norteamérica. Se documentaron un total de 421,466 ejemplares de mamíferos depositados en 120 colecciones mastozoológicas, de los cuales 233,116 ejemplares se encuentran en colecciones de Estados Unidos de América y Canadá, y 188,350 ejemplares en colecciones de México. Las colecciones con el mayor número de ejemplares de mamíferos de México son la Colección Nacional de Mamíferos (CNMA 46,000), la Universidad de Kansas (KU 44,301), y la Escuela Nacional de Ciencias Biológicas (ENCB 43,985). En colecciones mexicanas, los estados del norte de México están escasamente representados en número de ejemplares ( 3,000), y en las colecciones extranjeras, los estados del centro de México están pobremente representados. Los estados mexicanos mejor representados por número de ejemplares ( 10,000) son Baja California Sur, Chiapas, Oaxaca, Puebla y Veracruz. Los órdenes mejor representados por el número de ejemplares son Rodentia y Chiroptera (234,978 y 120,956, respectivamente). Los estados mexicanos con menor extensión territorial tienen la mayor densidad de ejemplares colectados (ejemplares/km 2 ): Distrito Federal (3.2), Tlaxcala (1.4), Colima (1.06) y Morelos (0.9). Se espera contar con una línea base que permita establecer estrategias adecuadas para completar el inventario nacional de los mamíferos mexicanos, y lograr que este patrimonio natural este adecuadamente representado en colecciones de México.