There are indications that western pond turtle populations are somewhat different from those on tributaries. Populations are being monitored and the reproductive implications of the smaller adult body size of western pond turtles observed on the mainstem are being assessed, particularly in comparison with the South Fork Trinity River. Proportions of females with eggs is low on both river forks and generally only larger turtles have eggs. In 2009, only two egg bearing females were detected on the mainstem (9.5%) and these were both older turtles originally captured and marked in the 1990s. On the South Fork, four relatively large gravid females were detected (16.7%).
Suggested further reading:
Welsh, H H Jr, Hodgson, G R; Duda, J J; and Emlen, J M (2010) Faunal assemblages and multi-scale habitat patterns in headwater tributaries of the South Fork Trinity River – an unregulated river embedded within a multiple-use landscape.
Ashton, D T; Bettaso, J B; Rousseau, J S; and Welsh, H H Jr (2010) Comparative ecology of the western pond turtle (Emys marmorata) on two forks of the Trinity River. Oral presentation provided at the 2010 Trinity River Science Symposium
Reese, D A, and Welsh, H H Jr (1998) Habitat Use by Western Pond Turtles in the Trinity River, California. Journal of Wildlife Management 62(3): 842-853.
Wilson, R A; Lind, A J; and Welsh, H Jr (1991) Trinity River riparian wildlife survey – 1990.