Body condition changes arising from natural factors and fishing gear entanglements in North Atlantic right whales Eubalaena glacialis

Abstract

Body condition has been correlated with survival and reproductive success in bothterrestrial and marine mammals, including North Atlantic right whales Eubalaena glacialis. Weused photographs of individually identified right whales to assess visual changes in body conditionin reproductive females, adult males, juveniles, and entangled whales. Images from sightingsof individual whales were grouped sequentially by habitat region, and each group of images wasassigned a body condition score of good, fair, or poor based on the dorsal profile posterior to theblowholes. Temporally consecutive groups of images (n = 1496) of 340 individual whales werecompared to investigate the frequency, direction, and minimum timeframe between changes inbody condition. Changes in body condition scores of right whales were significantly influenced bygroup category. Lactating females and severely entangled right whales were more likely toexhibit declining body condition than other groups. Resting females were significantly more likelyto improve in condition than other groups but exhibited the longest timeframe for improving condition.Young juveniles were less likely to improve in condition compared to adult males, butremained in compromised condition less frequently than older juveniles and adult males. Theshortest timeframes between changing body condition scores were 11 d for declining conditionand 12 d for improving condition. This study demonstrates that photographic analysis can detectrapid body condition changes and identifies groups of right whales that are particularly vulnerableto declining condition and delayed recovery from energetically taxing events.