Chapter 2 A Critical Review of the Effects of Marking on the Biology of Vertebrates Dennis L. Murray and Mark R. Fuller Vertebrates often are marked to facilitate identification of free-ranging indi- vidual animals or groups for studies of behavior, population biology, and phys- iology. Marked animals provided data for many of the topics discussed in this volume, including home range use, resource selection, social behavior, and population estimation. Markers can be classified into three general categories: mutilations, tags and bands, and radiotransmitters. The appropriate marking technique for a study depends on several considerations, including study ob- jectives, target species, marker cost, marker efficacy, and marker effects on the animals (Day et al. 1980; Nietfeld et al. 1994). Studies using marked animals are characterized by the assumption that marking does not affect animals or that negative effects are not important (Ricker 1956; Day et al. 1980; Nietfeld et al. 1994). The assumption of no significant marking effects is critical because it is the basis for generalizing data collected from marked individuals to unmarked animals and populations. However, the assumption has not been tested rigorously for most marker types or animal species, despite the often necessary use of seemingly invasive mark- ing techniques. The general paucity of marker evaluation studies apparently is related to the difficulties associated with conducting such tests in the field, as well as the belief that marker evaluation is tangential to most study objectives and therefore of minor importance to the researcher. In addition, studies that evaluate marker effects often suffer from small samples, thus leading to quali- tative conclusions or weak statistical inference (White and Garrott 1990). As a result, researchers tend to choose markers that intuitively seem least likely to induce abnormal behavior or survival, even though data supporting that asser- tion usually are weak or lacking. However, if the assumption of no marking 16 DENNIS L. MURRAY AND MARK R. FULLER effects is violated and the effect is not evaluated, then data collected from marked animals will be biased. It follows that if significant marker effects remain undetected or unaddressed, conservation and management actions based on those results might not be appropriate. In addition, recent guidelines established by institutional animal care and use committees require that mark- ing protocols minimize pain and stress to study animals (Friend et al. 1994). If researchers collectively ignore the development, evaluation, and application of animal markers acceptable to such committees, and fail to publish results of studies not finding significant effects, then some research might be needlessly jeopardized or precluded. The purpose of this chapter is to present examples of the effects markers can have on animals and to examine critically the treatment of potential mark- ing effects by ecologists. We use the word effect to mean unusual or abnormal behavior, an abnormal function, or abnormal reproduction or survival. We use significant to indicate statistical results and important to indicate an observed effect and implication for studies. We emphasize the shortcomings of various marking techniques to animal biology. Our discussion is restricted to effects of markers, and thus does not include a specific review of handling effects. Fur- thermore, we do not present results specific to causes of pain or stress because essentially no data exist from wildlife. First, we present the variety of marking techniques that are available for, and explore possible implications of markers on, various taxonomic groups. Next, we review recently published articles to examine how researchers consider potential marking effects. Finally, we discuss how potential marking effects can be minimized and evaluated in future stud- ies. Consistent with the theme of this volume, the approach we have taken is often critical of existing information and protocols. However, such an ap- proach is necessary if researchers are to improve the overall quality of data being generated from ecological studies (Peters 1991). ᭿ Review of the Literature Nietfeld et al. (1994) described available marking techniques (excluding mark- ing with radiotransmitters) and generally reviewed marking techniques for vertebrates (excluding fish). Samuel and Fuller (1994) provided similar infor- mation about radiotransmitters. Stonehouse (1978) edited a book about ani- mal marking, and other overviews dealing with selected vertebrate groups include Stasko and Pincock (1977), Wydowsky and Emery (1983), and Parker et al. (1990) for fish; Ferner (1979) for amphibians and reptiles; and Marion A Critical Review of the Effects of Marking 17 and Shamis (1977), Calvo and Furness (1992), and Bub and Oelke (1980) for birds. These sources will lead the reader to the literature dealing with many species, many marking methods, and various considerations associated with different techniques, different species, and study objectives. WHICH MARKERS TO USE? It is worthwhile to reiterate some important factors that Nietfeld et al. (1994) and others noted as important when deciding which markers to use for a study. Expense can be an important consideration because marking materials can range widely in cost (e.g., tags versus radiotelemetry via satellites). The proce- dures required to initially capture and mark animals and to obtain results from intensive field observations or recapture efforts also are important. Markers should be easily assembled and attached, recognized in the field, and durable enough to remain functional throughout the study. Additionally, all marking techniques should result in minimum pain or stress to the animal during application and use. Finally, markers should not cause abnormal behavior or affect survival. Clearly, it is difficult to address all these criteria satisfactorily before the initiation of a study, so some marking has undesirable effects on animals and research results. The adverse effects of marking often are species- specific and might occur only in conjunction with certain behavior (e.g., courtship) or environmental conditions (e.g., extreme temperature). Also, the magnitude and importance of such effects are highly variable among marker types. We present examples of marking techniques and their effects on verte- brate species. This material will help address questions about adverse effects that were raised by Young and Kochert (1987) and Nietfeld et al. (1994): Does the information obtained from the study justify marking of animals? Can the effects of marking be identified during data analysis? If marking effects are accounted for in the analysis, can the study objectives still be achieved? Such questions should be posed at the outset of any study involving the marking of animals. If one or more answers to these questions is negative or unknown, an alternative marker should be sought or the effects of the marker under consid- eration should be evaluated thoroughly. EFFECTS OF MARKERS AMONG TAXA We reviewed a sample of articles that had as a primary objective the evaluation of marker effects. The articles consisted of qualitative or quantitative assess- ments of the effect of specific marker types on study animals. We acknowledge 18 DENNIS L. MURRAY AND MARK R. FULLER that marker evaluation studies probably are biased toward those showing effects because results indicating no effects might be published less often. This implies that our sample of the literature overestimates the occurrence of marker effects in evaluation studies. However, the objective of our review is not to determine how often marker effects occur, but rather to provide exam- ples of the range and diversity of negative effects among marker types, species, and sex, and thus encourage biologists to consider seriously the effects of marking animals. Our review begins with these examples, presented by taxo- nomic group in the following sections and associated tables. Fish tagging Marking has been used widely in fish population estimation; accordingly, the earliest tests evaluating marker effects in vertebrates occurred in fish. Historically, most evaluations of marking effects were anecdotal (Mellas and Haynes 1985), but by the 1940s researchers were suspicious of the potential effects of markers and thus began evaluating their merit in the field. Early fish research often involved the use of commercially made plastic or metal tags, and fish tagging was considered an effective marking system because tags were inexpensive, easily applied and seen, and rarely lost by tagged fish. However, studies evaluating potential effects of tags often found that tags altered aspects of fish biology (table 2.1). For example, several field studies used mark–recapture techniques and concluded that tags reduced survival and growth of fish. In some situations (DeRoche 1963), negative effects persisted throughout the life of a fish, whereas in others (Carline and Brynildson 1972), the effects seemed to be short-lived. Tagged fish were found to experience reduced swimming ability because of increasing drag (Clancy 1963), but not all effects of tagging can be attributed directly to the tags themselves. For instance, choice of tag placement on the fish’s body can elicit marker effects (Bardach and LeCren 1948; Stroud 1953; Kelly and Barker 1963; Rawstron 1973; Rawstron and Pelzam 1978), and it is generally considered that tags placed in and around the mouth may interfere with feeding. It is notable that not all tag evaluation studies have shown negative effects of tagging (table 2.1), and with additional study some tags will be shown to be more appropriate than others. The recent development of passive integrated transponder (PIT) tags has allowed researchers to mark fish and other vertebrates with smaller tags than those used previously. PIT tags are electromagnetically charged microchips implanted either subcutaneously or intraabdominally, and are read remotely A Critical Review of the Effects of Marking 19 via a portable scanner (Nietfeld et al. 1994). Insertion of PIT tags usually is performed using a syringe, thus eliminating the need for extensive invasive surgery. So far, no negative effect of PIT tags has been found in fish (Prentice et al. 1990; Jenkins and Smith 1990), suggesting that this technique can become an important tool for marking fish and other vertebrates. However, one drawback of PIT tagging is that at present tags can be read only when near a scanner. mutilation Marking by mutilation, usually by fin removal or partial removal, is a permanent marking technique often used by fish researchers. However, fin removal often affects fish growth and survival (table 2.2). For example, evaluations using mark–recapture methods (Shetter 1951; Mears and Hatch 1976) show that fin removal causes lower probability of recapture and, by inference, lower survival. Excision of multiple fins generally appears to be more harmful than single-fin excision, and removal of the adipose fin usually is less harmful than removal of other fins (Nicola and Cordone 1973; Mears and Hatch 1976). Removal of dorsal or anal fins can be particularly damaging (Coble 1967), partly because under certain conditions such exci- sions may predispose some species to bacterial or fungal infections (Stott 1968) or predation (Coble 1971). However, as with tagging, not all studies evaluating fin removal have detected significant effects, suggesting that for certain species or age classes, or under specific conditions, this marking tech- nique could be acceptable. Clearly, evaluation of the effects of fin clipping on fish biology requires more attention, particularly under controlled laboratory conditions. radiotransmitters Radiotelemetry has become an important tech- nique in fishery research, allowing biologists to accurately monitor long-term movements and survival of many species that would otherwise be difficult to study. Transmitter sizes and types available for fish are variable, and they have been attached to animals either externally or internally (see review by Stasko and Pincock 1977). Laboratory studies have shown that externally mounted transmitters increase drag and reduce or prevent swimming, particularly in high-speed currents (Mellas and Haynes 1985). It has been suggested that fusiform, lotic fishes are more influenced by external mounts than non- fusiform, lentic, or pelagic species (McCleave and Stred 1975). Internal im- plantation can be achieved by force-feeding stomach transmitters, or by sur- gery to attach the transmitter either in the peritoneal cavity or intramuscularly. Implants are more commonly used than external transmitters and have the Table 2.1 Survey of Marker Evaluation Studies in Fish Marking Technique Species Parameters Tested Lab (L) or Field (F) Effect of mark Reference Tagging Alosa aestivalis Su, Be F n.s. Bulak 1983 Ameiurus nebulosus Gr, Su F n.s. Stroud 1953 Cynoscion nebulosus Ph L Ph Vogelbein and Overstreet 1987 Esox lucius Co F Gr Scheirer and Coble 1991 Esox niger Gr, Su F n.s. Stroud 1953 Gadus morhua Gr F n.s. Jensen 1967 Leiostomus xanthurus Ph L Ph Vogelbein and Overstreet 1987 Morone americana Gr, Su F n.s. Stroud 1953 Micropterus salmoides Gr, Su F n.s Stroud 1953 Su F Su Rawstron and Pelzam 1978 Gr, Ma, Su F n.s. Tranquilli and Childers 1982 Oncorhynchus gorbuscha Ph, Ma, Su L Ph, Ma, Su Saddler and Caldwell 1971 Oncorhynchus tshawytscha Gr, Su F n.s. Eames and Hino 1983 Perca flavescens Gr, Su F n.s. Stroud 1953 Ph F Ph Stobo 1972 Salmo gairdneri Gr, Su F Gr, Su Shetter 1967 Salmo salar Gr, Su, Ma F Gr, Su Saunders and Allen 1967 Ph L Ph Roberts et al. 1973 Salmo trutta Ma F Ma Schuck 1942 Gr, Su F n.s. Stroud 1953 Salvelinus fontinalis Gr, Su F n.s. Stroud 1953 Gr, Su F Gr Carline and Brynildson 1972 Salvelinus namaycush Gr F Gr DeRoche 1963 Tetracycline Onchorhynchus nerka Su F n.s. Weber and Wahle 1969 Fluorescent pigment Onchorhynchus spp. Su F n.s. Phinney et al. 1967 Salmo gairdneri Su F n.s. Phinney et al. 1967 PIT tagging Morone saxatilis Be, Ph, Gr, Su L n.s. Jenkins and Smith 1990 Onchorynchus spp. Gr, Su, Ph L n.s. Prentice et al. 1990 Salmo salar Gr, Su, Ph L n.s. Prentice et al. 1990 Sciaenops ocellatus Be, Ph, Gr, Su L n.s. Jenkins and Smith 1990 Fin removal Cristivomer namaycush Gr, Su F n.s. Armstrong 1949 Pr, Gr F n.s. Shetter 1952 Gr, Su F n.s. Shetter 1951 Esox masquinongy Gr, Su F n.s. Patrick and Haas 1971 Esox lucius Gr, Co F Gr Scheirer and Coble 1991 Huro salmoides Gr, Su F Gr, Su Ricker 1949 Lepomis macrochirus Gr, Su F n.s. Ricker 1949 Be, Gr, Su F Be Crawford 1958 Pr L Pr Coble 1972 Micropterus dolomieui Gr, Su F Su Coble 1971 Perca flavescens Gr, Su F n.s. Ricker 1949 Gr, Su F Su Coble 1967 Salmo gairdneri Mo L Mo Clancy 1963 Gr, Su F Su Shetter 1967 Mo L n.s. Horak 1969 Gr, Su F Gr, Su Nicola and Cordone 1973 Salmo salar Gr, Su, Ma F Gr, Su Saunders and Allen 1967 Salmo trutta Gr F n.s. Brynildson and Brynildson 1967 Salvelinus fontinalis Su F Su Mears and Hatch 1976 Sebastes marinus Gr F Gr Kelly and Barker 1963 Onchorhynchus nerka Su F Su Weber and Wahle 1969 (continued) Table 2.1 Continued Marking Technique Species Parameters Tested Lab (L) or Field (F) Effect of mark Reference Radiotelemetry Ictalurus punctatus Gr, Su L n.s. Summerfelt and Mosier 1984 Ph L Ph Marty and Summerfelt 1986 Morone americana Mo, Be, Pa L Pa Mellas and Haynes 1985 Pylodictis olivaris Gr, Su, Be F Be Hart and Summerfelt 1975 Roccus chrysops Su F S Henderson et al. 1966 Salmo gairdneri Mo L Mo Lewis and Muntz 1984 Mo, Be L Mo Mellas and Haynes 1985 Su, Gr F n.s. Lucas 1989 Salmo salar Mo L Mo McCleave and Stred 1975 Articles surveyed were published in the peer-reviewed literature and consist of qualitative or quantitative evaluations of marking effects. We report the effect of markers as being important/significant or not (n.s.), as interpreted by the authors in the article. Gr = growth, Su = survival, Be = behavior, Mo = movements, Ma = mass, Co = condition, Pa = parasitism/disease, Pr = predation, Ph = physiology. A Critical Review of the Effects of Marking 23 advantages of lying near a fish’s center of gravity, not being lost or entangled in the environment, and not creating drag forces. However, these advantages can be offset by reduction in swimming performance, increased handling time, and stress associated with surgery, as well as the higher chance of infection fol- lowing release. Also, implanted transmitters occasionally can be passively expelled from the body, although sometimes without causing mortality or morbidity (Lucas 1989). Some species appear more predisposed than others to postoperative complications and transmitter expulsion (Mellas and Haynes 1985; Marty and Summerfelt 1986), meaning that it may be necessary to tai- lor surgical technique and specific implantation site to the target species. How- ever, in some species, stomach implants seem to have fewer effects than either external mounts or surgically implanted transmitters (Henderson et al. 1966). In all telemetry studies, transmitter size is an important consideration, and smaller transmitters are always more desirable than larger ones from the stand- point of effects on the animal (Stasko and Pincock 1977; Marty and Summer- felt 1986). However, the general question regarding the effects of transmitter mass on fish still must be addressed in controlled studies (Stasko and Pincock 1977). Reptiles and amphibians tagging The use of marking in reptile and amphibian research is fairly new, so fewer studies have evaluated marker effects in these taxonomic groups. Many species of reptiles and amphibians have proven difficult to mark because of their epidermal sensitivity, small size, and potential for tissue regeneration. Tagging of reptiles and amphibians has included various types of branding and the use of polymers, pigments, dyes, and radioactive substances (Ferner 1979; Ashton 1994; Donnelly et al. 1994; table 2.2). Many of these markers are of limited utility because they were not tested adequately for marking effects (Donnelly et al. 1994); such limitations are particularly important for am- phibians, given the sensitivity of their skin. A field test of marking by dye injection did not find any effects on larval amphibians (Seale and Boraas 1974), but a controlled laboratory study did identify stunting in dyed tadpoles (Travis 1981). Although these studies used different dyes, the results call into question previous suggestions that some dyes are largely benign (Guttman and Creasey 1973) and suggest that laboratory studies might be more sensitive to detection of marking effects. Other color markers, such as fluorescent paint, often are used to monitor amphibians in the field (Taylor and Deegan 1982; Nishikawa and Service 1988; Ireland 1991), despite the fact that such paint Table 2.2 Survey of Marker Evaluation Studies in Reptiles and Amphibians Marking Technique Species Parameters Tested Lab (L) or Field (F) Effect of Mark Reference Paint marking Sceloporus jarrovi Su F n.s. Simon and Bissinger 1983 Sceloporus undulatus Su F n.s. Jones and Ferguson 1980 Staining Ambystoma tigrinum Gr, Pa, Mo F n.s. Seale and Boraas 1974 Hyla gratiosa Gr L Gr Travis 1981 Rana catesbiana Gr, Pa, Mo F n.s. Seale and Boraas 1974 Rana clamitans Su, Mo L Su, Mo Guttman and Creasey 1973 Rana pipiens Gr, Pa, Mo F n.s. Seale and Boraas 1974 Tagging Rana catesbiana Be, Mo, Ma F n.s. Emlen 1968 Thamnophis siritalis Ph F n.s. Pough 1970 PIT tagging Sistrurus miliarius Gr, Mo, Su F n.s. Jemison et al. 1995 Thamnophis proximus Ma L n.s. Keck 1994 Clipping Alligator mississippiensis Gr, Su L n.s. Jennings et al. 1991 Coluber constrictor Be F n.s Brown 1976 Toe clipping Bufo woodhousei Su F Su Clarke 1972 Cnemidophorus sexlineatus Mo L n.s. Dodd 1993 Scleoporus merriami Mo L n.s. Huey et al. 1990 Branding Alligator mississippiensis Gr, Su L n.s. Jennings et al. 1991 Ascaphus truei Ph, Ca F n.s. Daugherty 1976 Radiotransmitter Nerodia sipedon Be L Be Lutterschmidt and Reinert 1990 Thamnophis elegans Ph L n.s. Charland 1991 Thamnophis marcianus Mo L n.s. Lutterschmidt 1994 Thamnophis siritalis Ph L n.s. Charland 1991 Articles surveyed were published in the peer-reviewed literature and consist of qualitative or quantitative evaluations of marking effects. We report the effect of markers as being important/significant or not (n.s.), as interpreted by the authors in the article. Gr = growth, Su = survival, Be = behavior, Mo = movements, Ma = mass, Ca = capture probability, Pa = parasitism/disease, Ph = physiology. [...]... under the skin, in the body, by banding, collaring, wing tagging, harnessing, gluing, tying, suturing, clamping, and implanting (Kenward 1987; Samuel and Fuller 1994) Since the earliest uses of radiomarking in birds, it has been recognized that the transmitter attachment method can affect a variety of aspects of behavior and survival For instance, neck collars were shown to be effective in some cases... No Marking Marking Effects Tests or (explicit) Modifications 4 62 4 59 0 2 0 1 50 10 31 46 8 28 0 0 2 4 2 1 15 15 0 0 37 12 17 23 8 30 10 15 21 5 90 3 0 0 7 3 4 2 2 16 7 Journals, numbers of papers surveyed in which free-ranging vertebrates were marked, and percentage of papers that assumed (explicitly or implicitly) that marking had no effect on measurements All papers reviewed were published in 1995... Ornithology 51: 21 3 21 9 Andreone, F 1986 Considerations on marking methods in newts, with particular reference to a variation of the “belly pattern” marking technique Bulletin of the British Herpetological Society 16: 36–37 Animal Behavior Society /Animal Society for Animal Behavior 1986 ABS/ASAB guidelines for the use of animals in research Animal Behavior Society Newsletter 31: 7–8 Animal Care and... Copeia 1948: 22 2 22 4 Bartelt, G A and D H Rusch 1980 Comparison of neck bands and patagial tags for marking American coots Journal of Wildlife Management 44: 23 6 24 1 Barton, N W H and D C Houston 1991 The use of titanium dioxide as an inert marker for digestion studies in raptors Comparative Biochemistry and Physiology 100A: 1 025 –1 029 Baumgartner, L L 1940 Trapping, handling, and marking fox squirrels... “control” animals could result in an underestimation of effects of the targeted marker In some studies, control animals are not subjected to the same handling procedure as marked animals, thereby making marking effects indistinguishable from those of handling (Mears and Hatch 1976; Scheirer and Coble 1991) This can be particularly problematic in situations where handling causes significant stress or long-term... of the articles surveyed included information directly pertaining to potential marking effects Some authors attempted to minimize marker effects by allowing postmarking recovery to take place in captivity (Baupre 1995; Forrester 1995; Nelson 1995; Shine and Fitzgerald 1995) Although this approach might be effective when handling and marking are stressful or invasive (i.e., internally mounted radiotransmitters),... bobwhite in Missouri Journal of Wildlife Management 59: 401–410 Burley, N 1985 Leg-band color and mortality patterns in captive breeding populations of zebra finches Auk 1 02: 647–651 Burley, N T 1988 Wild zebra finches have band-colour preferences Animal Behaviour 36: 123 5– 123 7 Burley, N., G Krantzberg, and P Radman 19 82 In uence of colour-banding on the conspecific preferences of zebra finches Animal Behaviour... markings in free-ranging animals; where the use of this technique meets study objectives, it is more desirable than artificial marking It is essential that field personnel be adequately trained in the proper handling and marking of animals (Ad Hoc Committee on the Use of Wild Birds in Research 1988; Livezey 1990; Friend et al 1994; Samuel and Fuller 1994) This may involve practice with captive individuals... potential marking effects is a good first step, but whenever possible quantitative measurements of the biology of marked versus unmarked animals (Vekasy et al 1996) or comparisons of preand postmarking behavior of individuals should be included When markers were suspected of exerting short-term effects on animals, researchers excluded data obtained during an arbitrary period (2 14 days after marking; Baupre... lizard, Chlamydosaurus kingii, in tropical Australia Ecology 76: 124 –1 32 Clancy, D W 1963 The effect of tagging with Petersen disc tags on the swimming ability 49 50 D E N N I S L M U R R AY A N D M A R K R F U L L E R of fingerling steelhead trout (Salmo gairdneri) Journal of the Fisheries Research Board of Canada 20 : 969–981 Clarke, R D 19 72 The effect of toe clipping on survival in Fowler’s toad (Bufo . banding, col- laring, wing tagging, harnessing, gluing, tying, suturing, clamping, and implanting (Kenward 1987; Samuel and Fuller 1994). Since the earliest uses of radiomarking in birds, it. marking techniques (excluding mark- ing with radiotransmitters) and generally reviewed marking techniques for vertebrates (excluding fish). Samuel and Fuller (1994) provided similar infor- mation. recognized in the field, and durable enough to remain functional throughout the study. Additionally, all marking techniques should result in minimum pain or stress to the animal during application