Slow Down! Save the Butterflies and the Bears

If you’ve been driving around the park lately, you’ll see yellow caution signs on them with red bears. These mark places where bears have been hit by cars, which as far as I know is the leading cause of death to the parks bears.

Currently, there is a major population explosion of California Tortoise Shell butterflies, a relatively uncommon species in most years. They are being killed by the thousands by cars, but at 25mph they tend to flow over the car. Please slow down if you see tons of butterflies. Here’s the announcement:

Once again, we are experiencing an irruption in the population of the
butterfly, the California Tortoise Shell (Nymphalis californica) along El
Portal Road between Windy Point, to down past Yosemite View Lodge. This
beautiful orange and brown butterfly is being killed by vehicles in the
thousands in this area. While complete avoidance of hitting butterflies is
not possible, the carnage can be substantially reduced if drivers reduce
their speed. At around 25 mph, the butterflies tend to be swept over the
vehicle unharmed. At faster speeds, the butterflies are struck in large
numbers by the grills and windshield of vehicle.

So during this period, which may last through June, please slow down and
enjoy this spectacle. In most years California Tortoise Shells are a
relative uncommon species. But in certain years, they emerge in
overwhelming numbers. This species could be responsible for our county’s
name, Mariposa, which is Spanish for butterfly.

The larvae of the species feed mostly on ceanothus shrubs. Several
generations of egg-larvae-pupa-adult metamorphosis may occur in
spring-summer, but the butterflies tend to move progressively higher in
elevation as the year advances. Some scientists believe this is because
plants at these elevations have new, tender growth, and lower levels of
tannins later in the season, making them more nutritious for larvae. (S.
Thompson – 5/20/08)