Cold winter holds down roadkills: Peaks coincide with moon phases

From ANIMAL PEOPLE, September 1994:

DERRY, New Hampshire––The good
news is that roadkills will apparently claim 23%
fewer animal lives in 1994 than 1993. The bad news
is that the reason is probably not safer driving, but
rather the harsh winter of 1993-1994, which thinned
the numbers of many of the most vulnerable species.
Refinements of the survey method may
also account for some of the drop, from an estimated
total of 187 million animals killed in 1993 to just 137
million this year. The 1993 statistics were derived
exclusively from Dr. Splatt’s Roadkill Project, a
learning exercise then including students at 31 New
England middle schools, coordinated by Dr.
Brewster Bartlett of Pinkerton Academy, in Derry,
New Hampshire. 

The students conducted weekly
roadkill counts for nine weeks in the spring––obvi-
ously an awkward basis for a year-round national
projection, but nonetheless the only all-species basis
available since 1957, when the Humane Society of
the U.S. conducted a comprehensive single-day
count that had served as the basis for all other
national roadkill estimates.
This year the Dr. Splatt project included
students at 40 schools, again almost all in New
England, who tabulated data on 5,942 dead animals.
The Dr. Splatt data was balanced by an overlapping
year-round survey done by volunteers in 19 states,
coordinated by ANIMAL PEOPLE. Because many
Dr. Splatt participants also used the ANIMAL PEO-
P L E reporting forms, and because participation
from Ohio was very strong due to coverage in the
Cleveland Plain Dealer, the ANIMAL PEOPLE
survey was also skewed toward the northeast. Of the
1,736 dead animals the ANIMAL PEOPLE volun-
teers reported, 772 were found in Ohio and 654 in
New Hampshire. The reports could not be properly
weighted to achieve good geographical and seasonal
balance because other than New Hampshire and
Ohio, only Florida, Massachusetts, and New Jersey
provided enough data on enough occasions for their
tabulations to be considered representative. Thus the
real comparison between the Dr. Splatt and A N I-
MAL PEOPLE counts is between a spring tally and
a set of year-round tallies in similar habitat.
Only counts for which good records of
road miles covered on foot were kept were used in
extrapolating the 1994 total roadkill estimate. Last
year, Dr. Splatt participants recorded .93 roadkills
per week per mile in both urban and rural areas.
This year, counting vacant miles more carefully,
Dr. Splatt participants recorded just .36 roadkills per
week per mile. ANIMAL PEOPLE p a r t i c i p a n t s
recorded .63 roadkills per week per mile. ANIMAL
PEOPLE participants were asked for details of sur-
vey locations. Responses verified that in developed
areas, road type is a more important predictor of
roadkills than location. Roadkill ratios along routes
of similar characteristics were virtually identical in
lightly developed and heavily developed areas.
Whether roads were lighted or not also seemed to
make no difference. However, the reported roadkill
ratio more than doubled when the volume of traffic
increased from “residential” to “artery.” Four-lane
roads had fewer roadkills than 2-lane arterials, how-
ever, perhaps because they are more likely to be ele-
vated, fenced, and protected by sound barri-
cades––and possibly too because animals may be
less tempted to try rushing across four lanes.
Possibilities for prevention
Last year’s Dr. Splatt project produced data
suggesting that various species may be most vulnera-
ble to roadkills during repetitively predictable inter-
vals coinciding with young leaving nests, mating
activity, and the fruition of favorite food plants.
This in turn suggests that seasonally appropriate traf-
fic warnings could significantly reduce roadkills,
which are the leading cause of single-car accidents
after drunk driving. Peaks by species were less evi-
dent this year, but the Dr. Splatt data combined with
the ANIMAL PEOPLE data does show an apparent
predictable spike for all species combined in April,
coinciding with the arrival of spring; a gradual rise
in late summer, as squirrels––by far the most
vulenrable species––come into roadways to gather
nuts; and an abrupt drop for most species in
October, when foliage drops, giving animals a bet-
ter view of the road. Other studies show that
deer/car collisions peak in October and November,
however, coinciding with both the deer hunting sea-
son and the rut. Both hunting and rutting tend to
send deer running pell-mell.
The Dr. Splatt and ANIMAL PEOPLE
data for precisely dated roadkills also shows apparent
high risk assocated with the full moon, the first
quarter moon, and the new moon, with dips
between––evident in both total numbers of roadkills
and, to lesser degree, in number of roadkills per
report. In general, the volume of roadkills is propor-
tional to the amount of moonlight. The spike at the
new moon could reflect the response of animals to
the presence of some light after a night of darkness.

 

Roadkills by month
1993                                1994
(avg. 8.7 RK/report) (avg. 3.3 RK/report)
Count % of avg.         Count % of avg.
March 8.1 .93 2.5 .75
April 12.7 1.46 4.6 1.39
May 7.3 .84 2.7 .82
June 6.3 .72 (insufficient reports)
July 9.5 1.09 (insufficient reports)
August 9.1 1.05 [insufficient reports)
Sept. 10.6 1.22 [no reports)
Oct. 5.9 .68 (no reports)
Roadkills by species
Species %DS %AP Killed/mile Killed /year
Italic indicates strong likelihood of regional bias dis
torting estimates, due to disproportionate distribution
of species and reports. “DS” is Dr. Splatt; “AP” is
ANIMAL PEOPLE.
Amphibians 4.3 5.0 .084 16,908,528
(includes all frogs, toads, newts, and salamanders)
Armadillo .0004 80,500
Beaver 1.4 1.2 .008 1,610,336
Cat 4.3 4.4 .027 5,434,884
Chipmunk 2.8 0.7 .004 805,168
Deer 1.4 4.8 .030 6,038,760
Dog 0.7 1.0 .006 1,207,750
Fox 0.5 0.4 .004 805,168
Mouse 0.8 .006 926,000
Muskrat 0.8 .006 926,000
Opossum 4.0 6.7 .041 8,252,972
Porcupine 1.2 0.5 .003 603,500
Rabbit 2.6 7.4 .045 9,259,432
Raccoon 9.9 12.8 .079 15,902,068
Rat 1.9
Skunk 6.0 7.5 .045 9,058,140
Snake 1.5 .011 2,214,212
Squirrel 34.0 28.3 .173 34,823,500
Turtle 0.5 .008 1,610,336
Woodchuck 1.4 4.2 .025 5,032,300
All birds 11.0 18.0 .119 14,694,316
(The following percentages are of birds only.)
Gamebirds 0.3 0.3 44,083
Pigeons 17.5 0.8 .005 1,006,460
Raptors 6.5 0.4 50,000
Seagulls 7.5 2.4 352,664
Songbirds 39.0 48.5 .038 7,649,096
Waterfowl 10.0 41.6 .030 6,038,760
Species reported in insufficient numbers to permit
estimates include bat, coyote, mink, mole, moose,
otter, and pine martin.
Roadkills by moon phase
Moon phase Roadkills Reports Average
2 days before new 4 1 4.00
1 day before new 6 3 2.00
New moon 278 86 3.23
1 day past new 3 2 1.50
2 days past new 4 3 1.25
First quarter 161 47 3.42
5 days before full 5 5 1.00
4 days before full 21 15 1.40
3 days before full 21 10 2.10
2 days before full 23 9 2.56
1 day before full 16 6 2.66
Full moon 76 17 4.47
1 day past full 22 7 3.14
2 days past full 39 9 4.33
3 days past full 27 10 2.70
4 days past full 16 11 1.46
5 days past full 69 26 2.65
6 days past full 8 2 4.00
Roadkills by road type
Road type Roadkills Reports Average
Rural dirt 18 4 4.50
2-lane downtown 7 4 1.75
2-lane paved rural 397 118 3.36
2-lane res. suburb 239 148 1.62
2-lane res. urban 116 72 1.61
2-lane sub. artery 72 19 3.79
2-lane urb. artery 19 5 3.80
4-lane rural 39 14 2.79
4-lane residential 39 14 2.79
Lit, all types 354 97 3.65
Unlit, all types 201 62 3.24
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