Do sampling method and sample size affect basic measures of dolphin sociality ?

Although the fission-fusion social patterns of bottlenose dolphins have been described, defining and measuring sociality is difficult. No study to date has investigated how much data are necessary to accurately depict social patterns in a fission-fusion species and whether this amount differs depending on the measure used. Using the long-term Shark Bay bottlenose dolphin study we examined four different measures of sociality for mothers and dependent calves (n = 89). Our objectives were to determine (1) the amount of observation time necessary to accurately depict sociality using these measures, (2) correlations among these measures, and (3) if sampling method affects the validity of sociality measurements. A minimum of 10 h and 5 h of observations, respectively, were necessary to accurately capture calf associate numbers and percent time alone. A pairwise comparison of calf sociality measurements from focal and survey data found that calves spent from 0% to 70.2% of their time alone in focal data, but these same calves spent only 0%-7.7% alone in survey data. These findings indicate that (1) results differ depending on the type of sampling method and (2) the amount of observation time necessary to adequately capture individual variation differs depending on the measure of sociality.