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By Cheong H. Diong

Dissertation Committee:

John S. SiimSon, Chairman Reginald fi. Barrett

Williams I. Hugh Robert A. Kinzie III

Clifford W. Smith Sidney J. Townsley

We certify that we have read this dissertation and that in our opinion it is satifactory in scope and quality as a dissertation for the degree of Doctor of Philosophy in Zoology.



This study was supported by the United States National Parks Service under Contract CX 8000 8 0011, through the Cooperative Parks Resources Studies Unit, Department of Botany, University of Hawaii at Manoa. I gratefully acknowledge the funding. Haleakala National Park gave me permission to conduct this study in Kipahulu Valley. I thank the Park Superintendent, Hugo Huntzinger, and his chief rangers, Gordon Joyce, Kenneth Cox and Kimo Cababat, for their support and cooperation, Several park personnel assisted in field logistics and other aspects of the field work. I wish to especially mention John Kjargaard, Terrence Lind, Louis Pua, John Brown Jr.f Alexander Smith Jr. and Alvin Yoshinaga. The goodwill and kindness that I received so generously from the people of the Hana Community are pleasant and manorable experiences which I will always cherish.

Several institutions and individuals gave me their kind cooperation. I thank Hana Medical Center for use of its centrifuge; Qr. Milton Howell for the use of,his,facilities; Maui Community College in Kahuluif for extensive use of its science laboratories and welding workshop facilities; Department of Geography, Manoaf for use of laboratory facilities; Fronk Clinic and St. Francis Hospital/ Honolulu, for use ofradiographic facilities; Dr. Everitt Wingert for map reproductions; Roger Watanabe of the Soil Testing Service, Cooperative Extension Service, University of Hawaii and U.S.D.A. Cooperative, Manoa, for analyzing soil samples; and Stanley Ishizaki, Animal Science Department/ Manoa, for performing proximate analysis of plant specimens.

The following individuals painstakingly identified vertebrate and invertebrate specimens I sent to them: Dr. P. Quentin Tomich, State Department of Health, Hawaii; Dr. Gordon Gatesr Orange City, Florida; E. Easton, British Museum (Natural History), London, United Kingdom; Dr. Yoshio Kondo, Bishop Museum, Honolulu; and Alvin Yoshinaga, University of Hawaii at Manoa. The State Department of Agriculture assisted in the identification of parasites and in screening serum samples for diseases.

My fieldwork received renewed emphasis and momentum from Dr. Reginald Barrett1s field visit in March 1979. I thank him for his interest in my work and his many useful suggestions. Encouragement by Dr. Clifford Smith throughout the period of my fieldwork is most gratefully acknowledged. He counselled and rescued me on several occasions when public relation issues seemed either too sensitive or insurmountable for me to handle.

Dr. John Stimson served as my Dissertation Chairman. I thank him for advice on various aspects of my writing. Others who have provided suggestions on the organization of this dissertation include Dr. Reginald H. Barrett and Dr. P. Quentin Tomich. The entire dissertation was read by Dr. Tomichf who provided many helpful suggestions. The following critically commented on these chapters: Dr. C. S. Chung (Chapter 11); Drs. N. A. Polombok, A. Y. Miyahara, R. M. Nakamura and S. A. Perri (Chapter 10); Dr. C. H. Lamoureux (Chapter 2); and Terrence Lind, Jack Lind and Ximo Cababat (Chapter 4). The table on Nomenclature, synonyms, common names and distribution of wild pigs

(Table 1) was critically reviewed by Dr. C. P. Groves at the Australian National University.

My wife, by some misfortune, has become associated with this study, and in performing functions as diverse as stomach content analysis, pick-up of specimens at the airport and delivery to various departments for analyses, data analyses and deciphering my drafts for a typeprint-duties quite alien to her professional training but which she almost always obliged. Finally, I wish to acknowledge Peggy Daniel, June Saito and the Cooperative Parks Resource Studies Unit for assistance in producing this final draft on the HP3000 Text and Document Processor.


The population ecology of the feral pig (Sus scrofa) was investigated in a topographically closed Hawaiian rain forest in Kipahulu Valley, Maui. This population, with a feral history of 35 yearsf probably erupted six generations after the onset of feralization. Emphasis was placed on investivating: (1) the factors which could limit abundance, and (2) population processes unique to this habitat. A natural history approach was used to examine the hypothesis that food quality, rather than quantity, could be limiting the population. Additionally, because of specific information needs of the National Park Service, particularly with regard to control programs, this study also sought to obtain management-related information as a basis for management recommendations.

Food habits were characterized by: (1) an omnivorous diet, consisting mostly of plant matter, (2) a staple of tree ferns, (3) a seasonal switch from tree ferns to strawberry guava, and (4) a strong reliance on earthworms as a source of animal protein. The dietary range covered 40 plant species; 62.5% were herbaceous species, 32.5% trees and a woody vine. Seventy percent of the forage were native plants of which 35.7% were endemics. Tree ferns were the most concentrated source of sugar and starch. Plant foods were low in protein, but feeding habits of the pigs resulted in maximization of foods rich in nitrogen. Blood profiles showed adequate nitrogen intake and protein status. Pig feeding habits resulted in the death of some native trees and damage to the ecosystem.

Feral pigs actively disperse the strawberry guava by transporting large quantities of seeds in their digestive tracts. Gut transport did not affect seed viability but hastened germination.

2 Home ranges averaged 1.6 (0.7-2.9) km , and overlapped extensively.

Lateral exit movement from the upper plateau into Koukouai gulch was established. The diel activity pattern was biphasic, with high activity in early morning and late afternoon.

High juvenile mortality and a shorter ecological longevity characterize this population. The median age was 16.2 months; male:female:juvenile ratio was 2.6:2.8:1. Breeding occurs throughout the year. Prenatal survival was less than 73.3%, while postnatal survival from birth to six months was 40%. The factors which could limit abundance were categorized into those that act on: (1) juveniles, (2) adults in their second year, and (3) older animals. Accidental mortality, miring of the young, habitat factors and mongoose predation were identified as the sources of juvenile mortality. Metastrongyllid and kidney worm infection were considered important direct and indirect causes of adult mortality. Failure of dentition appears to be the most likely process limiting the lifespan of individuals.

Chemical blood analyses revealed neutrophilic leukocytosis in the population. The pathologic condition was a probable consequence to some disease factor, microbial milieu in the habitat or to nematode parasitism.

A 17-month mark-recapture program in the upper-plateau koa, ohia and lower plateau forests yielded a population estimate of 100-300 pigs, a catch success of 1.8 pigs per 100 trap nights. Density and trappability varied among forest types. Visitation frequency to trap sites averaged 17.5% of total trap nights.

Management is recommended principally because the feral pig disrupts and destroys native forests and replaces the native ecosystem with the exotic strawberry guava, which it effectively disperses. The management recommendations proposed herein incorporate a built-in eradication strategy to free the Valley of pigs and emphasize an integration of various control methods to maximally impact both young and old animals.








Semantics 8

  1. Pig, swine, hogf boar 8

  2. Wild, feral, domestic, pariah 8

The Pig 13

  1. Classification, nomenclature, and distribution...... 13

  2. Historical ecology of pig domestication 27

Differences among Domestic, Wild and Feral Pigs 30

  1. Morphology 30

  2. Cytogenetics 33

  3. Anatomy 35

(i) Teeth 35

(ii) Bones 36

(iii) Kidneys 36

(iv) Central nervous system 37

  1. Behavior 38

  2. Biology 39

Introduction of the Pig into the Hawaiian Archipelago 41

(a) Geographic origin of the Polynesian pig 41

(i) The history of pig domestication 43

(ii) The prehistoric migratory routes of the

Polynesians from their points of origin into

various major island groups in Oceania 44

(iii) The indigenous distribution of pigs in

South-east Asian Mainland, Indonesia and

the Sunda Islands 44

  1. Description of the Polynesian pig 51

  2. History of the feral pig in the Hawaiian islands.... 61

(i) Introduction and distribution 61

(ii) Forest pig versus mountain pigs 62

(iii) Feral pig eradication program, 1910-1958 63

(iv) Impact on native ecosystem 65

(v) Feralization: A hypothesis explained 66


Topography 75

Geology 81

Soils 81

Climate 84

Terrestr ial Ecosystem 90

  1. Plant communities 90

  2. Vertebrate fauna 96

  3. Invertebrate fauna 97

CHAPTER 4. FERAL HISTORY ...................................... 100


Physical Characteristics 108

Anomalies Ill

Weights and Body Measurements 115

Coat Color Composition 117

Discussion 120


Introduction 126

Materials and Methods 127

Results 129

  1. Stomach fullness 129

  2. Overall dietary composition 130

  3. Seasonal influence on diet in koa forest animals.... 134

  4. Diets of ohia forest animals 136

  5. Diets of koa forest animals as revealed by

scat analyses 139

  1. Foraging habits 139

  2. Nutrient quality of plant foods 154

Discussion 155

  1. Characteristics of food habits 155

  2. Impacts on rain forest ecosystem. 160


Introduction 169

Literature Review. 170

  1. Historical background 170

  2. Synonyms and varieties 172

  3. Introduction into Hawaiian Islands 173

  4. Economic importance and other uses 173

  5. Weed characteristics 174

(i) High tolerance for variation in

physical environment 174

(ii) High fecundity 175

(iii) Competitive ability 175

(iv) Well developed insect and pest

resistance 175

Materials and Methods 176

Results 177

  1. Description of the strawberry guava fruit 177

  2. Species of seeds germinating from coats

and from droppings 178

  1. Fecal seed load 181

  2. Effect of gut treatment on seed germination 182

  3. Effects of gut treatment on seed coat 185

Discussion 192


Introduction 201

  1. Livetrapping techniques 202

  2. Population estimates 206

  3. Age determination 206

  4. Survivorship and fecundity patterns 207

  5. Collection of reproductive data 208

  6. Group size 209

Results and Discussion 209

(a) Livetr apping 209

(i) Trapping success 209

(ii) Trap location and visitation 211

(iii) Baits 211

(iv) Trap design 214

(v) Bahavior of pigs in response to traps 215

(vi) Trap-revealed movement patterns 215

(vii) Survival in trapped animals 218

(b) Population estimation 221

(i) Marked pigs remained marked throughout

the trapping season 225

(ii) Marked and unmarked pigs die or leave the

valley at the same rate 225

(iii) No pig is born or immigrates into the

Valley between marking and recapture 225

(iv) The probability of capturing a pig is the

same for all pigs in the population 226

  1. Age-sex composition 228

  2. Survivorship and fecundity patterns 231

  3. Litter size and seasons of birth 236

  4. Group size composition and behavior 243


Introduction 249

Materials and Methods 252

  1. Transmitters 252

  2. Collar attachment .:.,... 252

  3. Monitoring methods 253

  4. Data analyses 254


  1. Effect of radiotagging on study animals 256

  2. Home range size and configuration 256

  3. Movement and activity patterns 266

(i) Daily movements and activity patterns 266

(ii) Movements into and out of the Valley 268

(iii) Barriers to movement 272

Discussion 273


Introduction 283

Materials and Methods 284

Results 287

  1. Blood chemistries 287

  2. Cellular hematology 290

  3. Age and sex variation 292

  4. Abnormal erythrocyte morphology 292

Discussion 294

  1. Sources of variation 294

  2. Comparison between domestic, feral and

wild populations 297

(c) Physiologic health: Total leukocyte count

and differential cell data 299

  1. Protein status 307

  2. Kidney, liver and thyroid functions 308


Entrapment in Mud 310

Weather 312

Parasites 313

Dento-alveolar Diseases 323

Other Diseases 331

Feral Dog Predation 331

Mongoose Predation 333


Introduction 335

Is a Management Decision Necessary? 337

(a) Nature of the feral pig problem 337

(i) Dispersal agent for the strawberry

guava, Psidium cattleianum 337

(ii) Reduction in abundance of native trees

and herbaceous plants 337

(iii) Disruption in forest subcanopy 338

(iv) Establishment of weedy species 338

(v) Soil erosion 338

(vi) Increase in the number of sites of

standing water 338

(b) The consequences of doing nothing 339

(i) Replacement of native forest formation

by the exotic strawberry guava 339

(ii) Increase in exotic species pool 339

(iii) Loss of native plants 339

(iv) Impact on native stream biota 340

(v) Reduced recreational quality at Oheo 340

  1. Reasons for initiating feral pig control... 340

  2. Present management practice 341

  3. The management decision 341

Management Goals and Objectives 342

Criteria for Selection of Control Methods 343

Management Units 344

Strategies 344

Control Methodologies 348

  1. Available management tools 348

  2. Recommended management tools 349

(i) Trapping 349

(ii) Shooting and dogging 353

(iii) Hunting 355

(iv) Fencing 356

(v) Poisoning 360

Some Considerations on Control Operations 362

Consideration of the Interests of the People of Hana District. 366

Research Direction 368




Table Page

1 Nomenclature, synonyms, common names and distribution of

wild pigs 19

2 Comparison of some major characters among extant species of

wild pigs 25

  1. Possible mating types among wild, domestic and feral pigs, and
    their expected karyotype frequencies. 31

  2. List of 17th-18th century illustrations of pigs in Hawaii and
    the Pacific area, as seen by artists, explorers and
    naturalists 49

  3. Kill statistics for feral pigs shot on all Hawaiian islands
    in the Eradication of Destructive Wild Stock Program,

1910-1958 64

  1. Land snails in Kipahulu Valley, Maui, Hawaii 99

  2. Weights and body measurements for 22 feral pigs in

Kipahulu Valley 118

  1. Coat color composition of feral pigs in the upper and lower
    plateaus of Kipahulu Valley 121

  2. Overall annual percentage composition (aggregate volume),
    occurrence and importance values of major food categories
    for feral pigs in the koa and ohia forests in Kipahulu

Valley, as revealed by analyses of 28 stomachs 132

10 Seasonal variation in diets of feral pigs in koa forest

(610 to 1190m), Kipahulu Valley 137

11 Average percentage composition of major food items in six
stomachs collected from February to October 1980 in ohia

forest (1180 to 1500m), Kipahulu Valley 138

12 Nutrient composition of plants eaten by feral pigs in

Kipahulu Valley, Maui, Hawaii 141

13 Results of the analysis of variance for the effects of soil
depth on the distribution of earthworms in the roseapple

forest, Kipahulu Valley 153

14 Abundance of earthworms at three forest sites in

Kipahulu Valley 153

15 Seedlings recovered from 123 plantings of feral pig droppings

from August 1979 to September 1980 in Kipahulu Valley 180

16 Germination parameters for gut-treated and untreated (control)
seeds of the strawberry guavaf Psidiun cattleianum

Sabine 183

17 Results of germination trials for gut-treated and untreated

seeds of .P. cattleianum in Kipahulu Valley 186

18 Summary table for a two-way factorial analysis of variance
(ANOVA) on the effects of germination site (guava zone vs.
guava-free zone) and gut treatment on the germination

rates of seeds of £. cattleianum 187

19 Percentage frequency in four types of seed coat
scarifications in seeds of ]?. cattleianum after their
passage through the digestive tracts of feral pigs in

Kipahulu Valley 191

20 Trap-night data for 136 feral pig captures and recaptures

in Kipahulu Valley from July 1979 through November 1980 210

21 Visitation frequency and trappability data of feral pigs
at individual trap site from July 1979 through

November 1980 212

22 Relative effectiveness of food baits expressed as the number

of captures per 100 visits to a trap site 213

23 Population size of feral pig by trapping session estimated

by four methods 224

24 Survivorship (&x) and fecundity (mx) values for

feral pigs in Kipahulu Valley 234

25 Examples of home range and movement studies in

free-ranging pigs using radio telemetry. 251

26 A summary of commonly used methods for calculation of

home range size 255

27 Biological data, length of radiotracking period and number

of radiolocations for 13 feral pigs in Kipahulu Valley 257

28 Home range size estimates for nine feral pigs in

Kipahulu Valley 260

29 Results of circularity test for home ranges of nine feral

pigs in Kipahulu Valley 264

30 Home range axis lengths for eight feral pigs in

Kipahulu Valley 265

31 Diel home range parameters for three boars and three sows
monitored from November 1979 to March 1980 in

Kipahulu Valley 267

32 Published home range size of feral and wild populations

of Sus scrofa 276

  1. Laboratory methods of blood analyses 286

  2. Statistical description of biochemical parameters for 31

feral pigs in Kipahulu Valley, Maui, Hawaii 288

35 Statistical description of hematological parameters for

feral pigs in Kipahulu Valley, Maui, Hawaii 289

36 Serum T3f T4 values by radioimmunoassay and free
thyroxine T7 index for 27 feral pigs in Kipahulu

Valley, Maui , Hawaii 291

37 Normal serum T3f T4 and T7 values in

domestic pigs 291

38 Serological parameters of feral pigs that show

differences between sexes 293

39 Serological parameters of feral pigs that show

significant differences between age classes 293

40 Comparison of selected biochemical parameters (means

and/or range) for feral, wild and domestic pigs 298

41 Comparison of lenkocytic variables for feral, wild

and domestic pigs 300

42 Comparison of erythrocytic variables (means and/or range)

for feral, wild and domestic pigs 306

  1. Data on feral pigs which died from natural causes 311

  2. Prevalence and intensity of parasite infestation in

feral pigs in Kipahulu Valley 315

45 Prevalence of nemoatode parasites in relation to age in

38 feral pigs in Kipahulu Valley 317

46 Age related prevalence of diseased, cupped or missing
permanent teeth per lower jaw in 68 feral pigs in

Kipahulu Valley 326

47 Example of a matrix form of organization for management

units and programs in Kipahulu Valley 363

48 Management options for the reduction and eradication of

feral pigs in Kipahulu Valley 365


Figure Page

  1. Venn diagram classification of modern day Artiodactyla 16

  2. Distribution of the aboriginal Polynesian pig in Oceania

during pre-European era 46

  1. Pariah population model explaining apparent delayed
    feralization of pigs in Polynesian times 72

  2. Map of Kipahulu Valley showing its location in Haleakala
    National Park and in the Hawaiian archipelago, as well
    as field installations and important landmark

reference points 77

5 A profile diagram of Kipahulu Valley and its surrounding

areas 79

  1. Soil sampling sites in Kipahulu Valley, Maui, Hawaii 83

  2. Soil sample analyses results 83

  3. Mean monthly temperature and precipitation for weather
    stations Haleakala RS 338 (2142m) and Kipahulu

258 (79m) 87

9 Mean monthly temperature and relative humidity for

Kipahulu Valley stations B (K665m) and C (E1447m) 89

  1. A generalized vegetation map of Kipahulu Valley, Haleakala
    National Park, Maui, Hawaii 92

  2. Pig invasion into Kipahulu Valley, Haleakala National

Parkf Maui, Hawaii 102

12 Feral pigs in Kipahulu Valley: (a) Two sows in a
strawberry guava (Psidium cattleianum) forest

at E700m, (b) A white and spotted pig in a dense fern

(Athyrium sp.) cover at L850m 110

13 Examples of ear abnormalities in feral pigs in

Kipahulu Valley, Maui 114

14 Coat color classes and composition of feral pigs in

Kipahulu Valley, Maui, Hawaii 116

15 Plot of individual stomach volume against age for 28 feral

pigs shot in Kipahulu Valley between 610 and 1500 m 131

16 Monthly variations in percentage composition of major food
categories as revealed by the analyses of 22 stomachs
collected in the koa forest (610 to 1190m),

Kipahulu Valley 135

  1. Monthly variation in the proportion of feral pig droppings
    containing seeds of Psidium cattleianum 140

  2. Vertical troughing of standing tree ferns (Cibotium sp.)

by feral pigs in Kipahulu Valley 147

19 Tree fern (Cibotium sp.) frond pulling and feeding

habits of feral pigs in Kipahulu Valley 149

20 (a) Vertical distribution of earthworms in Kipahulu
Valley, (b) depth distribution of earthworms in roseapple

forest, as determined by ten 0.5 x 0. 5m quadrats 152

21 Regression equations for seed count (y) per strawberry guava
fruit (Psidium cattleianum) against the fruit1s cross

diameter (x1) and polar diameter (x2) 179

22 Germination curves for gut-treated (voided) and untreated
(control) seeds of the strawberry guavaf

Psidium cattleianum. 184

23 Types of seed coat scarification in seeds of the strawberry
guava, Psidium cattleianum, after their passage through

the digestive tracts of the feral pig 190

  1. Location of corral and box traps in Kipahulu Valley 204

  2. Capture and recapture locations (trap sites) for all feral
    pig recaptures during the mark-recapture study from July

1979 to December 1980, in Kipahulu Valley, Maui 217

26 Recapture frequency for feral pigs tagged and released on

the upper plateau, Kipahulu Valley, Maui 222

  1. Age-sex composition of 122 feral pigs in Kipahulu Valley 229

  2. Crude and adjusted survivorship curves for feral pig
    populations in Kipahulu Valley 233

  3. Estimated breeding dates of (a) 18 groups of fetuses, and

(b) 52 trapped animals that were less than one year old 237

30 Prenatal and preweaning mortality patterns in feral pigs

in Kipahulu Valley \ 239

31 Group siza and group type frequency distributions in feral

pigs from koa and ohia forests in Kipahulu Valley 244

32 Home ranges of feral pigs delineated by the minimum-area
(solid lines) and modified minimum-area (broken

lines) methods 259

33 Composite home range maps of nine feral pigs in

Kipahulu Valley, Maui 263

34 Diel activity cycle of five feral pigs monitored from

November 1979 to March 1980 269

35 Locations and entry-exit movement patterns of three
radiotagged pigs in the lower section of the upper

plateau, Kipahulu Valley, Maui 271

36 Prevalence of diseased, cupped or missing teeth in erupted
permanent mandibular teeth in 68 feral pigs in

Kipahulu Valley 327

37 Subdivision of Kipahulu Valley into five

management units 346

38 Proposed live-trapping and fenceline activities for

management subunits 1A and 13 352

39 Examples of some management functions that could be built
into fencelines separating two management units or along
perimeter fences 359


The introduction of hoofed mammals into natural ecosystems not previously supporting them is one of man's activities which adversely affects the stability, organization, and productivity of biotic communities (de Vos et al. 1956; McKnight 1964; Fosberg 1977). Motivated by a desire for nostalgia, increased food resources, sport hunting, stock improvement, pest management and other reasons, exotic wildlife introductions have often been intentional, but are sometimes accidental. In the days of colonists and explorers, transport of domestic livestock as ship's stores and their subsequent introduction and release in new lands were standard practices. Frequently, animals were liberated on uninhabited shores "to multiply and become useful to navigators who might visit the coast" (Baudin in Cooper 1954).

One hoofed mammal widely transported, introduced world-wide, and left to multiply was the pig, Sus scrofa Linnaeus (1758). Whether it was introduced in its wild, domestic, or feral states, the pig often has adapted remarkably well, and in a relatively short period of time, to a new environment by establishing breeding populations. Examples of firmly established populations can be seen on both continents and islands.

In the continental United States, there were two phases of introduction, an early one involving the domestic pig and a later one of the European wild boar, a naturally wild species. The wild boar was

first introduced in 1912 and is now established in at least four states (Stegmen 1938; Shaw 1940; de Vos et al. 1956; Jones 1959; Laycock 1966; Sump 1970; Godin 1977; Barrett & Pine 1980). Domesticated pigs were introduced in 1539 (Towne & Wentworth 1950). By 1945, feral pigs were reported from 17 southern states (McKnight 1964) and were the most numerous feral ungulate in North America. Presently, feral populations are found in all of the Southeastern states (Wood & Lynn 1977f Wood & Barrett 1979), in California (Barrett 1977, 1978; Barrett & Pine 1980), 19 National Wildlife Refuges (Thompson 1977) and in nine National Parks (Singer 1981).

Outside the continental land mass of North America feral pigs have become well established on Santa Rosa, Santa Cruz, and Santa Catalina islands, California (McKnight 1964); on Ossabaw and Cumberland islands, Georgia (Smith et al. 1980; Singer 1981); on Horn and Gulf, islands, Mississippi (Baron 1980); on Robert's Island, Canada (Smith & Hawkes 1978); in the West Indies (Wiewandt 1977); and in Latin America (Petrides 1975). In the Pacific region: Santa Cruzf Floreana and San Salvador of the Galapagos Islands (British Admiralty 1943; Kruska & Rohrs 1974); Australia (McKnight 1976; Tisdell 1979, 1980a,b; Mclntosh & Pointon 1981); New Zealand (Wbdzicki 1950); Marianas (Wheeler 1979); Swain, Tokelau islands (Kirkpatrick 1966); Hawaiian Islands (Tomich 1969; Kramer 1971); on several coral islands (British Admirality 1943); and many other Pacific islands (British Admirality 1943, 1944, 1945a,b). Feral populations in these areas have radically different histories, but typically they originate from domestic stock, which has turned feral.

An exception is that on Robert's Island, Canada, where a 10-year-old population was established from a stock of nine feral pigs imported to that site.

It is well known by ecologists and environmentalists that pigs feralize easily, undergo eruptions in numbers, and are disruptive components of native ecosystems. This ease of adaptation to the wild and, in particular, of rapid population increase may be attributed to innate characteristics. Among ungulates, the pig is perhaps the most adaptable species and is a prolific breeder capable of producing two large litters a year. It is both a food and habitat generalist (Bratton 1974). Itiese aspects of the pigfs ecology have allowed it to adapt readily to a feral existence in a wide range of habitats.

Following introduction the population ecology of an exotic ungulate is relatively predictable (Elton 1958, 1966; Riney 1964). According to Riney (1964) and Caughley (1970, 1977), the population history of an exotic population passes through an initial establishment phase, followed by a single eruption and finally fluctuation to extinction or to some kind of resting or nonresting stability with the environment. Characteristic of all exotic introductions including the pig, is the lack of attention or import given to an introduction until numbers become high or individuals become dispersed. Concerns for controlr containment or eradication only then become urgent. Consequently, little is known about the population processes and habitat responses during the period of initial increase in population size.

World-wide evidence shows that feral pigs in new environments generate complex ecological and socio-economic problems (Wodzicki 1950; Howard 1964; Challies 1975; McKnight 1976; Barrett 1979; Tisdell 1979; Wood & Barrett 1979; Barrett & Pine 1980; Hone & O'Grady 1980). The feral pig has been declared a noxious animal, vermin, or pest in many countries. It is extremely disruptive to native fauna and flora. It alters species composition and upsets the stability of natural ecosystems (Bratton 1974; Baker 1975, 1979). Under insular conditions, perturbations are more severe, and destructive but less understood than in continental areas. In many instances management has been difficult or impossible. Consequently management and control of pig populations have become imperative in many of the above-mentioned areas.

As pointed out by Fosberg (1963) and Carlquist (1965, 1974), island ecosystems are unique due to their isolation, reduced species competition, high endemism, and extreme vulnerability to disturbance. In addition, the disruption of an insular ecosystem, unlike those in continental areas, once begun is often unidirectional and irreversible even when given time to recover or when remedial management is applied (Leopold 1969; Fosberg 1977). The Hawaiian archipelago, is a prime example of an oceanic island chain where biotic community response and tolerance to feral ungulate activity can be investigated. The pig and other terrestrial quadrupeds were not present in the islands in prehuman times; the only native mammals were the hoary batf Lasiurus cinereus, and the monk seal, Monachus schauinslandi, (Tomich 1969). Having evolved in the complete absence of mammalian herbivores, the vegetation

lacks many antiherbivore defenses such as thorns or harsh foliage, is noticeably nonpoisonous, and is particularly fragile and susceptible to animal trampling, rooting and grazing. With this evolutionary history in mind, an investigation of feral ungulate ecology in an insular environment may be considered a special case study.

Much of the research interest in feral ungulates in both island and continental areas is aimed at obtaining information concerning impacts on habitats and the population dynamics, with the object of improving the management of wildland resources. This study of the feral pig in a pristine montane rain forest in Kipahulu Valley (hereafter referred to as the Valley), Haleakala National Park, Maui, also has a management objective. The Valley was described by a Nature Conservancy sponsored Scientific Expedition as a sanctuary for many rare species and a "unique natural laboratory available nowhere else on earth for the study of endemismf ecological genetics, pedogenesisf and the complexities of pristine ecological systems" (Warner 1967). Ihey also found feral pigs which the Expedition identified as the primary destroyer of the rain forest ecosystem.

The Valley's pig population had its genesis in the 1940fs (see Chapter 5) and is a relatively late arrival at this site. Ranging into the rugged, and remote, closed-canopy rain forest, the feral pig thrived. Several factors may have contributed to its continued feral existence. These are examined below to help formulate a testable hypothesis.

Since its inclusion, in 1969, as a wilderness area within Haleakala National Park, the Valley has been closed to hunters and the public. The pigs in the Valley have therefore been protected from hunting. There are no known predators; the only other mammals living in the region are a mongoose, Herpestes auropunctatus, three rats, Rattus rattusf R. norvegicus, and R. exulansf and the house mouse, Mus musculus; all small introduced species. Hie pig is therefore a terminal member in the food chain in this biotic community. In addition the rain forest environment is favorable for pigs in three ways. First, there is no interspecies competition between the pigs and other mammals (Giffin 1978). Secondf the vegetation is green and luxuriant all year suggesting that food and cover may not be limiting factors. The continued feral existence suggests that the ecological requirements of the pigs, which permitted the original establishment in the wet forest/ are met adequately. Third, water, a critical resource for pigs in some habitats, is never limited in the Valley, even during summer. With these theoretical considerations in mind, it is hypothesized: (1) that the quantity of food, cover and water are not important in limiting population processes, and (2) population regulation comes about through food quality rather than competition for food and is more likely to be exerted from below rather than from above, because of protein dilution in plants (White 1978).

For this study, a choice of approaches was available to me; the natural history approach as outlined by Elton (1966) was adopted. In the Valley, where biological resources, other than those reported by the

1967 Scientific Expedition, have not yet been inventoried and are poorly understood, the natural history approach was considered most desirable for this study. My objectives were to investigate the population biology and ecological interrelations between the pig and its habitat. The overall goals were few but specific. First, because of the specific information needs of the National Park Service particularly with regard to control programs, this study seeks management-related information as a basis for management recommendations. Second, the study is designed to explain observed habitat changes and to predict future patterns. Third, it is intended to examine any population process that might be unique to a topographically closed rain forest ecosystem. Finally, while significant information on feral pigs has been accrued from studies elsewhere, one apparent conclusion is that pigs are extremely adaptable and ecological relations in pig populations differ from one locale to another. Sufficiently detailed studies are lacking in closed tropical forest habitats like the Valley. Thus, the present study should contribute to an understanding of pigs in this different area.


(a) Pigf swine, hog, boar

Ihe terms pig, swine, hog, and boar have been variously applied to all suids in their various states of existence, in a general, genitive sense or as distinguishing epithets. Pig and hog, but not swine have been applied to wholly unrelated nonsuid species (Skeat 1924; Mellen 1952). The origin of these terms is unknown. Hog has been accorded a Celtic origin and is thought to originate from either a Hebrew word meaning "to surround" or from the Arabic verb "viz/1 meaning "to have narrow eyes" (Miller 1976). In its original usage, pig refers merely to size, more specifically to the young or suckling of a suid which has not reached sexual maturity (Weekley 1952; Skeat 1924; Onions 1952). Extending this definition, it follows that sow and boar be applied to suids reaching sexual maturity and that suids before the breeding age be referred to as either a male or female pig. Hog was originally applied referring to age, that isf suids of the second year (Onions 1952) or weighing more than 55kg and reared for the purpose of slaughter (Standard Encyclopedia Dictionary 1968; Guralnik 1970).

The distinction between hog and pig appears to be one of domesticity and age or size. Swine refers to a domesticated suid (Standard Encyclopedia Dictionary 1968; Onions 1952). Its original

usage may have been either generic or restricted to a domesticated suid. Since only one suid species, S>. scrofa, has been domesticated, it follows, by definition, that the application of the term swine to the other seven suid species becomes invalid. According to Onions (1952), swine has been superseded in common use by pig or hog. Hie term boar when used as wild boar, European wild boar, or the boar generally carries a specific meaning and refers to the Palearctic-Asiatic species, SL scrofa, or any of its subspecies. Otherwise it is applied to mean a sexually mature male suid.

Clear examples of the original usage of pig and hog before the 19th century, though rare, can be gleaned from the journals of several explorers. In his journal entry on September 18, 1777, Cook wrote that he received "a hog, a pig and a dog" as a present from servants of a chief on the Society Islands (Cook 1784, Vol. II, p. 57). When receiving pigs from natives, Cook frequently records them as "small pig" or "large hogs."

In trading with the natives, "a small pig of 10 or 12 pounds" was traded for a spike, but "a hog" was exchanged for a hatchet (Cook 1784, Vol. I, p. 82). Although hog and pig have been used in an archaic sense for other animals (Skeat 1924; Mellen 1952), it is improbable that Cook had used pig or hog for another animal. The only quadrupeds present at the time of his visit were dogs, pigs and rats (Cook 1784, Vol. Ill, p. 113) and the fowl had never been termed as a hog. Ellis1 (1831) usage of the terms hog, swine, pig in his journals was close to the original meanings. Present day usage of pig/ hog, swine does not follow any

established rule. The literature shows that the same author, working on the same population of pigs in the same location, has on different occasions used hog, swine or pig. Subject disciplines, biogeographical regions and not to mention personal preference often influence the use of these terms. In the field of vertebrate zoology pig is applied to suids in their wild, domestic and feral states, whereas hog or swine is more commonly used in agricultural and veterinary sciences (Lapedes 1978). Looking at geographical regions alone, pig is applied almost exclusively to feral, wild and domestic suid populations in the Australasian, Indo-Malaysian, Asian, African and Pacific areas. In the continental United States, all three terms, hog, swine and pig, in this order'of frequency, are used to describe domestic, feral and wild populations.

It is apparent therefore that pig is more widely used than hog or swine. Although all these terms appear to be acceptable, pig is undoubtedly more genitive in the zoological sense (my bias), and its usage is probably more desirable than the other terms. Perhaps the genitive suid should be used when there is doubt. In this thesis, pig is used in the descriptive and genitive sense depending on context.

(b) Wild, feral, domestic, pariah

Four possible states of existence-wild, domestic, feral and pariah-may be described for pigs in various environments using the following two criteria: (1) the extent of influence by man on the gene pool and, (2) the action of natural selective forces. No taxonomic

distinctions exist among pigs in any of the four states defined below, all of which have been given the same specific designation, Sus scrofa.

A wild population is one which has no history of exposure to a domesticator population, and therefore has not been under the influence of artificial selection by man. The present and future gene pool of a wild population are under the direct control of natural selection (Brisbin et al. 1977; Brisbin 1977). When the natural forces acting on a wild population are removed or modified by man, a domestic population results. Thus a domestic pig population is one whose ancestral gene pool has been modified by the process of artificial selection. Modern man continues to modify the ancestral gene pool by intense artificial selection. This has resulted in the production of 87 recognized breeds of domestic pigs and another 225 breed-types (Pond & Houpt 1978). When man's existing influence on the future gene pool of a pig population is slight or negligible, as when a loose association develops between the pig and man near settlement areas, then a pariah population may be described (Epstein 1971; Brisbin 1977). In a pariah population, the future genetic composition of the population is determined by breeding patterns which are influenced, but not completely controlled, by man. True pariah pig populations probably exist near aboriginal settlement areas in the forests of the Indo-Malaysian region, and in the Pacific islands. Although Rappaport (1967) did not use the term pariah in his writings, the existence of true pariah pig populations among the primitive New Guinea highlands can be inferred from his studies. Feral pigs are those which originate from domestic stock but have reverted

from domesticity to become free-living and no longer depend on man for sustenance or breeding (Pullar 1953; Kruska & Rohrs 1974; McKnight 1976). Consequently, the gene pool of a feral pig population differs from that of its wild ancestor in that its ancestral gene pool had at some point in the past been modified by artificial selection imposed on it by man. By its return to a wild state existence the feral population is reexposed to natural selection which now acts on its future gene pool.

It is evident, therefore/ that each of the four states of existence has a precise definition of evolutionary significance. Unfortunately, usage of wild and faral are less than precise, and have been used interchangeably or synonymously to mean "living in the natural environment." Wild is commonly used in the vernacular sense to encompass both wild and feral states of existence (Wood & Barrett 1979; Barrett & Pine 1980). This disregard for usage of precise terms is probably inconsequential to the utilitarian hunter or sportsman, but may present ambiguity and problems to the law-enforcement officer, forensic veterinarian, connoisseur, or a biologist working in an area where pigs exist in more than one of the described states. The Asiatic wild pig, SL scrofa, in Peninsular Malaysia (Diong 1973) has, for example, been cited as "feral hog" by Wood and Brenneman (1978) and as "faral pig" and "wild pig" by Pavlov (1980). In this dissertation the various states of existence are used as defined above in their evolutionary sense and "free-ranging" when used, is applied to encompass both feral and wild populations.

In conclusion, the proliferation of somewhat questionable descriptive epithets for the feral pig in Hawaii such as the following might be pointed out here: "Hawaiian pig" (Warner 1959; Nichols 1962; Whitten 1977; Titcomb 1978); "Hawaiian pigs" (Hawaiian Audubon Society 1981); "Hawaiian wild pig" (Giffin 1977); "Hawaiian wild boar" (Swedberg 1963); "feral Hawaiian pig" (Wilson & McKelvie 1980); "wild pig in Hawaii" (Barrett-Connor et al. 1976); "wild pigs" (Bryan 1937; Tillett 1937; Tinker 1938; Vitousek 1941); "native pig" (Luomala 1962). The descriptive phrase "feral pig in Hawaii" or "Hawaii's feral pig" are preferred over those above. Use of the descriptive "Hawaiian" whereas valid when applied to the endemic seal, bat or fruitfliesf is unsuitable when applied to the pig, as the qualifier "Hawaiian11 connotes indigenousness. The pig first brought in by the Polynesians should be referred to as "the pig of the indigenous people," "the native's pig" or mora aptly the "Polynesian pig."

The Pig

(a) Classification, nomenclature, and distribution

The evolution and phylogenetic relationships of pigs have been reviewed by Mellen (1952), Simpson (1945) and more recently by White and Harris (1977) and Kingdon (1979) for African species. Ancestors of pigs arose from Condylarths by the early Eocene via the primitive palaeodonts. Wholly native to the Old World, pigs as a group have sometimes been termed "old pigs" with the antithesis "New World pigs" applied to peccaries. Although Simpson (1945) considers peccaries as an

offshoot of the Old World stock, peccaries are anatomically (Fradrich 1972) and immunologically (Duwe 1969) more related to present day ruminants than to pigsf which they only superficially resemble in appearance and behavior. The application of pig to peccaries is therefore invalid; the application of Old World to pigs is redundant, and ambiguous as it, like "true pigs,11 insinuates existence of the corresponding antithesis "New World" for another group of pigs.

The classification of modern day Artiodactyla, to which pigs and all other hoofed mammals belong, can be illustrated with a venn diagram (Figure 1). There are a total of 190 species, 92 of which are indigenous to Africa (Morris 1965). The affinities and differences among the nine families which are distributed in three orders have been reviewed by Haltenorth (1963). Within the suborder Suiformes, the family Suidae is represented by eight extant species. The East Asiatic pig, S>. _s. vittatus, was for a long time thought to be a distinct species, but vittatus has been reduced to a subspecies (Haltenorth 1963; Ellerman & Morrison-Scott 1966; Fradrich 1972). Therefore using venn notations, Suidae (pigs) = {Sus scrofa (common wild pig)/ Sus barbatus (bearded pig), Sus verrucosus (Javan pig), Sus salvanius (pigmy pig), Babyrousa babyrousa (babirusa), Phacochoerus aethiopicus (wart pig)f Hylochoerus meinertzhageni (giant forest pig), Potamochoerus porius (bush pig)}.

Nomenclature of pigs has been problematic and difficult (Allen 1940; Heptner et al. 1966; Hoogerwerf 1970). This is because taxonomic studies have been complicated by the fact that pigs, in particular S.

Figure 1: Venn diagram classification of modern day Artiodactyla.

«•••••- Order; - Suborder; Family. Numerals

within family subsets indicate number of species.

scrofa, are an extremely morphologically variable and adaptable group throughout their range. Geographic races differ in morphology, behavior and anatomy. Quite naturally, therefore, overzealous naturalists have described "species" within one group of pigs (Allen 1940) or from studies on a very limited number of skull samples (Medway 1965). The lack of consensus on characters which should be regarded as taxonomically distinct of the species and those characters that could have arisen as a result of isolation and adaptation have lead to an inevitable proliferation of "species" names. Fortunatelyf the generally accepted working definitions of species, race, and breed have helped in taxonomic studies of pigs.

Heretofore, museum studies have contributed significantly to pig taxonomy, but recent immunogenetic studies have demonstrated the potential of such methods in pig taxonomy and in elucidating evolutionary and pylogenetic relationships among suid species (Kurosawa et al. 1979). Most taxonomic work, however, has been done on ^. scrofa, the only Palearctic species, although there has been recent interest in African species (D'Huart 1978 in Barrett 1980; Kingdon 1979). Nothing is known about the geographic races or subspecific composition of present day feral pigs in the Pacific region. In Europe, biologists working on pigs, generally adopt the systematics as used by Haltenorth (1963), but considerable discussion has since arisen and a complete taxonomic review of Suidae is more than necessary (Fradrich 1981 Berlin, Germany - pers. comm.). Bratton (1977) attempted a review on the

nomenclature of the Palearctic speciesf but her work is very incomplete, most of which is cited generously from Heptner et al. (1966).

The recognized species and subspecies of pigs from the works of European, American and Asian taxonomists are listed in Table 1. Subspecific listing by Haltenorth (1963), and those not listed by other authors have in every case been checked, consulted and cross-referenced with at least two other (where available) regional authorities, for verification on the validity of subspecies recognition. Despite this approach, it should be pointed out that the subspecific listing (Table 1) should not be considered as final or complete, pending further work on suid taxonomy using conventional skull samples or more recent biochemical and serological methods mentioned above. Notwithstanding this, it can be seen that Suidae is represented by 81 subspecies. Sus is represented by four species, S>. scrofa with 35 subspecies, J3. verrucosus with 13 subspecies, ^. barbatus with six subspecies, and S^. salvanius, where nothing is yet known about its subspecific composition in its present range. S. £. scrofa, the continental wild pig and typical form of Linnaeus species (Bradford 1912)f is also referred to as German wild boar; its other synonyms are setosus, ferus, europeus, aper, and celtica (Bradford 1912; Haltenorth 1963; Ellerman & Morrison-Scott 1966; Heptner et al. 1966). Babyrousa, Phacochoerus, Hylochoerus and Potamochoerus are each represented by one species, with four, seven, three, and 13 subspecies respectively. Hylochoerus meinertzhageni is the largest species, whilst _S. salvanius, the smallest, was rediscovered in 1971 and is the only pig to be accorded Endangered status (Oliver

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