Nature

Fight for Survival

A monarch caterpillar munching. Hours and hours of NO drama.

Popular nature documentaries feature dramatic fights for survival. “Jaws and claws” scenes boost ratings, but routine survival is more about devouring….greens.

Insects—like good children—eat their veggies. And plants don’t run away fighting for their life. No conflict or drama. Very bad for ratings!

Sure, there are plenty of insect predators. Mantids are vicious killers. Ladybugs devour aphids. Spiders consume 400 to 800 tons of insects each year.

But most insects get most of their calories from plants.

Plants do fight back, but the fight happens in  S  L  O  W  motion.

Plants have evolved toxins. It’s not a coincidence that medicines and poisons come from plants. Or that the plants that we like to eat were selected over eons for their less bitter taste until—nearly defenseless—they could not survive on their own. That type of care and human selection—vs. natural selection—is called agriculture. 

Avoiding conflict. Munching AROUND the aphids.

Some insects are specialized eaters. They’ve evolved resistance to select plant toxins and thrive by eating what would kill other creatures.

Monarchs are so specialized that the only food a monarch caterpillar can eat is milkweed.

Specialization makes adaptive sense when a food source is abundant. But common Milkweed isn’t common anymore. And that’s one of many reasons why monarch populations are plummeting.

A monarch butterfly will only lay her eggs on milkweed.

The milkweed toxin (a steroid that can lead to cardiac arrest) builds up in the monarch caterpillar as it munches away. A bird that pecks on a monarch immediately tastes the nasty toxin and knows to never bother it again. 

The store of toxin is preserved during metamorphosis.  The monarch butterfly’s bright orange markings signal to birds that they’ll get a mouthful of poison if they were to take a bite.

Toxins. No jaws or claws required!

This type of co-evolution between plants and insects and birds has been going on ….since there have been plants and insects and birds.   

Look closely and you’ll witness slow-motion fights for survival everywhere, not just in monarchs.

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