Short-term reactions and long-term responses of bottlenose dolphins (Tursiops truncatus) to remote biopsy sampling

Abstract

We analyse short-term individual and group behavioural reactions and long-term individual responses of bottlenose dolphins (Tursiops truncatus) in New Zealand to remote skin biopsy sampling. The biopsy system employed uses a small stainless steel tip (5-mm diameter, 9-mm length) mounted on a lightweight polycarbonate projectile, fired from a modified veterinary rifle with adjustable pressure. Individual and group behavioural reactions were scored on a 5-point scale from 0 (no reaction) to 5 (strenuous reaction). A total of 187 individual and 145 group behavioural reactions were recorded from the Bay of Islands subpopulation, while 38 individual and 39 group behavioural reactions were recorded from the Doubtful Sound subpopulation. Short-term reactions (<1 min duration) were ranked from low or mild (levels 1–2), as evidenced by startle responses, to moderate (level 3), as evidenced by multiple leaps of the sampled individual. Most attempts (99%) resulted in only mild reactions with only two attempts resulting in moderate reactions. There were no strenuous reactions by individuals or groups and no significant differences in behavioural reactions between the two subpopulations. Analyses of resighting rates and capture probabilities based on individual identification records for 40 of the biopsied dolphins showed no evidence of long-term avoidance responses. Wound healing was documented in for 10 dolphins across periods of 3 days to 7 months. Results reported here agree with previous findings showing that remote biopsy sampling causes only short-term reactions in both the targeted individual and its group.