SOCIAL MONOGAMY AND EXTRA-PAIR FERTILIZATION IN AN AUSTRALIAN LIZARD,TILIQUA RUGOSA

This study investigates social monogamy in the Australian sleepy lizar d, Tiliqua rugosa. At a 70-ha site near Mount Mary, South Australia, w e radio tracked 55 adult female and 39 adult male lizards during their spring activity periods. Each lizard was observed in 1-5 years. Femal es were observed with a single male partner on an average of 10.8 days per year, although in 17.3% of cases, females were observed on 2 or f ewer days with a male. The most intense pairing period each year was 1 5 September-15 November when females were with male partners on an ave rage of 36% of observation days. Partnerships lasted an average of 43. 3 days each year. After mating in early November, the pairs separated. Observations of females pairing with other males were rare. Most male s (82%) were also consistently monogamous, although 7 were observed pa iring with 2 females within one season. To investigate paternity, we a llowed 21 gravid females to give birth to 42 offspring in the laborato ry. We determined genotypes at five polymorphic microsatellite DNA loc i for the females, their male partners and their offspring. Four litte rs (19%) and 6 of the offspring from those litters (14.3%) showed evid ence of extra-pair fertilization (EPF). Although the sample sizes are small, females of polygynous males were more likely to experience EPF.