Morphometrics and body condition of southern right whales on the calving grounds at Port Ross, Auckland Islands.

After near extirpation by nineteenth century whaling, New Zealand's southern right whales (Eubalaena australis) are recovering strongly, calving almost exclusively at the subantarctic Auckland Islands. Right whales are capital breeders; body condition is an important driver of their breeding success. Here we use unmanned aerial vehicles to characterise variation in individual size and shape, and to quantify the size structure of the subset of the population we sampled. Of 108 whales photographically identified we gained a comprehensive set of measurements from 63 individuals, as well as length measurements for 29 calves and six non-calf whales for which the full suite of measurements were not obtainable. Lactating females (n = 32) ranged in length from 11.84 to 15.22 m, apparent non-breeding adults (n = 9) were between 11.96 and 14.92 m, while subadults (n = 28) were between 8.82 and 11.72 m long. Calves were between 5.15 and 7.53 m. Principal component analysis of the measurement data showed that widths (particularly at the positions of 30–80% along total body length) were most influential in PC1 (40.3% variance explained). Measurements of structural features (i.e. head and flukes) related more closely to PC2 (18.2% variance explained) and PC3 (14.8% variance explained). We, therefore, interpret PC2 and PC3 as representing structural size, while PC1 represents body condition. Subadults and non-breeding adults showed more variation in body condition than lactating females, highlighting the need for this demographic to maintain their body condition within a tighter range to meet the high nutritional demands of raising calves. [ABSTRACT FROM AUTHOR]