Use of Emetics and Anesthesia for Dietary Assessment of Weddell Seals

Abstract

One female and 19 male Weddell seals, Leptonychotes weddellii, were injected with the emetic apomorphine hydrochloride. Fourteen of these were immobilised with combinations of ketamine hydrochloride and diazepam before the emetic was injected. One seal was administered the emetic tincture of ipecac while immobilised. The mean induction dose of ketamine hydrochloride was 7.99 ± 1.99 mg kg-1 (mean±SD) and that of diazepam was 0.05 ± 0.01 mg kg-1. The mean induction time was 23.07 ± 17.63 min and the mean duration of immobilisation was 127.00 ± 20.72 min. Six of the 22 seals apomorphine hydrochloride vomited and the seal given tincture of ipecac did not vomit. The mean dose of apomorphine hydrochloride that produced vomiting in immobilised animals was 0.18 ± 0.10 mg kg-1 and the mean dose of apomorphine hydrochloride that produced vomiting in non-immobilised animals was 0.22 ± 0.15 mg kg-1. Three seals died after drug administration during the study. Post-mortem examinations were conducted on these animals and nothing abnormal was found. Seals were weighed on 15 occasions (weight range, 137-402 kg) and the relationship between standard length (L, in centimetres) and body weight (W, in kilograms) was found to be: W=3.66L- 489.30. Food comprising five species of fish, two cephalopods and one gastropod were identified. Nematodes and gastroliths were present in most vomit samples. Centrally acting emetics and dissociative anaesthesia were both found to have limitations for use in Weddell seals.