Effects of darting duration for anesthetic induction on physiological parameters and anesthesia in sanctuary chimpanzees (pan troglodytes)

In many African sanctuaries, chimpanzees (Pan troglodytes) are darted for anesthesia induction to enable large-scale health examinations. This study evaluated the impact of prolonged darting duration on physiological parameters and anesthesia in 71 healthy sanctuary chimpanzees (41 males; 30 females) over a three-week period. Animals were darted with tiletamine-zolazepam (1.5–2.0 mg/kg) and medetomidine (0.015–0.02 mg/kg) IM; ketamine (1–2 mg/kg IM/IV) was hand-injected for maintenance, if required. Age, body weight (BW), preanesthetic activity score (PAS), darting duration, induction milestones, anesthetic time, and procedure duration were recorded. HR, RR, T, systolic (SBP), and diastolic blood pressure (DBP) were measured approx. every 5 min. Individuals were grouped by darting duration: A (< 2 min; n = 12), B (2 < 5.5 min; n = 27), C (5.5 < 10.5 min; n = 13), and D (10.5 < 25 min; n = 14), and by age: juvenile (n = 6), adolescent (n = 15), adult (n = 33), geriatric (n = 16). Median PAS was 3 (1–4), darting duration 4.0 min (0.5–23), time to first effects, light, and surgical anesthesia, and first blood pressure measurement were 2.0 (1.0–6.0), 5.0 (2.0–17.0), 8.0 (5.0–19.0), and 12.0 (8.0–28.0) min, respectively. Darting time did not significantly affect induction milestones, anesthetic time, procedure duration, or physiological parameters, except for SBP and DBP, which were higher in group D (P = 0.030 and P = 0.034, respectively) than groups A–C. PAS was positively correlated with darting time (ρ = 0.289, P = 0.015). Males had higher BW (P < 0.001), SBP and PAS (P = 0.035). Age class had no significant effect on darting duration or anesthesia, but adolescents had higher SBP and DBP (P = 0.014 and 0.004, respectively). Sanctuaries should adopt strategies to limit darting duration to ≤10 min to improve chimpanzee welfare.