Early physical maturation of female common bottlenose dolphin Tursiops truncatus in the eastern Levantine Basin

Abstract

Regional resource limitation in the eastern Levantine Basin was predicted to protract the growth of members of the Israeli sub-population of the common bottlenose dolphin (CBD), compared to CBD sub-populations of similar adult size. Growth curves were fitted to length-at-age data available for 24 male and 26 female CBD stranded or incidentally caught along the Israeli coastline between 2000 and 2009. The obtained model growth constants were compared to those of other CBD sub-populations from the southeastern coast of the United States and a correlation to regional seawater primary productivity was sought. As in other sub-populations, local CBD females initially grow faster than males for approximately 3–4 years and remain longer until around eight years old, after which males surpass them in length. Yet the steep early growth of females as well as its high rate of decay was found to be extreme compared to other CBD sub-populations, with 99% of the asymptotic length being reached at the age of six years. A positive correlation between seawater primary productivity and early growth rate as well as growth decay constants could be demonstrated for CBD males from Texas, Florida and Israeli coasts. Females of the same sub-population presented a non-monotonic relationship to primary productivity. Early female attainment of physical maturity in an ultra-oligotrophic region was unpredicted and is not readily explained. It may accompany early reproductive maturation, selected for as partial compensation for lower lifelong reproductive success.