장음표시 사용
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Radiotelemetry is a useful technique for studying certain aspects of the life history andecology of Snakes. In the present paper a comprehensive Overview is gi ven of ali the metho dological experiences of herpetological radiotelemetry in the past 25 years. A uses ut guideli ne shows how to plan and carry out a study on snakes using this adVanced method. Summaries and helpsul comments are presented os almost every chapter of such a project: the possibi e aims of the study the choice of the snake species in question. the selection of the study area and the different transmitters, attaching the transmitter to the snake's body obtaining optimum resulis and the analysis of the resulis. Separate chapters deat with the relevant technical aspects of radiotelemetry type, si Ze, lis e-span and efficiency of the different transmitters and receivers: immobili sation of the snakes anaesthesia and controi during and after the implantation Os me transmitter, coid immobili sation and locat anaesthesia. Resulis, whicli cara be obtained by radiotelemetry are thoroughly discussedo location os thesnakes with disserent techni ques, delatis of bellaviour. Deding breeding. hibernation and habitat preference. Mathematical formulas for identis ying and calculating home range si Zeand movement are briefly referred. Concepis and solutions of biotelemetry as a uses ut aid forstudying thermoregulation and the thermal biology of snakes is also described. AS an example, experiences frona a project on a sinali European grassiand vi per fri eraursinii res siensis) are presented in order to illustrate problenas and practical solutions when
Untii the beginning of the J0's only litile information could be gatheredabout the biology. life history, thermal and territorial ecology, and bellaviour offree living snakes. A revolutionary breakthrough was gained by the introductionos radiotele metric techni ques. The first suci, studies on snakes investigated the factors regulating their hody temperature MCGINNIS & MOORE l 969. OS GOODl9J0). Some monilis later FITCH and SHIER l9Jl) reported on radiotele metricstudies on 6J individuals of 8 species. The transmitters used were relative lyheavy, with a s hori distance operation and life spata. By continuo u sty improving
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the technique it hecame possibie to monitor the snakes' activi ty during a longerperiod. Even toclay, howeVer, hecause of the large siZe of transmitters relative tothe animal 's body), radiotelemetry is generalty considered more useful for large species. Iis efficiency, precision low time and energy requiremenis, and the factthat it can produce resulis on species otherwi se very difficult to study, makes thedispersion and further developinent of the method more justi ecl. In North America, Species of Crotalus, Ag istro lon and mrodia IACOB 9 PAINTER
were the objects of seeld investigations applying this technique. For a more de-tailed summary of radiotelemetric studies carned out on snakes, see Tabies i and 2. The present paper giVes a comprehensive overview of ali the methodological experiences of herpetological radiotelemetry in the past 25 years and at thesanae time, tries to give a USeml guidance on how to plan and carry out a studyusing this technique on snakes. It is bullt up according to the structure of an actual project: staning at the choice of the species to be studied, the possibie ainas, through the choice of the different transmitters and receivers, useful hinis for the application of the method. to the evaluation of the resulis.
PLANNINO A RADIOTELEMETRIC STUDY
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tion of SnakeS, howeVer, cara eaSily be reali Sed under natural circumStances aswell, provided that automatic data recording is aVallabie. Datly activity patiern of the animais can be recorded both in enclosures and in the fieid. Seasonat activitypatiern, on the other hand, is best to record in natural circumstances, since it is effected by a number of factors, whicli are difficult to reproduce Or forecast. There
their home range, dat ly acti Vlty patiem, Or Sonae phySiological parameterS, Ormaybe ali together In order to get data about the home range it is appropriate to Select a Simple, cheap and Smali transmitter, Whereas physiological record S canon ly be gai neu through the application os more complicated, heaVier, adVaneed SystemS. Ιf the purpose is to monitor body temperatum, the type and the fixing of the transmitter is an important matter, influencing the nature of data. Is the aim of the study is just to follow the Staine, a Single-Staged tranSmitterwith triangle-shaped signat is good enough for this purpose. The tength of the Signat of these transmitters and the pause in-between cannot be identi ed precisely - so there is no poSSibility to code more information than location. A two- Staged transmitter iS recommended for the collection os biotelemetrio data. Thistype of transmitterS has a So-called quadratio Signat, i. e. the tength of the signatand the pause cata be precisely identilied. Additional information can be gained by measuring these time intervat S. Depending on the physiological factors to be
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stud ted a transmitter with only two pause values so-called digital transmitter)can also be used . The di sadvantage of this type that it can only register two di ferent states se. g. ''Standing - layingV, 'motion - stili V, 'live deadV states). Iisu se on snakes due to their anatomy is quite limited. Only one study has mund this transmitter type useful to define the habitat selection of the North American hamnophis eleganS HUEY et al. l 989). When the animal was movin g, the signat impulse was doubled, so movemenis and resting could be identifled. Sensors called digital mortality sensors) detecting long lasting pause in motion can beused to observe the heginning and the end of hibernation FUISZ l 995). Mucii more widespread are the so-called analogue transmitters, which have continuoiasty changing signat parameters according to the factor they measure. Body temperature, hean rhythm, etc. of the snakes can eastly be recorded in this
The sire of the trianSmitter and of the sna e - Most of the investigators recommend a transmitter that cloes not infer the normal mobility of the snake. Alimit value os abolit 4 5T of the hody mass is generalty gi ven REINERT l 992 SECOR l 994. WEATHERHEAD 9 ANDER A l 984), hut in the case of smallerspecies tength and width of the transmitter can also be important. For a s mali flender snake the transmitter silould he accordingly stender WEATHER HEAD &ANDER A l 984). Our experiences also fhow that even is the transmitter is tessthan dia of the hody mass. having a large diameter object under the skin cancause intolerable inconvenience to the snnke. It is suggested to apply as smali transmitters as possibie. Table t shows this relation in the past 25 years. Although a decrease in the relative transmitter si Zecould have been expected, this is not the case undoubted ly due to unauoidable
The t eman of the transmitter and the tength of the Stu Period - Because of the high price of the transmitters. the troubles caused by the implantation, and the life cycle of the snakes, every scientist would like to use the equi pment theypurchase aS long as pOSSible. Unfortunately the smaller the transmitter includin ghatteries), the shorter is iis lifespan. In the case of large snakes the si Ze of the transmitter is a less important factor. hut in s mali vipers it is difficult to find an appropriate transmitter which gives signat s salaly and long enough. The lilaspanos a transmitter the amount of energy it uses - depends primari ly on iis type whether single- or two-stage), the strength of the signat. and the pulse tength and pulse frequency. One-Stage transmitterS need tesSer power Supply l. 3-l. 5 V) and work for longer period, accordi Iagly. A two-stage transmitter needs morethan double amount of power 3-3. 6 V), hut iis lifespan is considerably shorter. The Stronger the signat we want, the bigger power is needed. In order to increasethe lilaspan of the halteries, a signat ling combination of shon impulse - long pause is favourabie. A more ad vanced method is a transmitter with a miniature
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Thermosensitive Telonics ΙI C.
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bullt- in magnetic switch, and in the last few years programmabie transmitters have also been introduced to the market SZEMETHY l 995). In lalter, the transmitting period of a transmitter cala be pre-set with a computer according to the active life periods of the animal i. e. it cara be switched on during the longerresting period hibernation, aesti Vation. etc.). For the time be in g, Unfortunately the precision of this type of transmitters is largely depending on the ambient temperature sabout 20R deviation frona the pre-set time schedule), whicli makes the accurate programming more difficuli, and ultimately the animal could be lost. The maximal lifes pan of the radio transmitters for smali reptiles loday are around 6 8 monilis son 25'C), and this is not enough to cover a whole year life cycle. Maybe with the programmabie transmitters this period can be extended. hut we
The lifespan of the temperature sensitive transmitters hight y depends on theambient temperature NAULLEAU l 989). In high ambient temperature these transmitters give impulses at a higher rate, requiring more pOwer, whicli decreasOStheir lilaspan. A transmitter that works for 6 monilis at lo 'C will shorten iis activi ty to 4 monilis at 20' C and to 3 monilis at 30'C. respective ly. We have experi- enced simi lar resulis in Our study the manufacturer gaVe J-8 monilis as an expected lis espan at 25'C whereas the transmitters stopped signat ling after about 5 montiis. The ora ly possibie explanation is that during the summer at a body temperature of 30 35'C the transmitters nee led much higher energy than expected
The triariSmiSSion range cinci the Sire of the Stud' areia - During a radio te temetric stud y our primary aim is to find the animal with certainty but this depends on fie id conditions and the bellavi our of the si akes as well. In a relative lystat fiet d. without major sit ad ing and disturbing objecis, a s mali transmitter canproduce a signat detectabie frona large distances. In a forest Or a rocky area, howe ver where the signat can he reflected or absorbed by the complex structure of the habitat; it is beller to u se a transmitter With relatively stronger Signat S. The performance of the transmitter can be improved with the appropriate tength of iis antenna, and the range of receiving the signat s can be en larged by
using a more sensitive receiver and antenna System. With in creased performance of the receiver the effective transmission distance can be extended. A transmitterwith a usual 0.β meter transmission distance can eventu ally be used in an area of
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THE RADIOTELEMETRY TECHNICAL BASES
The recei VerA receiver of the best choice makes the work easter. the time of the locali sation s horter, heiace the efficiency of the transmitters bigger. It should he smali. lightweight. compact. willis tandwater shock and rough en Viron mental conditions. Walkie-taikies used in early works en abled on lytracking of moving animais OSGOOD l9J0). More novel instruments have a gain controi to in- crease sensitivi ty, a noi se si iter to reduce interserence, fine tu ning, channet Selection, etc. In so mecaSes automatic Or programmabie data processing is also avat labie. Some receivers have prefixed frequency range in whicli they can track a transmitter, usu atly burned into the memory by the manufacturing company. Frequency range was usualty wide in the early receivers, mean ing theyli ad high noi se ratio. New equi pments. like the Teloni cs sAri Zona USA, type TR-4 for i5 i54MHZ) used by us have a selectabie radio band width of lo kHZ. but there are also receivers with l-2 kHλ selecti Vity. For biotelemetric purposes a receiver able to measure the tength of and pauses between signat s has to be purchased . A simple basic equi pinent can also be upgraded to this level by appropri-ate accessorie S. NAULI EAU l 989) for instance. used an A. V. M. LA l2 v. Custom RH 4 6 receiverwith automatic data recorder to monitor bocly temperature. It had a limited receiving range of about 30 in radius without adjusting the antenna). Severat similar data processors signat indicators, etc.)can be attached to the Teloni cs receivers as well. These assemblies are generalty leSS expenSi Ve and cara be gradu atly developed to more ad vanced Systems. When investigating home range , Orsimply Starting a new study, it is usualty enough to invest into a basic equi pinent, and then adoptand complete it to the special conditions of the gi ven species. In our Opinion complex recei Ving instruments are less exploi table for radiotelemetric research on snakes, hecause the specific conditions mine inevitable the individual modifications.
An appropriate antenna Should be selected according to the measuring methods. For trackingpurposes directional H-type and Y agi antennas are a good choice. In the case of species with relatively smali ho me ranges, there are solding Or assembling modeis, whicli need litile space to carry. Y agi antennas are efficient for bigger distances as well, depending on their si Ze and the number ofelements. For exact identification of the location of the animal f short-distance loop antennas dotheir job. They are absolutely necessary lf One is to follow the animars movement precisely. Wecould track a burrowing vi per under the ground by the Teloni cs RX loop antenna almost centi metre by centi metre. In biotele metrio studies Y agi and H-type antennas are also usemi is combined with direction
automatic data recorder attached to a Y agi antenna in the fiet d. The original range was 200 meters hut due to the shadowing effecis of sield objecta it decremed to 30 meters. stili enough sor their study. When the purpose is definitely to collect only physiological parameters, and direction identification is not necessary. the omni directionat whip antenna can detect a signat hom a greater area. Iis advantage in not disturbing the animais hom a close distance is obvious GENT & SPELLEN BERGl 993. MERTENS i 994. SZEMETHY l 995). In enclosures a combination of severat whip antennas cancover the whole area. depending on the performance of the transmitters. Data collection is, however, more efficient is the ground area is equipped with a loop antenna system MCGINNIS &
When using a receiving antenna, the fact should he taken into consideration that the transmitting antenna in the snake has a hori ZOntal position snakes move usualty along the soli surface)whereas the signat gi ven is potari sed verti catly SZEMETHY l 995). It is important to orientate the receiving antenna according to this and also to the shadowing or mirroring effect of the fiet d objecis. The wave tength of the signat scalculated sto in the transmitting frequency. see below) gives a liliat