Factors influencing timing of puberty in Mexican gray wolves (Canis lupus baileyi)

The reintroduced population of Mexican gray wolves (Canis lupus baileyi) continues to rely on a carefully managed captive breeding program. Although success of that program depends on detailed knowledge of reproductive processes, age of puberty has not been determined. This study assessed male puberty status (presence of sperm in ejaculates), maintained in nine US facilities, during their first breeding season. Variables possibly associated with puberty were also evaluated. There was a significant effect of body weight, testis size, facility latitude, and date of collection, whereas a statistical trend was found for age and inbreeding coefficient. Social factors, including being housed with sire, had no effect. Over half the males in their first breeding season were producing sperm, although in some cases sperm quality was poor, suggesting possible infertility. Although there was no minimum body weight associated with presence of sperm, likelihood increased with increasing body weight, highlighting a possible critical role for nutrition. The trend for sperm production in males collected later in the breeding season and at lower latitudes suggests that later collections, especially at higher latitudes, might reveal a higher percentage of pubertal males. These results have potential implications for breeding program management and introduce the possibility that more wild gray wolves than previously thought might produce sperm during their first year, even if they do not sire young. Sperm was found in samples of more than half the young males aged 8-10 months and half of those were judged fertile based on percentages of motile sperm with normal morphology. Likelihood of producing sperm was related to body weight, implicating nutrition as a major influence. Latitude and date of semen collection relative to peak breeding season were also associated with sperm production, but living in a family group had no effect. La poblacion reintroducida de lobo mexicano (Canis lupus baileyi) depende aun de un programa de reproduccion en cautiverio cuidadosamente gestionado. Aunque el exito del programa depende del conocimiento detallado de los procesos reproductivos, la edad de la pubertad no ha sido determinada. Este estudio evaluo el estado de pubertad de los machos (presencia de espermatozoides en los eyaculados) mantenidos en nueve instituciones de los Estado Unidos, durante su primera temporada reproductiva. Tambien se evaluaron variables asociadas posiblemente con la pubertad. Se encontro un efecto significativo del peso corporal, el tamano de los testiculos, la latitud de la institucion y la fecha de recoleccion; mientras que para la edad y el coeficiente de consanguinidad se encontro una tendencia estadistica. Factores sociales, incluyendo estar alojado con el padre, no tuvieron ningun efecto. Mas de la mitad de los machos en su primera temporada reproductiva produjeron espermatozoides, aunque en algunos casos la calidad era deficiente, lo que sugiere una posible infertilidad. Aunque no hubo un peso corporal minimo asociado con la presencia de espermatozoides, la probabilidad aumento con el aumento del peso corporal, destacando el posible papel critico de la nutricion. La tendencia de produccion de espermatozoides en los machos recolectados en fechas posteriores en la temporada de reproduccion y en latitudes mas bajas, sugiere que recolecciones mas tardias, especialmente en latitudes mas altas, podrian revelar un mayor porcentaje de machos puberes. Estos resultados tienen implicaciones potenciales en la gestion del programa de reproduccion e abren la posibilidad de que mas lobos grises silvestres puedan producir espermatozoides durante su primer ano de lo que se pensaba anteriormente, incluso si no producen crias.