Among reptiles, reproduction in the absence of males is often assumed to result from long-term sperm storage. Through the application of molecular genetic tools, biologists are beginning to recognize that facultative parthenogenesis can also explain such reproductive events in snakes. We observed a Copperhead (Agkistrodon contortrix) give birth to a stillborn neonate and four infertile ova after 9 yr in isolation from male snakes. To test the hypothesis that the neonate was produced asexually, we screened a panel of 10 microsatellite loci to genotype the mother and her offspring, as well as wild-caught individuals in the mother's population of origin, to assess the probability of paternity. Confirming prior research on Copperheads that suggests parthenogenesis by terminal fusion automixis, we found that four heterozygous maternal loci were homozygous in the neonate. We calculated the probability of a random male from the population as a sire to the neonate to be 2.32 × 10−13 by using the population allele frequencies and the genotype of the neonate. These results further confirm that Copperheads are facultatively parthenogenetic and suggest that this reproductive mode may be general within the species.

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