Hwy 97 Small Animal Fencing - PreInstallation Surveys PreliminaryProject: Reduced vehicle-animal collisions with installation of small animal exclusion fencing
Contract: 133497
Deliverable 2: Preliminary report on pre-installation site monitoring, May to October, 2018
The first field season of the small animal road mortality study was conducted between May 9th
and October 17th, 2018. The length of the field season was determined by a combination of
animal activity and weather. A colder than average spring resulted in a start date later than
originally anticipated (i.e., April). Likewise, a cool start to fall had very few animals (and no
turtles) on the roads by mid-October.
For the 15 sites, each was typically sampled on a weekly basis through the field season,
resulting in 22 to 24 total visits per site. In a couple of instances, active road construction (i.e.,
resurfacing) prevented access to a site for a given week. In addition, during the first few weeks
of the season (May) we were not able to sample every site weekly, resulting in a small number
of gaps for this time period.
Study sites were delineated with spray paint to ensure consistency in monitoring effort.
Observers walked single file along each road segment, recording all mortality (and any live
animals) on roads and within the first two feet of the shoulder. Taxa recorded included turtles,
snakes, lizards, frogs, toads, birds, mammals, monarchs, and bumble bees. We encountered a
total of 2,096 animals, including 372 turtles; the vast majority of these observations were
deceased (Table 1). Four live turtles (all from Northeast Site 5) were observed crossing the road
over the course of the field season. When safe to do so, live turtles were assisted across the
highway in the direction they were headed.
Sites varied greatly in frequency of turtle encounters, ranging from 0 to 73 total turtles (Figures
1a - o). Because sites varied in length from ~76 to ~625 m, we standardized for segment length
to better facilitate comparisons among sites (see Table 1). We observed the highest rate of
encounters at Northeast Site 5 (8.6 turtles / 100 feet) and the lowest rate at Southeast Site 3
where no turtles were found. The latter result, however, was likely heavily influenced by nearby
road construction, where the southern end of the site was closed to traffic for the majority of
the field season. The “construction effect” for this site will be better assessed after an
additional 2 years of monitoring with the road open to traffic.
We investigated seasonal movements of turtles as well (Table 2 and Figure 2). We documented
an increase in turtle activity in late spring and again in the early fall. Presumably, the spike in
May / June was related to movements to foraging areas from overwintering sites and / or
females searching overland for appropriate nest sites. The peak in early fall was likely related to
the movements of turtles back to overwintering sites. We also observed several snapping turtle
hatchlings on roads in the early fall. Although seasonal trends in activity were generally
consistent for both painted and snapping turtles, we note that there was less relative activity
during mid-summer for snapping turtles.
Additionally, sites for fence installation were finalized this summer and bids solicited from
contractors. This process is being managed by MnDOT, and fence installation is scheduled to be
completed by early spring 2019. Selection of sites for fencing was semi-randomized, based on
the presence of target species, logistical feasibility of fence installation, anticipated costs, and
broad geographic representation. There are currently five sites selected for treatment, five as
corresponding controls, and five contingency sites, including two with little observed mortality
and three that could be used for future mitigation efforts. Although high mortality sites are
ultimately a priority for mitigation strategies, control and treatment sites were chosen
randomly among sites (given the above financial and logistical constraints) where the presence
of turtles was relatively consistent to facilitate robust statistical analyses. The selection process
ensures that each treatment site has a corresponding and comparable control site along the
same stretch of road. The locations of road mortalities from this season also helped to inform
length and positioning of fences. In general, hotspots for turtle activity were found in locations
where water comes closest to the road, identifying key target areas for future road underpass
installations and improvements.
Following fence installation during early spring, 2019, sites will be monitored on a weekly basis
when temperatures warm enough to promote movement of turtles, the target species. We will
deploy traffic counters in 2019 to quantify traffic volume as a potential predictor of road
mortality. We will also install cameras to document turtle movements and supplement our
weekly sampling, helping to determine if fencing is effective in redirecting turtles and other
animals away from roads and / or to existing through-road infrastructure (i.e., bridges and
culverts).
Table 1. Summary Field Season 2018: Pre-fence installation site monitoring
Sampling began on May 9th, 2018 and ended on October 17, 2018. During the field season each site was sampled 22 to 24 times. Monitoring occurred
weekly, on average, to evaluate seasonal variability in activity patterns and mortality. A small number of live animals were sighted on roads during
surveys. These included: 4 painted turtles, 5 leopard frogs, 7 toads, 6 snakes, 2 birds, 2 mammals, and 19 monarchs. All remaining individuals were
deceased.
Treatment (i.e. fencing) sites are indicated by bold/red text.
Turtles Anurans Snakes Other Herpetofauna Birds Mammals Insects Site
# Turtles/100 ft Region Site Painted
turtles
Snapping
turtles Unknown Leopard
frogs
Green
frogs
American
toads
Other /
Unknown All
species
All other species /
Unknown
All
species
Bats All other
species
Bumble
bees Monarchs Totals
Southeast 0 29 6 24 2 4 8 2 10 12 97 4.0
Southeast 1 11 4 1 1 5 1 1 5 29 4.3
Southeast 2 8 8 2 1 2 1 6 2 3 33 0.7
Southeast 3 5 1 1 1 1 9 0.0
Southeast 4 30 9 24 8 7 4 9 5 96 3.9
Northeast 5 64 8 1 14 1 5 6 5 1 13 1 2 8 5 134 8.6
Northeast 6 20 5 3 13 18 1 1 4 1 1 5 72 3.6
Northeast 7 3 3 1 3 4 5 1 20 0.8
Northeast 8 4 3 8 6 1 1 1 1 1 2 28 1.6
West 13 50 10 3 68 78 56 194 5 4 62 22 10 14 576 3.1
West 14 16 6 20 60 12 207 3 27 2 7 2 8 370 1.5
West 15 16 1 2 10 13 12 86 3 2 14 4 4 2 169 2.5
West 16 11 10 5 27 10 53 2 18 5 3 4 148 2.1
West 17 14 1 2 1 1 1 2 22 2.5
West 18 36 5 2 82 23 10 105 3 2 8 3 4 10 293 4.2
Total 312 60 9 274 209 150 695 28 14 164 4 78 40 59 2096
Table 2. Seasonal movement of all turtles by month. Data include painted turtles, snapping
turtles, and unidentifiable turtles.
Region Site May June July August September October Total # of
Turtles
Southeast 0 5 12 7 0 9 2 35
Southeast 1 8 5 2 0 1 0 16
Southeast 2 1 6 1 0 0 0 8
Southeast 3 0 0 0 0 0 0 0
Southeast 4 5 7 4 7 15 1 39
Northeast 5 12 26 7 5 21 2 73
Northeast 6 0 4 6 3 7 0 20
Northeast 7 0 2 0 1 0 0 3
Northeast 8 0 2 1 0 1 0 4
West 13 12 5 11 16 16 3 63
West 14 7 10 4 0 1 0 22
West 15 4 4 4 6 1 0 19
West 16 7 6 2 5 1 0 21
West 17 4 5 5 1 0 0 15
West 18 8 10 3 3 17 2 43
Total 73 104 57 47 90 10 381
Figure 1. a.-o. Turtle road mortality maps for 2018 by site. Labels indicate Control (a, g, k, l, m),
Treatment (e, f, j, n, o) and Contingency (b, c, d, h, i) sites. In figures, red markers with “X”
indicate deceased painted turtles, red markers with black dots “•” indicate live painted turtles,
red with “U” indicate unidentified deceased species of turtles, and yellow markers with star
symbols indicate deceased snapping turtles. Proposed fences are indicated by white lines in
treatment sites. There were no turtles found at S Site 3 (d).
a. Control
b. Contingency
c. Contingency
d. Contingency
e. Treatment
f. Treatment
g. Control
h. Contingency
i. Contingency
j. Treatment
k. Control
l. Control
m. Control
n. Treatment
o. Treatment
Figure 2. Encounters by month of all identifiable turtles, including both dead and live
individuals. Figure reflects total number of turtles by species: painted turtles (n= 312) and
snapping turtles (n=60).