First things first, an update:
Today blog readers I finally have some good news… we caught our first Colias butterflies! It was a beautiful day at Brush Creek and we say some yellow butterflies flying along the road and quickly stopped to catch them. We caught 11 butterflies and I’m really excited about catching more tomorrow!
Now onto the meat and potatoes of this blog post:
The snowmelt in the Rocky Mountains has been exceptionally late this year (see this interesting news story about decreased wilflower season). As you may know if you’ve been keeping up with my previous posts, this means that my butterflies have been a little delayed in their emergence times and it’s a good thing to or they would all freeze to death! Climatologists predict that there will be an increase in extreme climate events (such as drought, excessive rainfall, extreme heat waves, etc.) as well as an increase in average global temperature. In regards to my butterflies and all thermally sensitive organisms this means that there is a two-fold problem to deal with concerning climate change. Organisms must be able to adapt to a gradually warming climate or move to a new habitat with the right climate, however to really thrive organisms will also develop some way of dealing with extreme events.
This year because of the late snowmelt and the cold temperatures my butterflies have shifted their emergence date. They do this by sensing the temperature and the photoperiod (how long the sun is out). When conditions are right they emerge, when conditions are wrong they stay in their overwintering state. This late emergence is the direct opposite of last year when it was a particularly early snowmelt and so they emerged much earlier. The butterfly’s ability to sense both the light and temperature together is very important in its survival in dealing with springtime variability. This ability to shift certain traits based on environmental cues is called phenotypic plasticity. This is key in dealing with variable environments. If the butterflies were unable to shift their emergence date, a majority of them would have died and the population would have suffered in the cold weather this year.
What happens when extreme events occur and they affect something that is not a plastic trait, meaning it can’t change due to the variable environment? That may sound confusing so let me give you an example: It’s the middle of July and the Colias are now caterpillars munching away on their favorite leaves. For three days there is a heat wave and the high for these days is 88°F (which is very, very hot for out here). The caterpillars begin overheating at 85°F (this is an educated guess, I will have clearer data after this summer) and they stop feeding. Once they stop feeding they stop growing and developing. By the end of the summer some of the population died in the heat wave and others are smaller than in previous years. If these caterpillars are smaller that means the adult butterflies will be smaller, and they won’t be able to lay as many eggs. This could mean a decline in the population size of butterflies next year. Pretty scary huh?
Now, there have been extreme events before, but with climate change we are going to see an increase in the number of weird weather events, which may be difficult for some organisms to deal with. I am trying to tackle some of the questions that deal with “how will caterpillars respond to heat or cold shocks?” this summer, and I’ll keep you posted on my findings. If you are interested in reading more about this check out the story about the Bay Checkerspot butterfly and how some populations went extinct due to changes in precipitation.