THE LIFE HISTORY OF FREE-RANGING ATLANTIC SPOTTED DOLPHINS (STENELLA FRONTALIS): AGE CLASSES, COLOR PHASES, AND FEMALE REPRODUCTION
Article first published online: 26 AUG 2006
Marine Mammal Science
Volume 13, Issue 4, pages 576–595, October 1997
How to Cite
Herzing, D. L. (1997), THE LIFE HISTORY OF FREE-RANGING ATLANTIC SPOTTED DOLPHINS (STENELLA FRONTALIS): AGE CLASSES, COLOR PHASES, AND FEMALE REPRODUCTION. Marine Mammal Science, 13: 576–595. doi: 10.1111/j.1748-7692.1997.tb00085.x
- Issue published online: 26 AUG 2006
- Article first published online: 26 AUG 2006
- Received: 9 January 1996; Accepted: 15 March 1996
- Stenella frontalis;
- spotted dolphin reproduction;
- age class;
- sex composition;
- sexual maturity;
- color phase
Atlantic spotted dolphins (Stenella frontalis) were observed underwater and from the surface from 1985 to 1996 and photographed through successive years. Individuals were categorized into age classes by their degree of spotting and color phases. Dolphins spent an average of 3 yr in the two-tone color phase, 5 yr in the speckled phase, 7 yr in the mottled phase and up to 10 yr or more in the fused phase.
Sex ratios were close to parity, with old adults skewed towards females and juveniles and young adults skewed towards males. The average calving interval for 24 females was 2.96 years with a range of 1–5 yr. Females whose calves survived the first year had a significantly longer calving interval (3.56 years). The ages of first parturition for five females were estimated to be 10–12 yr. The age at sexual maturation was estimated to range from 8 to 15 yr.
Pregnancy rate fluctuated annually, with an average rate of 0.25 (range 0.07–0.57). Annual average birth rate was 0.08 (range 0.07–0.14), average calf production was 0.33 (range 0.06–0.52), average fecundity was 0.23 (range 0.13–0.30), and average recruitment was 0.06 (range 0.03–0.08). Most females who lost a calf conceived the same or following year.
Lactation lasted up to 5 yr, and 45% of visibly pregnant females were also lactating. Age of first parturition was associated with the mottled color phase. Average first-year mortality rate of calves was 0.24.