The feral hog at Dye Creek Ranch, California

Abstract

From 1967 to 1970, an extensive study was made of the life history and ecology of the feral hog (Sus scroja L.) inhabiting oak woodland in the Sierra foothills. A detailed description of the feral hog included chromosome number, size, conformation, skull characteristics, dentition, tusk development, coat color, communication, social structure, and behavioral patterns. Home ranges of boars and sows were estimated to be 50 and 10 km2, respectively; hogs were capable of homing at least 15 km. Acorns were the most important food item, but green grass and forbs, wild oats, berries, bulbs, roots, insects, and carrion were also eaten. Hogs grazing irrigated pastures during the summer consumed more green forage and crude protein and exhibited significantly greater growth rates than hogs without access to pastures. Pen-raised feral hogs were found capable of growth equal to domestic swine, but typical free-ranging hogs exhibited growth rates of only half their potential. Sows bred continuously after the age of 6 to 10 months, averaging two litters per year and 5.6 young per litter at birth. Sows with access to irrigated pastures produced 20 percent more fetuses than those without access. From birth to 6 months of age, piglets sustained a 70 to 90 percent mortality. Losses were due to accidents, predation and starvation. Insufficient milk resulting from low levels of protein in the sows’ diets was a major underlying cause of piglet losses. Hunting was the major cause of adult mortality. Tooth abscesses and related infections were the most important natural causes of adult mortality. Population density ranged from five to eight hogs per square kilometer on the 130-km2 study area. Although the annual kill averaged 21 percent, the population increased 10 percent per year from 1966 to 1970. Young hogs made up nearly half and yearlings made up nearly a quarter of the fall population in 1969. The proposed management program aims to economically control feral hog populations on private lands by paid recreational hunting, thus providing income for the landowner and recreation for the public.