PIGS & Natural Area Survey Report.Pdf

NATURAL AREAS ECOLOGICAL DAMAGE AND ECONOMIC COSTS SURVEY REPORT

SUBMITTED TO: All Interested Survey Respondents

PREPARED BY:

Rick A. Sweitzer and Blake E. McCann Department of Biology, University of North Dakota Grand Forks, ND 58202 e-mail: [email protected] July 2007 Sweitzer & McCann • Wild Pig Natural Areas Survey Report

TABLE OF CONTENTS BACKGROUND AND INTRODUCTION ...... 1

METHODS ...... 5

RESULTS ...... 7 Wild Pig Presence and Issues ...... 7 Resource Damages and Visitor Interactions...... 10 Habitat Protection and Management to Control Wild Pig Populations ...... 12 Economic Costs of Managing Natural Areas with Wild Pigs...... 16

DISCUSSION...... 18 Presence and Trends for Wild Pigs in Natural Areas ...... 18 Resource Damage and Visitor Interactions with Wild Pigs...... 19 Economic Costs Incurred from Wild Pig Damage and Removal Efforts ...... 20 Natural Areas Using Lethal Control to Reduce Wild Pig Populations...... 22 Lethal Control Options ...... 23 Non-lethal Control Options ...... 26

MANAGEMENT IMPLICATIONS ...... 27

RECOMMENDATIONS...... 28 Course of Action for Mangers Facing Feral Pig Damage...... 28 Non-lethal Damage Control – Fence Design...... 29 Trapping and Trap Design ...... 30 Dispatching Trapped Animals ...... 33 Shooting Free-ranging Wild Pigs...... 34

ACKNOWLEDGMENTS ...... 36

LITERATURE CITED ...... 36

Sweitzer & McCann • Wild Pig Natural Areas Survey Report

NATURAL AREAS ECOLOGICAL DAMAGE AND ECONOMIC COSTS SURVEY REPORT

Abstract: Wild pigs (Sus scrofa) are a large ungulate native to Eurasia and North Africa which are now widely distributed as non-indigenous species in many areas, including California. Because of their adaptability to new environments, reproductive capabilities and foraging behaviors, wild pigs cause numerous damages to natural areas and wildlife throughout the state. To assess these damages we developed and distributed a survey to managers of all identifiable natural areas in California. Our objective was to identify ecological and monetary costs associated with managing natural areas within the current range of wild pigs. Surveys were mailed to 333 representatives of natural areas across California between mid December 2006 and early January 2007, and by July 2007 we had received information on 573 individual natural areas. Survey results indicated that wild pigs were present at 137 natural area units. Managers of most of these natural areas reported moderate to high concern regarding presence of wild pigs related to rooting and other disturbances in grassland, oak woodland areas and riparian habitats. Many visitors to natural areas with wild pigs commented to managers on rooting damage and negative interactions with wild pigs while hiking or camping, while others asked about hunting access. Some adjacent landowners wanted managers of natural areas with wild pigs to reduce pig numbers, whereas other nearby landowners were less bothered and likely benefited by enhanced hunting on their properties. A significant subset of the 137 natural areas with wild pigs reported using some combination of lethal and non-lethal methods to reduce damages from wild pigs. A key trend identified from the survey was that increased numbers of natural areas developed management programs to reduce wild pig damages in recent years compared to in the past. The overall minimum economic costs to all natural area management entities that reported wild pig-related management costs were $11,300,132 over the last 3 years and $18,672,023 overall. However, this was a conservative estimate because the majority of expenditures were associated with exclusion or removal of wild pigs, and not representative of damages incurred to the natural resources themselves. There is a need for reliable methods of assigning monetarily value to undisturbed natural areas and native plants and animals to provide a consistent economic presentation of actual resource damage caused by wild pigs. Non-lethal control methods, such as caging around seedlings, small-scale exclusionary fencing around sensitive habitats, and perimeter fencing, can provide protection to resources from wild pigs or be used to aid in lethal control efforts. Lethal techniques ranging from trapping/shooting programs to aerial shooting and “Judas” animals were used for wild pig removal by managers of natural areas, representing all of the current primary options for wild pig population reduction. Detailed descriptions of how these different techniques can be applied are provided. Management of wild pigs in California will continue to be difficult and controversial in the future. Consensus will need to be reached on how to effectively manage a large, widespread population of wild pigs as a game species while achieving a more appropriate balance with the need to preserve and maintain California’s unique and diverse natural resources.

Sweitzer & McCann • Wild Pig Natural Areas Survey Report

BACKGROUND AND INTRODUCTION Feral pigs (Sus scrofa) are a large ungulate native to Eurasia and North Africa which are now widely distributed as wild animals in many areas, including California. Feral pigs (designated “wild pigs” in California) were initially established in coastal regions during the Spanish colonial period and remained regionally localized around original points of introduction for hundreds of years. However, significant range expansion has occurred since the 1950s by a combination of numerous additional releases of domestic and wild swine and natural dispersal from points of introduction (Figure 1; Waithman et al. 1999). The current distribution of wild pigs encompasses areas in parts of 47 of California’s 58 counties (Figure 2).

Figure 1. Estimated distribution of wild pigs in different counties in California during (a) 1965-67, (b) 1983-85, (c) 1992-94, and (d) in 2006-07 (current range). Distributions for the first three time periods were estimated from Annual Hunter Game Take Survey records (Waithman et al. 1999), whereas the current range was determined from from mapped positions of wild pigs that were killed by hunters (reported on wild pig tags) or removed under Depredation Permits.

Sweitzer & McCann • Wild Pig Natural Areas Survey Report

Figure 2. Estimated current distribution of wild pigs in California at the level of the county. Wild pigs are present in appreciable numbers in 47 of 58 counties in the state (small numbers may be present in 2-3 other counties). The distribution map was based on the mapped positions of wild pigs that were either killed by hunters (locations reported on wild pig tags) or removed on Depredation Permits during the period from 2004-06.

A basic wildlife habitat model (Mayer and Laudenslayer 1988) and our recent research indicates that wild pigs are most abundant in oak-dominated habitats in Central and North Coast regions of California, but they are expanding elsewhere. The distribution of wild pigs is closely associated with portions of six major floristic provinces/ecoregions where the combined presence of 8 native oak species and annual grasslands (hereafter oak woodlands) provide cover and forage (Figure 3). California’s oak woodlands provide watershed protection, public recreation and habitat and forage for over 3500 species of vertebrates and invertebrates (Garrison 1996, Pavlik et al. 1991). Regionally, this habitat type is of important conservation concern because of pressure from agricultural and urban development, recent spread of disease (Kelly and McPherson 2001), and limited or negligible regeneration in several key species (Bartolome et al. 1987). On a larger scale California’s oak woodlands are recognized as unique in North America (Rutledge et al. 2001) and one of the Earth’s 25 biodiversity hotspots (Myers et al. 2000). For these reasons, and because of the damaging effects of their presence and activities, biologists and managers of many natural areas are concerned for the presence of nonnative wild pigs in California oak woodlands.

Sweitzer & McCann • Wild Pig Natural Areas Survey Report

(a) (c)

(b)

Figure 3. Distributions of (a) 9 species of oaks (Quercus sp.) and (b) wild pigs in California. The combined distributions of oaks and wild pigs (panel c) illustrates the close association between wild pigs and oak woodland habitats in California. Data on the distributions of oaks were derived from the California Wildlife Habitat Relationships database, whereas the range for wild pigs was based on the locations of approximately 69,900 hunter harvested wild pigs identified within U.S.G.S. 7.5-min maps.

Wild pigs are generalized omnivores which have been implicated in the decline or extinction of many different species (Green 1981, Campbell and Rudge 1984, Cuthbert 2002). Rooting and foraging activities by wild pigs can impact natural areas by (1) reducing cover of herbaceous plants and shrubs (Bruinderink and Hazebroek 1996, Welander 2000), (2) damaging tree seedlings and limiting Formerly damaged oak seedling resprouting in tree regeneration (deNevers and Goatcher 1990, Sweitzer and rooted area. Photograph: R. Sweitzer

Sweitzer & McCann • Wild Pig Natural Areas Survey Report Van Vuren 2002), (3) altering competitive relations in plant communities and enhancing spread of invasive weeds (Votorov 1993, Kotanen 1995), (4) competition with native species for limited resources such as seed crops/mast (Focardi et al. 2000, Gomez et al. 2003), (5) direct consumption of a range of plants parts and vertebrate species (Loggins et al. 2002, Schley and Roper 2003). The presence of wild pigs may also alter food webs by providing native predators with alternative prey with cascading effects through multiple tropic levels (Roemer et al. 2001). Wild pigs are very adaptable animals with high reproductive potential and wide ecological tolerances (Lloyd et al. 1987, Mauget 1991), which makes them very difficult to eradicate except on small islands or in enclosed areas (Barrett et al. 1988, Katahira et al. 1993, Schuyler et al. 2002). Much research in Australia has evaluated and modeled control of wild pigs (Choquenot et al. 1996), indicating that an approximate 70% annual removal is needed to limit population expansion (Hone and Robards 1980). Unlike in Australia Adult sow with many piglets, Henry Coe State where wild pigs are managed as a pest species, wild Park. Photograph: R. Sweitzer pigs in California are managed as game mammals with sport hunting serving as the primary mechanism for widespread population control (Waithman 1995); depredation permits and memoranda of understanding (MOU) allow private landowners and state and national parks to remove or control wild pigs causing localized property or ecological damage (Updike and Waithman 1996). Waithman et al. (1999) suggested that combined sport hunting and permitted removals resulted in an approximate 40% annual offtake of the statewide population in the mid 1990s, which may have limited populations in some areas but not others. Because of the damaging effects that wild pigs have on native ecosystems and their continued range expansion into many new parts of California in recent years, wild pigs will be of increasing management concern in the future. In this study we used a mail-based survey to identify types of damages caused by wild pigs in natural areas in California to more fully understand the extent of economic costs and ecological threats posed by this nonnative mammal. We developed and distributed a survey to managers of all identifiable natural areas throughout the state. Our objective was to identify ecological and monetary costs associated with management, control,

Sweitzer & McCann • Wild Pig Natural Areas Survey Report restoration, and depredation by wild pigs in natural areas. This report provides a summary of the results from this research effort, which we are providing to all survey respondents indicating interest in receiving information on survey results.

METHODS The Natural Areas Ecological Damage and Economic Costs (NAEDEC) survey was based upon preliminary ideas and suggestions taken from the Adams et al. (2005) and Frederick (1998) surveys of wild pig damage in Texas and California, respectively. Our survey form began with background questions concerning the natural area, and followed with questions organized in four key areas: (1) presence and trends for wild pigs within the natural area, (2) occurrence of resource damage and visitor/user interactions with wild pigs, (3) background on methods being used to protect the natural area from activities of wild pigs, and (4) the economic costs incurred to repair habitats, facilities, and/or to reduce wild pig numbers. Respondents were asked to comment primarily on recent damages and costs associated with managing for wild pigs during the period 2003 – 2006.

We also requested an overall assessment of wild pig- related management costs for their individual unit for as long as those activities have been occurring. The NAEDEC survey form was sent during mid December 2006 and early January 2007. Recipients included managers and supervisory officials of California State Park Districts, University of California Davis Reserves, California National Forests, California National Parks and Monuments, California Demonstration State Forests, Audubon and other private preserves, reserves, and ranches, County Park Districts, recreation areas belonging to the U.S Army Corps of Engineers, California Army and Air Force bases with hunting programs, Bureau of Land Management Field Offices, tribal officials/chairpersons for all of the large (≥ 1000 acres) Native American Tribal Lands and Reservations, and large Land Trust areas within the boundaries of the state of California. Each survey packet contained a detailed cover letter, survey(s), and a pre-paid envelope for easy return of completed surveys. The cover letter explained that we were directing a

Sweitzer & McCann • Wild Pig Natural Areas Survey Report study to develop a statewide ecological and economic risk assessment for wild pigs in California and that the study was funded by the University of California Exotic/Invasive Pests and Diseases Research Program, a cooperative program involving UC Davis, UC Riverside and the U.S. Department of Agriculture. It also included UC Statewide Integrated Pest Management: brief background information on the introduction of wild Exotic/Invasive Pests & Disease Research pigs into California and their continued range expansion. The letter estimated that the survey would take approximately 30 minutes to complete and asked respondents to return it within 3-5 weeks. Some managers/supervisors that were surveyed were in charge of a number of natural areas varying in size and location, and it was likely that some areas would be exposed to wild pigs but others would not. In these cases we sent out multiple copies of the survey, which were designed so one survey form could be used to summarize the situation for several different natural areas, and suggested that a single survey form be used for groups of natural areas without wild pigs, and that another survey be used for groups of natural areas with wild pigs. We also informed managers that if they preferred to use one form for each location they could simply photocopy the form or contact us for additional copies. We explained that surveys had been addressed to the person our information suggested might be best qualified to complete it at the site, but that the survey should be completed by the most appropriate person in their organization, determined at their discretion. A short while after we mailed the Active link – UC EIPM “In the News” January 20, 2007 survey forms, the funding http://www.ipm.ucdavis.edu/NEWS/wildpigs-news.html organization, the University of California/USDA Exotic/Invasive Pests and Diseases Research Program, posted a news release on

Sweitzer & McCann • Wild Pig Natural Areas Survey Report the study on a specific web site. This provided an internet link where respondents could find more details on the study, including some of the research findings thus far. We allowed a period of at least 1.5 months after surveys were mailed for respondents to reply before reminder notices were generated. A series of two reminder notices were distributed during winter/spring 2007. The first set of paper and electronic reminder letters were sent out in mid to late February 2007 to each person or natural area that had not yet responded. At this time we noted that a quick e-mail or phone message alerting us of the absence of wild pigs in the area would suffice. A final set of e-mail reminder letters were sent during March 2007 to those who had still not responded. Returned survey data were recorded in a database for summarization and analysis, and paper copies were archived.

RESULTS Wild Pig Presence and Issues Surveys were mailed to 333 representatives of natural areas across California between mid December 2006 and early January 2007.

Response rates varied from 20% to Large group of 20+ wild pigs foraging at a camera 100% for 12 different natural area station bait site. Photograph: R. Sweitzer management entities. Survey information was received on 573 different individual natural areas by July 2007. Wild pigs were reported present at 137 natural area units (Tables 1 and 2). Ninety- two percent of all natural areas reporting presence of wild pigs were moderately to highly concerned by this situation. When natural area units were grouped based on similar management missions/approaches, over 80% of all units in each group except Army Corp of Engineers recreation areas/military bases reported moderate to high concern for wild pig presence (Figure 4). Landowners with properties immediately adjacent to natural areas with wild pigs expressed variable concerns to unit managers. Some adjacent landowners were concerned that wild pigs from these units were a source of damage to their properties and desired for the natural area management entity to lethally control their populations (Table 3). Other adjacent landowners were not concerned and viewed the nearby natural area as a source for wild pigs for hunting. Related to this, many natural areas with wild pigs (n = 91) reported receiving requests from the public to hunt

Sweitzer & McCann • Wild Pig Natural Areas Survey Report

Table 1. Summary of natural areas surveyed and responses to the presence of wild pigs.

No. Identified in No. Represented No. Reporting Surveyed unit types California in Survey Wild Pigs California State Park Districts State Parks 85 56 19 State Historic Parks 26a 19 1 State Beaches 32a 19 5 State Recreation Areas 39 27 4 State Reserves 17 11 5 Other and Uncategorized State properties 22 25 5 California County and Regional Park Districts Individual county/regional parks >109b 109 30 California State Forests Individual forests 6a 5 1 U.S.D.I. National Parks National Parks 8 5 3 National Monuments 5 6 1 National Historic Sites 5 2 0 National Recreation Areas 4 3 0 National Seashore and Preserves 3 2 0 USFWS Wildlife Refuge Complexes Individual Wildlife Refuge Units 39 33 2 University of California Reserves Individual Reserves 34 26 4 Private Preserves/Reserves/Land Trusts Individual Natural Areas 74 71 11 U.S.D.A. National Forests Forest Service Districts 68 59 14 Bureau of Land Management Field Offices Areas of Critical Environmental Concern 143 30 4 Other Special Areas >54b 54 22 U.S. Army Corps of Engineers Lake Sonoma/Warm Springs Dam 1 1 1 Hensley Lake/Hidden Dam 1 1 1 H. V. Eastman Lake/Buchanan Dam 1 1 1 Black Butte Lake 1 1 1 Federal Air Force/Army Bases Camp Roberts 1 1 1 Fort Hunter Liggett 1 1 1 Vandenberg Air Force Base 1 1 0 Other Installations 2 0 0 Indian Affairs Reservations Individual Tribal Lands 20 4 0

Totals: > 802b 573 137 a Natural areas < 0.81km2 and/or located in developed areas were removed from the survey list because of reduced likelihood of wild pig impacts to those areas, and to reduce the workload on respondents to facilitate better survey response. b There was difficulty determining the number of individual units for these categories in California.

Sweitzer & McCann • Wild Pig Natural Areas Survey Report

Table 2. Survey responses from natural area entities within California.

Natural area description/management Survey level within Surveys Survey Response entity management entity Sent responses rate

California State Parks State Park districts 31 24 77% County and Regional Parks Identifiable park districts 23 14 61% California State Forests Individual units 6 5 83% National Park System Individual units 20 16 80% National Wildlife Refuge System Refuges/refuge complexes 13 12 92% University of California Reserves Individual units 25 21 84% Private Preserves/Reserves/Land Trusts Identifiable entities 47 27 57% USDA Forest Service Forest Service districts 68 51 75% USDI Bureau of Land Management Field Offices 16 13 81% U.S. Army Corps of Engineers Individual properties 4 4 100% Federal Military Bases Individual bases 5 4 80% Native American Properties Individual Areas/Reservations 20 4 20%

Figure 4. Summary of responses to a survey question on how much concern natural area managers feel regarding the presence of wild pigs in their natural area units. Data are from natural areas reporting presence of wild pigs during the period 2003-2006. Natural areas were combined into five different groups based on the focus of management and whether or not hunting was a normal activity in the natural area.

wild pigs. Another 28 natural areas including all military bases and Army Corp of Engineer recreation areas, Forest Service and BLM lands, and a few private reserves responded that they already allowed hunting. Poaching likely occurred in 78 natural areas where wild pigs were

Sweitzer & McCann • Wild Pig Natural Areas Survey Report present. For natural area managers commenting in detail about poaching issues, 53% felt poaching compromised visitor safety, 22% thought poaching was not a major concern, 13% believed poaching helped control their wild pig populations, and 12% were concerned that poachers hindered their wild pig management activities and damaged unit property (Table 5).

Resource Damages and Visitor Interactions Three out of five natural area types reported having more negative than positive comments from visitors about the presence of wild pigs in units (Figure 5). Negative comment topics ranged from rooting damage (identified as a user complaint by 35% of unit managers), wallowing

Table 3. Natural Area Survey responses related to concerns/comments by visitors and adjacent landowners State, County, Public/State Private National Army Corp or Regional Reserves & Reserves and Forest, BLM and/or Parks and National Parks Land Trusts & Wildlife Military Questions Related to Public Use Forest (n = 70) (n=8) (n=11) Refuges (n=42) bases (n=6) Types of complaints/negative comments Rooting-related comments (anywhere) 43 4 7 2 1 Wallow-related comments 26 2 3 13 0 Caused damage to property in campgrounds/public use areas 18 0 0 0 0 Wild pigs in camp areas frightened/chased/approached 36 1 2 1 1 Other: Chased horses 2 Adjacent landowner comments/opinions on units with wild pigs No comments or opinions identified 22 3 5 17 3 Units wild pigs cause damage to their property 41 2 1 6 1 Would like us to control/reduce our wild pigs 26 2 2 8 0 Provides source population for huntable animals 24 2 4 21 3

(identified as a user complaint by 27% of unit managers), property damage (identified as a user complaint by 11% of unit managers), and frightening and approaching visitors and pets (identified as a user complaint by 27% of unit managers; Table 3). Army Corp Recreation Areas and military bases received the highest percentage of positive comments whereas visitors to state, county and regional parks relayed the highest percentage of negative comments (Figure 5). Rooted area in Mendocino National Forest. Photograph courtesy David Isle Natural area managers responsible for

Sweitzer & McCann • Wild Pig Natural Areas Survey Report units where wild pigs were reported as present during 2003-2006 were asked to identify (1) the types of damage caused by wild pigs, (2) patterns in where rooting was focused, and (3) any specific types of native plants, animals, or habitats affected by wild pigs within their individual units. Rooting was identified as a problem in 93% of all areas having wild pigs. Twenty nine percent of managers of natural area units with wild pigs indicated that rooting was focused around riparian areas (Figure 6). Twenty-six percent of units with wild pigs reported rooting in open grasslands, 24% noted rooting in oak woodland habitats, 11% reported rooting along margins of roads and trails, and 7% observed rooting in campgrounds and other public use areas (Figure 6).

Figure 5. Summary of responses to a survey question asking if natural area managers receive negative, positive, or both negative and positive comments from unit visitors about the presence of wild pigs in the area. Data are from natural areas reporting presence of wild pigs during the period 2003-2006. Natural areas were combined into five different groups based on the focus of management and whether or not hunting was a normal activity in the natural area.

Sweitzer & McCann • Wild Pig Natural Areas Survey Report

Figure 6. Summary of responses to a survey question asking about general patterns on where rooting disturbance occurs, or is focused in natural area units with wild pigs during the 2003-2006 survey period.

A wide array of biota was identified as threatened by wild pigs in natural areas with wild pigs during the survey period, including several species of oaks, many native grasses and forbs, multiple vertebrates within three different Classes, and some geophytes (Table 4). Notably, natural area managers identified 9 organisms of conservation concern (threatened, endangered or rare/uncommon in California).

Habitat Protection and Management to Control Wild Pig Populations We asked managers of natural areas reporting presence of wild pigs in their units a series of questions on how they were actively working to reduce damage/disturbances by wild pigs. Forty two percent of natural areas occupied by wild pigs had implemented an official policy for their management. Fifty-three percent of natural areas with wild pigs were undertaking active efforts to minimize habitat disturbance during the survey period. Among those natural areas with

Sweitzer & McCann • Wild Pig Natural Areas Survey Report

Table 4. Native plants and animals impacted by wild pigs within California natural areas. Native Organisms Number Reported Conservation Status Plants Native trees and shrubs Oaks in general (Quercus sp.) 26 Black oak (Quercus kelloggii) 2 Blue oak (Quercus douglasii) 3 Willows in general (Salix sp.) 2 California juniper (Juniperus californica) 1 Common manzanita (Arctostaphylos manzanita) 1 Rare/limited abundance

Native grasses and forbs Purple needlegrass (Nassella pulchra) 1 California oatgrass (Danthonia californica) 1

Native vascular plants Adobe lily (Fritillaria pluriflora) 1 Rare/limited abundance Bluedicks (Dichelostemma capitatum) 1 Brodeae sp. 2 Bulbs in general 18 California melica (Melica californica) 1 Cattails/bulrush 1 Contra Costa goldfields (Lasthenia conjugens) 1 Rare/limited abundance Diogenes' lantern (Calochortus amabilis) 1 Ithuriel's spear (Triteleia laxa) 1 Miniature (Lupinus bicolor) 1 Purple amole (Chlorogalum purpureum var. purpureum) 1 Rare/limited abundance San Francisco Popcorn flower (Plagiobothrys diffusus) 1 Threatened/endangered Scarlet fritillary (Fritillaria recurva) 1 Suisun thistle (Cirsium hydrophium var. hydrophilum) 1 Rare/limited abundance Wild radish (Raphanus sativus) 1 Yellow mariposa (Calochortus luteus) 1

Geophytes Lichens in general 17

Vertebrates Mammals 0 Acorn-eating/burrowing small mammals in general 2 Black tailed deer (Odocoileus hemionus) 1 Deer fawns 8 Deer mice (Peromyscus sp.) 1 Ground squirrels (Spermophilus sp.) 1 Harvest mice (Reithrodontomys sp.) 1 Moles (Scapanus sp.) 1 Pocket gopher (Thomomys sp.) 1 Tule elk (Cervus elaphus nannodes) 1 Voles (Microtus sp.) 1

Birds California quail (Callipepla californica) 4 California clapper rail (Rallus longirostris obsoletus) 1 Threatened/endangered

Amphibians Amphibians in general 2 Salamanders in general 2 California tiger salamander (Ambystoma californiense) 2 Conservation concern California red-legged frog (Rana aurora draytonii) 7 Conservation concern Pacific tree frog (Pseudacris regilla) 1

Sweitzer & McCann • Wild Pig Natural Areas Survey Report

Table 5. Natural Area Survey responses related to habitat protection and/or population control programs State, County, or Public/State Private Reserves National Forest, Army Corp Regional Parks and Reserves & National and Land Trusts BLM & Wildlife and/or Military Questions Related to Habitat Protection & Control Programs Forest N=(70) Parks n=(8) n=(11) Refuges n=(42) bases n=(6) Units reported having an official policy on wild pigs 48 1 1 7 1 Number with detailed wild pig management plans 13 1 3 0 2 Units reporting no official policy on wild pigs 22 3 9 33 5 Units actively managing to control or minimize disturbance 52 5 4 8 4 No, but developing a program/plan for this issue 2 0 1 3 0 Did in past but not currently 12 2 0 0 0 No, other issues a higher priority 2 2 5 31 2 Units using non-lethal efforts to reduce damages 30 2 2 12 0 Used fencing to protect habitats or resources 28 2 2 12 0 Other: Animal proof garbage cans 2 0 0 0 0 Number using lethal control to reduce damages 52 5 4 10 4 Unit personnel, opportunistic hunting or trapping 28 7 4 10 4 Hired outside contractor, hunting or trapping 41 1 0 1 1 Other: Sportsman’s hunting allowed 0 0 2 1 1 Details on lethal control efforts Control has been intensive or moderate 21 1 2 11 2 Control has been incidental or variable 40 4 2 11 2 Control has been done for more than 5 years 35 4 4 7 3 Control program was developed in last few years 19 1 1 1 1 Issues or other details on damage control efforts Goal of unit program is wild pig eradication 1 1 0 1 0 Plan long term population control (eradication not feasible) 17 1 3 0 2 Will likely conduct periodic control to reduce damages 33 1 2 8 0 Questions on hunting, poaching issues Public hunting is allowed 0 1 2 20 5 Hunting access has been requested by visitors 47 4 6 31 3 Poaching occurs but is not major issue 2 3 4 6 0 Poaching occurs and may compromise visitor safety 31 0 2 2 1 Poaching likely helps control our population 3 1 1 3 0 Other: Poachers hinder control efforts and damage property 8 1 0 0 0

Sweitzer & McCann • Wild Pig Natural Areas Survey Report

wild pigs that were not actively managing to protect resources during the 2003-2006 period, 22% reported previously managing to minimize wild pig disturbance, 10% were developing a management plan for the species, and 68% considered management of wild pigs of lower priority than other issues at their site (Table 5). Fifty five percent of natural areas

with wild pigs were using lethal control Group of wild pigs in trap, Pinnacles National Monument. to reduce damages, 34% used non-lethal Photograph: B. McCann methods (95% used fencing and 5% used pig-proof trash canisters) alone or in conjunction with lethal methods. The two most common methods managers were using for lethal control were trapping and hunting performed by unit personnel (reported used by 53% of unit managers with wild pigs), and trapping/hunting by outside contractors (reported used by 44% of unit managers with wild pigs). Sport hunting was used for management purposes on only 3% of natural areas attempting wild pig population control. Among natural area managers commenting on the intensity and duration of control/removal efforts, 39% reported maintaining moderate to intensive efforts, and 70% were engaged in long-term (>5 years) management programs (Table 5). Only three units had the goal of

wild pig eradication. Many natural Hardware cloth exclosures around planted oak seedlings, Joseph Grant County Park. Photograph: R. Sweitzer

Sweitzer & McCann • Wild Pig Natural Areas Survey Report

areas that were using long-term control to reduce damage by wild pigs (n = 23) commented that eradication was not feasible at their site, otherwise eradication would be preferable (Table 5).

Economic Costs of Managing Natural Areas with Wild Pigs Thirty one natural area units provided estimates of their costs for managing to reduce damage by wild pigs during the survey period and during all years that such activities were known to have been underway. Because of the large differential between management costs for wild pig eradication compared to management costs for non-lethal and lethal damage control, we reported management costs for these activities separately. The minimum wild pig-related damage and control costs incurred by different natural area management entities over the last 3 years were estimated at $1,054,131 (Table 6). Overall wild pig-related management cost for natural area management entities in California were around $2,235,132 (Table 6). Results indicated that management funds to reduce damages by this species were mostly directed towards lethal population control (Table 6). Significant management funds were also used to protect important habitats by fencing, and for repairing already damaged landscapes (Table 6). Further, a disproportionate level of funds that were spent to reduce damages by wild pigs (lethal + non- lethal) in recent years was by state, county, and regional parks or reserves/land trusts (Table 7). Although wild pig-related damage control costs identified for National Parks and Monuments appeared relatively small, several large-scale eradication programs were implemented and completed by the National Park Service at Pinnacles National Monument and Channel Islands National Park. Funds spent for complete eradication of wild pigs from Pinnacles National Monument and Santa Cruz and Santa Rosa Islands (Channel Islands National Park) exceeded $10,150,000 in 2003-2006 and $12,869,601 overall (Table 8). Also, the Catalina Island Conservancy spent over $3,400,000 to eradicate all but 1-2 wild pigs from Santa Catalina Island over a 14 year period from 1990 to 2003. The U.S. Navy completed the eradication of wild pigs from San Clemente Island by the mid 1990s, but we have been unable to acquire a cost estimate for this program. The combined economic costs to all natural area management entities for working to minimize damage by wild pigs through non-lethal methods, lethal control, or intensive eradication programs was estimated as a minimum of $11,300,132 over the last 3 years and $18,672,023 overall (Table 7).

Sweitzer & McCann • Wild Pig Natural Areas Survey Report

Table 6. Detailed summary of reported damage repair and management costs to natural areas by wild pigs in California during the survey period (2003-2006) and overall since pigs arrived on site.

2003-06 Overall

Units with Cost Units with Cost Type of expenditure or monetary loss costs estimates costs estimates Damage repair costs/activities Fencing/Habitat protection 31 $92,400 31 $187,700 Landscape/Restoration 27 $65,500 27 $65,500 Park facilities/Equipment 18 $23,000 18 $23,000 General repair 4 $10,600 11 $42,000 Wild pig population control Done by unit personnel only 10 $57,050 10 $210,850 Done by contractor ony 23 $513,081 23 $940,282 Done by unit personnel and contractor 17 $292,500 17 $292,500 General control costs not subdivided 9 $22,100 Damage or control costs non specific 22 $451,200 Totals: $1,054,131 $2,235,132

Table 7. Summary of wild pig-related management costs incurred by natural areas in California. Natural Area Unit/Area Type 2003-2006 Overall State Parks, Reserves, Forests $301,031 $533,732 County/Regional Parks & Land Trusts $681,700 $1,509,500 National Parks & Wildlife Refuges $6,800 $8,800 National Forests, BLM, Military Bases $36,000 $73,100 State & Private Reserves/Preserves $29,000 $110,000 NPS & Nature Conservancy Eradication Programs $9,444,601 $9,444,601 NPS Eradication Programs $736,000 $3,425,000 Private Organization Eradications (Santa Catalina) $65,000 $3,402,290 State Park Eradication Programs $165,000 Totals: $11,300,132 $18,672,023

Table 8. Summary of wild pig eradication programs on mainland California and the Channel Islands. Natural Area Name Duration of Project 2003-2006 Overall Pinnacles National Monument a 1987 - 2006 $736,000 $2,630,000 Santa Cruz Island a b 2004 - 2007 $9,444,601 $9,444,601 Santa Catalina Island a c 1990 - 2003 $65,000 $3,402,290 Santa Rosa Island d 1991 - 1993 $795,000 San Clemente Island e 1973 - 1990 Cost estimate not available Annadel State Park f 1985 - 1987 $165,000 Totals: $10,245,601 $16,271,891 a Information gained through the NADEC survey. b Information from NADEC survey, and Morrison et al. (2007). c Adapted from Schuyler et al. (2002), and Schulyer (personal communication). d Modified from Lombardo and Faulkner (2000), and Faulkner (personal communication). e We have contacted the U.S. Navy and are still attempting to gain information on this eradication program. f Adapted from Barret et al. (1988), and Barrett (personal communication).

Sweitzer & McCann • Wild Pig Natural Areas Survey Report

DISCUSSION We received well over 250 responses to our Thank You for Completing the Survey and Contributing NADEC Survey in the period from January 2007 to April Information for This Study!!

2007. Most responses were by U.S. mail and e-mail, but many individuals also contacted us directly by telephone. Survey responses were thorough, and it was evident that there is a great deal of interest in the situation with wild pigs in California natural areas. Many survey respondents expressed concern over the types of ecological disturbances induced by wild pigs, but others relayed comments on the recreational value/interest in

wild pigs for hunting. However, it was clear that the presence of wild pigs in natural areas is viewed primarily as a negative situation. Considering the current management of wild pigs as a big game mammal in California, their continued range expansion across private and public lands, and conflicting public views on lethal control and hunting activities, wild pig presence in natural areas is becoming an ever increasing and complicated management problem.

Presence and Trends for Wild Pigs within Natural Areas Although only a quarter of units that responded indicated wild pig presence within their natural area, this nonnative animal is well distributed throughout the state over a large portion of the California landscape. Additionally, moderate to high concern occurring among the majority of surveyed units with wild pigs indicates that they are of considerable management importance across a variety of management area types. However, managers were more concerned about the presence of wild pigs in natural areas that were focused on preservation, conservation, and nonconsumptive uses of natural resources (Figure 4). Managers of natural areas Sign posted on southwest boundary of Pacheco State Park. Photograph: R. Sweitzer

Sweitzer & McCann • Wild Pig Natural Areas Survey Report

where hunting would typically be allowed (BLM, U.S. Forest Service, wildlife refuges, etc.) were less concerned about the presence of wild pigs, very likely because visitors/users of those areas were more interested in sport hunting than visitors to other types of natural areas. Wild pigs were also of varying importance to neighboring land owners. Although adjacent landowners typically viewed wild pigs as damaging and would like to see their populations controlled, a considerable number viewed wild pigs positively as providing hunting opportunities. Poaching was a concern with respect to wild pig impacts on visitor safety in natural areas. However, it is unclear if wild pig presence was causing the poaching to occur, and therefore endangering visitors, or if an equal amount of poaching of other species would happen regardless. Reduced safety is a difficult category to quantify, but the potential apparently exists for this type of interaction to occur. Additionally, it is notable that poaching was most prevalent on state administered lands that do not typically allow hunting, and where sportsmen requested to hunt wild pigs (Table 5.). This exemplifies a direct relationship between desired access and illegal access attempts on restricted areas for hunting purposes and further exemplifies the impacts that wild pigs have on varying types of management units.

Resource Damage and Visitor Interactions with Wild Pigs As identified by survey respondents, numerous native plants and animals are at risk by exposure to wild pigs in many natural areas throughout California. It is well documented that wild pigs consume a wide variety of plant and animal biomass as part of their diet (Schley and Roper 2003). Negative impacts of wild pigs on native organisms can result by pigs directly consuming plants and animals, but also by competition for limited resources. Another part of this study has identified over 550 species of vertebrates and

at least 600 rare/uncommon plants that are exposed to wild Hiking trail, Big Basin State Park. Photo pigs by distributional overlaps. The plants and animals listed credit: Martin Beebee from internet in Table 4, however, highlight those that are on the forefront of current management activities in California natural areas today. Trends in negative versus positive views toward wild pigs were evident among natural area

Sweitzer & McCann • Wild Pig Natural Areas Survey Report types (Figure 5). Users of state, national, and regional parks were more likely to register complaints about wild pigs than visitors to National Forests, BLM lands, etc. (Figure 5). We believe that this finding is linked primarily to resource management priorities of different types of natural areas (preservation versus consumptive/sustainable use) and somewhat divergent interests of visitors recreating at different types of natural areas. Conversely, a variety of rooting damage was reported as a problem in most areas with wild pigs (Figure 6). Thus, wild pigs are damaging nearly all areas they occupy but the benefit of having them for recreational purposes (sport hunting) may outweigh their disturbance effects in some management area types (BLM and National Forests). This variable view of wild pigs as both a positive and negative part of the California landscape underlies the enduring conflict over how wild pigs should be managed.

Economic Costs Incurred from Wild Pig Damage and Removal Efforts To our knowledge this is the first study that has attempted to develop a minimum cost estimate for the efforts underway by different land management entities in California to reduce or repair ecological disturbances caused by nonnative wild pigs. Importantly, we consider the management cost values identified by the NADEC Survey to be a minimum, because (1) Wild pig rooting on a California hillside. we were unable to determine management costs Photograph: Rick Sweitzer for several natural areas where we know wild pig population control has occurred, and (2) it is very difficult to assess a cost value to many types of natural resource damage. Related to point 2, units reporting costs typically reported control costs while further indicating they could not assign a dollar value to rooting and other types of wild pig disturbances. As such, the lack of significant monetary damages for some natural area management entities is representative of a lack of management-based population control programs (other than public hunting), but not a lack of economically important resource damage. Considerable monetary funds were expended to manage wild pigs in California in recent years. This comes at a major cost to taxpayers and takes a large bite out of resource management budgets. Although wild pigs are managed as a big game species in the state, it is unlikely that

Sweitzer & McCann • Wild Pig Natural Areas Survey Report revenues from hunting tag sales outweigh the overall costs of natural resource damages or active control operations against wild pigs in natural areas. For example, during the 4 year survey period (2003 – 2006) $2,755,847 were generated from the sale of wild pig hunting tags (http://www.dfg.ca.gov/licensing/statistics/statistics.html; accessed August 2, 2007) (Table 9). However, the total cost of wild pig control and eradication projects in mainland California and for the Channel Islands far exceeded this amount during the same time period (Table 7).

Table 9. Summary of wild pig tag sales revenues during the period July 1, 2000 - June 30, 2006.

Resident tag Non-resident Tag/booklet Total Period value a b tag value sales b c revenues July 1, 1992 to June 30, 1993 $7.50 $10.00 31395 $236,073 July 1, 1993 to June 30, 1994 $7.50 $10.50 35652 $268,620 July 1, 1994 to June 30, 1995 $7.50 $10.50 35983 $271,388 July 1, 1995 to June 30, 1996 $7.50 $10.75 36963 $279,401 July 1, 1996 to June 30, 1997 $7.50 $11.00 34634 $262,839 July 1, 1997 to June 30, 1998 $7.50 $11.50 36146 $275,180 July 1, 1998 to June 30, 1999 $7.50 $11.75 41369 $315,955 July 1, 1999 to June 30, 2000 $7.50 $12.00 43149 $331,407 July 1, 2000 to June 30, 2001 $7.50 $12.25 44653 $343,986 July 1, 2001 to June 30, 2002 $7.50 $12.75 48582 $375,464 July 1, 2002 to June 30, 2003 $8.75 $13.25 47037 $421,892 July 1, 2003 to June 30, 2004 $8.75 $13.25 45533 $407,878 July 1, 2004 - June 30, 2005 $15.00 $50.00 46820 $745,000 July 1, 2005 - June 30, 2006 $15.25 $50.75 48702 $788,820 July 1, 2006 - June 30, 2007 $16.00 $53.25 48328 $814,149 a Wild pig tags were sold as a booklet of 5 tags to California residents during the period July 1, 1992 - June 30, 2003, and individually thereafter. b Tag values are based on sales revenue returned to the state minus licensed vendor proceeds. c Lifetime hunting license pig tags were excluded from sales and monetary values because they were issued as part of a comprehensive permit which includes other species.

Additionally, as discussed above, the majority of costs that were reported were incurred from management for reduction of wild pig numbers and construction and maintenance of exclusionary fencing. Therefore, true costs of damages to natural resources were largely underestimated, although expenditures to protect these areas are a good indication of perceived value. Moreover, the cost analysis listed here does not take into account damages to agricultural products and agricultural infrastructure. Frederick (1998) surveyed California County Agricultural Commissioners regarding wild pigs, and estimated pig-related damage to agriculture of around $1.7 million for 1996. As part of this study, we sent a Wild Pig Agricultural Damage Survey to all

Sweitzer & McCann • Wild Pig Natural Areas Survey Report

County Agricultural Commissioners and compiled damage reports for wild pigs from USDA Wildlife Services. Based on our Agricultural Damage Survey work, agricultural producers and businesses experienced around $1.2 million damage from wild pigs in 2006 (Sweitzer draft unpublished report). However, nonnative wild pigs are not viewed negatively by all constituent groups. For example, some landowners in California utilize wild pigs for economic gain through paid sport hunting activities on their properties (Fitzhugh and Loomis 1993, Work 1993).

Natural Areas Using Lethal Control to Reduce Wild Pig Populations Active efforts by managers to reduce damage by wild pigs at over 40% of natural areas with wild pigs emphasizes their importance. The expense of lethal control operations is often a limiting factor, and may explain the more common practice of using internal resources to reduce wild pig numbers, as opposed to contracting with an external entity. Additionally, the use of fence to protect Happy wild pig hunters, Santa Catalina Island. resources by nearly a third of natural areas indicates Photograph: G. Bennett a desire to invest in more long-term abatement practices to protect resources where possible. This trend is also identified by the dedication of resources to long-term management plans and intense population reduction programs. However, in some places wild pigs were just not a priority or their presence was considered of lesser concern than other management issues. Lethal control was used by the majority of natural areas actively managing against wild pigs. It is not surprising that trapping was a primary method, as where effective it can be employed with high efficiency. However, intensive control to maintain low wild pig populations in habitats that provide abundant cover and forage can become exceedingly expensive, as trap efficiency may be reduced and other less cost-effective methods, such as shooting and hunting with dogs, must then be employed to significantly reduce wild pig numbers (Schuyler et al. 2002). The conservative view of managers toward the possibility of eradication is understandable considering the intensity of removal efforts required to cause eradication and difficulty in isolating populations for focused removal in many mainland locations (Barrett et al. 1988).

Sweitzer & McCann • Wild Pig Natural Areas Survey Report

Lethal Control Options: In general, lethal methods of wild pig control include trapping, professional hunting/shooting, aerial shooting, trailing dogs, the use of “Judas animals”, recreational hunting, poisoning, and snaring. Poisoning and snaring are not generally acceptable techniques in California natural areas because of ethical considerations and non-target animal destruction, but they have been used with varying success elsewhere (Coblentz and Baber 1987, Katahira et al. 1993, Cruz et al. 2005). Trapping has proven to be a successful method of wild pig removal on the California mainland and Channel Islands (Barrett et al. 1988, Schuyler et al. 2002, Sweitzer et al. 1997a). Traps work well in a variety of habitats, but are limited in effectiveness by seasonal variations in forage availability in relationship to bait acceptance (Barrett et al. 1988, Coblentz and Baber 1987). However, this limitation can sometimes be overcome by offering bait over time to allow wild pigs to find bait and select it over natural forage (Saunders et al. 1993). The primary advantage of traps is cost-effectiveness. The initial costs of constructing traps can be considerable (depending on the design and number of traps that are made), but once traps are in place and set, they can work 24 hrs/day with little relative effort for personnel operating traps. Therefore, where wild pigs are plentiful and readily accept bait, large numbers of animals can be removed very efficiently. However, varying rates of trap success can be expected across the California landscape and it has been indicated that not all pigs can be trapped within a population (Barrett 1978, Saunders et al. 1993).

Corral trap with group of “piney wood rooters,” Santa Catalina Island. Photograph: Institute for Wildlife Studies

Hunting and shooting techniques can be used to remove significant numbers of wild pigs from a population where employed intensively (Coblentz and Baber 1987, Schuyler et at. 2002). However, when shooting is on an opportunistic basis or employed incidentally it is far less likely

Sweitzer & McCann • Wild Pig Natural Areas Survey Report

to have an impact on wild pig numbers. Hunting/shooting requires active searching for pigs in the environment, is more labor intensive and can be far less efficient than techniques such as trapping. It is also increasingly less efficient in denser habitat types (Coblentz and Baber 1987). However, a concentrated effort at hunting of wild pigs will contribute to overall control or eradication effectiveness by removing animals

Wild pig removed during eradication program, that are less susceptible to other techniques. Santa Catalina Island. Photo: T. Manuwal Aerial shooting has been used extensively for wild pig eradication programs in California and elsewhere (Choquenot et al. 1996, Schuyler et al. 2002, Morrison et al. 2007). Shooting from an aerial platform can be used to quickly and effectively reduce a wild pig population (Saunders 1993). Helicopter operations require a considerable amount of expertise and can be costly, although cost-per-pig estimates are competitive with other methods of control. However, there is a threshold wild pig density where helicopter shooting becomes exponentially less effective (Choquenot et al. 1999). Otherwise the greatest limitation to this technique is linked to relative density of vegetation at removal sites, and the fact animals can become habituated to the sound of an approaching helicopter and learn to seek cover, making observation and subsequent removal difficult. Last, this is a high profile technique that is more likely to draw public attention to removal activities than most other methods. Trained hunting dogs can be an effective means of wild pig removal, and have been used successfully for wild pig removal in California (Barrett et al. 1988, Schuyler et al 2002). However, dogs tend to be more effective at catching individuals than at dealing with groups of wild pigs (Caley and Ottley 1995), and dog-aided hunting is

generally not considered effective as a primary Hunting team with trained hunting dogs, Pinnacles National Monument. Photograph: B. McCann method for large scale reductions in populations (McIlroy and Saillard 1989). Therefore, while an effective means of wild pig detection and removal, dogs are most useful when employed to find residual animals left after other techniques

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have significantly reduced pig numbers, or where other techniques fail to be effective (Caley and Ottley 1995). Other considerations are non-target species interaction with dogs and impacts on visitor use. Additionally, a considerable amount of cost and effort is required both in care and upkeep of dogs and kennel facilities. The Judas pig technique requires capturing wild pigs, fitting them with radio-telemetry collars and releasing them into a control area. Once the Judas pigs begin associating with resident groups of wild pigs they are radio-located and non-collared wild pigs with them are shot. This process of locating Judas pigs and shooting associating animals is repeated until no further un- collared wild pigs are detected by Judas animals, at which point the Judas pigs themselves are removed. Judas pigs are primarily used for eradication purposes when populations are at low density to remove residual animals (McIlroy and Gifford 1997, Wilcox et al. 2004). They are not generally used for large scale and rapid reduction in wild pig numbers. This technique is primarily limited by the ability to observe collared animals and associates. Therefore, access to the removal area and a relatively open habitat type can aid in the success of this technique. Additionally, relatively expensive equipment and operational skill are required. Recreational or sport hunting as a primary means of pig control/removal has a number of possible advantages and disadvantages. The primary advantages are that it is potentially inexpensive and that carcasses will be removed from the site. Disadvantages include (1) heavy hunting pressure is necessary to cause a significant population decline (Hone and Robards 1980), (2) it may interfere with non-hunting recreational use of the natural area, (3) hunting access would require changes of policy for some natural area types, (4) safety of visitors could be compromised, and (5) viewing of native wildlife could be decreased because of perceived hunting pressure. Also, and in California, it remains unclear whether the achieved harvest rate has been sufficient to prevent the species from continuing to spread (Waithman et al. 1999, Sweitzer Unpublished data). The primary removal methods employed among surveyed natural areas were trapping and hunting by unit personnel and contractors; dogs and sport hunting were used to a far lesser extent. Costs of control by unit personnel during the survey period were $258,550, whereas costs derived from outside contractors during the same period were $1,234,081. For natural areas reporting costs and numbers of pigs removed (n = 22), unit personnel removed 579 wild pigs, outside contractors removed 1038 wild pigs, and areas combining efforts by unit personnel and outside contractors removed 1259 wild pigs during the last 2 years. These numbers do not provide a complete view of

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effectiveness and cost differences between in-house operations and contracted projects, but some inferences can be made. The involvement of contracted professionals results in the removal of more wild pigs, but contract removals come at a higher price. There are obvious advantages to using unit personnel but some limitations do apply. For example, unit personnel (1) must take on wild pig removal responsibilities in addition to or instead of other duties, (2) may not have the experience base or desire to dispatch trapped animals or effectively hunt free-ranging wild pigs, (3) need to become qualified to use firearms and be able to store them on site, (4) must deal with carcass disposal, and (5) are culpable as representatives of respective agencies for ethical concerns about the destruction of animal life. Non-lethal Control Options: Several non-lethal approaches have been employed or suggested for reduction of wild pig damage to natural areas, public use areas and agricultural resources. These include caging around seedlings, small-

scale exclusionary fencing around Fence exclosure protecting meadow habitat at Austin Creek State Recreation Area from wild pigs. Notice two black-tailed sensitive habitats (such as springs, streams Deer foraging inside the exclosure. Photograph: R. Sweitzer and ponds) or crops, perimeter fencing, animal proof containers, use of chemosterilants, and relocation of wild pigs. The most common approach is fencing for exclusion of wild pigs from entire parks or smaller areas encompassing sensitive microhabitats or individual plants. These methods have proven effective in a number of locations throughout California (Barrett et al. 1988, Didion and Lunsford 1993, Peart et al. 1994). Our survey revealed that approximately one third of surveyed areas were using fence to protect trees and/or habitats or to facilitate eradication projects and that two areas used animal proof garbage cans in campgrounds to prevent habituated pigs from accessing waste. Chemosterilants are currently thought to be impractical for most control programs because of technical problems with the approach (Miller et al. 1998, USDI, National Park Service, Pointe Reyes National Seashore Non-Native Deer Management Plan, Final Environmental Impact Statement, July 2006). Additionally, with this technique wild pigs would remain on site and continue to damage resources until their natural death. Relocation of wild pigs to other areas within California is not an acceptable option because of concerns about spread of disease.

Sweitzer & McCann • Wild Pig Natural Areas Survey Report

Protection of individual plants or habitats in surveyed natural areas ranged from $800 – $15,000 in fence material and $400 – $50,000 in personnel costs for establishment and maintenance of fences. It should be noted that the high range figures listed above refer to management practices at 16 county parks encompassing >160km2. Regardless, protection of small areas can be a relatively inexpensive management practice. Large- scale fencing projects, on the other hand, are more costly. On Santa Cruz Island 44km of fence were constructed at a cost of $1,224,001, equaling $28,169 per km of fence. However, fencing costs reported for eradication programs like the ones on Santa Cruz Island, Pinnacles National Monument, and Santa Catalina Island include both initial installation and subsequent monitoring and maintenance. For example, costs for construction and maintenance of fence at Perimeter wild pig fence at Pinnacles National Monument. Pinnacles National Monument from the mid Notice wild pig rooting on the left side of the fence, but lack of rooting on the right. Photograph: R. Saulino 1980s until present was estimated at $2,000,000 for 39km of fence, equaling $51,282 per km. Both examples are of very large fencing operations, but wear and tear of fence materials and damage from animals and weather events should be similar regardless of fence size. Therefore, managers intending to use perimeter fences to exclude wild pigs from natural areas could expect to pay $25,000 – $55,000 per km including installation and maintenance costs over a 20-year period.

MANAGEMENT IMPLICATIONS Statewide eradication is not currently feasible and possibly not desirable by all management agencies and members of the public. However, localized eradication and population control will likely continue and become a standard management practice in the future. For example, some 30% of areas commenting on the duration of wild pig control efforts reported that

Sweitzer & McCann • Wild Pig Natural Areas Survey Report

their program was developed in the last five years, indicating an increased awareness of resource damage issues with wild pigs (Table 5.). About one half of the natural areas with wild pigs were managing damages by lethal control. Based on survey responses, most other natural area managers with wild pigs plan to develop management programs and reduce wild pig numbers in their units during the next few years. Regardless of land use and resource goals, managers of the future will face the following questions: 1. What is a sustainable statewide population of wild pigs? 2. What is the threshold where wild pigs cause sufficient damage in natural areas to warrant active control through fencing or population reduction? 3. Can California management agencies reach consensus on a reasonable balance between the need to protect unique and highly valued natural resources with continuing hunting opportunities for wild pigs?

RECOMMENDATIONS We know that wild pigs can negatively impact natural processes, especially where they occur at high density, but monetary values are not easily reported for natural resources. However, an economic standpoint may be the only way to prompt large-scale action for the management of wild pigs. A process for monetarily valuing undeveloped land as a natural resource should be developed to provide a better presentation of the damages caused by wild pigs to natural areas in addition to expenditures for control operations. Otherwise, wild pig damage will continue to be undervalued and a clear view of their impact to California’s natural areas will not be possible. Additionally, a comprehensive reporting process should be developed for managers of natural areas to promote accurate recordkeeping of damages on a yearly basis. Frederick (1998) suggested a similar recordkeeping process for damage to agriculture in California. If both were implemented, they would provide trend information that could be useful in tracking changes within natural resource units and on a regional basis, including private landowners, to focus statewide and local management actions.

Course of Action for Managers Facing Feral Pig Damage Wild pig control in California’s natural areas, and reduction in wild pig damage, can be achieved with dedicated efforts by managers employing proven methods, such as exclusionary fencing, trapping and shooting. Many methods can be employed at moderate costs by unit

Sweitzer & McCann • Wild Pig Natural Areas Survey Report

personnel with good results. However, more intensive control/exclusion efforts may be necessary, depending on the goals of the natural area and acceptable levels of wild pig presence. Wild pigs are legally defined as game mammals in the state of California. Because of this there are a variety of restrictions and controls on their management on public and private lands. However, there are provisions (See California Fish and Game Code Section 4181, 4181.1; http://www.dfg.ca.gov/hunting/pig/regs.htm) that allow the taking of wild pigs causing damage to private property with a depredation permit issued by the California Department of Fish and Game. Likewise, wild pigs can be removed on public lands by establishing a permit agreement, or Memoranda of Understanding (MOU), with the Department of Fish and Game. This process is generally straightforward; because of continued expansion by wild pigs and negative impacts of wild pigs on both private and public lands, permitting for wild pig removal and restrictions on the numbers of wild pigs that can be removed are now much more liberal than in the 1990s. Nevertheless, obtaining the appropriate permits for lethal control of wild pigs in managed natural areas will require documentation of damages. Managers should develop and maintain photograph records of rooting and other disturbances by wild pigs (include reference objects in photographs for scale). Also, written records of the number of incidences of rooting and the extent of rooting in different areas will be useful. We also encourage development of formal wild pig management plans, which may help generate internal funds when wild pig management has been identified as an important priority for resource protection in natural area units.

Non-lethal Damage Control – Fence Design Fencing has been used successfully in many locations to exclude wild pigs from sensitive resources (such as rare habitats or crops), and to cordon off or isolate populations of wild pigs for eradication purposes (Barrett et al. 1988, Katahira et al. 1993, Schuyler et al. 2002, Morrison et al.

2007). Hone and Atkinson (1983) tested 8 variations of a Photograph: R. Sweitzer tensioned fence design (including electrified elements) against wild pigs. They found that a “netting design” or mesh design was necessary to fully prevent wild pigs from penetrating the fence barrier. Indeed, it is this type of non-electrified fence which has most commonly been employed during eradication programs in California (Barrett et al. 1988, Schuyler et al. 2002).

Sweitzer & McCann • Wild Pig Natural Areas Survey Report

A “pig-proof” fence can be constructed as follows (based upon a proven fence design at Pinnacles National Monument, California). Woven wire mesh (not larger than 15.24-cm squares) should be strung to a height of 66 cm with strands of barbed wire strung directly along the top and bottom of the woven wire, and two additional strands 10 and 40 cm above the woven wire. This will create a fence with a total height of approximately 110 cm. Fencing material should be fastened to sturdy metal fence posts at 2.4 m intervals and secured to the ground mid-way between fence posts with an

anchoring device (for example, a spade-type Example photograph of mesh style pig exclusion fence anchor affixed to steel cable or small diameter Photograph: R. Saulino

rebar bent in a U shape). Bracing structures can be built with metal or treated wood posts and spaced at straight stretch panel distances of no more than 50 m. All anchors, fence posts, and bracing structures should be set to a depth of 0.6 m. Brush should be cleared from the fence and nearby areas to facilitate access for repairs and detection of damage. To ensure

fence integrity, the entire fence must be hiked Photograph of hole excavated by wild pigs to move through a fence. Post segments inserted to prevent as often as possible, or no less than once a wild pig entrance. Photograph: G Wiscomb month and after any significant storm event. Whenever damage is detected repairs must be completed quickly. Gates through the fence must be secured at all times and all users must cooperate to ensure that this is the case. Additionally, cattle guards can be used to maintain open roadways through pig fence. See also Barrett et al. (1988) and Schuyler et al. (2002) for descriptions of fencing used for wild pig exclusion.

Trapping and Trap Design A number of trap designs have been developed for capture of feral pigs including box traps, corral traps (many different design configurations; Sweitzer et al. 1997) and panel traps. Common

Sweitzer & McCann • Wild Pig Natural Areas Survey Report

designs include swinging or guillotine-style doors mated to box or corral-style trap bodies. Triggering devices range from mechanical pressure plates and spring-loaded door mechanisms that are tripped by the weight of the animal to simple designs involving a stick holding the door and a string attached to a bait bucket. Regardless, a variety of mechanisms can be used with success. The primary advantage of box traps is that they are small and can be transported easily,

Trap Design and Photo by R. Kelly

Photographs of four different wild pig trap designs; illustrates the diversity of traps for capturing wild pigs

and that box traps limit the space that wild pigs can run to charge the sides of the trap, resulting in less wear and tear on trap materials. However, large groups of animals can be captured per setting in corral style traps (see photograph page 23, and Sweitzer et al. 2007a). Nevertheless, assembling corral traps in the field can be time consuming, and less conducive to rapidly moving traps from one active bait site to another. A good intermediate choice is the panelized corral trap (below),

Sweitzer & McCann • Wild Pig Natural Areas Survey Report

which can be designed to be easily disassembled for transport and rapid reassembly among multiple trap locations. In all cases the best design is the simplest, but with the important consideration that any wild pig trap will need to be built using durable materials capable of withstanding the efforts of enclosed wild pigs to escape. Trapping is most efficient during lean times of the year when natural forage is at a minimum (Choquenot and Lukins 1996, Sweitzer et al 2007a). Therefore, seasonal variations in bait acceptance will occur. Traps should be placed near natural travel corridors, or where wild pig sign Example photograph of a panelized corral trap. has been commonly or recently observed Photo: B. McCann (Saunders et al. 1993). They should be pre-baited with the door locked open (so pigs can enter and leave freely) for 1 week prior to being set, and bait should be checked daily and replenished as necessary. When pre-baiting, place a pile of bait (10 – 20 kg) inside the trap and run lines of bait from the trap to nearby game trails or patches of recent sign. A variety of baits will work on wild pigs, and everyone has their special formula, but we have found that plain old corn or corn-based commercial pig pellets work consistently well. Whole corn or cracked corn can be soaked in a large plastic bin (trash can) for several days (slightly fermented), which will increase bait volume, and impart an attractive smell to lure wild pigs to bait sites. Commercial pig pellets have the added advantage of being earth-colored, and therefore less conspicuous than kernels of corn to non-target avian species that consume bait. However, pig pellets tend to disintegrate in moist environments. Once wild pigs are readily accepting bait and frequently visiting traps (denoted by regular consumption of bait and wild pig sign in and around traps) the traps should be set. In hot and arid parts of California it is best to set traps in the evening and check them early in the morning to prevent exposing trapped animals to elevated mid-day temperatures without access to water (Sweitzer et al. 2007b). It is also a good idea to ensure that traps are placed in shaded secluded locations to prevent trapped animals from overheating and to prevent members of the public from

Sweitzer & McCann • Wild Pig Natural Areas Survey Report viewing and/or harassing trapped animals. Also, even though wild pigs captured in control programs will be dispatched for removal, all methods used must be humane and designed to minimize pain and suffering experienced by the animals. Depending on management goals a trapping program can be instituted in a variety of ways. If moderate reduction or control of a population is the goal, then traps should be pre-baited and operated (as described above) until they cease to capture wild pigs. After which time personnel can enter into an Wild pigs are intelligent mammals with a well organized social structure (female-based matrilineal groups). Humane methods inactive management phase until must be used in control programs to reduce animal pain and unacceptable amounts of damage suffering. Photograph: J. Johnson occurs again, and the baiting/trapping cycle starts once more. In the case of intensive control or eradication traps can be operated even in the absence of sign on the chance that a marauding wild pig will be trapped. Of course, a full range of trapping strategies can be developed to achieve intermediate levels of wild pig control. However, in instances where intensive control or eradication is the goal additional methods will likely be necessary to significantly reduce wild pig numbers to desired levels. Dispatching Trapped Animals: Trapped wild pigs should be dispatched with a single well- placed shot to the crania with a handgun or rifle (chambered in a low-velocity cartridge). It is important to ensure the safety of all personnel involved. Therefore, the person with the firearm should be in charge of the scene, and all other personnel should remain behind the shooter. Oftentimes multiple pigs are captured in a single trap and begin jumping and charging at the trap sides when shots are fired. Although this complicates the process and increases the stress of the situation (for man and pig alike) it is important to remain calm and make the most accurate shots possible to humanely euthanize all trapped pigs. We recommend resting the barrel of the firearm on or through the mesh on the side of the trap and picking a location to engage the pigs, rather than attempting to follow each pig around the trap. Look for a spot where they routinely stop to

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turn. Focus on that point and take the shot quickly when it presents itself. Note: for safety, assure that all animals are deceased before entering the trap to remove carcasses. Additionally, rubber gloves (and other protective equipment) should be worn when handling carcasses to prevent exposure to zoonotic diseases through blood and other bodily fluids.

Shooting Free-ranging Wild Pigs A variety of firearms and calibers will work effectively in Example of a rifle chambered in a pistol cartridge (http://www. hunting situations for collection of marlinfirearms.com/Firearms/1894Centerfire/1894.aspx) free-ranging wild pigs. High-power rifles with optical sights, such as .308 Winchester, .270 Winchester, and 30-06 Springfield are certainly effective choices, and they can be purchased in any number of action types and sight configurations, which range in price from relatively inexpensive to outrageously over-priced. Regardless, this type of firearm is most suitable where wild pigs will be engaged at distances of 100 m or more. In closed habitats a shotgun firing slugs or buckshot may be more appropriate. Manufacturers such as Marlin, Winchester and Ruger offer rifles chambered in pistol cartridges (.44 and .357 Magnum, etc.) that would be effective firearms out to 100 m, depending on sighting devices and user skill. Additionally, these firearms could be used by personnel uncomfortable with using a handgun to dispatch trapped animals, as low-velocity projectiles are preferable when shooting inside traps to reduce the chance of pass-through and ricochet. The primary advantage of using a rifle chambered in a pistol cartridge or a shotgun in California natural areas is reduced velocity and range, which is safer in public use areas or close to adjacent to urban zones. However, in the hands of experienced users all of the above can be employed effectively and safely. Suppressed firearms can be used to reduce disruption of visitor activities from the sound of gunshots and to carry out a discrete program, which can be important with controversial management actions. However, private individuals are not allowed to possess suppressed firearms in California. Federal agencies (National Park Service, USDA Wildlife services, etc.) and their agents can obtain and use suppressed firearms in California by special permitting with the Bureau of Alcohol Tobacco and Firearms. Because of this, contracting with USDA Wildlife Services may be a good option if suppressed firearms will be important elements of control operations.

Sweitzer & McCann • Wild Pig Natural Areas Survey Report

Negative article from L. A. Times (http://www.idausa.org/images/suit_to_stop_pig_eradication.pdf, accessed August 1, 2007)

A number of hunting techniques, such as stalking, still hunting and stand hunting can be employed effectively on wild pigs. Generally, it is a good idea to determine what resources wild pigs are seeking at any given time and focus hunting activities around areas that provide those commodities. Like many mammalian species wild pigs tend to be more active in the early morning or late evening, but they may forage throughout the night as well (Singer et al. 1981). Spotlighting can be an effective shooting strategy where wild pigs regularly forage in open areas that are secured from nighttime visitor activities. However, it is not uncommon to encounter wild pigs at any hour of the day where seasonal foods are available for a short time or other beneficial opportunities present themselves. Most importantly, care should be taken to ensure that there is a solid backstop to all shots that are fired and that animals are efficiently destroyed, as a high number of wounded animals will raise ethical concerns and may spark public outcry against the control operation. Finally, there are an increasing number of non-lead bullet alternatives for rifle, pistol and shotgun on the market today. Use of this type of projectile may be necessary where feral pig control is being conducted in areas where secondary lead poisoning of native species (such as California condor (Gymnogyps californianus)) is an issue.

Sweitzer & McCann • Wild Pig Natural Areas Survey Report

ACKNOWLEDGMENTS We thank the University of California/USDA Exotic/Invasive Pests and Diseases Research Program for funding and support of this research. Thanks to all participants of the NADEC survey for their time and effort in completing the survey forms. K. Folkedahl (right) was instrumental for administering the survey, and organizing and compiling initial results. D. Schaub and J. Didion contributed valuable time and effort administering and organizing survey responses from natural areas managed by California State Parks. J. Karlton, R. Pasquinelli, and K. Purcell provided helpful suggestions and contact lists for California State Parks and the USDA Forest Service, Respectively.

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Sweitzer & McCann • Wild Pig Natural Areas Survey Report

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Sweitzer & McCann • Wild Pig Natural Areas Survey Report

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Sweitzer & McCann • Wild Pig Natural Areas Survey Report

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PIGS &amp; Natural Area Survey Report.Pdf

PIGS & Natural Area Survey Report.Pdf