Animal Diaries Archive
Pivotal Temperatures
20 April 2007
G'day Folks! Summer time here in Australia is not only important for us to enjoy, but also for our reptiles, the hot summers play a very important role in our reptilian's lives. All of the Crocodiles, Sea Turtles, Freshwater turtles some lizards, and even our American Alligators here at the zoo are subject to Temperature Dependant Sex Determination (TSD). This is where the sex of the young is determined by the environmental conditions, such as temperature, during incubation.
Over the summer holidays both Roving Megan and myself (Roving Kate) were lucky enough to take our holidays and volunteer up at Mon Repos Conservation Park - one of Australia's most important Loggerhead Sea Turtle Rookeries where we were able to experience TSD first hand. Mon Repos Conservation Park, on the central coast of Queensland, is a predominantly female hatching-producing beach. This is because the temperatures in the sand are consistently above 28.5 degrees Celsius - the pivotal temperature for TSD in Sea Turtles. Any eggs incubated at below 28.5 degrees Celsius would be predominantly male. This means that the thousands of hatchlings coming off the beach every summer are almost all female.
On the Sunshine Coast, we also have many Sea Turtles coming to nest on our beaches - we have consistently lower temperatures than Mon Repos, so we produce more males than females! Our hot summers here in Queensland are getting worse every year. Scientists predict that Sea Turtles will be nesting here on the Sunshine Coast to gain a more mixed sex ratio of their hatchlings, to ensure the survival of their species!
Here at Australia Zoo we have recently had some American Alligators hatch out from our incubator. These little guys have a similar situation to the Sea Turtles - except upside down! Incubation of Alligator eggs at 30 degrees Celsius produces mostly females - and over 33 degrees Celsius produces mostly males!
PIVOTAL TEMPERATURES FOR TSD INCUBATION
American Alligators
30°C = Female
30 - 33°C = Mixed Sex Ratio
33°C = Male
Saltwater Crocodiles
> 31°C and <33°C = Female
32°C = Male
Sea Turtles
> 28.5°C = Female
< 28.5°C = Male
So folks next time you're at the zoo come and chat to the rovers about Temperature Dependant Sex Determination. Stay tuned to our Animal Diaries to find out more about our amazing reptiles!
Roving Kate
