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SHORT COMMUNICATION |
1 National Park Service, Pictured Rocks Science Center, Box 40, Munising, Michigan 49862, USA
2 Corresponding author (email: Jerry_Belant{at}nps.gov)
ABSTRACT:
The effectiveness of tiletamine plus zolazepam (Telazol) and xylazine as an immobilizing combination for fishers (Martes pennanti) was evaluated. Ten fishers were intramuscularly injected using a 5:3 mixture of Telazol (2.9±0.6 mg/kg [mean±SD]) and xylazine (2.1±0.4 mg/kg) at Pictured Rocks National Lakeshore, Michigan (USA) during May to October, 2001–05. Mean induction time was 4.7±4.4 min; mean recovery time was 94.6±46.0 min. There was no relationship between the amount (mg/kg) of Telazol-xylazine injected and time to first effect of immobilants, dosage and time to induction, or between dosage and time to recovery. Mean heart rate remained constant through 20 min postinduction. Respiratory rate and body temperature declined through 10 and 20 min postinduction, respectively. No mortality occurred and no adverse effects were observed in individuals up to 19 mo later. It was concluded that a 5:3 mixture of Telazol-xylazine is a safe and effective immobilizing agent for fishers when conducting nonsurgical field procedures. Immobilizing fishers with 6–7 mg/kg of the combination (3.8–4.4 mg/kg Telazol and 2.3–2.6 mg/kg xylazine) should provide 
30 min of handling time and allow full recovery in < 90 min.
Key words: Chemical immobilization, field study, fisher, Martes pennanti, Telazol, tiletamine, xylazine, zolazepam.
Chemical immobilization of fishers (Martes pennanti) has been conducted with numerous injectable anesthetics including chlordiazeproxide (Irvine et al., 1964), phencyclidine-promazine (Seal and Erickson, 1969), ketamine (Frost and Krohn, 1994; Mitcheltree et al., 1999; Dzialak et al., 2002), ketamine-acepromazine (Kelly, 1977; Jessup, 1982), ketamine-xylazine (Belant, 1991), ketamine-medetomidine (Dzialak et al., 2001, 2002), and tiletamine-zolazepam (Petrini, 1992; Mitcheltree et al., 1999; Dzialak and Serfass, 2003). Atipamezole and flumazenil has been attempted to reverse medetomidine-ketamine and tiletamine-zolazepam restrained fishers, respectively (Dzialak et al., 2001; Dzialak and Serfass, 2003). Kreeger (1999) recommended using ketamine-xylazine, with alternative combinations of ketamine-acepromazine or tiletamine-zolazepam. More recently, Kreeger et al. (2002) recommended use of ketamine-medetomidine with atipamezole as a reversal agent.
Telazol (100 mg/ml, Fort Dodge Animal Health, Fort Dodge, Iowa, USA) contains a 1:1 combination of tiletamine and zolazepam and has been used effectively on numerous wildlife species (e.g., Boever et al., 1977; Mitcheltree et al., 1999; Golden et al., 2002). Advantages of Telazol include a high therapeutic index, minimal respiratory effects, and good cardiovascular support (Kreeger, 1999). Xylazine (Xyla-ject®, 100 mg/ml, Phoenix Pharmaceutical Inc., St. Joseph, Missouri, USA) is an alpha2-adrenergic tranquilizer also used to immobilize wildlife, typically in combination with other anesthetics (Kreeger, 1999). Telazol-xylazine has been used on several ungulate species including white-tailed deer (Odocoileus virginianus) and bighorn sheep (Ovis canadensis) (Kilpatrick and Spohr, 1999; Merwin et al., 2000; Murray et al., 2000). For carnivores, this immobilizing combination was used successfully on grizzly bears (Ursus arctos), raccoons (Procyon lotor), and American martens (Martes americana) (Cattet et al., 2001; Belant 2004, 2005); use of Telazol-xylazine for immobilizing fishers has not been reported. The objective of this study was to assess the effectiveness of Telazol-xylazine for field immobilization of fishers.
The study was conducted from May to October 2001–2005 at Pictured Rocks National Lakeshore, central Upper Peninsula of Michigan (46°27'N, 86°33'W). Ambient temperatures during the study ranged from about 4–32 C. Fishers were captured in live traps (Model 108, Tomahawk Live Trap Company, Tomahawk, Wisconsin, USA) baited with sardines or chicken and commercial trapping lures or incidentally in barrel traps set for American black bear (Ursus americanus). Fishers captured in barrel traps were transferred to cage live traps by placing the set live trap inside the barrel trap and opening the bait door located at the rear of the barrel trap. This action caused the fisher to move into the cage trap; it was then removed from the barrel trap. After visually estimating body weight, all fishers were intramuscularly injected in the gluteus maximus, gluteus medius, or vastus laterallis using a 3 ml (0.10 ml graduations) hand syringe containing a 5:3 combination of Telazol and xylazine. Each 500-mg vial of Telazol was reconstituted with 5 ml of sterile water to create a 91mg/ ml solution. Xylazine (333 mg; 3.33 ml) was then added to the Telazol solution to create the 5:3 Telazol-xylazine combination.
Procedures used to document fisher response to immobilization followed Belant (1991, 1992). Induction time was defined as the interval between injection and lack of responsiveness to tactile stimuli. Recovery time was the interval between immobilization and the animal’s ability to maintain an upright posture and respond to external stimulation, including moving the livetrap to different positions. The time to first effect was defined as the interval between injection and when the animal exhibited initial signs of immobilization (e.g., head bobbing, inability to keep eyelids open). Rectal temperature, respiratory rate, and resting heart rate were recorded as soon as practical after immobilization (
3 min; hereafter 0 min) and at 10 and 20 min postinduction. Rectal temperature was recorded using a digital thermometer. Respiratory rate was determined by counting complete thoracic cycles (inhalation and exhalation) for 30 or 60 sec. Resting heart rate was determined by placing fingertips against the fisher’s chest and counting beats for 30 or 60 sec. Each fisher was weighed and received a tag in each ear (Model 1005-1, National Band and Tag Co., Newport, Kentucky, USA) and a radio transmitter attached using a collar (Advanced Telemetry Systems, Inc., Isanti, Minnesota, USA). Fisher collars weighed 28 or 43 g and were <2% and 1.1% of female and male body mass, respectively. In addition, an upper first premolar was extracted for age determination (Strickland et al., 1982). Fishers were placed in their respective livetraps after handling procedures were completed. All animals were released at the capture site upon full recovery. To determine whether doses derived using estimated animal weights affected immobilization parameters, linear regression (Zar, 1984) was used to determine the relationships between dose and time to first effect, induction time, and recovery time. Repeated measures analysis of variance with Tukey’s multiple range test (SAS, 1988) were used to compare heart rate, respiratory rate, and rectal temperature at 0, 10, and 20 min postinduction. Means are reported with ±1 SD; statistical significance was established as P0.05. Although descriptive statistics for each sex are reported in tabular form, small sample sizes precluded inferential analyses.
Ten fishers (6 males, 4 females) were captured and immobilized; weights ranged from 2.0–6.0 kg. All but one male fisher were >1 yr old. Fishers generally moved rapidly within the trap when approached prior to immobilization. Mean initial doses of Telazol and xylazine injected were 4.7±2.1 and 2.6±1.2 mg/kg, respectively. A second injection of 9 mg of the immobilant combination was required on one occasion to sustain sedation during handling procedures.
Mean time to first effect of immobilization was (1.46±0.85 min); mean induction time was (4.7±4.4 min; Table 1
). Although not quantified, mean time to first effect and mean induction time appeared to occur more rapidly in females. The fisher with the longest induction time (16.2 min) received 5.2 mg/kg of the combination and accounted for much of the variation observed in induction time. Excluding this animal resulted in a mean induction time of 3.5±1.9 min. Full recovery from immobilization occurred in 94.6±46.0 min. No relationship between dose and time to first effect (y=2.61–0.16x, y=time to first effect in min and x=dose in mg/kg; r2=0.38, P=0.06), between dose and induction time (y=8.52–0.51x, y=induction time in min and x=dose in mg/kg; r2=0.15, P=0.26), or between total dose and recovery time for fishers (y=36.29+9.00x, y=recovery time in min and x=dose in mg/kg; r2=0.17, P=0.27) was found. In contrast to mean time to first effect and mean induction time, mean recovery time appeared longer for females than for males.
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). Respiratory rates varied over time (F=12.00; 2, 27 df; P<.01) with rates at 0 min higher (P<0.05) than 10 or 20 min postinduction. Respiratory rates at 10 and 20 min post-induction were similar (P>0.05). Induction was generally rapid; loss of coordination occurred initially in the rear legs, followed by the front legs, neck, and head. Although depth of anesthesia was not evaluated quantitatively, fishers did not respond to attachment of ear tags nor did they respond to tooth extraction by attempting to move their head away from the stimulus. No salivation or defecation was observed during anesthesia. Pedal and palprebal withdrawal reflexes were observed within 10–15 min in only one individual, which necessitated the second injection. However, no signs of spontaneous recovery were observed. Fishers frequently attempted to become upright before returning to a lateral recumbent position during recovery due primarily to a lack of coordination in the rear legs. Fishers regained coordination during recovery in the reverse order of induction.
No mortality was observed during this study as a consequence of immobilization. Two fishers were recaptured on three occasions up to 19 mo after initial captures. No adverse effects of immobilization were observed; behavior of recaptured individuals subjectively appeared similar to behavior of fishers captured initially.
Telazol and xylazine doses used for livetrapped fishers in this study provided satisfactory induction times and adequate anesthesia for minor field procedures. Cattet et al. (2001) successfully used a 3:2 combination of Telazol and xylazine at 5 mg/kg to immobilize grizzly bears. Belant (2004, 2005) used this same combination to immobilize raccoons and American martens, recommending 5 and 7 mg/ kg, respectively. Based on available literature, Kreeger (1999) recommended using 25 mg/kg ketamine plus 5 mg/kg xylazine, with alternative combinations of 20 mg/kg ketamine and 1 mg/kg acepromazine or 10 mg/kg tiletamine-zolazepam. That lower doses were used successfully in this study could be in part because Telazol is about 2.5 times more potent than ketamine (Beck, 1972).
Fishers immobilized with Telazol-xylazine exhibited decreases in respiration and body temperature through 10 and 20 min post induction, respectively. American martens immobilized with this same combination exhibited declines in these parameters 10 min post induction (Belant, 2005). In contrast, raccoon respiration and body temperature remained constant through 20 min postinduction (Belant, 2004). Although baseline physiological values vary among species, mean initial respiration rate and body temperature of fishers was more similar to martens (Belant, 2005), and both were greater than those reported for raccoons (Belant, 2004). These differences could be a consequence of variation in physiology between genera. Alternatively, differences in behavior could have contributed to results observed. Both fishers in this study and martens (Belant, 2005) exhibited increased excitation and movements in cage traps prior to immobilization compared with raccoons (Belant, 2004), which could have resulted in elevated respiratory rates and body temperature observed.
A 3.2 C decline in body temperature through 20 min postinduction was observed. Body temperatures declined more rapidly than temperatures of fishers immobilized with ketamine-xylazine (Belant, 1991) or Telazol only (Mitcheltree et al., 1999), but were generally similar to temperatures reported in those studies and were within the temperature range reported by Frost and Krohn (1994) for fishers immobilized with ketamine. That females appeared to have lower body temperatures than males at 20 min post-induction was likely a consequence of females receiving higher dosages of Telazol-xylazine. Physiological depression can be induced by xylazine, which is known to cause respiratory depression and disruption of thermoregulation (Kreeger, 1999), and Cattet et al. (2001) reported that grizzly bears immobilized with Telazol-xylazine had depressed respiration for 15 min postinduction compared with immobilization using Telazol only. However, physiological depression was not observed in fishers in this study or in raccoons or American martens immobilized with Telazol-xylazine (Belant, 2004, 2005).
The initial mean respiration rate in this study was comparable to rates reported for fishers immobilized with ketamine (Belant, 1991) and Telazol (Mitcheltree et al., 1999). Similarly, respiration rates at 20 min post-recovery were similar to fishers immobilized with Telazol but less than individuals immobilized with ketamine or ketamine-xylazine (Mitcheltree et al., 1999). Reduced respiration rates observed could be indicative of mild respiratory depression observed in these immobilants (Mitcheltree et al., 1999; Cattet et al., 2001).
That a significant decrease in heart rate did not occur was not surprising. A previous study similarly failed to detect changes in heart rate of immobilized fishers (Dzialak et al., 2001; Dzialak and Serfass, 2003). Initial mean heart rate was similar to the mean initial rate reported by Belant (1991) but maximum values exceeded those of previous studies (Belant, 1991; Dzialak et al., 2001).
Little information is available on resting heart rate, respiration, and body temperature of nonimmobilized fishers to compare with immobilized individuals in this study. Research to describe these physiological parameters, as suggested by Mitcheltree et al. (1999), is warranted. Additionally, obtaining data on these metrics from active fishers to more fully compare and describe the effects of immobilization on fisher physiology is recommended.
Mean recovery time in this report was shorter than those of fishers immobilized with ketamine-xylazine, ketamine-medetomidine, or Telazol (Belant, 1991; Mitcheltree et al., 1999; Dzialak et al., 2001), but longer than fishers immobilized with ketamine (Mitcheltree et al., 1999). Observed mean recovery time was comparable to immobilized male fishers that were chemically remobilized 20 min postinduction (Dzialak, 2001). Shorter recovery times observed in this study were likely in part a consequence of generally lower mean dosages used.
Although observed recovery times were not unusually long, additional studies could be conducted with varying doses and combinations of Telazol and xylazine. Use of an antagonist such as yohimbine could further reduce recovery times. Yohimbine reverses the sedation effects of xylazine (Hsu and Lu, 1984) and, although its use has not been reported for fishers, yohimbine has been used for other medium-sized carnivores (Deresienski and Rupprecht, 1989). Cattet et al. (2001) reported that yohimbine was generally effective in reversing Telazol-xylazine immobilization in bears. Antagonists were not used in this study because of the overall low sample size and importance of characterizing immobilization without use of reversal agents. Finally, use of a Telazol-medetomidine combination for fisher immobilization should be explored. Medetomidine is more potent than xylazine and has been used successfully with Telazol to immobilize polar bears (Ursus maritimus) (Cattet et al., 1997, 1999). Medetomidine has also been used in combination with ketamine to immobilize fishers (Dzialak et al., 2001) and this combination has been recommended for fishers (Kreeger et al., 2002).
A 5:3 mixture of Telazol and xylazine is a safe and effective immobilization agent for fishers for minor field procedures. Although fishers in this study were immobilized with this mixture at doses ranging from 3.4–9.4 mg/kg, I recommend using combined 7 mg/kg (4.4 mg/kg Telazol, 2.6 mg/kg xylazine) for standard field procedures (e.g., tooth extraction, radio-tagging, blood sampling). This dose should provide 30 min of handling time and allow full recovery in <90 min.
Primary funding for this study was provided by Pictured Rocks National Lakeshore with additional funding from the National Park Service Challenge Cost Share and Recreational Fee Demonstration programs. L. Anderson, A. Hales, L. Kainulainen, N. Lapinski, K. Stanley, and J. Wolford provided field assistance. Trapping and handling procedures conformed to the American Society of Mammalogists Animal Care and Use guidelines and Pictured Rocks National Lakeshore Capture Operations Protocol.
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Received for publication 20 September 2005.
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