Suture Index and Growth in the Male South African Fur Seal, Arctocephalus pusillus (Pinnipedia: Otariidae)

The South African furs seal (Arctocephalus pusillus pusillus) is very closely related to the Australian fur seal (A. pusillus doriferus). We examine the relationship between skull suture index (S1*) and growth parameters in the male South African fur seal, basted on 42 animals of known age ranging from 10 m to 11 y 11 m. Twenty one (21) animals were aged based upon tagging as pups and 21 were aged based on dentine growth layets (1 to 11 y). Suture index and morphomctric information was available on an additional 27 males; 17 had no age information but 10 were known from their dentition to be >= 12 y. Age has previously been found to be approximately directly proportional to suture index. Here we estimate asymptotic size and growth kinetics from S1* using nonlinear growth models [exponential saturation (von Bertalanffy), Logistic, Gompertz] fitted to cross-sectional morphometric data (n 8 variables). The relationship between the following measurements was examined and suture index are presented in the present study: external body (standard body length, SBL; length of front flipper; length of hind flipper), skull (condylobasal length. CBL; Bizygomatic breadth; mastoid breadth; length of Mandible or Ramus length) and baculum (bacular length, BL). The asymptote values of these parameters are compared to those derived from chronological age and show very good agreement. The growth kinetic parameters calculated in terms of S1* when converted into years using the relationship between S1* and true Age (y) are also in close agreement with those calculated on tag and dentition aged animals.