Investigation of growth phases for bottlenose dolphins using a Bayesian modeling approach

Abstract

The Gompertz function is the most commonly used growth function for cetacean studies. However, this function cannot represent multiple phases of growth. In this study, we present a Bayesian framework fitting parameters of a triple‐logistic growth function to describe multiple phases of growth for bottlenose dolphins (Tursiops truncatus), simultaneously fitting and comparing all growth parameters between South Carolina (SC), Mississippi Sound (MSS), and Indian River Lagoon (IRL) cohorts. The fitted functions indicated a preliminary early, rapid growth phase, followed by a second phase of slower growth, and then a moderate growth spurt later in life. Growth parameters between geographic cohorts did not show obvious differences, although asymptotic length for SC dolphins was lower than MSS and IRL dolphins and significantly lower between females from SC and the IRL. Growth rate velocities between the sexes showed females exceed males initially (<1 yr), followed by males gaining an advantage around the ages of 3–4 yr until the age of around 15 yr when growth rates for both sexes approached zero (asymptotic length). This study demonstrates age‐related changes in growth rates between bottlenose dolphin sexes and evidence of at least some differences (i.e., asymptotic length) across geographic cohorts.

Small dolphins in a small sea: age, growth and life‑history aspects of the Black Sea common bottlenose dolphin Tursiops truncatus

“…The maximum age recorded in our sample (41 yr) is significantly older than that reported by Glazov & Lyamin (2000) (19 yr) and Karaçam et al (1990) (26 yr), but is similar to the estimates in other regions of the world (McFee et al 2010).…”

Growth of the skull of the bottlenose dolphin, Tursiops truncatus, in the Southwest Atlantic Ocean

“…Studies of the age-length relationship on this species in different areas of the western North Atlantic and Gulf of Mexico (Hohn, 1980;Cockcroft and Ross, 1990a;Mead and Potter, 1990;Fernandez and Hohn, 1998;Mattson et al, 2006, McFee et al, 2010 found a remarkable reduction in the growth rates after the fourth year of life. In the present work almost all measurements were still growing in the first two years of life; 91% have stopped at age 4 and only one (ARTPROWD) continued growing after age 5.…”

“…bottlenose dolphin total body length has been mathematically described using many different models (e.g. Fernandez and Hohn, 1998;Mattson et al, 2006;Siciliano et al, 2007;McFee et al, 2010), no study has used mathematical equations to model skull growth. From an initial screening of the data it was clear that different measurements exhibited different patterns of growth.…”

Small size in the common bottlenose dolphin ­Tursiops truncatus in the eastern Mediterranean: a possible case of Levantine nanism

“…Most studies (i.e. Read et al 1993, Fernandez & Hohn 1998, McFee et al 2010 found mature males to be ~10 cm longer than females. The reason for the absence of any evidence for sexual dimorphism in our study may be that the sample sizes studied here were too small to reveal such a difference (a trend of males being longer than females was seen in TBL of the Israeli and Spanish, but not of the French sample group; data not shown).…”

“…Differences in primary productivity and subsequently resource availability could explain some of the body size variation in BDs on a worldwide scale. For example, the Gulf of Mexico with the adjoining Atlantic waters is an oligotrophic basin with primary production generally comparable with that of the Mediterranean (Pennock et al 1999), and BDs in this region generally do not exceed the size of their Mediterranean conspecifics (McFee et al 2010), while BDs in the eutrophic waters of the northwest Pacific or northeast Atlantic are remarkably large (Wells & Scott 2009). Thus, food resource availability can stand as a working hypothesis for BD nanism in the Levantine Basin.…”