Bison Crossing and Caterpillar Buffet

We’re spending this week in Elk Island National Park, which is home to both Plains Bison and Wood Bison. When we arrived at the park, we saw a few lone bison along the road, but today on our way to visit our first site we saw a whole herd. We had to stop the bus because the herd was taking up the whole road. We drove behind them a slow pace until the bison eventually turned off into a meadow. We were all excited to see Canada’s largest land mammal, and it’s not every day you’re held up on the road because of bison traffic.

The bus following the bison
A large bison bull
The spiky caterpillars chowing down on aspen leaves

In insect news, today I spotted a young aspen tree being devoured by large black caterpillars. The thing that piqued my interest was that these young leps (butterflies and moths belong to the Order Lepidoptera) were covered in long, very sharp looking spines. I had never seen anything like them before, a bit of research revealed them to be the caterpillars of mourning cloak butterflies (Nymphalis antiopa). These guys actually overwinter as adults, and lay eggs in large bunches on a single tree. The new caterpillars hatch within ten days and promptly begin eating. They pass through 5 instars before they leave their natal tree in search of a safe place to pupate. The small aspen tree was nearly bare of leaves when we left, and if you stood underneath it you could actually hear the caterpillars chewing.

–         Jen

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