Winter is on the way, and for many people that means it’s time to start looking forward to spring – and to the abundance of plant and animal life that it will bring. As we pass the winter in our cozy homes, wrapped in sweaters and scarves, we probably haven’t considered what the other animals’ plans are to survive the coming rain, snow and cold.

Each animal’s plan is different, and in the case of our Taylor’s checkerspot butterflies, the plan involves fewer toques and sweaters than ours does…

By mid-summer, our Taylor’s checkerspots are fat caterpillars, having gorged themselves for on their favourite leaves since the day they hatched. They won’t become butterflies until next May, so they must survive the winter in caterpillar form.

When August arrives, our captive caterpillars are fat and fuzzy. Here a group of siblings take a break from eating leaves to bask in the sun and warm themselves.

One day in early August, the caterpillars decide that they have done enough growing for one year. In their defense, this decision isn’t made out of laziness – they simply run out of leaf-snacks. in August the food plant of Taylor’s checkerspots usually wilts and dies back until the following spring.

Cocooning, but not quite

The caterpillars stop eating, seek out a small crevasse in a log or sheltered spot between some leaves on the ground, and create a small web of silk. Though it is similar to a cocoon, this web is less dense and more of a temporary structure. It acts like a net, holding the caterpillar in place as well as securing the “walls” of their chosen hiding spot together.  Studies have shown that this silk web also regulates humidity and may aid in preventing invasion of fungi and bacteria. Inside the web, the caterpillar curls up and stays still, saving its energy for the arrival of spring. This phase of their life is called diapause.

Here at our lab at the Greater Vancouver Zoo, our caterpillars spend the winter in plastic cups, webbed up with their siblings among folds of paper towel. It may be slightly more cozy than being under a log, but they’ll still be exposed to the cold temperatures of winter, just like their wild counterparts.

Behind me in this photo are the tubs full of Taylor’s checkerspot caterpillars in diapause. Though peace and quiet is appreciated as they wait for spring, we are sure they won’t wake up grumpy – as long as there are plenty of leaves for snacks!

The secret to survival

When the thermometer dips below zero, the secret of Taylor’s checkerspot winter survival is anti-freeze! It is important to remember that insects don’t create their own body heat, and so the temperature of their environment dictates the temperature of their body.

Most animals’ cells would burst if they reached below freezing because the water inside of them would form jagged crystals. But our caterpillars can concentrate chemicals called cryoprotectants inside of their cells, so that their cells don’t actually freeze solid and burst. This is comparable to filling their cells up with antifreeze. So, even if they are cold as little caterpillar-popsicles, our Taylor’s checkerspots can survive until it’s time to resume eating and growing alongside all the other animals we look forward to seeing in the spring. 

Help the butterflies – leave your leaves!

If you, like me, are looking forward to  the abundance that springtime will bring, you can do something to help: You’ll be a biodiversity hero if you just… leave your yard messy!

Leaving a pile of leaves, some logs on the ground, or a brush pile sitting around provides the little hiding places that many creatures require to survive, just like Taylor’s checkerspots. Even if your favourite animal doesn’t overwinter in your ‘messy’ yard, it’s possible that it’s food source does. Remember that biodiversity is a complex web – leave space for the messy parts of it as well.

Leaving a bit of ‘mess’ in your yard can pay off – in biodiversity! Here’s a long-toed salamander that is living under a log near our lab, and enjoys our (very) relaxed approach to gardening and lawn care.

Kudos to all the little animals toughing it out in the cold, tucked away under leaves and logs… but we humans should probably stick to our sweaters and woolly socks! See you in spring, little guys!

Michelle Polley

Endangered Species Technician – Taylor’s Checkerspot Butterfly

Michelle is a Conservation Biologist and Field Naturalist with a special interest in Lepidoptera (butterflies and moths) and Herpetiles (reptiles and amphibians). Currently, she is the technician of WPC’s Taylor’s Checkerspot Butterfly program in Abbotsford, BC. She has worked with conservation projects for species at risk such as monarch butterflies and the turtles of Ontario.