A red stop sign. A flashing yellow light. A sign along the trail displaying a coiled rattlesnake. These are visual signals that tell us to slow down, back off or avoid the area. In nature, these visual signs are known as aposematic coloration or markings. They are used to warn potential predators to stay away.
That’s one reason why Monarch butterflies are so vividly colored. The color patterns send a message to would-be predators: don’t even think of taking a bite out of me. Not only do I taste horribly bitter, I will make you up-chuck.
How does this work? Monarch’s exosketons and wings contain toxins known as cardiac glycosides. These toxins are found in the leaves and stems of Milkweed plants (genus Asclepias). Monarch butterflies seek out Milkweed plants to lay their eggs. When the eggs hatch, the larvae eat the leaves, thereby accumulating toxins in their bodies. These toxins produce a bitter taste and can cause the predator to vomit. It doesn’t take long for the predators to recognize and avoid Monarchs.
But Monarch coloration is both vivid and subtle at at the same time. Click here to take a closer look at some subtle variations in wing color. Does this subtle variation also send a signal? Or does it have another purpose?
Using digital image analysis, scientists at the University of Georgia found that suble variations in color are also an indication of the ability to migrate. Researchers at the University of Georgia found “that migratory butterflies are darker colored than non-migratory ones, suggesting an association between darker color and increased fitness.” Specifically, in the lab they “found that those with darker orange wings overall flew longer distances than those with lighter wings.”
This labratory data supports the field observations: “The wings of fall migrating monarchs in eastern North America expressed a darker shade of orange (i.e. more red) relative to the wing color of non-migrating summer cohorts.”
Researchers do not know why this is so. Perhaps “pigment deposition onto wing scales during metamorphosis could be linked with traits that influence flight, such as thorax muscle size, energy storage or metabolism.” Looks like there’s more research to be done.
In the meantime, perhaps we need a new descriptive term for Monarch coloration that signals migration flight readiness. Instead of “aposematic”, how about “fysb” (pronounced fisbee) for “fasten your seat belts”?
If you want to learn more about our local Monarch Butterflies, here are a few sites to check out.
Here’s a recent article in SCV News by Evelyne Vandersande:
Here’s a link to the Goleta Butterfly Grove:
Here’s a link to an article on “Butterfly Migration” by Dr. Paul Levine in the Jan/Feb issue of “The Rattler”, the newsletter sponsored by the Placerita Canyon Nature Center Associates. See Page 4.
Upcoming Outdoor Events:
Trail Maintenance Schedule. Come join our volunteers as they help maintain our trails. Contact Steve at firstname.lastname@example.org for time and place.
Wednesday mornings, January 30; February 6, 13, 20, & 27.
Saturday mornings, February 2 & 16.
Saturday, February 16, 8:00 – 10:00 AM. “Wild Birds of February” at Towsley Canyon. Meet in the front parking lot at the gate. Click here for a map and directions.
Saturday, February 23, 2:30-4:30 PM. “The Earliest Wildflowers” at Towsley Canyon. Meet in the parking lot at the gate. Click here for a map and directions.
New trail maps available. If you’d like to explore a bit on your own, the City of Santa Clarita has a website with trail maps of our local open spaces: http://hikesantaclarita.com/.
There’s also a new website for bicycle riders. http://bikesantaclarita.com
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