The reproductive cycle and the size at maturity of Tupinambis rufescens (Sauria: Teiidae) in the Dry Chaco of Argentina

FITZGERALD, L.A.; CRUZ, F.B.; PEROTTI, M.G.

JOURNAL OF HERPETOLOGY

SOC STUDY AMPHIBIANS REPTILES

Año: 1993 vol. 27 p. 70 - 78

0022-1511

The reproductive patterns of Tupinambis rufescens have not been described. The presentstudy had three objectives: (1) to describe the reproductive and fat body cycles of T. rufescens from ourstudy site in the dry chaco of Argentina; (2) to elucidate and analyze the distribution of sizes at whichfemale T. rufescens reach sexual maturity; and (3) to discuss the conservation implications of the reproductivecycle of T. rufescens.Oviductal width increased significantly after females reached 320 mm SVL, and we presumed the increasewas due to stretching of the oviducts in females that had been gravid. Seventy-eight percent of the females>319 mm snout-vent length (SVL) and 84.3% > 349 mm SVL possessed oviducts > 3.5 mm wide, our criterionfor indicating a female had reproduced, while only 6.9% of the females <320 mm SVL had oviducts widerthan 3.5 mm. Additionally, all the oviducts > 3.5 mm wide were convoluted, while all the narrower oviductswere straight or striated. The reproductive and fat body cycles of T. rufescens at our study site werecharacteristic of lizards from seasonal environments, and appeared closely tied to the onset of the rainyseason and increasing spring temperatures. Mature females exhibited significantly longer ovaries in Novemberthan in other months, and nesting was observed in November and December. The average clutchsize was 21.4, and the smallest female we found with eggs was 330 mm SVL. Testis mass was significantlygreater in November than in other months, and declined slightly throughout the activity season. Somegonadal development in males presumably occurred while the lizards were inactive during winter. Fatbody volume was tightly linked to the gonadal cycle of both males and females. Females apparentlyallocated fat stores to developing eggs, while males probably used fat stores for spermatogenesis or formeeting the energetic demands of mate seeking.Large numbers of Tupinambis are exploited for their skins, and this study provides life history informationneeded to develop scientifically-based management plans, for example, the size distribution ofreproductive females, the timing of reproduction, and clutch size. Based on our analyses, managementstrategies aimed at harvesting adults and subadults could be evaluated because the proportions of theharvest comprised of adults can be reliably determined. We recommend that strategies aimed at classifyingharvests according to adults and subadults use 350 mm SVL as a cut-off point for mature females.