Friday, July 6, 2012

Back out to the Russel Glacier area today! We visited Eric Post's and his students' site to learn about caribou populations, vomiting caterpillars, and a curious fungus. Michael Avery explained the group's findings. They found that the changing climate is effectually causing an earlier spring in plant communities. What does this have to do with caribou? Warmer temperatures and more exposure to sunlight at an earlier time cause the plants to bud and leaf out sooner, bringing about a higher mortality rate in caribou calves. By the time the caribou herd arrives at its calving grounds (which has continued occurring at the same time each year), it has missed the short period of fresh, healthy, "new" vegetation critical to the mothers and their calves (without nutritious vegetation, the mothers can't produce nutritious milk for their calves). 

Mike's Lecture

Michael has been collaborating with other students on Eric Post's work (with the caribou), but individually, he studies invertebrates. Michael has been studying a particular caterpillar species (Eurois occulta) that experiences frequent population booms and crashes. While there are a number of plausible causes for the population booms, the reason the population crashes was a mystery to him until very recently. Michael discovered that there is a fungus (Zoophthora radicans) that has been targeting and infecting the caterpillars, evidence that it is a factor in the sudden decreases in population. The fungus slowly consumes the caterpillar from the inside, starting with the non-essential organs and working its way up to the brain. Before killing its host, the fungus floods the caterpillar's brain with chemicals and hormones that stimulate the caterpillar to climb as high as possible and clamp onto something tightly. Once the caterpillar "clamps on" and dies, the fungus matures and sporulates (the reason for stimulating the caterpillar to climb - the higher the caterpillar is, the greater the dispersion of fungus spores).


On a side note about the caterpillars: if you tease them enough, they will respond by vomiting a sticky string of chewed-up grass goo at you! (Some of you might be thinking "EWWWW!", but I say "AWESOME!") This behavior is actually a natural defense mechanism that Michael explained the caterpillars probably developed in an evolutionary "arms race" with the Greenlandic bird species that typically prey on them. In order to avoid being eaten, a caterpillar will rear up on its pseudopods (the suction cup-like "feet" on the end of the abdomen), regurgitate its grass "gunk", and, as Michael found on closer examination, eject an additional chemical substance into the emesis out of a tooth-like orifice located below the caterpillar's mandibles. All of this serves to create a very unappetizing deterrent that the birds have learned to avoid. How did Michael discover this behavior? Apparently, after weeks of collecting and examining caterpillars, you become kind of cynical and begin messing with your specimens for fun - thus Mike turned to purposefully making caterpillars vomit.


After learning about Mike's work and that of some of the other students, we went on a glorious trek up into the hills. Okay, so the trek wasn't all that fun - there was so much steep terrain - but the views were absolutely breathtaking! Marisa, Shelly, Lynn, Cecilie, Nivi, Charlotte, and I stumbled upon a rock face covered in garnets! The surface of the bedrock had been sheared off at some point in time by the glacier, and what remained was an exposed area riddled with loose garnets! Needless to say we took some samples for scientific purposes (*cough, cough* ;) ).


What a day! It was so much fun, but I'm exhausted again! Stay chillin!