Tuesday, March 31, 2015

You can lead a Treefrog to an underpass, but you can't make it enter...


We tested the effectiveness of our new fence design using wildlife cameras. Two cameras took time-lapse photographs of our fences at the entranceway of the culvert. Surveillance started in September 2014 but we did not get a chance to look through the images until this winter.




For the most part, Northern Red-legged Frogs and Northwestern Salamanders moved without hesitation along the ground at the base of the fences into the culvert. We counted more of them moving through to the other side on peak nights than in previous years.

Northern Pacific Treefrogs, however, did not take the culvert in stride. Our September surveillance period showed dozens of juvenile treefrogs climbing the fences just outside the entranceway.

The young tree frogs were not only good climbers, they also found the weak points where the fences joined the culvert. There was a cut in the fabric on one side, and a bunched fold on the other side. At each spot the overhanging fabric came close to touching the upright wall and gave the climbing frogs a relatively easy escape hatch. It was remarkable to watch so many of them follow the same route around the overhanging lip and over the top!





After realizing the flaws, we braced the overhanging fabric with wood at the joins.




We set out the cameras again in February to see if we had made the fence more escape-proof. Granted, a week of surveillance in February is not the same as a week of surveillance in September. There were no juvenile treefrogs around to test our improvements. Instead, we watched a few adult treefrogs and a salamander climb the fences. We were happy to see that none of them escaped. We will have to wait until next September to see whether our fix is also effective for the next generation of juvenile treefrogs.





Making an escape-proof fence for treefrogs is useful in reducing the number killed by traffic. We also hoped it would guide them to take the safe passageway under the highway. It was too difficult to detect juvenile treefrogs in the grass to track the number that actually did enter and move through the culvert. Perhaps some did, however seeing so many treefrogs climbing begs the question: are culverts effective in connecting habitats across roads for these climbers? 

We're not the first to wonder about this problem… Kenneth Dodd and colleagues showed that culverts and concrete barriers helped other amphibians, but not Green Treefrogs or Squirrel Treefrogs, cross a busy highway in Florida.

Various researchers in Europe have also noted that treefrogs do not readily move through culverts. A Dutch publication on Boomkikkers (the Dutch word for treefrogs) recommends not interrupting connections between breeding and foraging habitats across the landscape when new roads are planned.

The fence installation and effectiveness monitoring were financially supported by the B.C. Ministry of Transportation and Infrastructure, the Clayoquot Biosphere Trust and the Government of Canada, as part of the National Conservation Plan. 


Monday, August 25, 2014

New fences to guide amphibians to the tunnel


We are in the process of replacing the temporary plastic fences that lead frogs and salamanders to the entranceways of the culvert.

Straight-walled plastic sheeting was not ideal. We watched Northern Pacific Treefrogs, juvenile Rough-skinned Newts and Western Red-backed Salamanders climb over it on several occasions, and we frequently needed to patch it (although, it fared surprisingly well over the past 3 years). 




Deciding on a more effective and durable fencing design was a matter of checking out what other folks had tried, and testing to see which options would work for our local species. We chose four different types of materials that have been used to reduce road mortality of frogs and salamanders in other places in Canada. 


We tested to see whether our local species - Northern Red-legged Frogs, Northern Pacific Treefrogs, Northwestern Salamanders and Rough-skinned Newts could be contained within fence enclosures made of each material.


 We compared the frequency of climbing and escape behaviour by each species from each type of enclosure. We observed this behaviour using time-lapse photography with wildlife cameras.



The fabric and both types of solid fencing were more effective than plastic mesh. Northern Pacific Treefrogs escaped from the plastic mesh enclosure 43% of the time, much more often than the other types of enclosures. 




Red-legged Frogs, Northwestern Salamanders and Rough-skinned Newts were able to climb further up the walls of the plastic mesh than the other materials but were rarely able to maneuver around the overhanging lip.

Based on these results and the relative ease of installation along uneven terrain, we chose the polypropylene fabric as the best material for our new fences.



Instead of being straight-walled, the new fence has an overhanging lip, to stop those amphibians with specialized toe pads from climbing over the top!



We are using fabricated plastic wood for the upright stakes and cedar for the top rails. These should last a long time in the rainforest.



The trickiest part of the installation is keeping the fabric smooth. Sections are cut to fit along each segment of the sloping terrain. Overlapping pieces are attached to the rails and stakes with washers, screws, and staples.

The fabric is folded and buried under ground so that salamanders cannot burrow beneath it.



The final touch will be to add a cone of mesh on the backside of the fence every few meters to allow animals to climb over from that direction. We only want the fence to provide a barrier to keep animals from getting onto the road, not off it!



The Habitat Conservation Trust Foundation and Clayoquot Biosphere Trust provided funding to test different types of materials. Support for building the new fences is from the British Columbia Ministry of Transportation and Infrastructure. 

Of course, we are now thinking about ways to ensure that the new fencing will work as intended. We will continue to monitor amphibian movements through the tunnel and devise a way to see what happens when frogs and salamanders encounter the fence! 






Yesterday, we were delighted to show our new fence design to a film crew for a documentary series called “Striking Balance”. The SPLAT project will be included as part of their production on how people are working to find innovative approaches to living in harmony with nature in the 16 UNESCO Biosphere Reserves across Canada. 






Monday, October 28, 2013

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".

Saturday, May 25, 2013

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!

Thursday, January 26, 2012

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.

Saturday, October 15, 2011

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. 

Tuesday, May 10, 2011

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.