A REVIEW OF TECHNIQUESFORMARKING SNAKES
MATHIAS LANGDepartment of HerpetologyRoyal Belgium Institute of Natural Sciences
SMITHSONIANHERPETOLOGICAL INFORMATIONSERVICENO, 90
1992
SMITHSONIANHERPETOLOGICALINFORMATIONSERVICE
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COVER ILLUSTRATION. Radiotrackers ' ideal snake with a built-in antenna; drawn by Stephanie Ersek.
INTRODUCTIONSnakes present a serious difficulty to ecologists wishing tostudy them in the field. Due to their secretive behaviour andcryptic coloration, they are generally difficult to find, andbecause of their solitary lifestyle, they are usually only foundas isolated individuals. Whereas turtles, lizards, and crocodilianslend themselves easily to marking methods, snakes are the mostdifficult reptiles to mark effectively for field identification.Nevertheless, researchers have ingenuously developed a variety oftechniques for marking snakes. No less than twenty differentmethods have been used with more than fifty snake species(Appendix) . These techniques fall into several categories: 1)scale-clipping; 2) tagging; 3) painting/coloring; 4) tattooing, 5)branding; 6) recording of integumentary and scale patterns; 7)incising; and radiotelemetry . These are summarized in a subsequentsection.An ideal marking method for snakes should satisfy most of thefollowing criteria, as enumerated by Lewke and Stroud (1974) andRicker (1956). It should: 1) be as free of stress and pain aspossible; 2) not affect the mortality rate of the animals; 3)afford minimal opportunity for infection; 4) not affect behaviour;5) not inhibit normal movement; 6) not inhibit the sheddingprocess; 7) be permanent or at least long-lasting; 8) be easilyread to identify accurately individuals; 9) be adaptable to allsizes of animals; 10) be easily employed in the field or laboratorysituation; and 11) involve equipment and materials that are easilymade or obtainable at a minimal cost.Discussions of preferred methods of marking can be found inBrown and Parker (1976b), Clark (1971), Ferner (1979), Fitch(1949A; 1987), Kroll et al. (1973), Lewke and Stroud (1974),McGinnis (1967), Pendlebury (1972), Pough (1970), Reinert andCundall (1982), Schmidt and Davies (1941), Spellerberg and Prestt(1978), Swingland (1978), Turner (1977), Weary (1969) and Woodbury(1948; 1956)
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Considering the aforementioned references, enough informationis available for ecologists to choose an effective tagging methodfor their investigations according to their budget and thehypotheses to be investigated. To permit ready access andevaluation of the different methodologies, I offer the followingsummaries of the various marking techniques along with thepertinent literature.
2MARKING PROTOCOLSScale-ClippingSubcaudal clipping ( 1) .The first method ever used to mark snakes for an ecologicalstudy was devised by Blanchard and Finster (1933). It consisted ofcompletely removing three subcaudal scales with a pair of sharpscissors, using a code to designate those scales clipped. Bycounting caudad from the cloacal plate, and placing the left andright subcaudals on the respective sides of a dash, a typical codeof "2,5-4" represents the second and fifth subcaudal on the leftand the fourth subcaudal on the right as being marked.This method or variations thereof have been used, at leastuntil the recent advances in radiotelemetry, for the past fiftyyears by the overwhelming majority of ecologists. Published reportsindicate that close to 50,000 snakes have been marked by subcaudalclippings. It has been employed in studies by Blaesing (1979),Blanchard et al. (1979), Carpenter (1952), Fitch (1949b, 1958),Fitch and Fleet (1970), Fitch and Glading (1947), Fukada (1959;1960; 1978), Parker (1974), Reynolds and Scott (1982), Siebert(1950), Siebert and Hagen (1947), Test et al. (1966), and Tinkle(1957)
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Although Blanchard and Finster (1933) warned that scales onlypartially removed would regenerate through time, subseguent studiesdemonstrated that certain species have the ability to completelyregenerate even entirely removed subcaudals. Calstrom and Edelstam(1946) were the first to demonstrate this, and further noted howdifficult and harmful subcaudal clipping was with juveniles. Conant(1948) described a zoo specimen of Elaphe obsoleta in whichregeneration obliterated the original marks after five years.Regeneration was further verified by Fitch (1982), who studiedtwelve species of snakes over a 30 year period (22,000 individualsmarked) . He showed that regeneration of clipped scales was morerapid and complete in Elaphe obsoleta than in any other speciesthat he studied. After a few years, many clipped scales wereindistinguishable from natural injuries (Fitch, 1963a) . Otherspecies also possess good regeneration. For example, Diadophispunctatus are scared by bites from predators, and these scars areindistinguishable from those of clipping after two or three years(Fitch, 1975) . Similarly, Fitch (1963b) observed regeneration insome Coluber constrictor after two or three years.
Ventral clipping (2)
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Woodbury (1951) was the first to use ventral scales. Heclipped a portion of the ventral scale on either side, designatingthe right side with a capital letter and the left side with a^pmallletter. Scales were lettered craniad from the anal plate, ana sexwas indicated by M or F. Thus a code combination of "DaM" referredto a male snake with a clipped fourth ventral on the right and thefirst ventral on the left.Brown and Parker (1976b) modified Woodbury's methodology tofulfill the eight criteria of Lewke and Stroud (1974) for a goodmarking method. The modified method is claimed to be satisfactoryfor at least four years and was used by Brown (1973), Brown andParker (1974; 1982), Henderson et al. (1980), Jacob and Painter(1980) and Parker and Brown (1973; 1974a-b) . The Brown and Parkerprotocol remove half of a ventral in combination of one to threeclips with a total of 989 unique combinations. Ventrals are countedanteriorly from the anal plate on the left side in units from 1-9; on the right side they are counted in series of 10 ' s (10-90),100' s (100-900) , and 1000 's (if necessary) . A snake whose belly wasclipped on the left side of ventral nine and the right side ofventral three and eleven would be number 239. Regeneration does notappear to occur as readily in the ventrals as in the subcaudals.No ill effects were noticed in markings of more than 1000 Coluberconstrictor (Brown, 1973) . This methodology appears superior forscale-clipping, although some ambiguity may occur such asmisidentification of individual marks (Fitch, 1987)
.
Ventral and subcaudal clipping (3)
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Fitch (1958, 1960) proposed a combination of subcaudals andventral scale clippings. The first twenty subcaudals allow 362unique combinations. A typical code of "U 5L 2R" representsmarkings on the fifth left and the second right subcaudals.Ventrals are used to indicate the next series of 362 marks.Counting craniad from the anal plate, "G 1L" designates the firstventral on the left or "G 1R" the first right ventral, etc. Fitchemployed this technique in his later studies (1963a, b; 1965; 1975;1982), and it was also used by Clark (1970) and Piatt (1969).Another variant of scale clipping was devised by Clark (1971)
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Only two marks are necessary with the designation of a basalstarting point. For example, "BL-2L 3R" indicated a base mark onthe left and the subsequent ventrals second left and third rightare marked. To improve reliability, a scale is removed from thefirst dorsal scale row immediately adjacent to the basal markedventral
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Henderson (1974), Lang (1969), and Saint-Girons (1964) usedcombined clipping methodologies, but did not provide full detailson the numbering protocol.The disadvantages of all clipping methods are the timereguired to mark each snake, the freguently drawing blood andpossibility of infection, and the difficulty in marking smallsnakes (Weary, 1969)
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Most recent researchers favor the combined ventral-subcaudalmethodology of Prestt (1971) and Brown and Parker (1984) . Thismethod has been used successfully in studies on the populationdynamics of colubrids and viperids (e.g. Brown and Parker, 1984;Feaver, 1977; Parker and Brown, 1974 a,b, 1980; Prestt, 1971;Spellerberg and Phelps, 1977)
.
TagsMetal tags (4) .Hirth (1966) was the first to attach tags to snakes. He useduniguely numbered stainless steel tags clamped to the corner ofthe mouth. Fortunately, this location has not been usedsubseguently. Voris et al . (1983) attached numbered metal tags tothe tail tips of sea snakes. He discontinued the tagging when itbecame apparent that the tags collected debris, wore holes in thetails, and were often lost.Plastic plugs (5)
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Pough (1970) described the use of colored plastic plugs orserially numbered metal tags attached to the tail via a buttonerdevice. The technigue is presumably a guick and permanent methodof marking snakes. The tags were partially inserted into the caudalmusculature through the lateral subcaudal scales. Those insertedinto ventral scales fell off. Plugs cannot be attached to snakessmaller than 2 50 mm SV. During Pough' s studies there was noevidence of infection nor any indication that the plug interfereswith shedding or locomotion.Plastic disk (6) .Pendlebury (1972) initiated the attachment of colored disksto rattlesnake's rattles. A pair of disks are sewn on either sideof the basal rattle segment. With the use of a pair of disks in tencolor combinations 100 specimens can be uniguely marked. Two pairsof disks on each snake allows 10,000 unigue combinations. Thismethod, although limited to studies of rattlesnakes, has been usedsuccessfully by JACOB and Painter (1980) , Reinert and Kodrich(1982), Stark (1984) and Brown et al. (1984).
Plastic tag/colored beads (7) .Thin, yellow plastic tags were successfully used by Voris etal. (1983) to mark sea snakes; these tags were embeddedsubcutaneously in front of the tail on the right side of the body.Similar red tags hooked through the tail were found to be lessvaluable. Hudnall (1982) suggested the use of colored beads to marksnakes.Radioactive wire (8)
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Barbour et al. (1969) first used a radioactive wire to marksnakes. A thin wire is inserted subcutaneously in the tail via amodified hypodermic syringe. The wires were radioactive Cobalt(Co60 ) with a 50-80 microcurie dose. Hirth et al. (1969) and laterFitch (fide Ferner, 1979) used radioactive Tantalum (Ta 182 ) wirewith 4 00 microcurie amounts. Snakes so marked can be located ninemeters away when on the surface and three meters away when 30 cmbelow the surface. Tantalum and Cobalt have been the preferredsource of radiation. Cobalt has a more powerful gamma radiationwith a half-life of 5 years, whereas Tantalum has a half-life ofonly 6 months. The disadvantages of radioactive tags are that theymay injure and eventually kill the snakes carrying them.Furthermore they are readily shed and then become hazardous toother animals or humans (Fitch, 1987) . Radioactive tags arepreferable to radiotransmitters in smaller snakes. The use ofradioactive tags (and telemetry) are reviewed in Spellerberg andPrestt (1978), Swingland (1978) and Ferner (1979).The major problem for the effective use of external tags isthe choice of an adequate attachment site. The elongated, limblessbody of snakes offers no satisfactory attachment sites. Thepossible sites are the free edges of the anterior ventrals, thecloacal plate, the lower jaw, or the base of the rattle inrattlesnakes. The tags must be attached in a manner to avoidinterference with normal behavior and to reduce abrasion or lossof the tags.The aforementioned tags can be stitched to the skin with heavythread, thin wire or nylon. Utmost care must be exercised whenattaching tags to avoid injury. For example, pinched skin undergoesnecrosis thereby modifying the snake's normal behavior andincreasing the likelihood of tag loss (Fitch, 1987)
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Painting/coloringBrush paint (9)
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Fitch (1960) painted red, yellow, orange, and blue enamelmarks on snakes to check on their shedding cycle. Pough (1966) used
quick drying waterproof paint to number the basal rattle segmentof rattlesnakes. This method has been further altered forrattlesnakes by Brown et al. (1984). The head and neck of snakeswere painted by Parker (1976) for field identification.
Spray painting (10)
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Henderson et al. (1981) used rapid-drying fluorescent spraypaint (non-toxic) to mark arboreal snakes. Three quarters of theanimals spray-painted were later observed. Plummer (1985) also usedspray paint to mark Opheodrys .Water color pencil (11).Stebbins (1966) suggested the use of Mongol water colorpencils to temporarily mark specimens for field observations.The preceding three methods produce temporary marking,nonetheless they facilitate the recognition of individuals withoutrecapture in a variety of field situations. The marks are lost withthe shed exuvia or through wear. As Fitch (1987) points out, thesemethods have additional useful applications, such as for groupmarkings of snakes to obtain capture-recapture ratios that canserve for a Petersen index census. In population studies based onpermanent marking systems, these temporary marks provide the bestmethod for investigating ecdysis cycles.Most species of snakes however are too secretive for regularor long-term observations, so the short duration of paint markingis of little use. Another major disadvantage is that the coloredmarks render marked individuals more conspicuous to visuallyoriented predators, hereby distorting the capture-recapture ratio(Fitch, 1987). TattooingBattery powered tattooing (12)
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Imler (1945) was the first researcher to tattoo snakes witha battery-operated unit. He tattooed the venter of bullsnakes witha special code number. This method was subsequently redescribed byWoodbury (1948, 1951) for marking rattlesnakes at a den. Using aportable tattooing outfit and India ink, he tattooed large numbersof snakes on their throats, subcaudals and/or ventrals, and areaslacking pigments. Disadvantages include the tendencies of thetattoos to fade and the necessity of tattooing unpigmented orlightly pigmented areas.Electric powered tattooing (13)
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Weary (1969) improved the tattooing method by employing an
inexpensive pyrographic needle (50 W unit operated from a 110 voltsource) or a soldering pencil (powered by a 12 volt battery) toburn/scar scales without drawing blood.Tattooing is more labor-intensive than scale clipping andusually involves the transport of bulky equipment. Also a majordrawback is that during marking, there is a high risk of injuryand even death if the needle penetrates too deeply and pierces thebody cavity. Fitch (1987) points out two additional problemslimitimg the widespread use of these techniques. First, in darklypigmented individuals and species of snakes, the numbers aredifficult to read accurately and second, especially in snakesmarked as juveniles the ink spreads and sometimes blurs thenumbers. Branding
Hot (flame) branding (14).Clark (1971) described the use of a heat source, a Bunsenburner in the laboratory or a small propane torch in the field, tobrand numbers on snakes by heating a branding wire of 2 0%chromium/80% nickel (Chromel A) and applying it to the scales.Cold (freeze) branding (15).Lewke and Stroud (1974) employed a superchilled brandinginstrument of copper wire to mark snakes. The technique was devisedby Farrel (1966) for use with livestock. Of the three coolantstested (dry ice and 95% ethyl alcohol, Freon 12, and Freon 22), dryice and alcohol was the most successful. Chromatophores aredestroyed by quick-freezing the skin surface. The brand appears asa white area (Fitch, 1987)
.
Although this method is a good field-marking technique, adisadvantage is that the mark is not evident until after ecdysisand there is a minimal size limit of the branding iron used.Branding shares the same problems and disadvantages with tattooing.It is labor-intensive, sometimes causes injuries and may bedifficult to read with heavily pigmented snakes.
Recording integumentary and scale patternsNatural marks (16)
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Calstrom and Edelstam (1946) employed the innovation ofrecording a snake's color pattern because each has a uniquepattern. They photographed or sketched the fourth through eighth
8
ventrals (from anterior end) of Natrix natrix . These patterns weresufficient, in conjunction with other scuttelation data toreidentify individuals. Snakes with distinctive skin patterns likeCoronella and Vipera were treated in the same manner by recordingtheir dorsal patterns. The use of this technique was consideredfeasible for Pelamis by Kropach (1973) . Fitch (1987) suggests amethodology for recognition of individual Aqkistrodon contortrixbased on the arrangement of complete and incomplete "hourglass"marks on the body.Scale formulae (17)
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Blanchard and Finster (1933) mentioned an unsuccessfullattempt to recognize individuals with scuttelation data. However,Fukada (1978) described recording the arrangement of temporalscales in Elaphe climacophora as an adjunct to scale-clipping.
Both of these pattern-recognition techniques are laborintensive in recording and recognizing specific patterns andfurthermore prone to reading errors. As Fitch (1987) suggests,natural marks should be noted and used to confirm theidentification of individuals based on other marks or tags.IncisionsTail-notching (18) .In Kropach's unpublished dissertation (1973), he described atail notching protocol for seasnakes. He (Kropach, 1975) laterelaborated on this technique.RadiotelemetryFitch (1987) recommends two fundamental criteria that shouldbe met for the use of radiotransmitters. The transmitters shouldbe small enough not to burden the snake during its normalactivities such as feeding and locomotion, yet large enough to havea sufficient transmission range for easy localization.Oral insertion (force fed) (19)
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McGinnis and Moore (1969) pioneered the use of radiotelemetryin snake studies, adapting the technique used for lizards byMcGinnis (1967) . They force-fed a Boa constrictor with a miniaturetemperature sensitive transmitter with a range of 100 meters.Various types of radio transmitters, antennae and battery sourceshave been used subsequently in snake studies. Transmitters arecoated with paraffin/beeswax mixture or silicone, and are eitherpalpated into the animal's stomach or sewn into a food item and
9then force-fed. Battery life ranges from a few days to severalmonths. Orally inserted radiotransmitters have been used by Brownand Parker (1976a), Brown et al. (1982), Fitch and Shirer (1971),Galligan and Dunson (1979) , Hammerson (1979) , Henderson et al.(1976), Jacob and McDonald (1975), Jacob and Painter (1980),Johnson (1972), Landreth (1973), Montgomery and Rand (1978), Moore(1978), Nickerson et al. (1978), Osgood (1970), Parker and Brown(1972) , Reinert (1981) and Reinert and Kodrich (1982)
.
Some disadvantages of this method are that the effective rangeof the transmitter is small, the transmitter may be regurgitated,and the transmitter in the stomach may cause behavioral changes inthe snake. Fitch and Shirer (1971) tied a string around the bodyand sewed it to a ventral scale to prevent their snakes from losingthe transmitters. Early studies demonstrated that the beeswaxcovering are digested by the snake, causing the transmitter tomalfunction.Surgical insertion (20) . In order to alleviate the above mentionedproblems, Fitch and Shirer (1971) surgically implanted transmittersinto the abdomens of snakes. Brown and Parker (1976a) encapsuledtheir transmitters in polyethylene and inserted them abdominallywith minimal bleeding. The sutures healed completely within twoweeks. Other workers using this method include Brown and Parker(1982), Henderson et al. (1980), Jacob and Painter (1980). Reinertand Cundall (1982) improved the transmission of radiotelemeter bythe implantation of both the transmitter and the antenna, thelatter subcutaneously . Their transmitters had a maximum range of1.5 km, a vast improvement over previous techniques. Furtherexamples of studies using this technique are those by Reinert etal. (1984) and Madsen (1984).Surgical implantation method involves anesthetizing the snakeand inserting a foreign object into the body cavity. Although thehealing process and fibrotic encapsulation may be rapid, behavioralalterations may occur (Fitch, 1987) .During the past two decades, the quality, longevity anddistance of the emitted signals have been ameliorated. Inconjunction with better radiotelemetry units, more efficientcomputerized radio-telemetric systems are now available to monitorfree-ranging snakes (Stanmer, 1988) . Furthermore, the implantationtechniques are more refined (Weatherhead et al., 1984).Fitch (1987) suggests that radiotelemetry may be the choicetechnique for most ecological research involving the marking ofsnakes. It allows for quick and effective monitoring of individualsin open terrain. In closed biotopes such as swamps, subterranean
10habitats or rainforests, the situation is less favorable.
SUMMARYEcologists have a variety of different techniques at theirdisposal for the marking of snakes for field studies. With thesophistication now present in radiotelemetry , snakes can be trackedover long distances and recordings can be made for lengthy periodsof time, such as overwintering in hibernacula.The following appendix and bibliography identify the variouspublished marking techniques and the primary literature sources.The most widely used method for marking snakes may remain theventral and subcaudal scale clipping. It is permanent, cost-efficient, and it allows the unique marking of each individual ina population. This method also has no permanent ill effect on themarked animals.
ACKNOWLEDGMENTS
I would like to thank Van Wallach (Museum of ComparativeZoology, Harvard University) for his help in providing referencesand Stephanie Ersek (Austin, Texas) for her imaginative coverillustration.
11Appendix - This list is a partial overview at best of the speciesof snakes that have been tagged for field studies. Many morespecies have been marked in Masters theses and Doctoraldissertations as well as other publications that are not listed inthe zoological records. See numbers in text for the identificationof methods.
TAXON METHODS USED
FAMILY BOIIDAEBoa constrictorMorelia spilotes 1919FAMILY COLUBRIDAECarphophis amoenusCarphophis vermisColuber constrictorCoronella sp.Coronella austriacaDiadophis punctatusElaphe climacophoraElaphe obsoletaElaphe quadrivirqataElaphe subocularisHelicops anqulatusHeterodon nasicusHeterodon platyrhinosLampropeltis calliqasterLampropeltis trianqulumLeptophis depressirostrisLiophis reqinaeMasticophis lateralisMasticophis taeniatusNatrix natrixNerodia fasciataNerodia sipedonNerodia taxispilotaOpheodrvs aestivusOpheodrys vernalisOxybelis aeneusPituophis melanoleucusRhabdophis tiqrinusSpilotes pullatusStoreria dekayi
81,31,2,3,4,8,12,19,201631,2,3,8,1711,3,191119331,3,191,2,20191192,3,4,8,9,12,1916,17,20191,3,191910131,2,3,12,191191,3,8
12Storeria occipitomaculataThamnophis butleriThamnophis eleqansThamnophis ordinoidesThamnophis radixThamnophis sirtalisUromacer catesbviUromacer oxyrhynchus
111111,3,5,191010
FAMILY HYDROPHIIDAEEnhydrina schistosaLaticauda colubrinaPelamis platurus 4,7318FAMILY VI PERIDAEAakistrodon contortrixBothrops atroxCrotalus atroxCrotalus cerastesCrotalus horridusCrotalus mitchelliCrotalus molossusCrotalus scutulatusCrotalus viridisSistrurus catenatusTrimeresurus flavoviridisVipera sp.Vipera berus
1, 3, 9, 16,19191, 9, 19191, 2, 3, 19, 20191, 91, 91, 2, 6, 8, 12, 19, 206, 1919,201620
13LITERATURE CITED
BARBOUR, R.W., HARVEY, M.J. & HARDIN, J.W. 1969. Home range,movements, and activity of the eastern worm snake,Carphophis amoenus amoenus . Ecology 50 (3) : 470-476.BLAESING, M.E. 1979. Some aspects of the ecology of the easterngarter snake ( Thamnophis sirtalis sirtalis) in a semi-disturbed habitat in west-central Illinois. J. Herpetol.13 (2) :177-181.BLANCHARD, F.N. & FINSTER, E.B. 193 3. A method of marking livingsnakes for future recognition, with a discussion of someproblems and results. Ecology 14 (4) : 334-347
.
BLANCHARD, F.N., GILREATH, M.R. & BLANCHARD, F.C. 1979. Theeastern ring-neck snake ( Diadophis punctatus edwardsii) innorthern Michigan (Reptilia, Serpentes, Colubridae) . J.Herpetol. 13 (4) : 377-402
.
BROWN, W.S. 197 3. Ecology of the racer, Coluber constrictor mormon(Serpentes, Colubridae), in a cold temperate desert innorthern Utah. Ph.D. dissertation, Univ. Utah,BROWN, W.S. 1982. Overwintering body temperatures of timberrattlesnakes ( Crotalus horridus) in northeastern NewYork. J. Herpetol. 16 (2) : 145-150
.
BROWN, W.S., GANNON, V.P.J. & SECOY, D.M. 1984. Paint marking therattle of rattlesnakes. Herpetol. Rev. 15:75-76.BROWN, W.S. & PARKER, W.S. 1974. Population structure anddemography of the snake, Coluber constrictor , in Utah. Amer.Zool. 4:1294 (abst.)BROWN, W.S. & PARKER, W.S. 1976a. Movement ecology of Coluberconstrictor near communal hibernacula. Copeia1976(2) :225-242.BROWN, W.S. & PARKER, W.S. 197 6B. A ventral scale clipping systemfor permanently marking snakes (Reptilia, Serpentes). J.of Herpetol. 10 (3) : 247-249
.
BROWN, W.S. & PARKER, W.S. 1982. Niche dimensions and resourcepartitioning in a Great Basin desert snake community. Pp59-81 In SCOTT, N.J. (ed) , Herpetological Communities.US/FWS Wild. Res. Rep. 13.BROWN, W.S., PYLE, D.W., GREENE, H.R. & FRIEDLANDER, J.B. 1982.Movements and temperature relationships of timberrattlesnakes ( Crotalus horridus ) in northeastern NewYork. J. Herpetol. 16 (2) : 151-161.CALSTROM, D. & EDELSTAM, C. 1946. Methods of marking reptiles foridentification after recapture. Nature 158 (4021) : 748-749.
14CAMPER, J.D. & DIXON, J.R. 1988. Evaluation of amicrochip markingsystem for amphibians and reptiles. Texas Parks & Wildl.Dept. Res. Publ.CARPENTER, C.C. 1952. Comparative ecology of the common gartersnake ( Thamnophis s. sirtalis) , the ribbon shake ( Thamnophiss. sauritus) , and Butler's garter snake ( Thamnophis butleri)in mixed populations. Ecol . Mono. 22 (3) : 235-258
.
CLARK, D.R., Jr. 1970. Ecological study of the worm snakeCarphophis vermis (Kennicott) . Mus. Nat. Hist., Univ. Kansas,Publ. 19(2) :85-194.CLARK, D.R., Jr. 1971. Branding as a marking technique foramphibians and reptiles. Copeia 1971(1) : 148-151.CONANT, R. 1948. Regeneration of clipped subcaudal scales in apilot black snake. Nat. Hist. Misc. (13):l-2.FARRELL, K. 1966. The freeze-branding technique. Proc. Freeze-brand Seminar, Washington State Univ. pp. 5-11.FEAVER, P.E. 1977. The demography of a Michigan population ofNatrix sipedon with discussions of ophidian growth andreproduction. Ph.D. Thesis. Univ. Michigan.FERNER, J.W. 1979. A review of marking techniques for amphibiansand reptiles. Society for the Study of Amphibians andReptiles, Herpetol. Circ. (9):1-41.FITCH, H.S. 1949a. Outline for ecological life history studies ofreptiles. Ecology 30 (4) : 520-532
.
FITCH, H.S. 1949b. Study of snake populations in centralCalifornia. Amer. Mid. Natur. 41 (3) : 513-579
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FITCH, H.S. 19 58. Home ranges, territories, and seasonal movementsof vertebrates of the Natural History Reservation. Mus.Natur. Hist. Univ. Kansas Publ. 11 (3) : 63-326.FITCH, H.S. 1960. Autecology of the copperhead. Mus. Natur. Hist.Univ. Kansas Publ. 13 (4) : 85-288FITCH, H.S. 1963a. Natural history of the black rat snake ( Elapheo. obsoleta) in Kansas. Copeia 1963 (4) : 649-658
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FITCH, H.S. 1963b. Natural history of the racer Coluberconstrictor . Mus. Natur. Hist. Univ. Kansas Publ. 15(8) :351-468.FITCH, H.S. 1965. An ecological study of the garter snake,Thamnophis sirtalis . Mus. Natur. Hist. Univ. Kansas Publ.15(10) :493-564.FITCH, H.S. 1975. A demographic study of the ringneck snake
( Diadophis punctatus ) in Kansas. Univ. Kansas Mus. Natur.Hist. Miscel. Publ. (62): 1-53.FITCH, H.S. 1982. Resources of a snake community in prairie-woodland habitat of northeastern Kansas. Pp. 83-97. InSCOTT, N.J. (ed) Herpetological Communities. US/FWSWildl. Res. Rep. (13)
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15FITCH, H.S. 1987. Collecting and life-history techniques. Pp. 143-164. In SEIGEL, R.A., COLLINS, J.T. & NOVAK, S.S. (ed) .Snakes: Ecology and Evolutionary Biology. Macmillan Publ . Co.New York.FITCH, H.S. & FLEET, R. 1970. Natural history of the milk snake
( Lampropeltis trianqulum ) in northeastern Kansas.Herpetologica 26 (4) : 387-396.FITCH, H.S. & GLADING, B. 1947. A field study of a rattlesnakepopulation. California Fish and Game 33 (2) : 103-123
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