Biology & Negative Impacts of Feral Hogs
Greg YarrowProfessor of Wildlife Ecology
Clemson University
Beaver & Feral Hog Management Workshop
March 30, 2011
Wild Hogs - HistoryScientific Pedigree
Wild Hog (or Pig or Swine)
Wild Hogs - HistoryScientific Pedigree
Wild Hogs - HistoryHistory in the Southeast
• Wild hogs have a long history in the Southeast
• Populations date back to the mid 1500s
• Derived from domestic swine that went wild (i.e., becoming feral hogs)
• Feral hogs were widespread in the Southeast by the early 1900s
Wild Hogs - HistoryHistory in the Southeast• Pure Eurasian wild boar introduced into NC in 1912
• Fenced hunting preserve on Hooper Bald
• Animals escaped enclosure • Hybridized with feral hogs in surrounding area
Wild Hogs - HistoryHistory in the Southeast• In 1900, only three of the states in the SE did not have wild hogs
• By the 1970s, all states in SE had wild hogs
• Recent expansion seen in most states in SE
OK
WVAR
TX
LA
MSAL
SC
VA
NC
FLGA
KYTN
Wild Hogs - EcologySize, Shape and Color
• Males are larger and heavier than females
• Average adult weights:• Males – 200 lbs.
• Females – 175 lbs.
• Born at <2 pounds
• 30 inches at shoulder
• Total length is 5 to 6 feet
Wild Hogs - Ecology Size, Shape and Color
“Half-Ton Hog Phenomenon”
Wild Hogs - Ecology Size, Shape and Color
• Coat coloration is highly variable (e.g., solid, spotted, belted, etc.
• Most variation is due to the mixed ancestry of these animals (feral hog crossed with wild boar)
Wild Hogs - Ecology Food Habits/Diet• Wild pigs are classified as
opportunistic omnivores• “If it has a calorie in it, and
they can get their mouth around it, wild pigs will eat it”
• Typical composition of diet:• 88% plant matter• 10% animal matter • 2% fungi• <1% misc. (e.g., soil, rocks, sticks, garbage)
Wild Hogs - Ecology Habitat Requirements• Adaptable to a wide variety of habitats
• Need year‐round access to: • Food and water• Shade• Escape cover
• Recent increase of numbers in urban habitats
Wild Hogs - Ecology Reproduction
• Very high reproductive potential
• Early sexual maturity (3‐6 months of age)
• Large litters
• Average of 6
• Maximum of 16
• Breed year‐round
• Multiple litters per year
Wild Hogs - Ecology Social Unit Organization• Basic unit ‐maternal or family group (i.e., sow with her litter of piglets)
• Mature males solitary
• Multiple family groups of related sows as pigs get close to being weaned
• Large groups (100+ animals) can occur around a localized attraction or resource
Wild Hogs - Ecology Home Range
• Exhibit a “home range” behavior
• Average of 4 sq. mi.
• Maximum of 50 sq. mi.
• Varies depending on spatial availability of food, water, shade and escape cover
• Home range composition:• Core areas
• Network of paths
Wild Hogs - Ecology Daily Activity Pattern
• Difficult to regard them as either diurnal or nocturnal
• Varies by location• Intense hunting pressure and human activity will drive them to be nocturnal
• Seasonal variation
Wild Hogs - Ecology Movement Pattern• Drifting or wandering movement pattern
• Move in relation to supporting resources
• Disturbance will cause them to move
• Capable of long‐range movement over the short‐term (up to 200 miles)
Wild Hogs - Ecology MobilityWild pigs can:
• Run up to 30 mph
• Jump a 3‐ft fence
• Swim across 2 miles of open water
• Turn sharp corners while running
• Ascend very steep inclines
• Jump/climb over 5‐6’ corral trap walls
Wild Hogs - Ecology Senses
• Smell ‐ Excellent• 5‐7 miles over surface• 25 feet below grade
• Sight ‐ Good• Field of vision is 260 to 275 degrees
• Some binocular vision• “See” threat over 1 mile away
• Hearing ‐ Fair• Highest role in thick cover
• Unknown sounds or noise may cause pigs to go into a “freeze” or alert posture
• “Touch” (Taste)• Done with the mouth• “Mouth” objects to evaluate them
The Nose Knows!
Wild Hogs - EcologyWild Pig Tracks• Typical cloven‐hoofed print
• Resembles a rounded “W”
• Lateral or dewclaw prints often present
• Deer tracks – toe print are pointed
Wild Hogs - EcologyWallowing and Rubs• Wallow to cool themselves
• Can be almost any wet depression
• Use rubs for comfort and mud removal
• Rubs are not always associated with wallows
Wild Hogs - EcologyNests and Beds• Build two types of unique structures: • Farrowing nests
• Resting or loafing beds
• Somewhat similar in appearance
• Can be simple to very complex
Wild Hogs - EcologyAggressive Behavior• Wild pigs can be very aggressive
• Typically when cornered or threatened
• 5‐10 people killed annually due to wild pig attacks
• Do not “like” dogs
Negative Impacts of Wild Hogs
• Ecological Damage
• Economic Losses– Agriculture Damage
– Livestock Depredation
– Reforestation Failure
– Damage in Suburban Communities
• Disease Threats Photo Credit: Chris Jaworowski in West et al. (2009)Managing Wild Pigs: A Technical Guide
Ecological Damage
• Impact of Rooting
• Damage to plant & animal communities
• Increase in exotic plants
• Increase in soil erosion
• Decreased water quality
• Affects on other wildlifePhoto Credit: Chris Jaworowski inWest et al. (2009)Managing Wild Pigs: A Technical Guide
Ecological Damage
• Impact of rooting
• Besides man, greatest vertebrate modifier of natural communities
Ecological Damage• Damage to Native Plant Communities
• Direct & indirect effects
• Rooting, trampling, soil compaction, water infiltration
• Disruption of nutrient cycle• Effects most pronounced in wetland areas• Documented declines in NP communities in FL & HI
Ecological Damage• Damage to Sensitive Plant & Animal Species
• Destruction of rare & endangered plant communities in SC Heritage Preserves
• Depredation to threatened loggerhead sea turtle nests on North Island, Winyah Bay, SC
• FL endangered turtles nests destroyed
Ecological Damage
• Increase in Exotic & Less Desirable Plants
• Frequent rooting disturbance favors competitive non‐native plants
• Out compete native plants
Ecological Damage
• Increase in Soil Erosion
• Loss of soil fertility, plant growth, plant diversity
• Effects on water quality from siltation
Photo Credit:Eddie Parham in West et al. (2009)Managing Wild Pigs: A Technical Guide
Ecological Damage• Decreased Water Quality
• Soil runoff & bacterial contamination
• Impacts aquatic flora & fauna
• Freshwater mussels & insects impacted
• Fecal coliforms in some streams exceeds human health standards
Ecological Damage
• Effects on Other Wildlife
• Damage to habitat
• Direct predation
• Significant predators of ground nesting bird nests
• Competition for resources, especially soft & hard mast (fruit)
• Spread of diseases & parasites
Economic Losses• Agricultural Damage
• $ 1.5 billion lost annually in U.S.
• Consume & trample crops, damage pastures by rooting & digging
• Hay, small grains, corn, peanuts, vegetables, watermelons, soybeans, cotton, tree fruits & others
• Damage to fences, roads, dikes
Economic Losses
• Livestock Depredation
• Prey on lambs, goats, newborn cattle, poultry, & exotic game
• Predation on young animals usually occurs on calving or lambing grounds, may be attracted to afterbirth
Pattern of Wild Pig Predation• Difficult to verify, entire carcass is usually consumed, leaving little evidence.
• Also scavenge carcasses killed by other animals.
• Kill prey by biting & crushing skull or neck; carcass skinned & stomach contents consumed.
Economic Losses• Forestry/Reforestation Challenges
• Regeneration of hardwoods from seed may be difficult
• Hardwood & pine seedlings (especially longleaf) are very susceptible to pig damage through consumption, rooting, & trampling
Photo Credit: Steve Gulledge inWest et al. (2009)Managing Wild Pigs: A Technical Guide
Economic Losses
• Damage in Suburban Communities
• Yard, landscape & ornamental plant damage
• Garden damage
• Golf course damage
Photo Credit: Billy Higginbotham inWest et al. (2009)Managing Wild Pigs: A Technical Guide
Economic Losses
• Management for Game Species
• Destruction of wildlife plantings & food plots
• Consumption of corn & other supplemental foods at feeders
• Damage to habitats Photo Credit: Chris Jaworowski inWest et al. (2009)Managing Wild Pigs: A Technical Guide
Disease Threats• Carry disease that affect humans, livestock, & wildlife
• Humans ‐ brucellosis, leptospirosis, salmonellosis, toxoplasmosis, sarcoptic mange, E. coli, & trichinosis
• Livestock & Wildlife ‐pseudorabies, swine brucellosis, tuberculosis, vesicular stomatis, & classical swine fever
• Serve as a reservoirs & amplifier for other diseases (e.g. foot & mouth disease)
Positive Impacts of Wild Hogs ?
• Increased hunting opportunities
• Increase revenue from hunts
• Rooting may stimulate production of native plants that require disturbance
Wild Hog Efforts in SCChange in regulation last year
2 past research projects (Congaree NP)
Two workshops in August 2009
Other workshops scheduled• March 30th in Lexington, SC
• May 12th Brosnan Forest
• June 9th, Sandhills REC
Cost‐sharing in 2 counties by Conservation Districts
Formation of SC Wild Hog Task Force
Questions ?