Seasonal variations in habitat selection and spatial distribution of wild boar (Sus Scrofa) in the Camargue, Southern France.

Seasonal habitat selection and use by wild boars were studied in relation to major vegetation cover types and flooded areas, on a sampling area of 1047 ha. Six habitat types were delineated: "sansouire" (local name), "enganes" (local name), halophytic grasslands, scrub grasslands, deep and shallow marshes, fallow or cultivated farmlands. Once a season in 1982, this sampling area was systematically examined and mapped for wild boar signs left in the following places : bedding places, farrowing nests, wallows, rubbing trees and rooting sites. Marshes are the most frequently used areas throughout the year since all activities can be conducted there. Scrub grasslands, although less common, are also important, because of scrubs of Phillyrea angustifolia used for resting and dense groves of Ulmus campestris used for rubbing. Rooting activity, predominantly done in marshes, is also conducted in all types of grasslands (even cultivated) during the winter, and in farmlands during the summer. In the sampling area, seasonal variations in the counts of activity signs as well as in the number of wild boar sightings suggest correlated variations of density. The estimated autumn to spring density is higher (2.5-2.9 animals/km2) than the summer one (0.6 animals/km2). These seasonal variations are explained by spatial adjustments according to environmental conditions. In the early warm season, drying out of marshes and soils in the study area leads to emigration of part of population onto neighbouring grounds where agricultural crops are available. Return movements are presumably causally related to different factors : onset of the rains, hunting disturbance and harvest of crops. Fluctuations of environmental factors require a flexible strategy of habitat utilization. We propose a model for the organization of wild boar populations, which would be formed by "nuclei" presenting environment-dependent densities.