Monitoring and managing the harvest of tegu lizards in Paraguay

Abstract

Two species of tegu lizards, the black-and-white tegu (Tupinambis merianae) and the red tegu (T. rufescens), are hunted for their skins to supply the exotic leather trade. Tegu lizards were among the most exploited reptiles in the world. During the 1980s, the annual harvest averaged 1.9 million skins, and current quotas for Argentina and Paraguay are 1 million and 300,000, respectively. Commercial trade in Tupinambis is legal in these countries, and management programs require monitoring the harvest. Skins are traded according to width: class 1 (>30 cm), class 2 (>25-29 cm), class 3 (<24 cm). Management guidelines consist of the national export quota, and a ban on commerce of class 3 skins, aimed at reducing the number of subadults harvested. I studied the tegu management and monitoring program in Paraguay. I recorded snout-vent length (SVL), width, sex, and species from skins measured at check stations and in tanneries from 1991 to 1998. Comparison among field sites and tanneries allowed me to evaluate efficiency of the management guidelines and analyze harvest trends. Analyses of 8 seasons of harvest data showed a statistically significant, but slight, increase in SVL, and an increase in the proportion of males harvested for both species. The sex ratio (M: F) of harvested black-and-white tegus and red tegus varied in different years, but was generally biased toward more males. Corresponding to the general increase in skin size, the proportion of subadults in the harvest decreased during the sampling period. For black-and-white tegus, skins < 24 cm wide occurred in a higher proportion at check stations than in tanneries, presumably due to re-stretching of the skins by middlemen. Results indicate that tegu lizards are withstanding the harvest in Paraguay. There is no indication of overharvest, and no indicators of population decline. However, more field studies are needed to obtain data on hunting effort, and to assess the impact of the harvest at regional levels. Recommendations to improve the management program include the creation of a special committee involving governmental and non-governmental agencies and organizations related to the tegu trade and conservation of renewable resources.