Northern Prairie Wildlife Research Center
Karen L. Machin, Department of Veterinary Physiological Sciences, 52 Campus Drive, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5B4 Canada
Intra-abdominal radio transmitters are used preferentially over externally-mounted transmitters because they appear to have less impact on behavior, health, survival and reproduction in ducks. Isoflurane and methoxyflurane are inhalant anesthetics often used for surgical procedures but they require expensive equipment such as a vaporizer and oxygen delivery systems. Anesthesia with methoxyflurane has also been employed to help reduce nest abandonment after handling and external transmitter attachment. Propofol is a new, rapidly-metabolized intravenous anesthetic which provides smooth induction and recovery, excellent muscle relaxation and short duration of anesthesia requiring additional boluses to maintain anesthesia. Rapid recovery characteristic of isoflurane anesthesia precludes placement of ducks into their natural environment prior to complete recovery. However, the use of propofol allows recovery to take place on the nest.
Anaesthesia with propofol and isoflurane were compared during 2 field seasons (1995 and 1996) in nesting female canvasback (Aythya valisineria) and ruddy ducks (Oxyura jamaicensis). Female canvasback ducks were assigned randomly to one of three treatment groups: propofol (n = 39), isoflurane (n = 39) or control (n = 40; flushed not captured). Nesting female ruddy ducks were assigned randomly to one of two treatment groups: nest-trapped only (n = 16) or propofol (n = 17). Complications encountered during anesthesia were resolved through a systematic approach of examining equipment and increasing artificial respiration. Monitoring and appropriate ventilation are important in ensuring the bird's safety.
Overall nest abandonment differed among canvasback treatment groups (X2 = 6.115, df = 2, P = 0.047), with lower than expected abandonment in control and propofol groups. No significant difference in abandonment was detected between propofol and control groups (X2 = 1.22, df = 1, P = 0.27), confirming that the relationship was driven by the higher than expected abandonment in the isoflurane group. There was no significant difference in nest abandonment of ruddy ducks that were captured only and those that received radio implants (Fisher's exact test, P = 1.0). Stress at time of recovery may be responsible largely for nest abandonment. Propofol requires minimal equipment, reduces anesthetic cost and decreases the risk of investigator induced abandonment making it an ideal anesthetic for field studies of waterfowl.