REPRODUCTIVE STRATEGY OF GERBILLINE RODENTS IN MOROCCO.

Abstract

This investigation of the reproductive strategy of Gerbilline rodents is based on field studies conducted in southwestern Morocco, in the arid zone of North Africa. A mark-recapture method was used on live trap grids established at two locations. Demographic and reproductive data were recorded with each capture. Snap trap lines were used to obtain specimens for necropsy studies on the internal reproductive organs. Growth and development were observed on individuals raised in the laboratory. Monthly changes in population density, species biomass and percentage of reproductive activity were analyzed for three gerbilline species: Gerbillus hesperinus, G. campestris and G. nanus. Those changes were compared to monthly variations in rainfall, temperature photoperiod, and population density. Correlation between periods of high precipitation and increasing percentages of reproductive activity were found in all three species. The percentage of G. hesperinus and G. nanus females reproductively active increased markedly 2-3 months after periods of high precipitation. Although a similar interval was observed in G. campestris, the correlation was more closely associated with long-term rainfall patterns. The 2-3 month interval suggests a relationship to primary productivity rather than actual rainfall. The percentage of reproductively active males reached the highest levels earlier than in females and remained high for a longer period of time. During optimal conditions all three species exhibited characteristics associated with r-strategists. These characteristics include early female reproductive maturity, multiple litters in a single reproductive season and relatively large litters.