Mastozoología Neotropical ISSN: 0327-9383 [email protected] Sociedad Argentina para el Estudio de los Mamíferos Argentina Villamizar-Ramírez, Ángela M.; Serrano-Cardozo, Víctor H.; Ramírez-Pinilla, Martha P. REPRODUCTIVE ACTIVITY OF A POPULATION OF Nephelomys meridensis (RODENTIA: CRICETIDAE) IN COLOMBIA Mastozoología Neotropical, vol. 24, núm. 1, julio, 2017, pp. 177-189 Sociedad Argentina para el Estudio de los Mamíferos Tucumán, Argentina Available in: http://www.redalyc.org/articulo.oa?id=45753369015 How to cite Complete issue Scientific Information System More information about this article Network of Scientific Journals from Latin America, the Caribbean, Spain and Portugal Journal's homepage in redalyc.org Non-profit academic project, developed under the open access initiative Mastozoología Neotropical, 24(1):177-189, Mendoza, 2017 Copyright ©SAREM, 2017 http://www.sarem.org.ar Versión impresa ISSN 0327-9383 http://www.sbmz.com.br Versión on-line ISSN 1666-0536 Artículo REPRODUCTIVE ACTIVITY OF A POPULATION OF Nephelomys meridensis (RODENTIA: CRICETIDAE) IN COLOMBIA Ángela M. Villamizar-Ramírez1, Víctor H. Serrano-Cardozo1, 3, and Martha P. Ramírez-Pinilla2, 3 1 Laboratorio de Ecología, Escuela de Biología, Universidad Industrial de Santander, Bucaramanga, Santander, Colombia. [Correspondence: Víctor H. Serrano-Cardozo <[email protected]>] 2 Laboratorio de Biología Reproductiva de Vertebrados, Escuela de Biología, Universidad Industrial de Santander, Bucaramanga, Santander, Colombia. 3 Grupo de Estudios en Biodiversidad, Escuela de Biología, Facultad de Ciencias, Universidad Industrial de Santander, Bucaramanga, Santander, Colombia. ABSTRACT. We studied the annual reproductive activity of a population of Nephelomys meridensis in an Andean oak forest in the Cordillera Oriental of Colombia. Monthly during a year, Sherman live traps were established in 5 fixed stations (20 traps per station) during 4 nights per month, along an altitudinal range of 2530-2657 m. Reproductive condition was established in adult females by external morphology including nipple development, abdomen distension, and features of the vaginal opening. Adult females were categorized as pregnant or in lactation. Additionally, female reproductive condition was complemented with the analysis of vaginal smears of each female with open vagina and with a general description of the estrous cycle for some females in captivity. Females of this population of N. meridensis reproduce continuously throughout the year, and females were pregnant, in lactation or in estrous several months. The presence of postpartum estrus both in captivity and in the field was observed. Under captivity conditions, the estrous cycle can last more than 5 days because some phases were extended more than 2 days. No relationship was found between the frequency of reproductive females in each reproductive state and the monthly average of rainfall or with the variation in the environmental availability of food (arthropod abundance and oak fructification). Therefore, in this popula- tion of N. meridensis females have an aseasonal polyestric pattern suggesting a constant offer of environmental resources for reproduction. RESUMEN. Actividad reproductiva de una población de Nephelomys meridensis (Rodentia: Cricetidae) en Colombia. Estudiamos la actividad reproductiva anual de una población de Nephelomys meridensis en un bosque andino de roble en la Cordillera Oriental de Colombia y otros aspectos reproductivos de esta población. Mensualmente y por un año se establecieron 5 estaciones fijas en un intervalo altitudinal de 2530 a 2657 m; en cada una se ubicaron de manera aleatoria 20 trampas Sherman. La condición reproductiva se estableció en hembras adultas por morfología externa del desarrollo de las mamas, la distensión abdominal y la de la abertura vaginal; las mismas se categorizaron como preñadas o en lactancia. Adicionalmente se complementó el análisis de la condición reproductiva con el análisis de frotis vaginales realizados a cada hembra con vagina abierta y con la descripción a manera general del ciclo estral de hembras en cautiverio. Las hembras de esta población de N. meridensis se reproducen continuamente a lo largo del año. Se encontraron hembras preñadas y en lactancia casi todos los meses y hembras en estro en varios meses. Se determinó la presencia de estro post-parto tanto en cautiverio como en campo. Bajo las condiciones de cautiverio, el ciclo estral puede durar más de 5 días Recibido 13 julio 2016. Aceptado 20 marzo 2017. Editor asociado: M Busch 178 Mastozoología Neotropical, 24(1):177-189, Mendoza, 2017 AM Villamizar et al. http://www.sarem.org.ar - http://www.sbmz.com.br debido a que algunas fases se extienden por más de 2 días. No se encontró una relación entre la frecuencia de hembras reproductivas en cada estado y la variación en el promedio mensual de lluvias, ni tampoco con la variación en la oferta ambiental de alimento (abundancia de artrópodos y fructificación del roble). Por tanto, en esta población de N. meridensis las hembras tienen un patrón de poliestría no estacional lo que sugiere una oferta ambiental constante de recursos para la reproducción. Key words: Andean forest. Environmental factors. Nephelomys meridensis. Reproduction. Palabras clave: Bosque andino. Factores ambientales. Nephelomys meridensis. Reproducción. INTRODUCTION al., 2005; Yener et al., 2007; Caligioni, 2009; Byers et al., 2012; McLean et al., 2012), but is Reproductive activity in small mammals has poorly known in wild rodents. However, it has been documented mainly for species living been studied under laboratory conditions in in temperate latitudes, where factors such as Mastomys natalensis (Johnston and Oliff, 1954), photoperiod, resource availability, environ- Baiomys taylori (Hudson, 1974), Peromyscus mental temperature and precipitation influence californicus (Gubernick, 1988), and Proechimys reproductive patterns (Bronson, 1985). chrysaeolus (Sabogal-Guáqueta et al., 2013), There are few studies in the tropics where among others. The estrous cycle consists of most of the mammals live; therefore, a big four phases called proestrus, estrus, metestrus gap in the understanding of the regulation of and diestrus; each distinguished by the type reproduction by environmental factors exists for and amount of vaginal epithelial cells, and the most of the tropical mammals (Bronson, 2009). presence or absence of leukocytes in the vagina Several studies suggest that reproduction in (Yener et al., 2007; Byers et al., 2012.). tropical rodents is continuous (Lacher, 1992). Nephelomys meridensis is a rodent of the This is the case in Oryzomys capito (Fleming, Cricetidae family, formerly in the “albigularis” 1971), O. nigripes, O. trinitatis (Fonseca and group of Oryzomys (Weksler et al., 2006), Kierulff, 1989), Proechimys semispinosus, Hoplo- N. meridensis is distributed from the Northeast mys gymnurus (Alberico and González-M., of the Cordillera Oriental of Colombia in the 1993) and Nyctomys sumichrasti (Romero and Department of Boyacá to the North of the Timm, 2013), among others. However, there is Sierra de Mérida in Venezuela, at elevations of evidence of reproductive peaks during either 1100-4000 m (Percequillo, 2015). Individuals the highest or the lowest precipitation seasons of the genus Nephelomys are terrestrial, so- (Lacher, 1992; Bronson, 2009); for example, cial and nocturnal; they take refuge inside Oryzomys intermedius, Trinomys iheringi, fallen trees and rock formations covered with Nectomys squamipes have their reproductive moss, and food includes fruits, arthropods peaks during the peak of the rainy season and seeds (Rivas, 1997; Gibson, 2014). Díaz (Bergallo and Magnusson, 1999); in Akodon de Pascual (1981) mentioned that the diet of cursor the reproductive peak starts at the end O. albigularis includes 50% endocarp of guama of the rainy season and goes until the end of fruit (Inga sp.), 20% insect larvae, 20% palm the dry season (Fonseca and Kierulff, 1989). seeds, 2% fungi, and 2% flowers of Heliconia sp. Then, seasonal reproductive activity in tropi- No additional detailed information is available cal rodents would be related to the intensity on the natural history of this species. and duration of the rainy and dry seasons and We studied the annual reproductive activity its relation to the availability of resources for of females and other aspects of the reproduc- reproduction. tion of a population of Nephelomys meridensis The estrous cycle has been widely studied in living in an Andean forest with a bimodal laboratory mice and rats (e. g. in Hubscher et regimen of rains. The study contributes to the Nephelomys meridensis REPRODUCTIVE BIOLOGY 179 knowledge of reproduction and its relationship mula C.S. = (I.C / C.E) x 100, where: S. C = capture with environmental factors in small mammals success, I.C. = Number of individuals captured and that inhabit upland forests in the Neotropics. C.E = capture effort (Steinmann et al., 2003; Gallina et al., 2008). MATERIALS AND METHODS Reproductive activity This work was done in an Andean oak forest in the Cordillera Oriental of Colombia at an altitude of From morphological measurements, weight and 2600 m, in Santa Barbara municipality, Santander, head-body length (HBL), and hair dorsal color of the Colombia (7º 01’ 9.9’’ N, 72º 53’ 33.6’’ W). The individuals captured in this study, we defined three forest is characterized by the dominance of trees categories of age: adults, sub-adults, and juveniles of Quercus humboldtii,