Development of a novel anaesthesia technique in a critically endangered anuran: Mountain chicken frog

The Mountain chicken frog (Leptodactylus fallax) is a Critically-Endangered anuran, endemic to the Caribbean. As the species became near-extinct in the wild due to severe, chytridiomycosis-associated, population declines in the early 2000s a conservation captive population was established in order to ensure its long term survival. In captivity, anaesthetic techniques previously-described in anurans did not provide reliable and consistent anaesthesia. The lack of safe anaesthetic regimes (i) impacted the welfare of the captive-population through limiting the veterinary diagnostic and therapeutic options, and (ii) limited re-introduction efforts by preventing surgical placement of radio-transmitters, necessary for monitoring animals post release.

Chester Zoo and Durrell Wildlife Conservation Trust developed a novel anaesthetic technique for this species using isoflurane and oxygen first in an anaesthetic chamber, followed by endotracheal intubation using a specially-modified endotracheal tube. Subsequent anaesthesia was stable, safe and sufficiently deep for surgery. This technique was utilised in 114 frogs anaesthetised to place intracoelomic radio-transmitters. Animals were anaesthetised for a duration of 21.6 ± 6.4 minutes. All animals consistently achieved a safe surgical anaesthetic depth. No significant complications were observed.

The development and evaluation of this anaesthetic technique has had a significant impact for captive management and the conservation programme. Veterinary diagnostic and therapeutic options are increased whilst post-release monitoring is now an option.

Chester Zoo and Durrell Wildlife Conservation Trust submitted this project to the BIAZA Awards Animal Husbandry, Care & Breeding category for 2020 and won a Gold award.