Project recognized for contributing to conservation!

The Habitat Conservation Trust Foundation, one of our major funders, presented us with an award for constructing the amphibian underpass system. The award recognizes the value of providing safe passage routes for amphibians and other wildlife under highways. In accepting the award, we acknowledge the B.C. Ministry of Transportation and Infrastructure and many local community members. Without their support, the tunnel installation would never have happened.

To see how we've shared our project as an example of conservation-in-action check out the links on the sidebar under "Sharing the SPLAT story".

Counting Amphibians on the Move

We have tallied the numbers! 

For 175 nights of surveillance during the fall of 2011, and spring, late summer, and fall of 2012 the total count caught on camera was...
                                                                                  

134 frogs and 95 salamanders! 

On average, one frog or one salamander moved through per night but there was a lot of variation. Some nights had none, others had over a dozen. The biggest count was in late April 2012 with a parade of 16 frogs and 3 salamanders! You can watch the action for that night in the video clip below.

Our mark-recapture results tell another story. A small proportion of the amphibians caught and marked on one side of the highway were recaptured on the opposite side: 5% of 631 Red-legged Frogs; 13% of 248 Northwestern Salamanders.

We know the exit traps did not capture every amphibian that traveled through the tunnel because we have pictures of some that were not trapped. But we also know many marked individuals stayed on the same side of the highway where they were first caught because we recaptured them there. We are investigating the exact location of recaptures to learn whether individual frogs and salamanders tended to head away from or toward the culvert after they were first trapped along the guiding fences.

At this stage, the tunnel has provided safe passage for over 200 amphibians that ventured through it. We will continue to look for interactions between amphibians and other wildlife using the tunnel, including a number of predators, such as mink, marten and ermine. 

Stay tuned!

Monitoring Movements through the Tunnel

We chose two methods to find out whether amphibians are using the new tunnel as a safe passage under the highway.

Method 1:

We marked amphibians that we caught in the forest on each side of the highway. We gave animals on the west side a different colour than the ones on the east side. We set up traps at each end of the tunnel, to intercept some of the amphibians as they exited, while not blocking others from entering in the opposite direction. We caught the ones that were intercepted and checked to see if they were marked on the opposite side of the road. If so, we gave them a second mark so we wouldn’t count them twice if we happened to catch them again.

Trap and fence to intercept amphibians exiting the tunnel in the foreground

Juvenile Red-legged Frog with foot marked in two colours after moving through tunnel

Results so far: 

We caught 22 marked frogs and salamanders on the opposite side of the highway after they crossed through the tunnel. That’s exciting, but on closer examination we realize it’s a relatively low percentage of the total number we marked – over 380. One explanation is that lots of marked amphibians may have avoided our tunnel traps. Another is that they may have decided not to cross through the tunnel.

We also caught lots of unmarked amphibians, but we're not sure if they came from the opposite side, or turned away from the tunnel entrance on the same side. Our second monitoring method will help us decide how many amphibians actually moved through and which explanation about the marked ones is true.

Method 2: 

We set up a remote camera to photograph animals inside the tunnel. This is more labour intensive than you’d think. Amphibians are cold-blooded so they don’t trigger infrared camera sensors in the same way that people, bears or mice would. We had to set the cameras to take a picture every minute and now we’re looking through thousands of images.

Results so far: 

We still have more images to look at before we can compare numbers crossing each night with the numbers caught in traps, but, so far, we have photographed 30 different frogs and salamanders in the tunnel over 50 nights. Here are some of the images taken in the tunnel. Look carefully for the frogs & salamanders… they are little.

We also saw some warm-blooded animals moving through…. 

Whoa, how'd you fit in there!

We plan to continue monitoring when the weather warms up this spring. Stay tuned for more results as they become available.

In the meantime, for more information on monitoring salamanders using tunnels, check out this interesting publication of research done at Waterton Lakes National Park.

Leading Frogs and Salamanders to the Tunnel

In addition to describing the installation of the tunnel, we would like to explain how we set up fences to guide amphibians to the tunnel entrances.

There are lots of different types of fencing materials to choose from: cement, wood, metal, plastic mesh, PVC or Big O pipe cut in half, landscape cloth, etc. ACO Systems Ltd even makes a specially designed fence product for amphibians (http://www.acousa.com/wildlife/index.htm).

For now, we decided to stick with the clear plastic sheeting (6-mil polyethylene) that we have used for roadside barriers. We knew it would successfully block Red-legged Frogs, Northwestern Salamanders, Rough-skinned Newts and Western Red-backed Salamanders. Pacific Treefrogs can climb over it, but they seem to be able to climb everything!  

The clear 6-mil polyethylene lasts a long time in the shade (our roadside fences have lasted six years), and it’s inexpensive. We decided to keep our investment low until we see how well the new tunnel works.

We cut pieces that were 50 cm tall and attached them to wooden stakes with duct tape and thumbtacks. We dug the lower edge of the plastic 10 cm under the soil so that salamanders and frogs could not burrow beneath it.

It is important to position fences on angles that direct animals toward the tunnel entrance, rather than placing them perpendicular to the direction that amphibians are travelling. We angled fencing at 20 to 45 degrees from the edge of the road into the forest for up to 60 m.

The topography was uneven so it was a challenge to keep the fence taut. We chose the path of least resistance, but still needed to cut away a few logs and several small roots. We piled soil up on top of the plastic in places where we could not bury it under large roots.

Connecting the plastic to the tunnel entrance was easy because the box culvert has straight vertical walls. It also helped to have a thick layer of dirt on the floor of the tunnel. We extended each plastic fence about 1 metre into the tunnel, dug it into the dirt, and held it against the wall and ceiling with wooden stakes and wire. This created a smooth transition from plastic to concrete wall.

We are monitoring amphibian movements along the fences and through the tunnel this fall. Our next post will describe our monitoring techniques and some of the results to-date. 

Installation Completed!

The second half of the tunnel was put in place last Wednesday and repaving happened today. Here are some more photos to demonstrate how smoothly the whole process went.

May 4, 8:00 AM:  The excavator uncovered some large pieces of wood only about 0.5 m deep in the road bed on the west side.

Fortunately, the deeper material was good and gravelly.

9:00 AM:  The base was compacted quickly after adding crush and checking the height.

Two and a half more sections of culvert were lifted into place to complete the 13.4-m tunnel.

The most gruelling part of the job - filling the inside of each section with substrate 0.3 m deep to make the interior of the tunnel level with the ditch.

12:30 PM:  Several truck loads of "pit run" delivered to cover the culvert.  Loads came quickly one after another from a quarry just a few hundred metres from the site.

14:00 PM:  Substrate at the entrance of the tunnel was compacted and sloped away to prevent water from pooling inside. 

15:00 PM:  Compacting the road surface so it could be left until the repaving crew arrived.

10 May, 9:00 AM:  A paving crew arrived from Nanaimo to do our job as well as some others on the west coast.

The first layer of asphalt applied smoothly over the prepared surface. 

Torching the first layer to dry it before applying the next.

12:00 PM: Finishing the second layer.

12:15 PM:  Installation Completed! We'd like to express a huge thank you to Simon Stubbs, Ministry of Transportation & Infrastructure, for overseeing the installation. Simon, you rock!!! More thanks to come in our next post.

Day One of the Tunnel Installation

One half of the amphibian tunnel was installed today!! These pictures tell the story:

7:15 AM: Safety meeting with the site safety coordinator .

7:30 AM: Setting out safety cones and signage.

7:35 AM: Laying out lines for the trench.

7:55 AM: Rock-hammer punching through the pavement along the lines. 

A red squirrel come running out of the forest to perch, inquisitively, on the roadside fence. Rock-hammers do sound somewhat like a the trill of a squirrel, only much louder!

9:00 AM: Excavating the top layer of pavement before digging the trench.

Carefully making the trench size match the layout.

10:00 AM:  Adding crushed gravel over the bottom of the trench.

A hydraulic hoe-packer compacting the "crush" before it is raked smooth.

Making sure the base is at the right level.

12:30 PM:  Loading the trailer with culvert pieces that had been stored at a nearby gravel yard.

Delivering the culvert pieces to where the crane waited to lift them into the trench.

Each piece weighs over 19,100 pounds or 8.6 tonnes.

Lining the first piece up on the centre line of the highway.

 

Filling each culvert piece with natural substrate, slid down the board to the back end.

Natural substrate is a mix of soil from the forest floor (called "overburden" in the quarry industry) and crushed gravel.

Downed wood and litter placed on top of substrate in each section.

Lifting in the second section of culvert.

Lining the sections up to fit snuggly. 

No gasket or seal was needed because the culvert will not carry water.

13:50 PM: Lifting in the third section of culvert.

Adding and compacting "crush" around the box culvert.

16:15 PM: Culvert fully buried to the shoulder. Rip rap will be added tomorrow.

16:30 PM: Metal plate laid over top makes it secure to drive over.

Sure hope the frogs and salamanders will like it!

The Arrival of the Tunnel

Today, we’re celebrating the arrival of a six-pack of large concrete tunnel pieces that are intended to become a well-used passageway for frogs and salamanders under Highway 4.

Langley Concrete and Tile Ltd cast the box-shaped structures that will fit together to form a 13.5-m long tunnel under the highway.  There are five and a half pieces to join. Each full piece measures 2.2 m wide, 1.3 m tall and 2.4 m long, and weighs over 7 tonnes. The sixth piece is half the length and weight of the others.

It took a mighty machine and skilled operators to lift the pieces off the B-train transport truck. Using chains and specialized hooks, called “clutches”, a front-end loader carefully moved each piece to where it will be stored until installation happens later this spring.

“Why concrete?” you ask. Indeed, it is heavier and more expensive to make and move than plastic or metal. It has advantages, though, when it comes to providing a spacious passageway under a shallow road-bed. Concrete is strong enough to hold up traffic (literally!) with only a small amount of material covering it to the road surface.

While the transport driver watched the off-loading, he described his step-daughter’s excitement about him delivering a tunnel for frogs. “She loves collecting frogs, identifying them and writing about them in her journal”, he said. A budding herpetologist, no doubt. We invited him to bring her along next September to see the frog migration and the new tunnel in action.