Invasives on Land

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Written and narrated by Gavin Hankey, vertebrate zoologist at the Royal BC Museum.

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You can't miss the invasive Himalayan blackberry, spurge laurel, common ivy, holly. These were all introduced from gardens and they've spread rapidly on Vancouver Island. I remember holly, ivy, and blackberries from England when I was a child. They are nostalgic for me, but they should never have been planted here. Our climate is not that different from England, so there's no surprise that British plants would thrive here. Even the common dandelion is introduced and easy to find around Swan Lake.

 

Down in the soil, under the leaves and fallen wood are sowbugs, pill bugs, earwigs, leopard slugs, even the common earthworm, and a few other species are found here at Swan Lake Sanctuary have invaded from Europe. They are now so common people forget they're introduced.

 

Look up in the trees and in the shrubs, every time I'm here I see European starlings and house sparrows.  These were released in New York and spread here on their own. If you are lucky you can find a California Quail with their comma-shaped crest as they scuttle through the undergrowth. They were introduced here for hunting, but our urban centres are pretty safe habitat for these nervous birds. One of the easiest invasive species to find is the Eastern grey squirrel. They’re bold and comfortable around people. The population here stems from three which escaped from a farm in Metchosin in the 1960s. They’ve spread far and wide since.

 

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You may also see rabbits while walking along the trails here at Swan Lake. All rabbits on Vancouver Island are introduced. There are also feral or even domestic cats that are still going home at night running around the neighbourhood will be killing many mammals, small mammals, birds. The impact of domestic cats globally is huge and they certainly impact things here at Swan Lake.

 

Invasive species are a problem here in British Columbia and around the world because they disrupt native ecosystems, they displace native species, and they cause significant economic damage.

 

Without a doubt, my favorite invasive is the common wall lizard. It was first seen on the borders of the Swan Lake Sanctuary in 2020. Today, there must be over 700,000 of these green lizards in British Columbia all from the original 12 lizards released here around Brentwood Bay in 1970. In some places, these lizards are so abundant that you can't take a step without hearing a lizard skittered away. The wall lizard is distinctive. One, it's very skittish. So an alligator lizard, which are native species, you can almost walk up and touch them. They rely on camouflage. But a wall lizard will run if you get within a few meters of it. But wall lizards are slender. They have bright green scales down their back. And the native species here has much larger scales on its back. So, they are easily distinguished just based on colour alone. If you see a bright green lizard that runs away from you as soon as you walk up, it's the invasive wall lizard here.

 

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Well, the lizards alone are my favorite because as a child I always had pet lizards. So the fact that I get paid to study lizards now, in the wild, I find it hilarious. It's fun. I smile every time I catch one. They're pretty, neat little charismatic lizards. They shouldn't be here. The bottom line is they should never have been introduced, but it is certainly fun to study them.

 

The wall lizards, we have not yet studied their diet but one of the problems we have found them killing baby Garter snakes. So that definitely is an impact. They’re big enough that they could eat baby shrews, baby mice. They eat pollinators. So bees, like honey bees, mason bees, bumblebees. They eat wasps. They eat a range of insects, spiders. We know they eat each other. So a wall lizard can eat a lizard a third of its own length, which is amazing and disgusting at the same time. So their impact is really intense 'cause a lizard delete multiple things a day and there are thousands of these lizards in the area. So definitely, it's a problem here and it's a problem across Victoria on Vancouver Island.

 

Select the map button to enjoy more Swan Lake reflections.