TECHNIQUE

Alphachloralose Sedation of Cranes (Disease Investigation & Management - Treatment and Care)

Summary Information
Type of technique Health & Management / Disease Investigation & Management / Techniques:
Synonyms and Keywords  
Description
  • Identify a target social group of cranes (e.g. a territorial pair or family).
  • Identify a suitable baiting site, away from water, away from disturbance (e.g. agricultural activities) and where it will be possible to observe the cranes from a distance. (P91.1987.w7)
    • An ideal baiting site is used immediately after the birds leave the roost, for about 2-3 hours. (P91.1987.w7)
  • Feed the cranes bait (a large grain, e.g. whole corn) at a bait station to condition the cranes to eat the bait.
    • Initially place bait every other day, then for 3-5 days before the intended capture date, place every day. (P91.1987.w7)
    • Do not use an excessive amount of bait; a limited amount encourages cranes to go to the bait site soon after leaving their roost site, reduces waist and reduces problems with other animals eating the bait. (P91.1987.w7)
  • On capture day, place bait mixed with Alphachloralose  at the baiting station just before dawn.
    • 0.39-0.48 g alphachloralose per 280 mL cup of corn. (B703.10.w10)
    • Initially 0.39 grams alphachloralose per cup of corn, increasing to 0.48 g per cup in later years. (J1.39.w6)
    • 11.5 g per 6,900 cc moistened wheat (0.5 g per 300 cc wheat). (J720.93-94.w1)
    • 0.45 - 0.50 g per cup of corn enabled capture in 1-3 hours. (J40.37.w3)
    • For the capture of large numbers of cranes, bait was scattered sufficiently to allow each crane to feed without disturbance from the other cranes. (J720.93-94.w1)
  • Wait while the cranes eat the bait.
    • Each crane needs to ingest 0.5 - 1.0 cups of corn to reach sufficient sedation.
    • If possible, discourage non-target individuals and other species from accessing the bait station
  • After about 20-30 minutes the sedated crane becomes ataxic, rests more, may be unable to fly or fly with difficulty.
    • For Grus canadensis - Sandhill cranes fed bait with 0.40 - 0.62 grams per cup of corn, first signs of narcosis were detected at 20 minutes, they ceased feeding within an hour and walked slowly from the bait site, "occasionally  stumbling and falling backwards." (J40.37.w3)
    • Time before capture was possible was noted as 1-3 hours with 0.48 g per 284 cc cup of corn, versus 2-3 hours with 0.4 g/284 cc cup of corn. (P87.1975.w5)
  • The crane goes to sternal recumbency, and may or may not become unresponsive to external stimuli.
  • Assess the level of sedation: (J1.39.w6)
    • Light sedation: the crane holds its head up at least 75% of the time, it kicks its legs at intervals under 10 minutes, it responds to external stimuli (visual, auditory, tactile) more than 75% of the time and has no audible gurgling on respiration.
    • Light-moderate sedation: the crane holds its head up 51-74% of the time, it kicks its legs at intervals of about 15 minutes, it responds to external stimuli 51-74%% of the time and gurgling may be heard occasionally on respiration.
    • Moderate sedation: the crane holds its head up about 50% of the time, it kicks its legs about every 30 minutes, it responds to external stimuli about 50% of the time and gurgling is noticeable on respiration.
    • Heavy-moderate sedation: the crane holds its head 26-49% of the time, it kicks its legs about every 45 minutes, it responds to external stimuli 26-49% of the time and gurgling is constant on respiration.
    • Heavy sedation: the crane holds its head up less than 25% of the time, it kicks its legs about every 60 minutes or less often, it responds to external stimuli less than 25% of the time and gurgling is heavy on respiration.
    • Very heavy sedation: the crane holds its head less than 10% of the time, it kicks its legs about every 60 minutes or less often, it responds to external stimuli less than 10% of the time and gurgling is excessive on respiration.
  • Approach quietly from behind and immobilise the sedated crane
    • The crane may be captured by hand or with a long-handled net (approach from behind the crane). (P91.1987.w7)
    • It may be necessary to capture cranes which are still on their feet, but walking aimlessly, sometimes in circles. (P91.1987.w7)
    • Grasp and the legs close to the hocks, not near the feet. See: Bird Handling & Movement - Holding & Carrying
  • A hood and a body wrap (keeping the wings against the body, held closed with e.g. Velcro) can be placed on the crane to reduce stress and minimise movement during transport, with the legs taped together carefully above the tibio-tarsal joints (hocks) to reduce kicking by the bird during handling. (J1.39.w6, P91.1987.w7)
    • Restraints should be in place for as short a time as possible. (P91.1987.w7)
  • Give fluids, up to 30 mg/kg lactated Ringer's solution subcutaneously. (J1.50.w1)
  • Keep sedated cranes protected from extremes of cold or heat/sun.
  • After any procedures have been carried out (e.g. blood sampling, measuring, banding), hoods, wraps and tape are removed, and the crane's wings and legs manipulated to stimulate circulation (passive physical therapy). (J1.39.w6)
  • Place the crane in a darkened holding pen (e.g. 2.5 x 2.5 x 1.5 m) to recover.
  • Monitor every 3-4 hours during the day to determine level of sedation.
  • Release the crane once it is fully recovered.
    • Recovery time varies depending on the amount of drug eaten, the individual crane, and ambient temperature. (P91.1987.w7)
    • Release the following morning if sufficiently recovered (about 24 hours after sedation); (J1.39.w6)
      • Release has been carried out about 12 hours after sedation if cranes appeared fully alert and mobile. (J1.39.w6)
        • Signs that the crane have recovered include that it holds its head up, walking alertly and briskly with no shaking or quiver in the legs, vocalising if approached by a  human, and attempting to defend itself vigorously, or attacking aggressively. (P91.1987.w7)
      • Do not release within an hour of sunset; cranes need time to reorientate themselves after release before time for roosting. (P91.1987.w7)
      • Holding for 24 hours may be advisable to increase the chances of detecting and treating Capture Myopathy. (J312.21.w2)
    • Release cranes by allowing them to walk/fly from the enclosure when they are fully recovered from the sedative. (P87.1975.w5)
  • Monitor post-release for any signs of abnormal behaviour in alertness, mobility, integration into the social unit or flock.
Appropriate Use (?)
  • To capture wild cranes for research. (B703.10.w10)
  • To capture cranes which have escaped from collections. (B703.10.w10)
  • No visible capture equipment is needed, so extensive camouflage is not needed. (J1.39.w6)
Notes
  • Recovery time is related to dose: cranes too lightly sedated to be captured may start to recover by three hours after ingestion of the bait. (P87.1975.w5)
  • Holding wild cranes overnight in a quiet pen in which they can be watched without disturbing them may be advantageous following capture and restraint, to detect effects of myopathy that might not be visible immediately, thereby reducing the risk of affected cranes being released prematurely and dying following release. (J312.21.w2)
  • Place bait just before dawn, to capture cranes in the morning. (P91.1987.w7)
  • If catchers are to observe from a blind or vehicle, make sure the cranes are used to the blind/vehicle being present before the day of capture. (P91.1987.w7)
  • It is important that the alpha-chloralose is weighed accurately using a scale which weighs to 0.01 g. (P91.1987.w7)
  • Effects of alpha-chloralose: (P91.1987.w7)
    • A general depressant.
    • Reduces body temperature
    • Reduces respiration.
    • Reduces heart rate.
    • Increases mucus production.
    • Causes drooling and gurgling.
    • Causes increased ocular discharge.
    • Causes loose, runny droppings. (P91.1987.w7)
  • The pre-release holding pen should be high enough for the cranes to stand upright. It should be predator proof, and provide shelter from the elements (including from hot sun, rain and cold). It should have a dirt or sand substrate (not cement, wood, smooth plastic). (P91.1987.w7)
    • Water should not be available initially in the recovery pen, due to the risk of cranes drowning, and because drinking can result in drug overdose (increased absorption). (P91.1987.w7)
    • A small, shallow container of water can be provided if cranes have been captured in the morning and are being held overnight. (P91.1987.w7)
  • Once the sedated crane(s) have been captured, remove any remaining drugged bait so that other animals will not eat it, and put out fresh, untreated bait (so that there is much more untreated than treated bait present, and any animal eating it is unlikely to consume enough treated bait to be affected by the drug). (P91.1987.w7)
  • Although cases of Capture Myopathy have occurred, a study using physiological monitoring of 18 adult cranes did not indicate metabolic acidosis (associated with capture myopathy). It was noted that the highest creatine phosphokinase levels at one hour and 22 hours post capture were in the cranes with the lightest sedation levels; those more heavily sedated had lower CK levels. (P20.1998.w12)
  • In Grus canadensis - Sandhill cranes in Wisconsin, captured as part of a long-term study, initial analysis indicated higher mortality when cranes were captured in August or October rather than in September (J1.39.w6). Restricting capture to September and early October was associated with a modest increase in capture efficacy, probably due to feeding behaviour of the cranes being more predictable at this time. Additionally, subcutaneous administration of lactated Ringer's solution at up to 30 mL/kg produced faster recovery times. The proportion of cranes diagnosed with exertional myopathy (Capture Myopathy) reduced from 7/188 (3.7%) to 3/129 (2.3%) after the changes were implemented. (J1.50.w1)
Complications/ Limitations / Risk
  • Avoid using oral sedation close to water: (J40.37.w3, P87.1975.w5)
    • Risk of sedated cranes Drowning if sedated too close to water. (B336.20.w20, J40.37.w3, P87.1975.w5)
    • Risk of cranes consuming sedative then drinking, resulting in excessive drug absorption and consequent overdose. (J40.37.w3, P87.1975.w5)
    • Cranes with wet feathers may result in chilling, which can be fatal. (P87.1975.w5)
  • Risk of development of Capture Myopathy hours to weeks after capture.
  • Risk of sedated birds being attacked by un-sedated cranes (P87.1975.w5, P91.1987.w7)
  • Risk of sedated cranes being attacked by predators. (B336.20.w20, P91.1987.w7)
  • Lightly sedated cranes may fly from the baiting site. These should be located and captured as they are vulnerable to predation or attacks from other cranes. (P91.1987.w7)
  • Birds confined in boxes or bags are more likely to develop permanent leg injuries or shock. (P87.1975.w5) See Capture Myopathy
  • Do not use restraints (body wraps etc.) for long periods. (P91.1987.w7)
  • When a larger group of cranes is sedated, cranes may become disturbed by the abnormal behaviour of other cranes which have become sedated more quickly. (J720.93-94.w1)
  • One crane of 60 common cranes was paralysed, unable to stand or fly, following mass sedation and capture. (J720.93-94.w1)
  • Correct drug concentration is important. In an early trial:
    • Higher doses (0.62 g per cup of corn and 2.0 g/cup) resulted in excessive mortality. (J40.37.w3)
    • Too low doses (0.35 g/cup) were ineffective. (J40.37.w3)
  • Do not use in cold weather or on a rainy day, as this drug lowers body temperature [thus risking hypothermia]. (P91.1987.w7)
  • Risk of hyperthermia in hot weather (B336.20.w20) if sedated cranes are not provided with shade.
  • Heavily sedated cranes may regurgitate bait or mucus. The cranes mouth and throat should be cleared - hold the crane up, with the neck and head hanging down, allowing gravity to clear the throat. (P91.1987.w7)
Equipment / Chemicals required and Suppliers
  • Alphachloralose - a fine white powder, odourless and nearly tasteless. (P91.1987.w7)

  • Bait such as whole corn (maize) or whole wheat.

Expertise level / Ease of Use
  • Should only be used by personnel who are familiar with cranes, able to judge sedation level by observation, and and practiced at capturing and handling cranes. Veterinary support is important in case of any problems (e.g. suspected capture myopathy).
Cost/ Availability
  • It may be difficult to obtain alphachloralose.
Legal and Ethical Considerations
  • It is important to consider the risks associated with this method of capture, and to minimise these risks as far as possible.
  • Special permits may be required for the use of alpha-chloralose for oral sedation.
    • In the USA, authorisation from the U.S. Department of Agriculture, Animal and Plant Health Inspection Service, Wildlife Services. (J1.50.w1)
  • In some countries there may be legislation restricting the use of this type of technique to licensed veterinarians. For example in the UK: "The Veterinary Surgeons Act 1966 (Section 19) provides, subject to a number of exceptions, that only registered members of the Royal College of Veterinary Surgeons may practice veterinary surgery." (See: LCofC1 - RCVS Guide to Professional Conduct 2000 - Treatment of Animals by Non-Veterinary Surgeons).
Author Debra Bourne MA VetMB PhD MRCVS (V.w5)
Referee  
References B336.20.w20, B703.10.w10, J1.39.w6, J1.50.w1, J40.37.w3, J720.93-94.w1, P91.1987.w7, P87.1975.w5

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