North America is home to 7 of the 30 different species of mole. The 4 of those seven that live on the west coast are;
Moles are insectivores, not rodents, meaning they only eat what creeps crawls and wriggles. That means they don't ever have to come above ground. In order for a mole to survive, they have to eat half their body weight in worms every day. That's almost 100 worms a day!
The mounds you see popping up in your yard are the excess soil from a mole making a feeding tunnel. The mole is strong enough to move through the dirt by pushing it to the side but then it's too dense for a worm to move through. The mole will go back through the tunnels and loosen up the soil sending the excess upon your perfectly manicured lawn.
Moles love to follow landscaping ties, paving stone, sidewalks and driveways. If you lift a paving stone you'll see why. It's like a creepy-crawly buffet!
You might think your yard is infested with moles but they are actually very territorial. One mole patrols its encampment which varies in size depending on how many worms you have in your yard.
Remember it has to eat half its body weight every day. The mole leaves a scent trail in its tunnels to keep neighbouring moles out.
Once a year in the winter the moles have to reproduce. The males are now seeking a female and this is where you might see one mound pop up in December and then nothing. It's likely a male passing through looking for a female.
Once he finds a female he can't stick around too long. Get the job done and get out! He's in her territory and she will fight to protect it.
Usually, by May she will give birth to 2 - 4 young. By June they are old enough to eat worms and she can't have them taking from her supply. She will chase them out to find their own territory.
If they can't dig fast enough they may come up out of the ground to getaway. This is generally the only time you might see a mole above ground.
Moles are active year-round. They have to eat to survive so they go where the worms are. Some worms burrow deep below the frost line so that's where the mole will go.