Patterns of growth in wild bottlenose dolphins, Tursiops truncatus

Abstract

The growth of bottlenose dolphins is described from observations made during a capture release programme that has operated in coastal waters of the eastern Gulf of Mexico from 1970 to the present. Measurements of standard length, girth and body mass were recorded from 47 female and 49 male dolphins, some captured as many as nine times. Ages were known from approximate birth dates or estimated from counts of dentinal growth layers. In all three measurements. females grew at a faster initial rate than males, but reached asymptotic size at an earlier age. This extended period of growth in males resulted in significant sexual dimorphism in length, girth and mass at physical maturity. The growth of both sexes was well described by three‐parameter Gompertz models using either cross‐sectional data or a mixture of longitudinal and cross‐sectional data. There was considerable variation in size‐at‐age for both sexes in all year classes. Residuals of size measurements were used to derive measures of relative size for individual dolphins; most dolphins demonstrated little ontogenetic change in relative size. Body mass was adequately predicted by multiple regression equations that incorporated both length and girth as independent variables.

Reproduction, Growth and Development in Captive Beluga (Delphinapterus leucas)

“…Indeed, sexually dimorphic growth patterns in cetaceans are not lacking from the literature [Best, 1970;Christensen, 1984;Cockcroft and Ross, 1990;Read et al, 1993]. Analyses of growth in total body length in the present study were consistent with those seen in wild beluga [Burns and Seaman, 1986;Doidge, 1990;HeideJorgensen and Teilmann, 1994] in that adult males were larger than females, but grow at a slower rate.…”

“…Previous investigators describing growth in other cetacean species have experienced similar paradoxes, albeit when describing body length and not weight [Best, 1970;Christensen, 1984;Duffield and Miller, 1988;Cockcroft and Ross, 1990;Read et al, 1993;Read and Tolley, 1997]. In general, two hypotheses are presented to explain this disparity.…”

“…The Gompertz model provided an adequate fit as evidenced by an examination of the residuals. Additionally, due to the prevalence of this particular model in cetacean age and growth studies [Perrin and Henderson, 1984;Doidge, 1990;Read and Gaskin, 1990;Read et al, 1993;Ferrero and Walker, 1995;Fernandez and Hohn, 1998], we concluded its use for this dataset would be most appropriate because it would allow intraspecific comparison of growth parameters to those currently in the literature [Doide, 1990;Heide-Jrgensen and Teilmann, 1994]. The specific form of the Gompertz model used was taken from Fitzhugh [1975] …”

Congenital Scoliosis of a Bottlenose Dolphin

“…The trunk length (TL minus skull length) was compared with animals from similar size ranges. MML0535's trunk length of 177 cm was well below the distribution of similar-aged animals and is comparable to the 4-yr-old age class (Read et al, 1993). The pattern of deformity included sequences of hemivertebrae (formation defects; Fig.…”

Morphometric relationships of franciscana dolphin, Pontoporia blainvillei (Cetacea), off Rio Grande do Sul coast, southern Brazil

“…Steller sea lions, Eumetopias jubatus, Castellini and Calkins (1993); northern elephant seals, Mirounga angustirotris, Haley et al (1991); southern elephant seals, Mirounga leonina, Bell et al (1997); Weddell seals, Leptonychotes weddellii, Ireland et al (2006)) and cetaceans (fin and sei whales, Balaenoptera physalus and B. borealis, Lockyer and Waters (1986); bottlenose dolphins, Tursiops truncatus, Read et al (1993); harbour porpoises, Phocoena phocoena, Lockyer (1995); Read and Tolley (1997); killer whales, Orcinus orca, Clark et al (2000); estuarine dolphins, Sotalia guianensis, Rosas et al (2003)). In the case of the franciscana, mass estimation models can be found in the literature, but consist solely of simple regressions of mass versus total length (Kasuya and Brownell, 1979;Rosas, 2000;Rodriguez et al, 2002;Botta, 2005) and do not account for seasonal or developmental variations in body mass.…”