Copyright © 1998 Province of British Columbia
Published by the Resources Inventory Committee
[Back to TOC] [Previous] [Next]
This section contains a literature review of different transmitter techniques and their relative success when used on different groups of species. It is intended to provide as much information as possible about what has worked in the past and what has not for different species. It is impractical to standardize transmitter attachment for all of British Columbia's species. In light of this, all telemetry projects should operate within the general protocols outlined in the previous chapters; however, specific details of transmitter attachment will vary from project to project. Inclusion of a method in this review should not be equated with a recommendation.
[Back to TOC] [Previous] [Next]
Amphibians pose a number of interesting challenges when it comes to telemetry because:
Because of these difficulties, telemetry has had limited use in this group in the past. However, new techniques and technology are resulting in an increase in the popularity of amphibians in telemetry studies. Much work is still experimental and very few techniques have been adopted by the majority of amphibian researchers.
Ingested tags are either force fed or hidden within food items. Behavioural change has been exhibited in individuals that have been equipped with too large a transmitter (Kenward 1987). However, several studies have used ingested tags quite successfully with both frogs and toads (Kenward 1987). Oldham and Swan (1991) force fed 2.5 g transmitters to fourteen adult Common Frogs (Rana temporaria) and Common Toads (Bufo bufo). The transmitters were regurgitated in 2 to 13 days in the frogs, and 2 to 38 days in the toads. The authors felt they were able to get useful short term data using this technique although it is unclear whether the transmitters influenced the animals' behaviour.
Surgical implants can be used in longer term studies provided the animal is large enough to accommodate the tag. For example, Red-legged frogs (Rana aurora) have not been implanted due to size constraints (N.J. Scott, National Biological Service, San Simeon CA, pers. comm.). Implantation is typically characterized by a lateral incision directly into the coelomic cavity (Sinsch 1988; Seitz et al. 1992). A common anaesthetic used for surgical procedures in amphibians is MS-222© (Sandoz; Ethyl-m-amnobenzoate-methane-sulphonate) used at a concentration of 200 to 300 mg/l (Bonath 1977). Recovery periods vary between studies, but Seitz et al. (1992) were able to release animals back to their place of capture after only a few hours. This procedure requires training prior to its use in the field.
Rathbun and Murphey (submitted) have developed a waist-belt made of ball or beaded chain which has been used on California Red-legged Frogs (Rana aurora draytonii). Preliminary studies suggest that aluminum is the best material since it does not corrode or weigh as much as brass (Rathbun and Murphey 1993). The transmitter normally sits dorsally, but is unaffected if it rotates to the ventral position. This procedure takes approximately five minutes. There is a small danger of the chain becoming snagged on vegetation and it may cause irritation of the skin if the chain is too tight. Some frogs have slipped out of their belts following weight loss occurring towards the end of the dry season (Scott, pers. comm.).
Bartelt (1994) has developed a single harness belt for use with more terrestrial frogs and toads. This harness consists of soft, surgical grade polyethylene tubing that fits around the waist of the animal. This particular belt caused severe skin abrasions in Oregon Spotted Frog (Rana pretiosa) after one month, so it is not recommended for highly aquatic anurans in studies which will exceed one month. Western Toads (Bufo boreas) however, have slightly thicker skin and did not exhibit abrasions like R. pretiosa. The condition of telemetered individuals should be checked every two weeks. This technique is inexpensive, like that of Rathbun, but it probably advantageous in that the harness can be sized precisely in the field, it is very lightweight (0.01 g), and has been known to break off the animal after three to four months in water (or when the animal outgrew it).
Bartelt (pers. comm.) has also tried other techniques which involved using elastic straps. He found that these other methods affected behaviour or caused localized edema and are not recommended.
Transmitters may also be housed in a small pocket on the back of the vest with the antenna trailing behind. Any loose-weave elastic fabric (e.g., spandex) that allows air transfer is a suitable material (Anderka and Angehrn 1992). Others have used plastic (silicon) tubing (Loman, pers. comm. in Rathbun and Murphey) and latex rubber straps and bands (Van Nuland and Claus 1981; Fukuyama et al. 1988; Richards et al. 1994). The system develop by Van Nuland and Claus (1981) for the Common Toad (Bufo bufo) involved passing each of the animal's legs through different perforations in a piece of latex, creating a harness to hold the transmitter on the toad's back. No discernible effects on the toad or any noticeable changes in behaviour were observed but the harness occasionally caused a skin irritation and could be displaced in dense vegetation. Girdle material has also been successful as a harness with toads (Kingsmill 1991).
Surgically implanted transmitters have been successfully used on Pacific Giant Salamanders (Dicamptodon tenebrosus) greater than 10 cm (snout to tail), and Northwestern Salamanders (Ambystoma gracile). Transmitters (1.85 g) have been surgically implanted in Ambystoma (anaesthetized with MS-222©) by making as small an incision as possible in the peritoneal cavity. Individuals of 25 to 30 g were preferred for implantation although animals as small as 20g were also used. Wounds are reported to heal in about 8 to 10 days following surgery (A. Stringer, Univ. of Washington, Seattle WA, pers. comm.). Suture material should be of a non-absorbable type in order to avoid improper healing; however, it is important to note that there are many different types of non-absorbable suture, only some of which are suitable for amphibians. Researchers will often keep study animals in the lab until recovery is complete (Mallory, pers. comm.).
[Back to TOC] [Previous] [Next]
By far, the majority of snake telemetric studies use implant methods. Obviously, body shape plays an important role in this and also the manner in which snakes digest food (i.e. large bolus moves down the body after ingestion and makes it difficult for external attachment devices to remain secure, given the stretching of the skin). Implants also usually afford the researcher the ability to measure body temperature. This method is limited, however, to larger snakes because of restrictions in size availability of implantable tags (L. Norman, Univ. of Victoria, Victoria, BC, pers. comm.). Generally, transmitters in snakes are kept at 5% of body mass, but some suggest that perhaps 3% would be a better figure to limit impact on snake behaviour (D. Parizek, SW Rodents, Vail, AZ, pers. comm.). Norman (pers. comm.) found that she could not implant any snakes under 60 g, which biased her study to the largest snakes in the population she was working with (i.e., adults, females, and larger species). Some researchers have experienced problems with stiff subcutaneous antennas in the past (N.J. Scott, National Biological Service, San Simeon, CA, pers. comm.), but antennas are now more flexible. Most implantable tags come equipped with whip antennas so that an adequate signal range can be achieved. Secor (1994) reports ranges of 250 to 600 m in his studies.
At least three types of anaesthetic have been used in British Columbia studies: isofluorane, halothane and methoxyfluorane. Use of inhalant anaesthesias should be preceeded by consultation with a veterinarian familiar with the species in question. It is important to understand that the immune system and surgical healing in poikilotherms is affected by their ambient temperature, and thus recovery from implantation will take longer than in birds or mammals. Because of this, the seasonal timing of surgical implants is also an important consideration.
Many species of snakes within British Columbia have been outfitted with implants including the Common Garter Snake (Thamnophis sirtalis), Western Terrestrial Garter Snake (T. elegans), Western Rattlesnake (Crotalus viridis), and Gopher Snake (Pituophis catenifer) (C. Shewchuk, Univ of Victoria, Victoria, BC, pers. comm). These are based mainly on size of species and abundance. For example, the Northwestern Garter Snake (T. ordinoides) has not been implanted because of its small size (Norman, pers. comm.).
Most researchers use either intra- or extraperitoneal implantation by making a small incision on the mid-lateral area of the snake with the whip antenna running up the longitudinal axis (direction varies between researchers).
Some researchers have experienced problems with infections developing at the implant site (up to 75% , W. Card, Dallas Zoo, Dallas, TX, pers. comm.; Norman, pers. comm.). Chances of infection can be markedly decreased with proper surgical technique (e.g., using sterile instruments, suturing incision properly, making sure transmitter parts are biologically inert, not implanting a snake that is close to shedding its skin). K. Larsen (Alberta-Pacific Forest Industries, Inc., Boyle AB, pers. comm) noticed high degrees of scar tissue around implanted transmitters, and suspected that a transmitter may deterred female reproduction in his study. Norman (pers. comm.) used extraperitoneal implantation and reported that occasionally transmitters slip up the side of the animal and may even push out through the initial incision site or break through the skin.
Forcibly inserting transmitters so that they are ingested, has also been tried with snakes (Fitch and Shirer 1971; Fitch 1987; Lutterschmidt and Reinert 1990). Plummer and Congdon (1994) tested the possibility that intragastric placement may be a satiation stimuli, but found this not to be so in the Racer (Coluber constrictor) populations they tested.
A limited number of studies have used external attachment sites (Ciofi and Chelazzi 1991; Rathbun et al. 1993). Transmitters were taped to the tail skin of snakes with poor success.
Telemetry is difficult with lizards and skinks because few attachment sites are available. Most work has been done on slow moving "sit-and-wait" lizards and very little has been done on active species (T. Doan, Univ. of S. Florida, Tampa, FL, pers. comm.). In British Columbia, we have one very rare, slow moving species, the Pigmy Short-horned Lizard (Phrynosoma douglassi) and three quick ones: the Western Skink (Eumeces skiltonianus), Northern Alligator Lizard (Elgaria coerulea) and the introduced European Wall Lizard (Podarcis muralis). To our knowledge, none of these species have been tagged in British Columbia. It is unlikely that anyone would ever embark on a study of Phrynosoma within B.C., since only two specimens have ever been recorded within the province (Gregory and Campbell 1987).
Implants have the advantage of being concealed and remove any likelihood of an animal getting caught on vegetation. However, the major limitation associated with lizard implants is that body size dictates which species can be implanted. Although in past smaller implants have been associated with a decrease in the duration of battery power, new technology has allowed for the development of increasingly efficient and smaller power sources. Perhaps in a few years, technology will be at a stage where transmitters are small enough to make most, if not all, lizard species implantable.
Fast moving species can be more challenging to track than slower ones, and implants may create further difficulties. Range is reduced with the helical antenna and this can be further compounded by dense vegetation (Doan, pers. comm.). Many implant studies are concerned with internal body temperature as well. This method is well suited to this goal but more recently Bouskila (Ben-Gurion Univ. of Negev, Beer-Sheva, Israel, pers. comm.) developed an external package which can be used to measure body temperature (see below).
External transmitters can be very practical when long term continuous monitoring is not needed. They offer a great advantage in that transmitters can be reused on several individuals with relative ease and can be removed and deactivated to save batteries. External attachment also minimizes chances of infection due to experimental manipulation.
External transmitter may be mounted with backpacks or adhesive mounts, in those situations where implantation is not possible or desired. Several designs have been used to attach transmitters to lizards. One of the newest methods for backpack attachment in lizards has been developed by Fisher and Muth (1995) with the Flat-tailed Horned Lizard (Phrynosoma mcalli), a congener of P. douglassi. The method involves attaching the transmitter to polypropylene pleating tape, and using polyurethane elastic to form harnesses for attachment dorsally behind the neck. Packages that approach 25% body weight have been used in P. mcalli, and this appears to be approximately equal to the mass of an egg clutch in this species (Pianka and Parker 1975; Fisher and Muth 1995). Captive lizards resumed feeding immediately after transmitter attachment, and released lizards also resumed "normal" activities.
Munger (1984) used a similar system to Fisher and Muth except that he used a loop antenna to secure the transmitter to the body. This is similar to the method employed by Muth et al. (1978) with desert iguanas (Dipsosaurus dorsalis). Individuals were outfitted with a rectangular package that was mounted slightly anterior to or between the forelegs with the antenna passing anteriorly and over the base of the neck. A yoke closely followed the body contour and fit snugly around the neck to prevent snagging. This method was designed specifically to alleviate abdominal constriction during egg development; however, the authors note that a simple "waist collar" would be suitable for non-gravid individuals, with the transmitter attached to a belt and mounted against the lizard's lower back (Muth et al. 1978).
Some researchers have had success using tape to secure transmitters to the tail (Houston et al. 1995). There is, however, the possibility that this makes the animal more obvious to predators (S. Burgin, Univ. of W. Sydney, Hawkesbury, Richmond, Australia, pers. comm.). Bouskila (pers. comm.) used externally attached transmitters (above the base of the tail) with cloacal probes to measure body temperature, a measure which previous to this relied upon implants. These were attached temporarily by gluing a Velcro patch at the dorsal base of the tail and then doing the same with the transmitter, for ease of removal. Researchers interested in this technique should be aware that some lizard species are capable of shedding their tails and this presents certain problems during handling and attaching these units, as well as for maintaining them.
Most turtle researchers employ carapace mounts with few exceptions (Galbraith et al. 1987; Kaufmann 1995). We have included references for several non-native species of turtles and tortoises because the techniques are applicable to turtles found within B.C. Freshwater turtle species in the province are essentially limited to the Painted Turtle (Chrysemys picta), a blue-listed species found in portions of southern B.C. Although there have been sightings of other freshwater species (e.g., Snapping Turtle) in the province, these are not known to occur in established populations. Recently however, several populations of the introduced Red-eared Slider (Chrysemys scripta) have established themselves (C. Shewchuk, Univ. of Victoria, Victoria, B.C., pers. comm.).
The predominate way to attach a transmitter to a turtle is by mounting the tag on to its carapace. Different techniques of accomplishing this have met with varying levels of success depending upon life-history traits, age, and size of study animals. Mounting a transmitter on top of a turtle provides an obvious possibility for utilizing solar power; however, Scott (National Biological Service, San Simeon, CA, pers. comm.) reports difficulties with this approach as each time a turtle dives, the signal is switched off, making it difficult to locate individuals. Care must always be taken when fastening objects to the carapace to minimize any interference effects on mating (Holland, pers. comm). As well, antennas should be kept as short as feasible to minimize snagging on vegetation (de Solla, Holland, pers. comm.).
In terms of attachment, one method has been to use drilled holes and wire to attach transmitters (S. de Solla, Univ. of Guelph, Guelph, ON, pers. comm). Other researchers have used "five-minute" epoxies to secure the transmitter to the carapace; however, both submersion and ultraviolet light are suspected to cause degradation and detachment of the unit within 2 to 12 weeks (Rathbun et al. 1992; D.C. Holland, Fallbrook, CA, pers. comm; R.A. Saumure, McGill University, Montreal, PQ, pers. comm). Carter (Virginial Poly. and State Univ., Blacksburg, VA, pers. comm.) uses a liquid vinyl coating (e.g., Pastidip©) over epoxy to ensure waterproofing of the attachment site, whereas other researcher choose alternatives such as PC-7 (a water-resistant epoxy paste available in most hardware stores) or dental acrylic. Wilson (Univ of S Florida, Tampa, FL, pers. comm.) found that when transmitters were glued to the carapace in juvenile tortoises that the shell deformed somewhat near the transmitter site. Saumure (pers. comm.) attempts to avoid interfering with shell development by first making a well out of silicon before applying PC-7 adhesive so that when the transmitter is pressed into place, the resin will not cross over a scute line and impede growth. In addition, when it is time to remove the transmitter, it can be gently pried loose in one piece with no residue.
Brown (1990) has used thermistor (a resistor which is sensitive to changes in heat) implantation in order to gather data on internal temperature. Studies with larger oceanic turtles (e.g., Green) have used subcutaneous implants (inguinal region) in the past, but this method has largely fallen out of use with recent advancements in adhesive technologies. A few researchers have used esophageal ingestion as a means of measuring internal body temperatures (S. Eckert, San Diego State Univ., San Diego, CA, pers. comm).
[Back to TOC] [Previous] [Next]
Collars have been used on a variety of species. In some cases, they provide surprisingly strong signals; Douglass (1989) reported a signal range up to 160 m with collar transmitters fitted on deer mice. Typically, collars for rodents have consisted of a radio package encased in some sort of plastic tubing with the antenna circling the neck. However, in some instances an encasing material was not used in the collar design. The design of rodent collars should strive to minimize any potential for snagging. For example, Mahon (Simon Fraser Univ., Burnaby, B.C., pers. comm.) reports that 25% of voles and mice in his study died as a consequence of getting caught up in vegetation. Other reported problems associated with rodent collars include: transmitter loss, neck irritation and/or hair loss, restricted movement through burrows and/or dense vegetation, increased ectoparasite load beneath the collar and changes in behaviour (Hamley and Falls 1975; Madison 1977; Smith and Whitney 1977; Filipovich 1983; Eagle et al. 1984). Because radios are external, they can also be damaged by extreme weather conditions, mechanical wear (Eagle et al. 1984), and / or mutual grooming episodes (Madison 1977). Todd (Univ. of Herfordshire, Hatfield, UK, pers. comm) reports habituation to collars within one day in wood mice.
Jumping mice have been radio tagged using glue-on methods ("superglue") to the back (Wunder, Colorado State Univ., Fort Collins, CO, pers. comm). The package was frequently dislodged at 3 to 4 days. Range was reported as approximately 80 m even when the animal was 0.6 m underground.
Subcutaneous implants have been used in small mammals since 1964 (Rawson and Hartline 1964). However, intraperitoneal implants were found to be superior and used successfully with a variety of species (Neely and Campbell 1973; Smith and Whitney 1977; Smith 1980a,b; Koehler et al. 1987). Eventual adhesion of implanted capsules transmitters to peritoneal structures was noted following abdominal implantation in beavers in one study (Guynn et al. 1987).
Fenton et al. (1985, 1993) tagged bats using 0.9 g transmitters attached to the lower mid back with "skin bond" cement. These transmitters had a range of 2.5 to 4.0 km, but other studies using the same techniques, only reported a 1 km range (Brigham and Fenton 1986). The same method was used by Brigham (1991) with Big Brown Bats (Eptesicus fuscus) in B.C. The package used in his study was 6% body weight and the study animals showed no adverse effects. Most bats lose their transmitter 1 to 20+ days after attachment (R. Barclay, Univ. of Calgary, Calgary, AB, pers. comm.).
Lancaster et al. (1992) glued transmitters to the heads of bats using eyelash adhesive. The head fur was first removed using a hair removal lotion ("Neet"). This study was done under controlled conditions (i.e., captivity) and signal range was only 3 m. Grindal (pers. comm., Axys Environmental Consulting Ltd., Calgary, AB) notes that exposing the skin beneath a bat's fur is generally unnecessary for transmitter attachment and potentially detrimental to a wild bat. Hair removal lotion should not be used. Caution should also be exercised when using eyelash adhesive as Fry (Minneapolis, MN, pers. comm.) reported "considerable damage to the skin" under the transmitter.
Fenton et al. (1985) radio tagged bats using 4.5 g transmitters attached by collars. These transmitters had a range of 10 km.
Little telemetry work has been done on this group, probably because of their fossorial nature and small size. Most studies use radioactive substances to track as opposed to telemetry (Meese and Cheeseman 1969). Gorman and Racey (1992) glued transmitters to the dorsal surface of the tail. Radio signals were readily detectable through the soil and an accuracy of +/- 0.25 m was reported.
Collars have been used by Rado and Terkel (1989) on mole rats (a subterranean rodent) with some success. One type of collar failed because the transmitter protruded too far from the collar, and interfered with movement in the tunnel. Their second, more streamlined type was more successful, and had a range of 30 to 100 m from within the mole tunnel. Merritt (Carnegie Museum, Pittsburgh, PA, pers. comm.) reports that many animals cannot forage properly with collars on.
Implants have been used by Gorman and Racey (1992). The transmitters were placed intraperitonealy, by a mid-ventral incision, in moles anaesthetized with halothane.
More recently, McShea (Smithsonian Institute, Front Royal, VA, pers. comm) has implanted Star-nosed Moles (Condylura cristata) and Merritt (pers. comm.) has implanted shrews. Merritt reports close to 100% survivorship following surgery using inhalant anaesthesia.
[Back to TOC] [Previous] [Next]
Radio collars are the most popular method for attaching transmitters to most furbearers and large carnivores (Anderka 1987). Collars have been used successfully on coyote (Babb and Kennedy 1987), fisher (Arthur 1988), marten (Hodgman et al. 1994), wolverine (Whitman et al. 1986), lynx (Schwartz and Becker 1988), bobcat (Knick 1990), snowshoe hare (Keith et al. 1984; Boutin and Krebs 1986), raccoon (Jordan et al. 1986; F. Lebebvre, Univ. de Sherbrooke, Sherbrooke, PQ, pers. comm), black bear (Schwartz and Franzmann 1991), grizzly bear (Hamilton and Archibald 1985), wolves (Peterson et al. 1984; Fuller and Snow 1988), and cougar (Beier 1995). Design of transmitter attachments for large carnivores should be extremely sturdy and long-wearing, as these animals are very powerful.
Although they have been successful in many past studies, collars may not be the best choice for every situation. Rigid collars of metal wire are not recommended for mammals which live in burrows or crevices, as the collars may become lodged and result in the animal's death (Skirnisson and Feddersen 1985). G. Mowat (Nelson, BC, pers. comm.) notes that collar fitting is critical for mustelids, as the difference between head and neck circumference is very small. Melquist and Hornocker (1979) attempted to use collars on river otter, but reported problems with collar loss, poor reliability and neck irritation. They recommended the use of implants in this species, an approach used in later studies (Melquist and Hornocker 1979, Reid et al. 1986). Implanted transmitters have also be used for beaver (Gyunn et al. 1987), striped skunks (Rosatte and Kelly-Ward 1988), mink (Eagle et al. 1984), muskrats (Lacki et al. 1989), marmots (A. Bryant, Nanaimo, B.C., pers. comm.; van Vuren 1989), wolverines and kits (J. Krebs, Nelson, BC), and a number of canids (Green et al. 1985). However, some negative effects of implants have been reported (Woolf et al. 1984). Implanted transmitters have been used on grizzly bears (Philo et al. 1971) and black bears (Jessup and Koch 1984), as have ear-mounted transmitters (Serveen et al. 1981).
Expanding breakaway collars have been used on young black bears (Strathearn et al. 1984) and coyote pups less than six weeks old (Andelt 1985). In the latter case, the pups lost their collars very quickly so implants were used instead. The implants had poor range, so when the pups reached three months old, they were fitted with standard radio collars.
Harnesses are generally not practical for use on most medium-sized mammals due to the danger of entanglement. However, expandable harnesses have been used on bobcat kittens (Jackson 1985; Blackwell et al. 1991). Backpack-mounted satellite transmitters are available for use on wolverine and foxes (Burger and Carroll 1994).
[Back to TOC] [Previous] [Next]
Collars are the preferred method of attaching transmitters to ungulates in most situations. Collars have been used on caribou, mule, white-tail and black-tail deer (Gillingham and Bunnell 1985; Harestad 1985), moose (Simpson et al. 1995), elk (Edge and Marcum 1989), mountain goats and mountain sheep (Krausman et al. 1989). Expandable collars have been used on deer fawns (Keister et al. 1988) and moose calves (Boertje et al. 1987), but may be lost prematurely due to grooming activities (Schulz and Ludwig 1985). Bighorn sheep rams may damage transmitter crystals during head-butting contests during the rut, so Krausman et al.(1989) placed two transmitters on each collar that was fitted on a mature ram.
As some ungulate species are wide-ranging, satellite collars are a practical means of tracking individuals over long distances (Craighead and Craighead 1987; Fancy et al. 1989; Keating and Key , n.d.). However, current sattelite collar designs are heavy, and anecdotal information suggests that animals may become very disturbed by the weight of the collar continually hitting their chins each time the put their heads down to graze.
Levine (Merlin Systems Inc., Meridian, ID, pers. comm.) reports that testing of a subcutaneous implant for elk is underway. The implant is designed to be inserted under the skin between the shoulder blades, and is being tested as an alternative to visible transmitter attachments such as collars.
Ear-tag transmitters (Bartmann et al. 1992) have also been used on deer. Implanted biotelemetry transmitters have been used in mule deer and mountain sheep (Stemp 1982; Garrott and Bartmann 1984). Vaginal implants have recently been used in plains bison in Yellowstone National Park to determine time of partuition or abortion.
[Back to TOC] [Previous] [Next]
A variety of transmitter mounting methods has been tried on these species. Collars have been used on Redheads and Marbled Murrelets (Sorenson 1989; A. Derocher, Ministry of Forests, Vancouver Forest Region, pers. comm.). Transmitters have been sutured to the backs of Mallard ducklings (Mauser and Jarvis 1991), adult ducks (P. Pietz, National Biological Service, Jamestown, ND, pers. comm.; Wheeler 1991), Rhinoceros Auklets and Marbled Murrelets (G. Davoren, Univ. of Victoria, Victoria, B.C., pers. comm.). Giroux et al. (1990) used tail-mounted transmitters on waterfowl. Morris and Burness (1992) used transmitters epoxied to metal leg bands to locate Common Terns. Implanted transmitters with external whip antennas have been used successfully on Mallards and Canvasbacks (Korschgen et al. 1996). Nasal-saddle mounted transmitters have been used on this group of birds (Swanson and Keuchle 1976), but have been found to cause behavioural changes (Perry 1981). Harness-mounted transmitters (Dwyer 1972) have also been reported to have adverse effects (Greenwood and Sargeant 1973; Amlaner et al 1978; Perry 1981). Harnesses also produce drag and possible loss of insulation in water birds (Kenward 1987).
Satellite transmitters attached as backpacks have been designed for use on swans and geese (Burger and Carroll 1994).
C. Marn (Oregon State Univ., Corvallis, OR, pers. comm.) has sutured <1.5 g transmitters to the backs of newly-hatched American Avocets and Black-necked Stilts, and reports no problems due to infection. Glue-on transmitters seem to be the preferred method of instrumenting birds in this group. R. Butler (Canadian Wildlife Service, Delta, B.C., pers. comm.) glued 0.8 g transmitters to the backs of Western Sandpipers, and M. Robert (Canadian Wildlife Service, Sainte-Foy, PQ, pers. comm.), and P. Shepherd (Simon Fraser Univ., Burnaby, B.C., pers. comm.) used the same technique on Yellow Rails in Quebec and Dunlin on the Fraser River, respectively.
Tail-mounted transmitters are generally the choice of most researchers working with raptors. Sodhi et al. (1991) reported no apparent effects of tail-mounted transmitters on Merlins, and Taylor (1991) reported no effects on Barn Owls.
Backpack-mounted transmitters with elastic-web or Teflon harnesses have been used with species such as Barn Owls (Andrusiak 1994), Boreal Owls (Hayward et al. 1993), Bald Eagles (Garrett et al. 1993), and Red-tailed Hawks (Demarchi and Searing 1995). However, Foster et al. (1992) reported deaths and life-threatening abrasions caused by improperly fitting harnesses on Spotted Owls. Harnesses which place the transmitter ventrally on the breast of the bird have also been used on owls, but had adverse affects on the birds (Nicholls and Warner 1968). Solar-powered transmitters may be useful for diurnal raptors which commonly hunt in open areas (Snyder et al. 1989). Backpack-mounted and neoprene-harnessed satellite transmitters have both been used on Peregrine Falcons (S. Feliciano, pers. comm.).
Some telemetry suppliers offer bewit-mounted transmitters which are attached to a raptor's tarsi via a bewit. "Bewit" is a falconry term which refers to a piece of prestretched leather which is normally used to attach a bell to a raptor's leg. This method of attachment is not recommended for hard-stooping birds as the shock may damage the transmitter T. Weiss (Saarbruecken, Germany, pers. comm.) used this type of attachment on an eagle, but observed that the antenna seemed to always be in contact with the bird's toes. He also felt that the bird's ability to capture prey may have been compromised.
Poncho-mounted transmitters and necklaces similar to those used on game birds have proven to be useful in studies on Burrowing Owls (Haug and Oliphant 1990; D. Grier, Univ. of Guelph, Guelph, ON, pers. comm.). Patagial tags have been used on California Condors (Ogden 1985).
Game birds have frequently been studied with the use of radio-telemetry (Hill and Robertson 1987). Poncho-mounted transmitters have been used on many game bird species (Amstrup 1980; Pekins 1988). Solar-powered transmitters mounted on herculite ponchos worked well on Ring-necked Pheasants (Leif 1994). Burger et al. (1991) used bib-mounted transmitters and reported that heavier transmitter weights were correlated with decreased survival. Slaugh et al. (1990) and Lutz et al. (1994) used backpack transmitters on Chukar and Attwater's Prairie-chicken, respectively with apparent success, but harness-mounted transmitters have been reported to have adverse effects on Red Grouse (Boag 1972) and Woodcock (Ramakka 1972). Sharp-tailed Grouse have been fitted with radio collars (Marks and Marks 1987). Necklaces have gained favour for use on game bird species in recent years (Riley and Fistler 1992).
This group of birds has long legs which are suitable for attaching leg-mounted transmitters (Melvin et al. 1983). Implants have also been used on Sandhill Cranes (Klugman and Fuller 1990). Backpack-mounted satellite transmitters have also been used on Sandhill Cranes by B. Johns (Canadian Wildlife Service, Saskatoon, SK, pers. comm.).
We could not find any reference to swift radio tagging in the literature. Glue-ons have been used by Brigham (1989) with Barn Swallows, but he found that the tags affected foraging in a negative manner. Brigham (1989b, 1992) has used a backpack comprised of two elastic hair bands knotted in a figure-eight pattern and slipped over the wings in Common Nighthawks and Common Poorwills. Both of these species have bred successfully wearing radio tags which are attached in this manner, suggesting that the transmitters do not have negative effects on their behaviour (Csada and Brigham 1994b; Wang et al. 1995).
Five % of body weight is the generally accepted size for avian telemetry work, but the rationale behind this figure is really not known (Caccamise and Hadin 1985). Certain studies of thrushes and warblers have had apparent success using weights between 5 to 10% (Graber and Wunderle 1966; Knittle et al. 1985; Cochran et al. 1987). Caccamise and Hedin (1985) have developed data which suggests that small passerines can handle a greater transmitter:bird weight ratio because they are more aerodynamically suited than larger birds.
Raim (1978) pioneered some of the first passerine work. He glued transmitters interscapularly to cowbirds using a piece of cloth glued to the skin and feathers and another piece glued to the transmitter. This technique was duplicated by Sykes et al. (1990) who trimmed the feathers of Common Yellowthroats and Kirtland's Warblers to within 1 to 3 mm prior to mounting transmitters via chiffon fabric. They report little success when using only adhesive without the fabric layer. However, Walters (Univ. of Victoria, Victoria, B.C., unpubl. data) had very good success without using any fabric with his work on Orange-crowned Warblers, Pygmy and Red-breasted Nuthatches, and Hermit Thrushes. Perhaps this difference is related to the adhesive used: Walters used cyanoacrylic glue whereas Sykes et. al. (1990) were using latex eyelash adhesive. For the Kirtland Warbler work, however, Sykes et al.(1990) switched to skin bond cement which they found held longer, dried quicker, and was generally easier to use. Walters (unpubl. data) has found that birds can be tagged in less than 10 minutes with the adhesive method, and batteries usually give out long before the tag falls off. In another version of this attachment technique, Sykes et al. (1990) used Velcro in addition to the chiffon fabric. They found it was not as aerodynamically sound as the other method and do not recommend it.
Other researchers working on Red-winged Blackbirds have gone one step further to not only glue the transmitter, but suture it in place (Martin and Bider 1978). For suturing, inhalant anaesthetics, such as isofluorane, can be used in consultation with a veterinarian. The advantage with this method of attachment is that it is unaffected by moult, unlike adhesive methods alone (Martin and Bider 1978).
Sykes et al. (1990) found median retention was 24 days for transmitters mounted using adhesive and cloth. As well, when the transmitter fell-off, it pulled the attached feathers out of the folicle with it. This stimulated new feather growth within 2 to 4 days, producing fully-formed feathers in 17 to 24 days. Winker et al. (1990) report that tags fell off Wood Thrushes after 40 days because of feather growth. Zebra Finches, whose feathers were plucked during a study by Langman (1973), dislodged the transmitter within 3 to 7 days. It is usually recommended that feathers be cut, as opposed to plucked, to guard against this stimulated growth pattern.
Knittle et al. (1985) report an unbelievable range of 13 km for their 1.1 gram tags when signals were received by aircraft at altitudes of 500m to 1500m. Ground tracking ranges were significantly less with values of 400 m to 8 km depending on terrain. This is in marked contrast to Langman (1973) whose finches' transmitters had a range of 3 m during physiological experimentation.
Harnesses have rarely been used with passerines, mainly due to weight constraints. Sykes et al. (1990) designed one for use with Common Yellowthroats (neck and abdominal loops), but found adhesive methods to be superior. One characteristic of harnesses is that they rarely fall off, compared with adhesive methods; this can be advantageous for data collection but also detrimental to the long term well-being of the subject animal.
Traditional harnessing methods such as wing loop or neck loops have met with less favour in recent years due to problems with behavioural changes. In the past, studies have reported harness slippage in approximately 10 to 15% of tagged birds, generally resulting in immobilization of the study animal (Rappole and Tipton 1991).
Rappole and Tipton (1991) have developed a harness method that they claim allows faster processing time and longer tag retention. Their method involves slipping looped ligature material over each thigh with the transmitter sitting dorsally over the synsacrum. The method only works well with species that have long, external thighs, so it will not be effective on ducks or doves.
Implant work with doves has begun by Schulz (Missouri Dept of Conservation, Columbia, MO, pers. comm.). Mourning Doves have been outfitted with subcutaneous and intra-abdominal transmitters. External antennas pass through the skin or body wall and thus yield a better signal for detection by the researcher.
Besides the interscapular gluing method, Knittle et al. (1985) have used tail mounts (base of the four central tail feathers) with Pine Siskins, MacGillivray's Warblers and Yellow Warblers. This method proved satisfactory during their study, but premature loss of tail feathers poses a potential problem. This method has not been adopted by any other researchers, as far as we are aware.
The more traditional raptor technique of rectrice attachment has been used successfully on Northern Shrikes (Atkinson 1993). This method differs from Knittle et al.'s (1985) as the transmitter is tied to the central retrices rather than glued.
Another form of tail mount has been used in Gray Jays where the tag has been attached to the two central retrices with duct tape. Barnard (Norwich Univ., Northfield, VT, pers. comm.) has usually had the batteries fail before the tag has become dislodged.
Nesbitt et al. (1978) were some of the first researchers to tag woodpeckers. They glued the transmitter interscapularly with a cotton fabric cushion between transmitter and bird. Tags weighed approximately 6.5 to 9% body weight. Several others have used the technique since (Odom et al. 1982; Hooge 1991; Bull et al. 1992; E. Walters, Univ. of Victoria, Victoria, B.C., unpub. data; C. Steeger, Ymir, B.C., unpub. data); but without the piece of cotton fabric. Tags were secured with cyanoacrylic glue ("superglue") in most cases.
The work by Odom et al. (1982) with endangered Red-cockaded Woodpeckers was not very successful, and they suggest that glue-on transmitters impaired the function of an already stressed bird. Their study was compounded by the fact that they were tagging relocated individuals.
One bird in Walters' studies was found to be unable to exit its cavity with the transmitter on its back. The tag jammed against the roof of the cavity, effectively trapping the bird within the hole. The entrance had to be slightly enlarged (2 mm) to enable the bird to exit (Walters, unpub. data). This problem should be considered with any method when cavity-nesting species are involved.
Harnesses have been used mostly with Pileated Woodpeckers (Renken and Wiggers 1989; Bull et al. 1992; Mellen et al. 1992; Bull and Holthausen 1993; R. Bonar, Weldwood of Canada Ltd., Hinton, AB, pers. comm). The package is held to the bird with Teflon ribbon and sits dorsally in the mid-region of the back. The harness extends around the body on both the anterior and posterior edges of the wing to hold the package in place mid-dorsally. Broken or bent antennas caused by Pileated Woodpecker preening were reported by Mellen et al. (1992).
A comparison of harnesses with glue-on methods was made by Hooge (1991) in Acorn Woodpeckers. He found that harnesses decreased flying behaviours even when compared to heavier packages applied with adhesive. As well, attachment time increased markedly as did the chance of entanglement when using harnesses.
Several studies have used the tail-mount method to monitor woodpeckers (Goggans et al. 1988). The transmitters are attached to the underside of one central tail retrix by a series of nylon ties extending along the feather shaft. Some researchers have reported whip antennas becoming stuck in bark when this method is used with woodpeckers, a family of birds which normally forage on trunks using the tail as a brace.
[Back to TOC] [Previous] [Next]
HTML Created: August 98
Copyright © 1998 Province of British Columbia
Published by the Resources Inventory Committee