Fertility Management for Feral Swine in the US A Managers Perspective Michael J. Bodenchuk, State Director Texas Cooperative Wildlife Services Program USDA-APHIS-Wildlife Services
Feral Swine in the US Invasive Species Reported in 35 States- Increasing Nationwide 6,000,000+ $1B US in damage annually Negative impacts to agriculture, natural resources, human health and safety
Feral Swine Biology Age at first breeding 6-7 months Gestation 115 days Average Litter size 6 (r = 1-12) 3 litters every 2 years (7-8 months between litters) Adult annual survival 60-80% Female will have 7+ litters in her lifetime
Model Population Growth
Current Management Heavily focused on lethal control Eradication where feasible Damage management where eradication is impractical Management is cost:effective but in Texas we are unable to reduce statewide populations
Fertility Management Suggested by numerous authors Cowan, D.P., G. Massei and R.J.B Mellows, 2006 - Model showed reduced female population with 10-90% contraception Burton, J.L., J.D. Westervelt and S. Ditchkoff, 2013 – Model showed greatest efficacy (reduced population growth) with hunting and contraceptives used in combination Massei, G. and D.P. Cowan, 2014 – Discuss current state of knowledge regarding human-wildlife conflicts
Management Complications Feral swine are a meat animal in the US Delivery to a sufficient number of females Total contraception v. smaller litters Biology with fertility management in place Compensatory survival of juveniles Compensatory survival of adults Changes in damage- reduced consumption, less rooting, etc. Seasonality, need to keep bait out year-round
Management Implications Damage Management v. Eradication Difficulty in targeting females in low density Species specific baits Species specific delivery systems Herd contraception v. individual contraception Changes in damage due to behavior, age structure, nutritional requirements or reduced population level
Applications Damage Management- if population decreases, behavior or other factors affect the pigs Disease Management- if reduced populations and changes in behavior are reflected in contact rates between pigs and wildlife/livestock Population Management- if keeping some pigs on the landscape is desirable for alternate prey, recreational hunting, or ecological purposes (i.e. native populations in Europe/Asia)
Research Needs Examine free-ranging pigs with management to determine: % population able to be targeted Changes in fecundity/natality/survival Changes in behavior/diet Changes in damage (rooting, E. coli, disease prevalence) Validate the models
Research Needs Validate delivery methods Examine human risks associated with meat consumption Examine secondary risks associated with contraceptive drugs Examine relative costs and maximum integration of methods Determine seasonality of application