This past weekend I returned to the Pacific Northwest to continue research on a large-scale project looking at how Painted Turtles (Chrysemys picta) locally adapt to variation in climactic conditions.
This past June, I ventured to field sites in Idaho and Oregon with a team lead by our advisor, Dr. Dan Warner. Our goal - to locate and observe female turtles laying eggs (without spooking them), capture the female afterwards, and excavate the nest to measure and count her eggs.
Female painted turtles spend most of their lives in water and basking on logs. However, they leave the water and search for suitable nesting locations on land from May to July. Once a suitable location has been found, the female excavates a hole around 8 to 15 cm deep using her rear legs. Then she lays a clutch of eggs that ranges from 1 - 21 eggs before covering them back up. Females can lay up to three clutches throughout the nesting season, and larger turtles tend to lay larger clutches.
Female nest site choice is very important because the sex of the offspring is determined by the temperature the embryos experience during development (temperature-dependent sex determination). How crazy is that?! Colder nest temperatures produce males, whereas warmer temperatures produce females.
This past June, I ventured to field sites in Idaho and Oregon with a team lead by our advisor, Dr. Dan Warner. Our goal - to locate and observe female turtles laying eggs (without spooking them), capture the female afterwards, and excavate the nest to measure and count her eggs.
Female painted turtles spend most of their lives in water and basking on logs. However, they leave the water and search for suitable nesting locations on land from May to July. Once a suitable location has been found, the female excavates a hole around 8 to 15 cm deep using her rear legs. Then she lays a clutch of eggs that ranges from 1 - 21 eggs before covering them back up. Females can lay up to three clutches throughout the nesting season, and larger turtles tend to lay larger clutches.
Female nest site choice is very important because the sex of the offspring is determined by the temperature the embryos experience during development (temperature-dependent sex determination). How crazy is that?! Colder nest temperatures produce males, whereas warmer temperatures produce females.
We are interested in how these turtles have evolved to deal with variation in temperatures at different locations across the United States. Do females choose warmer nest sites in the North where the climate is colder? Have populations evolved so that the temperature which produces about 50% of each sex matches local temperatures? These are the kinds of questions we wish to answer.
To do this, back in June, we measured a number of parameters for each nest site females chose. After measuring the eggs, we placed them back inside the nest with an I-button data logger (to record nest temperature) and covered them back up with soil. Then we nailed a sheet of wire mesh over the nest to keep predators from digging up the eggs. Then we moved on to find another nesting female.
Fast forward to this past weekend. We returned to excavate the nests again. Only this time, there were baby turtles looking back at us! By looking at the sex of the turtles and comparing that to the temperatures from I-buttons pulled from the nest, we will be able to get a sense of what kinds of sex ratios are produced at certain nest temperatures for our study sites. This will then be compared to data collected by collaborators from other sites across the USA. We will also be able to see if female nest site choice varies across sites.
This work is headed by Dr. Fredric Janzen at Iowa State University and has broad implications for how species will be affected by regional climate change.
To do this, back in June, we measured a number of parameters for each nest site females chose. After measuring the eggs, we placed them back inside the nest with an I-button data logger (to record nest temperature) and covered them back up with soil. Then we nailed a sheet of wire mesh over the nest to keep predators from digging up the eggs. Then we moved on to find another nesting female.
Fast forward to this past weekend. We returned to excavate the nests again. Only this time, there were baby turtles looking back at us! By looking at the sex of the turtles and comparing that to the temperatures from I-buttons pulled from the nest, we will be able to get a sense of what kinds of sex ratios are produced at certain nest temperatures for our study sites. This will then be compared to data collected by collaborators from other sites across the USA. We will also be able to see if female nest site choice varies across sites.
This work is headed by Dr. Fredric Janzen at Iowa State University and has broad implications for how species will be affected by regional climate change.