ARS | Publication request: Mark-recapture estimates of recruitment, survivorship and population growth rates for the screwworm fly, Cochliomyia hominivorax

Submitted to: Medical and Veterinary Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 16, 2008
Publication Date: N/A

Interpretive Summary: Prior to eradication from the U.S., Mexico, and Central America using the sterile insect technique, screwworms were severe pests of animals. If screwworms were reintroduced to the U.S., estimates of losses to the livestock industry approach $1 billion per year; losses to wildlife, pets and humans are inestimable. Responding to and eliminating outbreaks of screwworms requires large investments of time and resources. We used previously published information, to calculate estimates for rates of recruitment, survivorship and growth for a population of screwworms; parameters useful to those responsible for responding to screwworm outbreaks. These estimates indicate that outbreak populations of screwworms, assumed to originate from small numbers of introduced flies, could double in about 2-3 months. If not detected early, and given optimal conditions of available hosts and weather, an outbreak could become difficult to manage in 4 to 6 months and be of substantial cost the U.S. producers. Thus, maintaining and improving quarantine measures against screwworms will enhance protection for the U.S., and all areas from which screwworms have been eradicated, from the extreme damage caused by this pest to all warm-blooded animals.

Technical Abstract: Pradel model mark, release, recapture estimates of survivorship, recruitment, and the rate of density-independent population growth, are presented for eight mark-recapture studies of the screwworm Cochliomyia hominivorax from Costa Rica, totaling 19,714 released and 4,504 recaptured flies. Corroborative estimates of survivorship and the rate of population growth based on an extensive review of the literature are also reported. Weighted-mean +/- SEM mark, release recapture estimates of survivorship, recruitment and the rate of population growth were: mean survivorship = 0.797 +/- 0.008, mean recruitment = 0.193 +/- 0.008 and mean population growth =1.005 +/- 0.002. Population doubling time was estimated from mean population growth at 139 d. Estimates of survivorship and population growth from the literature both exceeded those calculated by mark-recapture methods and estimates of population doubling times were consequently shorter.