The Blanding’s turtle and the effects of global climate change

Blanding’s turtle (Emydoidea blandingii):

Look at the picture above and take a guess at the Blanding’s turtle’s most distinguishable feature – what do you think?  The yellow throat is pretty hard to miss!  If I may: for some reason, the colour and texture reminds me a bit of the underside of a peach ring (of course, leave it up to me to make a food reference):

Aside from its brightly coloured throat, the Blanding’s turtle can also be identified through its long tail and a dark coloured carapace which is scattered with yellow dots and lines.  These markings tend to be brighter in young turtles, and may fade with age (18).  The length of the carapace can reach up to 27 cm (18).  Do you get the impression that Blanding is smiling at you?  Yes, it’s quite adorable!  Blanding’s turtles’ mouths are naturally curved upward, which is why these turtles look to be in a permanently good mood.  Their distribution in Ontario can be found below:

This species is primarily aquatic.  Adults can live beyond the ripe old age of 75, and like to spend their lives chilling by the water. They don’t particularly mind being out in the open.  Young ones, on the other hand, are far more shy and prefer the refuge of densely vegetated areas (18).  Canadian Blanding’s females are late bloomers that mature at age 25.  This is problematic since adults are highly susceptible to road mortality and thus may not be able to produce many offspring before they die (4).    What makes them susceptible?


Credit YouTube user: Canuckboy123

Okay, so watching a turtle cross the road isn’t exactly my idea of excitement either, but were you holding your breath?  I sure was!  That was scary to watch.

In addition, females like to dig their nests in loose substrate, such as gravel and dirt found by the side of roads – I’m sure you can detect the problem here.  Since eggs are only laid once every few years and it takes a long time for females to “hit puberty” (to put it in a more anthropogenic term), adult mortality can really hurt the population.

The Great Lakes population of Blanding’s turtle was last assessed as “Threatened” by both SARA and COSEWIC in May 2005 (18).  Currently, conservation efforts are directed at increasing connectivity between populations, and preserving the habitat in which these animals live (18).

Another unique feature exhibited by the Blanding’s turtle is temperature dependent sex determination (TSD).  Eggs incubated below 28°C will result in males, and eggs incubated at above 29°C will result in females.  The range of temperature within which these eggs can survive is between 22°C and 32°C.

Global climate change:

Have you ever seen “An Inconvenient Truth”?  If you can ignore all the allusions to politics, economics and social issues (sorry, a substantial chunk of the movie), Al Gore will give you a pretty good summation of what global climate change is.  Although there are obvious skeptics out there, for the sake of this discussion, let’s just consider that this is a reality.  What is global climate change?  The term can be translated quite literally: the Earth’s climate is changing.  I’m sure we have all had first hand experience with the wacky weather that mother nature has served us over the past few years.  Global climate change is often synonymously associated with global warming, which can be deceiving.  Although there are places that are getting warmer, there are also places that are getting cooler.  The exact science of global climate change could be a whole blog by itself, and I can’t even feign comprehension as it is a highly complex problem.

As I mentioned yesterday, habitat issues are often the focus when researching Ontario’s turtle population decline.  In terms of the effect of global climate change on turtles, studies have largely revolved around sea turtle populations (19)(20)(21)(22).  This is not applicable to Ontario’s species, but climate change is still a worthy area of discussion since it is becoming a conservation issue of global concern.  Research surrounding the effects of global climate change on TSD species have forecast negative outcomes, especially in combination with preexisting conservation issues like habitat alteration (22).  In fact, studies on loggerhead sea turtles (Caretta caretta) have even shown that climate change has altered the natural history of these animals.  For the past decade, they have exhibited earlier nesting behaviours in response to warming ocean temperatures (23).  However, in the case of Ontario’s turtles, warmer temperatures may also be advantageous since it would allow them to extend their range farther north.  Ranges are often limited by temperature (1).

The main issue with climate change in TSD species is that it has the potential to skew sex ratios.  In the case of the Blanding’s turtle, just one degree can mean the difference between a male and female egg.  In the future generation, this could translate into too many females and not enough males (or vice versa) – again, detrimental to reproductive output.  One could argue that these effects could be offset by strategic placement of nests.  For example, if it got too hot, it would make sense for a momma turtle to lay her eggs near shaded forests which are naturally cooler.  Makes sense – but logical solutions aren’t always feasible.  What if there are no forests?  It is for this very reason that scientists have predicted disastrous coastal deforestation effects for the critically endangered hawksbill sea turtle (Eretmochelys imbricata) (22).  One may also speculate that a slight increase in temperature could be beneficial under certain contexts.  Blanding’s females are more susceptible to road mortality than males since they prefer to nest near roads (18), thus, maybe an increased female-to-male ratio could serve as a benefit (within limits).

Ontario’s TSD turtles (the Blanding’s and the common snapping turtle) have not encountered these problems yet, but it is impossible to predict what the future holds.  A past study on the effects of temperature on Blanding’s turtles has conclusively shown that temperature affects sex ratio as well as embryo success, and also hypothesizes that these turtles may use shaded and unshaded areas accordingly (24).  Will deforestation also cause this turtle trouble, then?  As it did in the loggerhead turtle?  Climate change is an inescapable consequence of our resource use, how will it affect Ontario’s turtles?  I have presented these issues as insight into potential outcomes, hopefully you will be able to formulate your own opinions with this information.

What can I do?

Fortunately, despite the fact that climate change is a global issue, we can combat it locally!

  • Walk, bike, carpool, take local transportation!  Do what you can to reduce your carbon emissions.
  • Eat locally!  Visit some farmer’s markets.  Think about all the emissions you could be avoiding – it takes a lot of resources to import and transport food.
  • Switch out those old lightbulbs for fluorescent ones.
  • Take cooler, shorter showers
  • Change your computer’s energy saving settings so that it will shut down faster when it is inactive
  • Remember to switch off lights and appliances that you don’t plan to use
  • Learn more about renewable energy – check out Bullfrog Power
  • Tell people about what you’ve learned!

References

Side note: Happy St. Patrick’s Day everyone!  It’s a beautiful day outside.  I can’t help but be in a good mood, especially after witnessing my housemate and her sister all dressed in green and dancing to Honky Tonk Badonkadonk.  I felt the urge to join in, but I resisted.

 

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4 thoughts on “The Blanding’s turtle and the effects of global climate change

  1. “Yes, it’s quite adorable!” – gotta leave it to cheryl to give turtles a personality.

    “Blanding’s turtles’ mouths are naturally curved upward, which is why these turtles look to be in a permanently good mood. ” – I have yet to find a turtle that matches my persona.

    Interesting discussion on the effects of climate on TSD species. I always knew about the two separate topics but never did make the connection.

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