Population And Biomass Estimation Of Turtles At Spring Meadow Lake State Park, Helena, Montana

Abstract

This study was conducted to estimate the population density and biomass of turtles in an urban lake. I calculated that 74 turtles over 9.0 cm in width were living in the Park, which was 6.1 turtles/ha of water. The approximate turtle biomass was 3.1 kg/ha. This is low compared to other studies. The difference may be accounted for because I only estimated the population and density for turtles over 9.0 cm in width, due to capture methods. Mapping of turtles from visual sightings revealed that the turtles changed their basking locations during the day. This was most likely due to maintaining body temperature. The only exception was in Area E, which provided little protection for the turtles on the west and north shores. I also tested to see if there was any evidence of species, especially non-native species, being introduced into the area. Although there was evidence suggesting that turtles from outside the lake were introduced into the lake, only Painted turtles (Chrysemys picta), which are native species, were captured or observed during the study. Sex ratio for the population was approximately 1 female : 1 male. Differences in population density between portion of the lake were correlated with the level of public use and availability of concealing cover.