contact rates and other vital information for disease 

 risk models and management are tenuous at best. 



NWRC scientists are developing a database of 

 genetic information from free-ranging pregnant 

 sows and embryos to provide a robust estimate 

 of rates of multiple mating across South Texas. 

 The goal of this ongoing study is to investigate the 

 mating behavior of feral pigs using genetic methods. 

 Because some diseases (e.g., pseudorabies and 

 brucellosis) are transmitted by contact among 

 individuals, including sexual contact, the frequency 

 of multiple mating provides a means of estimating 

 rates of contact among individuals. 



As of October 2007, more than 30 litters have been 

 obtained, and researchers have found evidence 

 for multiple paternity (siring of offspring by more 

 than one boar) in 48 percent of litters. That high 

 rate of multiple mating suggests that the risk of 

 transmitting diseases spread by direct contact 

 is significant. Results demonstrate the value of 

 genetic techniques to provide insight into difficult 

 wildlife-management problems and supply timely 

 information for predictions of disease transmission 

 within feral pigs. 



Evaluation of Population Estimation Techniques 

 for Feral Pigs — For land managers, feral pigs are 

 a concern because they cause environmental 

 and economic damage. Population estimates 

 for feral pigs are critical in determining efficient 

 management strategies. However, density 

 estimation techniques used for native ungulate 

 species, such as white-tailed deer, are inaccurate 

 and unreliable in determining feral pig populations. 

 New techniques using motion-sensing cameras and 

 ingestible biological markers help reduce the cost, 

 manpower, and time necessary to obtain population 

 density estimates of free-ranging wildlife and may 

 prove useful for feral pigs. 



NWRC scientists and cooperators evaluated 

 population-monitoring techniques at study sites 

 located in southern and central Texas. They 

 assessed (1) a mark-recapture technique using the 

 biological marker tetracycline, which is an antibiotic 

 that produces a fluorescent mark on growing bone; 



(2) traditional aerial surveys and spotlight surveys; 

 and (3) passive and active tracking indices using 

 motion-sensing cameras. Results showed that 

 tetracycline is a suitable biological marker for feral 

 pigS; aerial surveys and spotlight surveys did not 

 provide reliable estimates for feral pig populations; 

 and motion-sensing cameras showed promise in 

 monitoring feral pig populations. 



Mammalian Visitation to Candidate Feral-Hog 

 Attractants — Few data exist regarding suitable 

 feral-hog attractants in the United States. NWRC 

 researchers compared species-specific visitation 

 and contact rates of mammals to 11 candidate 

 feral-hog attractants at scent stations using motion- 

 sensing digital photography. Of the 720 scent 

 stations monitored, scientists found feral hogs 

 had greater visitation to stations featuring apple 

 and strawberry scents than to control stations. 

 Raccoons and collared peccaries were less likely 

 to visit stations with strawberry versus other scents, 

 such as berry or apple. 



NWRC scientists recommend that natural-resource 

 managers consider using strawberry attractants 

 for feral-hog-specific applications. If, however, a 

 general feral-hog attractant is needed, then apple, 

 berry, or caramel attractants may perform well. 



Biologists are working to identify suitable feral-hog baits and 

 attractants. 



Developing Methods 29 



