Animal Crossing by: Colin Glover

"Well I want to voice my opinion on something that's been on my mind for a very long time."

A caller begins, on a segment called the "Vent" on radio station Y94 Playhouse in North Dakota.

"Over the past 2 years, I've been in 3 separate car accidents involving deer... "

"Mmhmm", replies one of the show's hosts.

"...Each of these incidents, occurred shortly after seeing a deer crossing sign on the highway." She continues," well, my frustration is that Minnesota and North Dakota department of transportation, would allow these deer crossings to be in such high traffic areas."

This is Donna the Deer lady, on her first call in to Y94 about deer related accidents.  The hosts, while "holding down their chuckle bone" as Donna calls it a later conversation,  try to gently explain the true purpose of deer signs is not to direct deer to cross the road when it's safe, but to alert drivers to the hazard. Donna isn't quite convinced yet, and poses a solution to her problem of collisions with wildlife." You'd think they'd put deer crossing in smaller towns, maybe like a.. a school crossing! You know, it would be a safer place for them to cross." (III, V)

 On YouTube, the video version of the exchange has 3.8 million views, and it makes sense, cause it's a hilarious segment.  But Donna might be on to something here, why don't we make crossings for wildlife that are safer, just like a school crossing?

Well, this is actually true for some places, where wildlife crossings and protected fencing were constructed to facilitate two main objectives: to reduce wildlife vehicle collisions (WVC) and to provide corridors, or connections between fragmented habitat for wildlife (VIII).  One particularly successful implementation of wildlife road crossings are in Banff National Park in Alberta, Canada.  This park boasts the most wildlife crossings and fencing on the planet, with 44 wildlife crossings and 82 km of protective fencing (VI). These corridors allow species like: black and grizzly bears, wolves, cougars, moose and of course, deer, to cross in relative safety, and find new habitat for foraging or mating opportunities.  

Banff National Park Overpass
Photo credit: RWS, Netherlands

WVC's can cost thousands of dollars of damage to the vehicle, and passengers can get injured in a collision with wildlife, especially with a large animal, like moose. They can also indirectly incur cost to local agencies like the Department of Transportation, who have to remove roadkill and repair broken infrastructure like fencing (VIII). However, the Trans-Canadian Highway has seen more than an 80% drop in WVC's over a period of 5 years, once wildlife had time to learn the locations and the safety these crossings provide (VI).  

In order for these wildlife crossing structures (WCS) to be effective, both in relation to the environment and economy, we have to know our options.  Many types of crossings exist: there are large open overpasses, often covered with vegetation, as well as split overpasses, and even closed in structure like culverts.  In addition, protective fencing is used to prevent crossings in more dangerous stretches of road, and can help funnel wildlife to the corridors.  Use of these structures are not the same for every type of animal however(I, IV).  For example a 2003 study showed that species like: grizzlies, elk, deer, and wolves prefer open, short, and wide overpasses. Cougars and black bears preferred the closer quarters of culverts.  Other parameters of the WCS like distance affected the frequency of crossings, and also differed among species.  Cougars were less likely to cross with greater distances to cover, while grizzlies, elk and deer were more likely to cross (I).  

White Tailed Deer passing through a culvert in Montana
Photo: The People's Way Partnership

These crossings have been a topic of debate in the past decades, mainly focusing on whether these crossings effect on wildlife are worth the cost of construction.

One study from Montana State University, researched the effectiveness of different types of these crossings for Grizzly and Black bears in Banff National Park.  The results are interesting, again showing that grizzlies preferred large, open overpasses, while black bears would cross more often at culverts than their grizzly cousins.  The most interesting finding however, is the level of connectivity afforded by these crossings.  To analyze this, they used a conservative criteria of connectivity, in this case: for two patches of habitat to be considered "connected", at least 10% of the wildlife population in question that occupies those spaces  travel between the two areas.   

They found was that 15-20% of the grizzly population, and 11-18% of the black bear population were using these crossings, supporting that these corridors do indeed effectively connect the habitats bisected by roads (VII). 

Another argument against these passes is the "Prey-Trap Hypothesis", which essentially means that predators, like wolves and cougars,  are learning the locations of the crossings, and capitalize on the funneling effect that the corridors have on passing prey, like deer or moose.  However, another study by Montana State University observed the frequency of killings near these crossing, and  the frequency of predator and prey crossings using motion sensing cameras and track-pads.  They analyzed data from kill sites from 1981-2009, in which 59% of the sites occurred after wildlife crossings had been constructed.  What they found was there was no significant decrease in the distance of kill sites from the highways since the construction of the crossings.  In addition they found 19% of the kills prior to the construction occurred less than 100 m from the highway, while 12%  of kills occurred at the same distance after the crossings were built (II).  

When Donna the Deer Lady calls in to Y94  the second time, she thanks the hosts for being so polite and not laughing at her on the air.  She also updates us on her newfound understanding on the actual purpose of animal crossing signs, and seems to take the sudden online infamy very well (V).  But as funny as it is, this concept stuck with me.  I imagine a crossing guard in an orange vest and a whistle in their mouth, guiding deer safely across the street, a silly idea without a doubt.  But really, this idea isn't so far off from what some wildlife populations need. And this is refreshing to see in the world of conservation.  To see an environmental problem that man has created but, at least to some degree, can also solve.  Banff National Park is the poster child for these management techniques, and show that while some paths create divisions, others can also make connections.  

Works Cited:

I) Adam T., Ford, et al. "Comparison of Methods of Monitoring Wildlife Crossing-Structures on Highways." The Journal of Wildlife Management, no. 7, 2009, p. 1213. EBSCOhost, doi:10.2193/2008-387.

II) ADAM T., FORD and CLEVENGER ANTHONY P. "Validity of the Prey-Trap Hypothesis for Carnivore-Ungulate Interactions at Wildlife-Crossing Structures." Conservation Biology, no. 6, 2010, p. 1679. EBSCOhost, doi:10.1111/j.1523-1739.2010.01564.x.

III) beyourbestmn. “ORIGINAL - Please Move The Deer Crossing Sign.” YouTube, YouTube, 17 Oct. 2012, www.youtube.com/watch?v=RFCrJleggrI.

IV) Clevenger, Anthony P. and Nigel Waltho. "Performance Indices to Identify Attributes of Highway Crossing Structures Facilitating Movement of Large Mammals." Biological Conservation, vol. 121, 01 Jan. 2005, pp. 453-464. EBSCOhost, doi:10.1016/j.biocon.2004.04.025.

V) josewwe1. “Please Move Deer Crossing Part 2!!!” YouTube, YouTube, 24 Oct. 2012, www.youtube.com/watch?v=1JWuFGMq3ZA&t=196s.

Copy & paste citation

VI) Parks Canada Agency, and Government of Canada. “Wildlife Crossing Structures and Research.” Parks Canada Agency, Government of Canada, 1 Apr. 2017, www.pc.gc.ca/en/pn-np/ab/banff/info/gestion-management/enviro/transport/tch-rtc/passages-crossings.

VII) SAWAYA, MICHAEL A., et al. "Demographic Connectivity for Ursid Populations at Wildlife Crossing Structures in Banff National Park." Conservation Biology, vol. 27, no. 4, Aug. 2013, pp. 721-730. EBSCOhost, doi:10.1111/cobi.12075.

VIII) “Wildlife-Vehicle Collision Reduction Study: Report To Congress.” U.S. Department of Transportation/Federal Highway Administration, Aug. 2008, www.fhwa.dot.gov/publications/research/safety/08034/exec.cfm.