Volume 46, Number 9 · December, 1978 The Feral Hog on the Dye Creek Ranch, California Reginald H. Barrett END OF VOLUME JNIVERSITY OF CALIFORNIA DIVISION OF AGRICULTURAL SCIENCES From 1967 to 1970, an extensive study was made of the life his­ tory and ecology of the feral hog (Sus scrota 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, com­ munication, social structure, and behavioral patterns. Home ranges of boars and sows were estimated to be 50 and 10 km", 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, averag­ ing 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 acci­ dents, 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 mor­ tality. Tooth abscesses and related infections were the most im­ portant natural causes of adult mortality. Population density ranged from five to eight hogs per square kilometer on the 130-km~ 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 pro­ gram aims to economically control feral hog populations on pri­ vate lands by paid recreational hunting, thus providing income for the landowner and recreation for the public. THE AUTHOR: Reginald H. Barrett is Assistant Professor of Forestry and Re­ source Management, Department of Forestry and Resource Man­ agement, Berkeley. Reginald H. Barrett The Feral Hog at Dye Creek Ranch, California! INTRODUCTION MAN HAS }{NOWN the pig Sus scrota as This dissemination increased greatly a domestic animal for 8,000 to 9,000 during the age of exploration, when years (Sillar and Meyler, 1961; Zenner, explorers, sailors, and settlers intro­ 1963; Bokonyi, 1970; Epstein, 1971; duced swine into a multitude of new Protsch and Berger, 1973). Today it habitats. Pigs were first introduced to provides a major source of animal pro­ the United States in 1539 and subse­ tein for mankind, and pork is second quently spread throughout the South­ only to beef in pounds consumed per east (Towne and Wentworth, 1950). capita in the United States (Ensmin­ They presently occur in several parts of ger, 1961:24). The use of miniature Anglo-America, including California swine for biomedical research is in­ (McKnight, 1964:42). Feral hogs have creasing (Mount and Ingram, 1971), been in California since the arrival of and pig physiology continues to be the Spanish in 1769 and were released studied in great detail (Braude, 1972). by the Russians at Fort Ros-s in Sonoma In contrast, the wild pig has received County, perhaps as early as 1812 little attention. Most works are oriented (Hutchison, 1946: 21). The greatest in­ towards the sportsman (e.g., Wardrop, crease in their distribution throughout 1914; Snethlage, 1967), although major the state probably occurred during the ecological studies of the European wild homestead era, which continued from boar have been made in Germany the Gold Rush in 1850 into the twenti­ (Oloff, 1951; Briedermann, 1973), Rus­ eth century. sia (Sludskii, 1956; Bromlei, 1964), and By the 1840s, men such as Lassen, Poland (Haber, 1969). Native races of Su« scrota that have no history as domesticated animals will subsequently be termed "wild boar." Wild boar will be distinguished from the "feral hog" which has been defined by McKnight (1964:3) as "... one that was once domesticated, or with domesti­ cated ancestors, but now living as a wild creature. It is not under the effec­ tive ownership of humans and does not receive protection, care, or food as a deliberate gift from man." Due to the pig's usefulness as a pro­ Feral hogs in eastern Tehama County stem ducer of meat and lard, it has been from releases of domestic swine by homestead­ spread by man throughout the world. ers as early as 1880. I This manuscript was accepted for publication May 31,1978. [283 ] 284 Barrett: The Feral Hog at Dye Creek Ranch 2 I II Km Fig. 1. Dye Creek Ranch study area. Toomes, and Dye established rancheros hands, a few old-timers, and hunters along the Sacramento River in Tehama were the only people entering the road­ County and introduced domestic swine less foothills. Ranch employees and lo­ and other livestock. Settlers were hunt­ cal citizens, hunting with dog'S, kept the ing feral hogs in the foothills northeast feral hog population under control along of Red Bluff in the 1880s (Leslie, the valley edge. In 1963, William Keeler 1966), and by the turn of the century purchased the Dye Creek Ranch (Fig. had exterminated the Yahi Indians 1) and instigated a policy of multiple (Kroeber, 1967) and the grizzly bear land use. In addition to continuing a Ursus arctos (Storer and Tevis, 1955). cattle operation, he set up a commercial This facilitated intensive homesteading hunting preserve. Hunting pressure by of the foothills from 1890 to 1920 with local people was removed but partially the consequent introduction of domestic replaced by the Preserve's first boar swine (pers. c.omm. with Mrs. Ward season in the winter of 1966-1967. and Mr. A. H. Clough of Los Molinos, European wild boar have twice been 22 January 1970). Swine were an im­ introduced into North America as a portant source of lard for the home­ sporting animal (Manville, 1964). In steaders who generally released their 1911, 13 young European wild boar pigs to fatten during the acorn season were shipped from Germany to Hoo­ (E. B. Shaw, 1940: 245). Apparently, per's Bald, North Carolina, where their the feral hog has taken advantage of descendants interbred with feral hogs the niches vacated by the bears and the already in the region (Jones, 1959). Indians. Some of these descendants were intro­ During the 1920s most of the home­ duced into Monterey County, Califor­ steaders moved from the area, and cow- nia in 1923. The wild boar eventually HILGARDIA • Vol. 46, No.9· December, 1978 285 spread south through the Santa Lucia 1970; Wood, 1977). The present study mountains and interbred with the exist­ was undertaken to obtain ecological in­ ing feral hogs (Blocker, 1937; A. C. formation for use in the management Shaw, 1940; Bruce, 1941). Wild boar of the feral hog on the Dye Creek from Monterey County have now been Ranch. Particular effort was made to transplanted to several areas of Cali­ describe the manner in which this large, fornia including 'I'ehama County. De­ exotic: mammal has adapted to the Dye spite this, the feral hog is still the pre­ Creek area. 'I'ho most likely mechanism dominant type of wild pig found over of natural population regulation ap­ most of the state, including the Dye peared to be through the effect of the Creek Ranch. quantity and quality of available food Several studies have been made of on lactation and piglet survival. A com­ the wild boar in America (Stegeman, parative study was planned to investi­ 1938; Bruce, 1941; Matsehke, 1962, gate this hypothesis. The field work was 1963, 1964, 1967; Henry, 1968, 1969, carried out from June, 1967, to Septem­ 1970; Pine and Gerdes, 1973), but little ber, 1967, and continued from June, work has been done on the feral hog 1968, to January, 1970. (Hanson and Karstad, 1959; Sweeney, METHODS The major activities conducted was determined from 100 points taken throughout the study were analysis of at random in each type with a 10-pin, vegetation, field observation, capturing point frame. This work was done in and marking of hogs, and collecting and April, 1970, when mo.st herbaceous spe­ autopsy. Other methods used will be cies were flowering. described in the appropriate sections. Nomenclature used follows Miller and Field observations Kellogg (1955) for mammals and Munz Binoculars (8 x 40) were the stan­ and Keck (1959) for plants. dard equipment for field observations. Cards listing the tagged and otherwise Analysis of vegetation identifiable hogs for each five subunits A collection of 322 plant species was in the study area were continually made and housed in a herbarium at the updated as new individuals were ob­ Dye Creek Field Station. After prelim­ served. I recognized many untagged inary study of aerial photos and on-the­ hogs simply by their coat-color pattern. ground reconnaissance, the vegetation I recorded 1,824 separate observa­ was subjectively divided into eight tion periods in which a total of 14,707 types. The botanical composition of hogs were tallied including repeated each type was sampled using six, ram­ observation of many individuals. Ap­ domly located, 100-point transects in proximately 500 hours were spent actu­ each vegetation type as outlined on ally watching free-ranging feral hogs.