"It's beginning to look a lot like Christmas..."
Looking out the window this morning from my southern Ontario home, I was greeted with a lovely blanket of white fluffy snow. Some grumble at the sight, while others smile and enjoy the beauty. Some of us (particularly of the canine species) are ecstatic and the snow is an excuse to run and frolic.
What about the blacklegged ticks? What does snow mean to them?
Snow is actually 'good' for ticks. In the winter months, when conditions are not favourable for them to be active, they will remain in the leaf litter layer in the forest. Snow provides a nice protective layer of insulation.
The main factor that influences if a tick population can survive and reproduce is the climate in the non-winter months. During each life stage, the tick will take one blood meal and then undergo a period of inactivity called diapause. During diapause, the tick develops to the next life stage. Temperature influences how quickly development can occur (to a limit), with development occurring faster at higher temperatures. If development takes too long, the tick will starve before it reaches the next life stage to look for another meal.
In a nutshell, the non-winter months need to be warm enough, for long enough for tick population survival. In the entomology world, this is measured using cumulative degree days.
That all being said, we need to be careful that we do not associate snow with no risk of ticks. Although they reside in the leaf litter layer, this is only when conditions are unfavourable (i.e., >4 degrees C). If there is a nice warm winter day and a tick 'wakes up' hungry, they will actively start to look for a host.
In many areas of Canada, it has become increasingly difficult to predict the tick season. It is a good time to have a conversation about tick prevention throughout the winter months. You might be in an area where winters are very cold and ticks are never seen between December and March. However, many of us live in areas where the winter temperatures fluctuate and risk may still be present at times when we are not thinking much about ticks.
Enjoy the snow!