Efficacy of Marking Snakes with Disposable Medical Cautery Units

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© 2006 by Society for the Study of Amphibians and Reptiles
Efficacy of Marking Snakes with Disposable
Medical Cautery Units
chased in large numbers) and in many field studies the recapture
rates of snakes are too low to justify their use. Even if funding is
unlimited, the limited girth of some neonates and small species
precludes the use of PIT tags (Gibbons and Andrews 2004).
Alternatively, snakes can be marked externally by a number of
methods. The most commonly-employed technique is clipping of
ventral scales anterior or posterior to the vent, in a pattern that
varies with the researcher (Brown and Parker 1976; Ferner 1979;
Woodbury 1956). These marks are of variable permanence (Shine
et al. 1988), and difficulties with readability of marks or mortality
of animals often arise if the marks are applied with too little or too
much enthusiasm. Clipping scales leaves an open wound subject
to possible infection, and marking small snakes is especially difficult (Weary 1969). Freeze-branding has been used by some researchers (Lewke and Stroud 1974; Measey et al. 2001), but this
method requires availability of liquid nitrogen, Freon, or similar
fluids that may be difficult to transport in field situations.
Heat branding has been used to mark reptiles and amphibians
by a number of researchers (Clark 1971; Ehmann 2000; Ferner
1979). Methods of branding have been extremely varied, and equipment has included pyrographic needles (Weary 1969), resistance
wire heated by Bunsen burners (Clark 1971) or by electricity
(Ehmann 2000), and soldering irons (Ehmann 2000). The majority of this equipment has been improvised from a variety of materials, a task that may be beyond the abilities of the typical herpetologist. These units may also require electrical current from a
wall socket, or require use of bulky and/or potentially explosive
equipment to heat wires.
Herein, we report on the use of disposable medical cautery units
(“Aaron Medical Change-A-Tip cautery units;” Aaron Medical,
St. Petersburg, Florida 33710, USA; www.aaronmed.com) as an
efficient means of marking snakes. These units are small, inexpensive, field-portable, and capable of quickly and precisely marking even very small snakes. Marks on most species are easily seen
for at least two years.
Medical cautery units are designed for a variety of surgical applications and are available in two temperature classes. We have
successfully used both high-temperature units (1204°C; ~US $25,
available with two different handle styles [one operates on 2 C
alkaline batteries, the other on 2 AA alkaline batteries]) and low-
CHRISTOPHER T. WINNE*
JOHN D. WILLSON
KIMBERLY M. ANDREWS
Savannah River Ecology Laboratory, Drawer E
Aiken, South Carolina 29803, USA
and
ROBERT N. REED
Department of Biology, Southern Utah University
Cedar City, Utah 84720, USA
* Corresponding author; e-mail: winne@srel.edu
In many situations, marking snakes for recapture purposes is
fraught with difficulty. Toe clipping has obvious drawbacks for
snakes, and externally attached tags are easily lost via shedding or
abrasion against surface objects. Passive integrated transponders
(PIT tags) have near 100% reliability and are typically permanent
if correctly implanted (Gibbons and Andrews 2004). However,
PIT tags are expensive (a minimum of US $3.50 per tag if pur52
FIG. 1. Medical cautery units used to heat-brand snakes. From top to
bottom: high-temperature, 2 CC battery handle; high-temperature, 2 AA
battery handle; low-temperature, 1 AA battery handle.
Herpetological Review 37(1), 2006
TABLE 1. Summary of recapture (RC) data for snakes branded with
disposable medical cautery units on the Savannah River Site, South Carolina.
Species
Seminatrix pygaea
Agkistrodon piscivorus
Coluber constrictor
Nerodia fasciata
Farancia abacura
Lampropeltis triangulum
Elaphe obsoleta
Tantilla coronata
Crotalus horridus
Thamnophis sauritus
Nerodia taxispilota
Cemophora coccinea
Lampropeltis getula
Heterodon platirhinos
Regina rigida
FIG. 2. Illustration of a snake heat-branded with ID # 36. For each mark,
we branded the anterior portion of the ventral scale and extended the
mark diagonally onto adjoining lateral scales. Illustration drawn by
Rebecca Taylor.
temperature units (704°C; operates on 1 AA alkaline battery; ~US
$20) designed for ophthalmological applications (Fig. 1). Both
units are small and field-portable (Fig. 1). We have used individual
units for over a year, marking hundreds of snakes. We replace
broken/worn out tips (US $3.50 each) as necessary. Batteries last
longer when marking small snakes, but in general batteries must
be replaced fairly frequently. Due to the high temperature of the
cautery units, marks should be applied with caution whenever fresh
batteries are used.
From June 2002 to May 2005, we used medical cautery units to
individually mark snakes as part of a long-term mark-recapture
study of semi-aquatic snakes on the Department of Energy’s Savannah River Site in the upper coastal plain of South Carolina.
We also marked a smaller number of individuals of other species,
which were not part of any extensive mark-recapture study, to
demonstrate the utility of this technique for small and terrestrial
species. On each snake, we branded 1–3 ventral scales anterior to
the anal plate, forming a unique numerical code (Fig. 2). For each
mark, we branded the anterior portion of the ventral scale and
extended the mark diagonally onto adjoining lateral scales. We
used high-temperature cautery units to mark medium and large
snake species, such as Black Swamp Snakes (Seminatrix pygaea),
Cottonmouths (Agkistrodon piscivorus), Racers (Coluber constrictor), watersnakes (Nerodia spp.), and Timber Rattlesnakes (Crotalus horridus), and low temperature units to mark juveniles and
small species (e.g., Cemophora coccinea, Lampropeltis triangulum,
N
RC Interval
Range (days)
Mean RC
Interval (days)
105
37
22
32
8
3
3
2
2
1
1
1
1
1
5–784
9–778
9–785
5–1058
4–744
32–420
41–201
18–576
14–59
221
41
27
26
19
320
259
135
183
187
164
127
—
—
—
—
—
—
—
1
17
—
Tantilla coronata). We found heat branding to be faster than traditional scale clipping for small-bodied snakes.
An important assumption of capture-mark-recapture studies is
that marks are permanent. In the field it is virtually impossible to
determine if brands may be lost in some individuals or species,
unless a second marking technique (e.g., PIT tags) is used or researchers can maintain a 100% recapture rate in the field. Alternatively, a laboratory colony of snakes can be maintained to determine mark retention rates over time. We chose this second method
to asses the reliability of the brands. In spring 2002, we marked 36
neonate Antaresia childreni and A. maculosa from four different
litters, and have kept them in the laboratory since that time (minus
four individuals that were sacrificed for various reasons).
We have recaptured 220 heat-branded snakes of 15 species (Table
1) on the Savannah River Site, suggesting that this technique works
well for a variety of taxa. The longest recapture interval was 1058
days, and we recaptured individuals of nine species after an interval > 200 days (Table 1). Additionally, long-term recaptures in
small species (e.g., Tantilla coronata, 576 days; Lampropeltis
triangulum, 420 days) attest to the effectiveness of marking delicate snakes with low-temperature cautery units. In general the
brands were readily observable, even after greater than two years
between captures and bouts of substantial growth (e.g., Agkistrodon
piscivorus, grew 30.1 cm snout–vent length [SVL]; Seminatrix
pygaea, grew 16.4 cm SVL). Similarly, the brands on Antaresia
childreni and A. maculosa have remained obvious and readable in
the laboratory for over three years, even as the snakes have tripled
in length and increased many-fold in mass: no snake displayed
marks that were appreciably faded. In combination, these results
demonstrate that heat-branding with medical cautery units is an
effective, dependable, and inexpensive technique for multi-year
mark-recapture studies of snakes.
Herpetological Review 37(1), 2006
53
Acknowledgments.—We thank T. Madsen for demonstrating his system for marking ventral and lateral scales on snakes. We thank X. Glaudas
and C. A. Young for capturing and processing some of the snakes. The
procedures used in this study were approved by the University of Georgia animal care and use committee (A2003-10024) and the South Carolina Department of Natural Resources (Collection permits: 56-2003, 072004). Research was supported by the U.S. Department of the Interior
(Fish and Wildlife Service, Division of Scientific Authority), and manuscript preparation was aided by the Environmental Remediation Sciences
Division of the Office of Biological and Environmental Research, U.S.
Department of Energy through Financial Assistance Award no. DE-FC0996SR18546 to the University of Georgia Research Foundation.
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equipment has been used increasingly in studies (Hughes and
Shorrock 1998; Jury et al. 2001; McQuillen and Brewer 2000;
Roberts and Anderson 2002; Shivik and Gruver 2002; Stevens
2002). However, the technique has not been exploited to its full
potential by biologists, due primarily to the high initial cost and
length of time to extract data from cassettes (Stewart et al. 1997;
Sykes et al. 1995). Time-lapse video is widely used by developmental biologists (Kulesa and Fraser 1998; Peppo et al. 2001;
Rezaie et al. 2002) but has enormous scope in applications for
wildlife research and until recently has been cost prohibitive. The
advantages of a video surveillance system include gaining a permanent record of events that can be replayed as many times as
necessary to retrieve data, reduction in observer bias and missed
observations, easy habituation by the study animal and the ability
to document events that are not easily detected using direct observations. Video surveillance can be used to record activity at a focal site (such as entrance or exit to a shelter site or burrow, the
removal of baits by target and non-target species), identify individuals, document predation events, and detect nocturnal, crepuscular or elusive species (Brown 1997; Deufel and Cundall 1999;
Stewart et al. 1997; Tobler and Schwierin 1996).
Equipment and set-up.—I used inexpensive miniature monochrome (MINI-M20A) video surveillance cameras attached to an
existing PC computer via a 4 channel PC digital surveillance recording system (Go Video DVR4, PCI PC capture card and software) available from Allthings Sales and Service (Kelmscott, Western Australia; www.allthings.com.au). Allthings Sales and Service
economically and reliably ship worldwide via airmail or EMS
speed post, with typical airmail rates to the USA for a 0.5–2kg
package ranging from $US 8 to $27 depending on weight. The
entire system can be purchased as a complete package and attached
to an existing IBM compatible computer from as little as $US
210; the system (discussed below) consists of a 4 channel PCI PC
capture card, software, 4 monochrome cameras, and a Plug-in DIY
AV 20 meter cable/adaptor set for 4 cameras. Several optional color
camera upgrades are also available from $US 60 to $140. Alternatively, each component can be purchased separately and a system
Herpetological Review, 2006, 37(1), 54–56.
© 2006 by Society for the Study of Amphibians and Reptiles
An Inexpensive Video Surveillance Technique for
Wildlife Studies
KYLIE A. ROBERT
School of Biological Sciences and Institute of Wildlife Research
Heydon-Laurence Building (A08), The University of Sydney
NSW 2006, Australia
e-mail: kylie_robert@hotmail.com
Most wildlife behavioral studies require time consuming direct
observations of animals (Altmann 1974) or the use of expensive
closed-circuit television (CCTV) cameras and time-lapse video
equipment (Wratten 1994). Direct observation of animals is limited by how practical observations are of the species and how easily the species is habituated to an observer (Stewart et al. 1997).
The use of video applications in wildlife research has been well
documented as a useful technique (Pulliainen 1971; Stewart et al.
1997; Sykes et al. 1995; Wratten 1994) and video surveillance
54
FIG. 1. Snapshot image of experimental enclosure showing camera identification, date and time display.
Herpetological Review 37(1), 2006