On the threat to snakes of mesh deployed for erosion control and wildlife exclusion

Abstract

Concerns about snake mortality due to entanglement in plastic mesh deployed for erosion control and horticultural pest exclusion have been previously raised. However, little new information has been published on the subject, although the threat may not have abated. Herein, we provide evidence that snake entanglement in such materials continues to occur by reviewing new case examples from Wisconsin. We also summarize information about a variety of materials used for erosion control and horticultural pest-exclusion and give our perspectives on the potential threats (if any) these pose to snakes. This document is meant, in part, to serve as a reference for natural resource regulators, academics, and environmental consultants when making suggestions on the application of such materials. We hope this will help reduce the likelihood of snake entanglement. Further research focused on testing the level of threat posed by mesh entanglement and the best methods for application of mesh in a variety of settings is warranted.

Full text

Herpetological Conservation and Biology 6(1):1–9.
Submitted: 21 January 2011; Accepted: 15 March 2011.
1
ON THE THREAT TO SNAKES OF MESH DEPLOYED FOR EROSION
CONTROL AND WILDLIFE EXCLUSION
JOSHUA M. KAPFER1AND RORI A. PALOSKI2
1Department of Biological Sciences, University of Wisconsin-Whitewater,
Whitewater, Wisconsin 53190, USA, e-mail: kapferj@uww.edu.
2Wisconsin Department of Natural Resources, P.O. Box 7921, Madison, Wisconsin 53707-7921, USA.
Abstract.—Concerns about snake mortality due to entanglement in plastic mesh deployed for erosion control and
horticultural pest exclusion have been previously raised. However, little new information has been published on the
subject, although the threat may not have abated. Herein, we provide evidence that snake entanglement in such
materials continues to occur by reviewing new case examples from Wisconsin. We also summarize information about a
variety of materials used for erosion control and horticultural pest-exclusion and give our perspectives on the potential
threats (if any) these pose to snakes. This document is meant, in part, to serve as a reference for natural resource
regulators, academics, and environmental consultants when making suggestions on the application of such materials.
We hope this will help reduce the likelihood of snake entanglement. Further research focused on testing the level of
threat posed by mesh entanglement and the best methods for application of mesh in a variety of settings is warranted.
Key Words.—entanglement; erosion control; erosion fences; mesh, risk.
INTRODUCTION
Entanglement of reptiles in anthropogenic objects is
not a new phenomenon (examples reviewed by Dean et
al. 2005). In snakes, numerous accounts of
entanglement in a variety of materials have been
reported including wire (Campbell 1950), beer cans
(Groves and Groves 1972; Herrington 1985; Iverson
2010), and other materials (Fauth and Welter 1994;
Bonnie et al. 2004; Vann et al. 2005; Ortega and Zaidan
2009). With the exception of Ortega and Zaidan (2009),
these reports mostly describe individual observations or
a limited number of observations. Some past reports
have specifically raised concerns about snake mortality
due to entanglement in plastic mesh deployed for soil
erosion control and horticultural pest exclusion (Stuart et
al. 2001; Barton and Kinkead 2005; Walley et al.
2005a,b). Over five years after the majority of the
reports related to plastic mesh entanglement were
published, we review recent case examples of related
phenomena from Wisconsin, USA.
To provide wildlife managers, environmental
consultants, and regulatory agencies with an up-to-date
document on this subject, herein we summarize the
categories of materials that are used in a variety of
situations. We give perspectives on these materials as
they relate to snake entanglement. We cannot make
definitive recommendations due to a lack of available
information and research on snake entanglement in mesh
or netting. Yet, we believe it is important to have
baseline information and perspectives available in the
scientific literature for reference, particularly because
plastic mesh continues to result in snake mortality. We
hope this document will provide a conceptual framework
for future research and as an aid to decision-making in
current projects.
SUMMARY OF EROSION CONTROL AND WILDLIFE
EXCLUSION PRODUCTS AND APPLICATIONS
Erosion control products—The diversity of materials
and applications associated with erosion control products
may confuse the novice (Lexau 2009). Knowledge of
basic industry descriptions and applications can help
wildlife biologists make effective recommendations to
land managers, developers, or government agencies
seeking advice on projects in areas where snakes may be
present. Therefore, we summarize the current product
terminology discussed in Lexau (2009) and by the
Erosion Control and Technology Council (ECTC;
Erosion Control and Technology Council. 2008.
Available from http://www.ectc.org [Accessed 20
January 2011]). The ECTC is an organization that
provides information for erosion control product
manufacturers; as well as, to those who work for entities
that regularly use erosion control materials. ECTC
indicates that their goal is to be the industry authority in
standards development, review of methods for
installation, and testing of erosion control products.
Although ECTC has no regulatory authority and their
suggestions are non-binding, they have created standard
industry terminology. We have also sought the advice of
experts in the field of erosion control material
application and efficacy for advice.
The most straight-forward type of material to employ
for erosion control purposes is a simple layer of loose
Copyright © 2011. Joshua Kapfer. All rights reserved.

Kapfer and Paloski.—Risk of Snake Entrapment During Erosion Control.
2
organic matter (wood mulch, wheatstraw, woodstraw,
coconut/coir, etc.) with no associated weave or mesh.
Although this method is often employed and may be
suitable for small-scale application (i.e., the flower or
vegetable beds associated with a private residential
property), it has extremely limited application in other
situations. It is not effective for many large scale
projects with significant ground disturbance, projects on
substantial slopes, or in areas subject to frequent
inundation or flowing water. Longer lasting and stable
erosion control materials are usually required in
commercial and industrial situations. Sometimes a
Mulch-control Netting (MCN) is applied to help stabilize
a loose mulch layer. MCNs are unrolled over loose
organic layers and seeds, then stapled or staked into
place. They are usually designed of woven natural or
geosynthetic fibers that are reported to be degradable.
Rolled Erosion Control Products (RECPs) are
classified as either temporary (e.g., open weave textile,
OWT; erosion control blankets, ECBs; Mulch-control
Net, MCN; see above) or permanent (e.g., turf
reinforcement mats, TRMs). OWTs are typically made
of organic or synthetic strands that are woven into a
matrix (Fig. 1). ECBs are commonly employed to
control erosion and usually constructed of a continuous
fiber matrix comprised of layers that may be structurally
bound. The ECB matrix may include layers of organic
materials, polypropylene fibers or a polymer mesh with
apertures that range from less than 5 mm2 to over 25
mm2 (Fig. 2). Examples of organic materials employed
range from straw and coconut (coir) to wood fiber and
jute or burlap. The mesh layers are often stitched to the
matrix with a polypropylene thread or biodegradable
fiber such as cotton. OWTs and ECBs are used for a
wide variety of purposes. They are employed to provide
fast protection to exposed soil that will quickly become
stabilized with vegetation. Occasionally, OWTs are
used as an underlay to reinforce sod. In addition to
control of erosion, these products are often designed to
hold moisture and stabilize seeds or young plants. They
may be applied in urban and rural areas for residential,
commercial, and industrial projects. They are also used
along roadside embankments, ditches, drainage ways,
stream banks, and riparian areas. Although some OWTs
and ECBs are designed to degrade over time, the speed
of degradation depends on the materials used in their
manufacture (synthetic vs. organic materials). As a
result, their life spans can range from several weeks to
several years.
TRMs are often applied in situations where vegetation
is not able to grow to a point that controls erosion
without additional stabilization (Fig. 3). They may also
be applied to inundated areas, locations that experience
flooding, or areas subject to high velocity flowing water.
Typical situations where they are employed include
stream banks, stormwater channels, and slopes subject to
heavy stormwater run-off. TRMs are usually permanent,
and often incorporate synthetic fiber, plastic filaments,
or wire mesh, with a range of aperture sizes (< 5 mm2 to
> 25 mm2). This mesh is frequently bonded at filament
intersections, but may also be discontinuous or loosely
held together by weave, stitch, or glue. Mesh that is not
bonded at the intersections may not be permitted in some
states under certain applications (Wisconsin Department
of Transportation. 2010. Erosion control Product
Acceptability Lists (PAL). Prepared by WisDOT ECSW
Committee (Peter J. Kemp, Chair). Prepared for the
WisDOT Engineers and Project Development Staff and
Consultants. Available from http://www.dot.wisconsin.
gov/business/engrserv/docs/pal.pdf [Accessed 21
FIGURE 1. Example of an open textile weave (OWT) erosion control
product. (Photograph of a manufacturer’s sample square by Josh
Kapfer)
FIGURE 2. Example of an erosion control blanket (ECB) product that
incorporates biodegradable woodstraw and two layers of a synthetic
polymer mesh (note elongated apertures). (Photograph of a
manufacturer’s sample square by Josh Kapfer)

Herpetological Conservation and Biology
3
January 2011]). This non-degradable mesh may (or may
not) be used in conjunction with layers of degradable
material. All of these layers are then bound into a matrix
that is secured to the ground permanently. The type of
materials incorporated into the TRM matrix can be
chosen to meet the specific needs of the project. TRMs
are expected to last for long periods of time and give
vegetation the support necessary to establish and thrive
under conditions with potentially high volume and
velocity run-off.
Hydraulically applied erosion control products
(HECPs) are relatively new in the erosion control
industry (Erosion Control and Technology Council.
2008. op. cit.). Usually, HECPs include numerous
components, such as fibers (organic and synthetic),
tackifiers, absorbents, polymers, and other materials
designed to stimulate plant growth. These are mixed
into a slurry that is sprayed or spread on over an area in
need of ground stabilization and vegetation
establishment (Fig. 4). They are reported to be
particularly useful along banks, slopes and even in
relatively flat locations. They do not perform as well if
inundated or even subject to periodic flooding, due to the
buoyancy of their components. Although application of
these products have become popular, according to
ECTC, the cost-effectiveness or other benefits of this
material is largely unknown.
Wildlife control products.—Plastic netting of various
mesh size (often referred to as “deer fence,” “snake
fence,” “bird netting,” or “wildlife netting”) is frequently
employed to exclude animals considered pests, such as
birds, ungulates, or snakes. These are applied in large
and small-scale horticultural operations and to prohibit
birds and bats from nesting within buildings. They are
occasionally promoted by bird enthusiasts as a means to
successfully deter snakes from entering bird houses
when it is affixed to poles, or other structures, to which
bird houses are attached (Walley et al. 2005a). Plastic
mesh has also been recommended as a type of fencing
material that will keep snakes from entering homeowner
lawns and gardens (e.g., Pierce 2003), and is sold by
some manufacturers specifically to entangle snakes for
this purpose (Fig. 5).
RECENT ACCOUNTS OF SNAKE ENTANGLEMENT
The following are recent accounts of snakes entangled
in RECPs or netting used to exclude horticultural pests
FIGURE 3. Example of a turf reinforcement mat (TRM) product that
incorporates several synthetic layers bonded together (note mesh
includes square, not elongated, apertures). Although the product in
this example includes a degradable layer (coir), numerous products
with no degradable layers exist. (Photograph taken from a
manufacturer’s sample square by Josh Kapfer)
FIGURE 4. Example of a hydraulically applied erosion control product
(HECP) being applied in-situ. (Photographed by Marc S. Theisen)
FIGURE 5. Bullsnake (Pituophis catenifer sayi) entangled in netting
deployed to deter birds from crops in a private horticultural setting
(Dane County, Wisconsin, USA). (Photographed by Bruce Ellarson)

Kapfer and Paloski.—Risk of Snake Entrapment During Erosion Control.
4
in Wisconsin. These accounts were relayed to us from a
variety of sources. In some cases, the observations were
made by co-workers of RAP. In other instances, the
observations were made by private citizens and sent to
the authors. All observations were accompanied by
photographs for verification, and were sent to the authors
because of our current employment by a state regulatory
agency, or our knowledge of snake ecology. These
accounts are case examples and do not represent every
occurrence of snake entanglement in plastic mesh in
Wisconsin. Given the fact that: (1) most cases likely go
unreported, or unnoticed; (2) multiple species of various
sizes and life-history requirements are reported herein;
and (3) the accounts listed here have been reported from
throughout the state, this information can give some
indication of the frequency at which such mortality
occurs. It can also give a general indication of the level
of threat these materials pose to a wide range of species.
Future studies are needed to assess what impact this
mortality has on snake populations.
Bullsnake (Pituophis catenifer sayi).—11 June 2010,
Dane County, Wisconsin. An adult individual was
found entangled in polypropylene mesh used to exclude
birds from a strawberry bed (ca. 2.54 cm2 mesh aperture
size; Fig. 5). The snake was removed from the fence and
released upon encounter. A mass of bird feathers was
found within the netting near the captured snake and it is
possible the snake was attempting to (or had succeeded
in) prey upon birds when entangled. This species is
listed as Special Concern/Protected in the state of
Wisconsin (Christoffel et al. 2008).
Common Gartersnake (Thamnophis sirtalis).—9 May
2008, Waupaca County, Wisconsin. Several adult
individuals (exact numbers not reported) were found
dead after becoming entangled in erosion control matting
(mesh size unreported but from pictures appears to be
1.27 cm2). The mesh was used for soil stabilization as
part of a recent road and bridge construction project.
Eastern Hognose Snake (Heterodon platyrhinos).—
20 June 2010, Eau Claire County, Wisconsin. One adult
individual was found dead after becoming entangled in
plastic monofilament netting commercially available to
exclude White-tailed Deer (Odocoileus virginianus)
from a vegetable garden (mesh aperture size 1.92 cm2).
Northern Watersnake (Nerodia sipedon).—11 May
2009, Lafayette County, Wisconsin. Adult individual
was found dead in erosion control matting (mesh
aperture size un-reported but based on pictures was
likely 1.27 cm2). The erosion control mesh was
deployed in associated with a stream and several
wetlands.
Western Fox Snake (Pantherophis vulpinus).—On 20
June 2004, 22 adult individuals were observed trapped in
erosion control blankets associated with the Menominee
River along the border of Marinette County, Wisconsin
and Menominee County, Michigan, USA. Sixteen
snakes were cut free and released from plastic mesh,
while six were dead-on-arrival. Mesh aperture size was
unreported but likely 1.27–1.90 cm2.
Western Fox Snake (Pantherophis vulpinus).—8 and
9 May 2010, Wood County, Wisconsin. Three adult
individuals were found entangled in polypropylene
netting attached to the base of apple trees to deter
wildlife. These observations made over two days and
the trapped snakes were released as encountered with no
reported mortality. Mesh aperture size was not reported
but likely ca. 2.54 cm2.
In the past several years, the Wisconsin Department of
Natural Resources has received several anecdotal reports
of Butler’s Gartersnakes (Thamnophis butleri; a
threatened species in Wisconsin) and additional
Common Gartersnakes entangled in plastic erosion
control matting. Unfortunately, specific information
regarding dates or locations of observations was not
provided for these reports. Walley et al. (2005a)
summarized personal communications with Gary Casper
regarding several Butler’s Gartersnakes entangled in
plastic erosion control mesh in Ozaukee County,
Wisconsin observed in 2004. We have also received
anecdotal reports of deceased snakes frequently
observed in erosion control mesh from the southeastern
United States (David G. Cooper, pers. comm.).
PERSPECTIVES ON MESH APPLICATION
We emphasize that we have not conducted controlled
experiments on the efficacy of these products as they
relate to erosion control, or snake “safety.” We base our
comments on: (1) product descriptions; (2) visual
assessment of products within the categories discussed
previously; (3) knowledge of potential product
applications; (4) discussions with erosion control
industry specialists; (5) knowledge of snake ecology and
biology; and (6) reports of entanglement. We did
visually assess in-hand examples of the products in
categories mentioned. We do not endorse one product or
company over another.
Erosion control products.—Regulations and standards
for acceptable erosion control materials vary by state, by
governing body, and by institution. These regulations
are also likely to change over time. Therefore, it is
difficult to create overly-specific, “snake-friendly”
recommendations for application of erosion control
materials that comply with state regulations across the

Herpetological Conservation and Biology
5
country. For example, the Wisconsin Department of
Transportation (WDOT; op. cit.) has criteria that
products must meet to be considered acceptable, and it is
up to the manufacturer to submit evidence that supports
their acceptability. Product acceptability is based on
how well they hold up to shear stress (i.e., the force that
flowing water exerts on an obstacle in its path) and how
well they cover a given area. These requirements are
necessary for the product to effectively control erosion,
but do not consider how likely they are to entangle
snakes. WDOT considers an erosion control product
acceptable for use in “environmentally sensitive areas” if
it has biodegradable components, which includes the
mesh material, and an open non-bonded mesh weave.
Although it is encouraging that anecdotal information
suggests this WDOT requirement for environmentally
sensitive areas has effectively reduced snake mortality
(Melissa Gerrits, pers. comm.), this has not been
rigorously vetted.
Wisconsin has specific state regulations for
application of erosion control materials (which may or
may not reduce snake entanglement), but these products
may not be regulated this stringently in all states. It may
be necessary for wildlife biologists to make
recommendations on projects in states where regulations
do not exist, or are more lenient. We make the following
suggestions to aid in this process. We also expect these
perspectives will be improved upon with future research
and as experience with products grows.
From our own observations and past reports, snake
morality due to entanglement appears to be more
common with products that incorporate plastic mesh
with small, square apertures. For example, all of our
case examples above involve mesh with small square
apertures ranging from 1.27–2.54 cm2. Of the erosion
control applications discussed, it seems those least likely
to entangle snakes are loose layers of organic materials,
such as wheatstraw, woodstraw, wood mulch and
coconut (coir), and HECPs (used alone and not in
conjunction with a plastic mesh). These possess no
interconnected matrices, nets, or weaves that may
accidentally entangle snakes, assuming an MCN is not
also applied. Should an MCN be used in concert with
loose organic layers, the tightness of the weave must be
considered to assess the threat of snake entanglement.
Unfortunately, loose organic layers and HECPs often
contain buoyant components and do not effectively
control erosion in areas of frequent inundation (Peter
Kemp, pers. comm.). As a result, the use of some type
of RECPs is often required.
Based on product manufacturer’s descriptions and
visual inspections of products, we make educated
assumptions about the applied efficacy of several
RECPs. It appears that OWTs that incorporate a “leno”
or “gauze” weave provide a reasonable option for the
reduction of snake entanglement. The weave of these
blankets should allow individual strands to move
independently. This potentially gives snakes greater
ability to pass through the weave while still maintaining
product durability. Anecdotal evidence and reports from
industry employees suggest that the use of such
materials in place of plastic netting in sensitive areas has
reduced observations of snake entanglement in
Wisconsin (Melissa Gerrits, pers. comm.). We have
noticed that in some products the weave of OWT strands
is tight. In the products we assessed, this tight weave
made it difficult for us to easily pass our fingers through
the product (Fig. 6). We can imagine snakes would have
FIGURE 6. Wildlife exclusion net with large apertures that are unlikely to entangle snakes (left) and an unwoven, unbound RECP with organic
fiber matrix and no associated plastic mesh (right). Compare above products to the tightly woven, open textile weave (Fig. 1), unwoven, unbound
RECP with organic fiber matrix with associated plastic mesh (Fig. 2), and the smaller meshed turf reinforcement mat (Fig. 3). (Photographs taken
of a manufacturer’s sample square by Josh Kapfer).

Kapfer and Paloski.—Risk of Snake Entrapment During Erosion Control.
6
equal difficulty passing through the material. Some
RECP products are constructed of an unwoven and
unbounded organic fiber matrix. Visual assessment
revealed that this matrix produced no resistance to our
fingers when we attempted to pass them through it (Fig.
6). It appears that such products are less likely to
entangle snakes than a tightly woven OWT. Yet, RECPs
that have no woven or bound matrix may not adequately
control erosion in all situations (e.g., steep slopes,
exposed to high water velocity).
Some state regulatory agencies require that erosion
control products contain biodegradable components if
they are applied in environmentally sensitive areas (Peter
Kemp, pers. comm.). Products made solely of
biodegradable materials (jute, woodstraw, coir, etc) may
result in reduced snake mortality compared to products
made of synthetic mesh, even if those synthetic materials
are photodegradable. Care must be taken when using
natural, biodegradable products (i.e., hay or straw) in
erosion control to insure that the seeds of non-native or
invasive plants are not accidentally introduced with the
product. To help avoid this, many companies provide
products that are certified as weed-free.
It should be noted that some ECBs contain layers of
both organic, biodegradable materials, and plastic mesh.
These products potentially pose the same risk as those
made of only synthetic materials. A logical option to
avoid snake entanglement may be to employ products
that do not use plastic mesh or netting, particularly in
areas with potential for sensitive or legally protected
species. It is possible that biodegradable and
photodegradable mesh still poses an entanglement
hazard to snakes. Particularly if mesh aperture size is
too small and snakes become entangled before the
product degrades. Unfortunately, the ECTC indicates
that erosion control materials without some form of
netting are not sufficient for application in steep slope
and high water velocity situations. In such cases, plastic
mesh products with elongated apertures have been
recommended, as there is some evidence to suggest they
pose less of a threat to snakes (see below).
Past observations of numerous snakes entangled in
plastic mesh with aperture sizes of 1 and 2 cm2 at
restoration sites in South Carolina (USA) have been
reported (Barton and Kinkead 2005). They suggest
employing permanent TRMs with a very small mesh size
of < 0.5 cm2 to reduce snake mortality in areas where
protected species exist. Although this may be an
effective means to reduce adult snake mortality,
hatchlings and juveniles of many species, particularly
the smaller natricine species (Thamnophis and Storeria
sp.), may still be subject to accidental capture. Although
most reports that we have received or encountered in the
literature are of adult snakes, juvenile snakes that die in
netting may be less obvious, eaten by predators, or
decompose before they are noticed.
Several RECPs with plastic mesh exist that are
promoted as being “wildlife-friendly.” To our
knowledge, these claims have only been tested as they
apply to snakes for a product called NatureZone,
manufactured by Conwed Global Netting Solutions
(Minneapolis, Minnesota, USA; Guangda Shi, pers.
comm.; see Fig. 2 for an example of a product that
includes elongated apertures). These plastic mesh
products have been developed with mesh apertures that
are more elongated than those of traditional plastic mesh
with square apertures. This type of mesh construction
has been promoted as allowing passage of snakes, and
substantially reducing entanglement-related mortality.
Controlled experimental trials have been conducted on
NatureZone ® (Conwed Global Netting Solutions,
Minneapolis, Minnesota, USA) and other products with
various aperture sizes, to determine the level of snake-
entanglement risk it poses (Tony Gamble, pers. comm.;
Guangda Shi, pers. comm. ). The experimental animals
(all adults) used in these trials were two Racers (Coluber
constrictor), three Corn Snakes (Pantherophis guttata),
two ratsnakes (Pantherophis obsoleta and P. emoryi), a
Gophersnake (Pituophis catenifer) and two Common
Gartersnakes (Thamnophis sirtalis). Snakes were
housed with RECPs possessing one of four possible
mesh sizes (1.27 x 1.4 cm, 0.635 cm x 3.175 cm; 2.03
cm x 4.32 cm; 7.62 cm x 10.16 cm; no more than one
mesh type per trial, with exposure times of up to 165 h).
Although the results of this research have not been
published in the open scientific literature, the findings
shared through personal communication with Conwed
employees and university researchers hired to conduct
the tests indicate that mesh sizes of ca. 1.27 x 1.4 cm
were most likely to result in snake entanglement. On the
other hand, products such as NatureZone ® with
elongated mesh apertures (0.635 cm X 3.175 cm; 2.03
cm X 4.32 cm; 7.62 cm X 10.16 cm) captured fewer
snakes (Tony Gamble, pers. comm.; Guangda Shi, pers.
comm.). This supports the claim that products with
elongated mesh apertures reduce the likelihood of snake
entanglement. However, based on our recent report of a
Bullsnake becoming entangled in mesh with large
apertures ca. 2.54 cm2, it is possible that products with
enlarged apertures still pose a risk to larger, heavy
bodied species if the mesh is fixed at thread
intersections. It will be necessary to carefully consider
the application of any product comprised of a mesh with
fixed thread intersections in areas with high densities of
snakes, or known to possess species that are rare and/or
large in diameter.
Wildlife control products.—Documented observations
of mortality due to entanglement in wildlife control
products are uncommon, likely because they are rarely
reported. However, Stuart et al. (2001) discuss an
account of several Coachwhips (Masticophis flagellum)

Herpetological Conservation and Biology
7
entangled in mesh deployed to protect fruit trees from
birds. Numerous examples can be found on internet
blogs and websites of snakes trapped in plastic mesh
deployed to protect bird houses. Recommendations for
the use of netting to exclude horticultural pests in ways
that reduce the risk of snake mortality are difficult to
make. This is primarily because the use of netting in this
fashion is not regulated or monitored as stringently as
erosion control materials. In addition, no controlled
testing has been performed on the level of threat they
pose to wildlife. Some materials are also employed
specifically to entangle snakes in order to protect bird
nest boxes, or exclude snakes from residential properties.
Although some bird-enthusiast web pages report that
captured snakes were released prior to death, snakes may
quickly reach lethal body temperatures if the mesh is
exposed to direct sun. Plastic cones, affixed to the pole
on which a nest box is attached, may also deter some
snakes, but anecdotal reports of snakes gaining enough
purchase to bypass these cones exist. Anecdotal
examples also exist where food-grade oils (i.e.,
vegetable oil, olive oil, or shortening) have been
successfully employed for this purpose, with better
results than inverted cones. We recommend application
of food-grade oils be considered carefully, as their use
may attract other unwanted nest predators (i.e.,
Raccoons; Procyon lotor). As an alternative, it seems
logical that application of a synthetic lubricant (such as
WD-40) to poles that nest boxes are mounted on may
effectively prevent snakes from gaining access to these
boxes. Most lubricants have limited application in nest
boxes that are not mounted on metal poles or other
smooth surfaces.
Incorporation of netting with large apertures should be
considered if the primary goal is to protect crops or
ornamental plants from larger grazing wildlife species,
such as ungulates. Even apertures as large as 8–10 cm2
should exclude ungulates, while posing little risk to
snakes (Fig. 6). If the goal is to exclude birds (either
from grazing on crops or from nesting within buildings)
and smaller net apertures are required, use of products
with elongated apertures may prohibit birds and pose a
reduce entanglement threat to snakes. Care must be
taken with application of such mesh on homes and trees,
as other small vertebrates like bats may still become
accidentally entangled regardless of aperture size and
shape. Unfortunately, plastic netting with elongated
apertures is not widely available for such applications.
CONCLUSIONS
Erosion control materials are valuable in stabilizing
soil and seed banks; as well as, reducing soil run-off into
adjacent water-bodies. The exclusion of horticultural
pests is also important for a variety of reasons, including
economic purposes. Therefore, it is necessary to
determine what types of materials can be employed to
meet these needs, yet do not entangle snakes. It is
plausible that mortality due to entanglement in such
materials poses minimal or no threat to snake
populations. However, this cannot be assumed and
research to further assess the level of threat is warranted.
The easiest material to use in soil stabilization is a
loose layer of broadcasted organic material (e.g., wood
mulch, coir, etc.). It is unlikely to entangle snakes
because it does not contain any type of mesh or woven
layers, assuming an MCN is not also applied. It also
appears that HECPs pose little to no threat of snake
entanglement for the same reason. We believe that the
use of loose organic layers or HECPs are sound options
if one hopes to avoid snake entanglement, assuming the
substances used as part of the HECP slurry (i.e.,
tackifiers, etc.) are not toxic. RECP products
constructed of an unwoven and unbounded organic fiber
matrix may also pose a reduced threat of entanglement
compared to those with plastic mesh layers (Fig. 6). For
example, OWTs with strands woven such that they move
freely should allow passage of snakes. If the weave is
too tight and strands have little mobility, a threat may
still be present. Unfortunately, woven strand products
without a plastic mesh may not be as effective at
controlling severe soil erosion.
The traditionally employed plastic mesh with small
square apertures and filaments bonded at the
intersections is well known to entangle snakes. It has
been suggested that RECP products made of plastic
mesh with large elongated apertures may pose a reduced
risk of snake entanglement. Preliminary controlled
experiments on erosion control products with this design
have yielded positive and encouraging results. However,
the likelihood that these products will entangle snakes
has not been tested with large sample sizes, or in applied
situations in the field. We feel strongly that further
experimentation on these products is necessary (see
Suggestions for future research below).
The Erosion Control and Technology Council gives
recommendations for the application of materials to
reduce the impact to snakes that are mostly in-line with
our perspectives (Erosion Control and Technology
Council. Wildlife and Erosion Control. Available from
http://www.ectc.org/resources/WildlifeAndErosionContr
ol.pdf [Accessed 20 January 2011]). Although we agree
with many of their suggestions, they indicate that plastic
netting or mesh can be used if it is possible to insure that
it is “fastened securely to the ground and terminal edges
are trenched and/or secured properly to eliminate
bridging of the underlying soil and buckles/loose edges
in the netting.” They suggest this reduces the chances
that snakes will try to move “through the RECP netting
structure and get lodged in its opening.” However, this
claim has yet to be confirmed through controlled
experiments.

Kapfer and Paloski.—Risk of Snake Entrapment During Erosion Control.
8
Local and state regulations for acceptable products
employed to reduce soil erosion may vary. These
products may also vary in their likelihood to entangle
snakes. Therefore, we suggest that wildlife biologists
also become familiar with their local regulations when
making recommendations on projects.
Suggestions for future research.—There has been
very limited rigorous research conducted on the potential
impacts of erosion control and wildlife control products
on snake mortality and populations. Further controlled
experiments on a variety of OWTs, nettings, and mesh
types with various aperture sizes are warranted. Such
experiments should attain greater replication than has
been possible in the past: a higher number of individual
snakes, multiple species, and multiple age classes of
these species per category of erosion control and wildlife
control products. More concentrated effort should be
placed into assessing the threat that snake entanglement
poses to populations. Most of our reported observations
of snake entanglement occurred serendipitously. It
would be valuable to conduct surveys for snakes
entangled in various erosion control and wildlife control
products in situ. These surveys should start immediately
after application of the product and continue for, at least,
three to six months (or until the materials have degraded
and no longer pose an entanglement threat). It would be
useful to conduct these surveys on several different types
of materials (mesh, OWTs, and simple organic layers)
deployed in several different habitat types. Long-term in
situ studies that incorporate large sample sizes to explore
snake entanglement rates in plastic mesh with large
apertures would be very useful. This is largely because
plastic netting is often a requirement for suitable soil
erosion control in many situations.
Research is necessary to test the ability of various
wildlife control products to exclude target wildlife
species without entangling snakes (e.g., ungulates
feeding on ornamentals, or birds nesting in buildings).
This should include (controlled and in situ) experiments
on mesh or netting with various aperture sizes, made of
various materials, and in a variety of settings.
The suggested studies would be relatively easy to
design and conduct, if materials could be obtained from
manufacturers for testing, or researchers were given
access to conduct surveys in areas where products have
been recently deployed (i.e., recent road construction or
development projects). Furthermore, the results of such
experiments must not be proprietary. To be accessible
for those that are most likely to incorporate it in
decision-making (i.e., environmental regulators,
consultants and conservation biologists), the results of
such research must be freely available in the open
scientific literature.
Acknowledgments.—Bruce Ellarson, Fred Fetter, J.
King, and Paul White (Wisconsin Department of Natural
Resources); Bill Poole (Project Manager, Stantec, Inc.);
Denise Tiller, Ed Rodgers, and Tom Wagner all sent
information on observations of snake entanglement.
Tony Gamble (University of Minnesota) commented on
work conducted to test snake entanglement in certain
products. Melissa Gerrits (Wisconsin Department of
Transportation) helped track down information about
erosion control products approved for Wisconsin. Peter
Kemp (New Products Engineer, Bureau of Technical
Services, Division of Transportation System
Development, Wisconsin Department of Transportation)
provided invaluable insight and input on the application
and testing of erosion control products. Sean Syring and
Guangda Shi (Conwed Global Netting Solutions;
Minneapolis, Minnesota) provided information on
results of product testing. Numerous companies
provided free product samples and provided photographs
depicting their products in-situ to be used in this
manuscript. Lisie Kitchel (Wisconsin Department of
Natural Resources) graciously reviewed an earlier
version of this manuscript.
LITERATURE CITED
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Lexau, E. 2009. Blankets and mats: roll with the times.
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Erratum fixed 5-5-2011. Figure 6 required alteration in text and picture.
JOSHUA M.
K
APFER (pictured here showing undergraduate students a
copperhead, Agkistrodon contortix, captured in a funnel trap) has been
involved in field research on the ecology of amphibians and reptiles for
over a decade. Josh received his B.S. (1999) and M.S. (2002) in
Biology from the University of Wisconsin-La Crosse, and his Ph.D.
(2007) in Ecology and Evolution at the University of Wisconsin-
Milwaukee. He has worked as a State Regulator with the Wisconsin
Department of Natural Resources (Bureau of Endangered Resources)
and as an Environmental Consultant with Stantec, Inc. He is broadly
interested in wildlife ecology and conservation, with a particular focus
on habitat selection, spatial ecology, and how these are affected by
land-use patterns. Josh is currently an Assistant Professor in the
Departments of Environmental Studies and Biology at Elon University
(North Carolina, USA), and an Associate Researcher at the University
of Wisconsin-Milwaukee Field Station, Wisconsin, USA.
(Photographer unknown)
R
ORI A. PALOSKI (pictured here in Costa Rica) is a Conservation
Biologist with the Wisconsin Department of Natural Resources. She
received a B.S. from the University of Wisconsin Eau Claire
in Biology (1998) and a M.S. from the University of Wisconsin
Stevens Point in Natural Resources (2006) where her research
investigated the impacts of lakeshore development on anurans. Her
interests include the effects of urbanization on wildlife, amphibian and
reptile conservation, Northern Cricket Frog (Acris crepitans)
ecology, and endangered/threatened species policy. (Photographer
unknown)