How do reptiles adapt to a warming climate?

Howdy y’all, this is Noah from the Herpetology Department! There are some seriously awesome reptile and amphibian adaptations, and the “hot” topic of recent research has been their behavioral and physiological responses to a warming climate. The annual average temperature on our planet has been warming for a while now – in fact, for about the past 20,000 years. As many of you all are aware, this rate has increased a bit recently as well, due to the anthropogenic effect of more carbon dioxide in the atmosphere (via industrial emissions). Here’s how some of our scaly friends have adapted to temperature increases.

Banded bock rattlesnake (Crotalus lepidus klauberi): Our male can be seen in his habitat in the Scaly Slimy Spectacular here at the Zoo. These rattlesnakes from Mexico and America’s Southwest give live birth in the springtime. But what happens when there has been an increase in spring temperatures? These rock rattlesnakes adjust to warmer springs by giving birth about six days earlier than normal gestation times last. Although it seems like no harm-no-foul, there is an increased likelihood of baby abnormalities. For now, these rattlesnakes appear to possess advantageous phenotypic plasticity – meaning they can change their gestation period depending on the temperature that spring. Pretty amazing! But wait, there’s more! Read on!

Alligators: Although we probably won’t be seeing our African slender-snouted Crocodile friends (like Meci and Babu in Scaly Slimy Spectacular in our Atlanta backyards in the near future, the American alligator population has been taking advantage of the warmer seasons. Alligators now frequently spend time in southern Virginia, and several sightings have been confirmed in southwest Tennessee (near Memphis). Some reptiles, such as the common snapping turtle, made rapid migrations north following the last ice age, while alligators appear to be taking a more slow-and-steady approach to warmer regions.

Salamanders: Even though you probably associate warmer temperatures with the animals in the Herpetology Department (you’ve probably noticed heat lamps in their habitats), salamanders are quite the opposite as far as preference goes. In fact, amphibian activity in Atlanta increases the colder it gets! This also means the warmer it gets, the active period for amphibians decreases. This may lead to restricted eating during the “colder” months, even though metabolism may be higher. Lungless salamanders (or Plethodontids) of the Appalachians have compensated for this warmth with an 8% reduction in body size over the past 55 years. Since they cannot escape the warming seasons, they have adapted to them!

One last point I want to make is that sometimes, and unfortunately, advantageous evolutionary adaptations cannot keep up with environmental changes – especially increased rates of global warming. One of the worst amphibian disease outbreaks (i.e., a fungus colloquially called “chytrid”) is associated with rising temperatures in montane regions. Chytrid not only decimated global frog populations during warmer years, but actually drove about 90 species to extinction and still wreaks havoc to this day. Additionally, the populations of some reptiles may be affected by their sex ratio, as the temperature of egg incubation determines the sex. Green sea turtle clutches on Heron Island, Australia have been profoundly affected, as researchers rarely find male hatchlings (99.1% are female).

Hopefully you found this Keeper Blog interesting. Hope to see y’all at the Zoo sometime soon!

Noah C.
Keeper II, Herpetology