Name: Barros M

Biodeserts supervisors: Boratyński Z

Title: Predictability of population density by past weather conditions on Sahara desert

Institution: University of Porto

Status: Completed




In this study several analysis were made to test if past occurrences of precipitation has an effect on the population density of the desert rodents, more specifically the Gerbillus species. Gerbillus sp. live in the Sahara and its neighbouring areas, which is, nowadays, the most arid zone of the planet.

The climate is a crucial factor for species biology, including the ones that live in the desert, since there the precipitation is scarce and it is the main factor that acts in the productivity and may be the responsible for the reproduction and conservation of populations of these species. In this study it was verified that precipitation follows a tendency throughout the seasons, in spite of having been registered some changes in the last years, may these ones be related or not with the climate changes. I tested if chances of capturing and observing individuals of Gerbillus sp. increased after occurrences of the rain. I investigated how past events of rainfall affected population density. There weren’t detected any differences between the ecoregions, the latitude, the longitude, the year or the day the sampling was made. Two thirds of the data were obtained through the capture by hand or observation, and the major sampling was collected in 2011 and in the smallest period of time. The precipitation that occurred in the months 1, 13, 18 and 34 before the captures and the observation of the individuals has had a positive effect in the population density. The short term response occurred for the levels of precipitation during the month before the capturing/observing of individuals. It could be a direct effect of activity pattern in Gerbillus sp. or emergence of fast developing vegetation and insects, main food of Gerbillus sp. The strong long term response observed for the rainfall levels on 13,18 and 34 months before capturing/observing animals, is likely due to an increase on reproduction rates in response to the abundant productivity in habitats.

To study the effects that climate change might have in the population density it will be necessary a bigger and better sampling, for a longer period of time and performed by a larger number of people in the field.