Reproductive Characteristics of Rio Grande Cooters (Pseudemys gorzugi) inWestern Texas

Testudines is a reptilian order characterized by low annual recruitment and delayed sexual maturity. One testudine species of conservation concern is the Rio Grande cooter (Pseudemys gorzugi), a taxon native to the southwestern United States and the westernmost species in this genus. A clear understanding of the reproductive biology of turtle species in the wild better informs conservation management options. The reproductive biology of P. gorzugi has been formerly investigated in the Black River of southeastern New Mexico. Because life history strategies of chelonian taxa may vary across geographic gradients, we examined the reproductive biology of this species at 3 sites in west Texas from 2017 to 2019. We detected follicle enlargement beginning in the fall with shelled eggs appearing as early as 7 April and as late as 12 August. We found a significant quadratic relationship between day of year and maximum follicle diameter (r(2) = 0.22, F-2,F-100 = 15.61; p < 0.05). A significant relationship between turtle size and clutch size was not detected nor was there a significant relationship between turtle size and egg width. We detected a record clutch size of 17 eggs and a mean 6 SD clutch size of 11.4 +/- 3.11. We observed a single instance of production of 2 clutches. The smallest gravid female we detected with shelled eggs had a plastron length of 179 mm. We also found that the probability of capturing a female gravid with shelled eggs was highest in early June. Our results suggest geographic variation occurs in the reproductive biology of P. gorzugi and highlight the importance of range-wide, temporally extensive sampling. Data presented herein can be included in population viability assessments and inform conservation recovery plans.