BACULAR AND TESTICULAR GROWTH, ALLOMETRY, AND VARIATION IN THE HARP SEAL (PAGOPHILUS-GROENLANDICUS)

We investigated quantitative relationships of bacular size to age, len gth of body, and testicular size in the harp seal (Pagophilus groenlan dicus), based on collections made in the northwestern Atlantic from 19 85 to 1992. Bacular growth was faster than growth in length of body ex cept in old seals (>9 years of age), in which relative growth was isom etric. A pubertal spurt in growth in bacular size occurred between 3 a nd 4 years of age when length increased by 48.3%, mass by 331%, and de nsity by 185%. Concurrently, length of body showed a spurt in growth o f 7.2%. Bacular length reached 90% of its asymptotic size of 17.4 cm a t ca. 9 years of age, and bacular mass reached that point relative to its asymptote (49.6 g) later at ca. 20 years. In contrast, length of b ody reached 90% of asymptotic size (176 cm) at only 5-6 years of age. In old seals, bacular length was correlated positively with length of body and age independently. It averaged 9.9% of length of body in old seals. Bacular size was variable: CV = 8.3% for bacular length and 32. 8% for bacular mass in old seals. Testicular size peaked in February a nd March. For young seals (less than or equal to 9 years old), growth in bacular length was isometric, and growth in bacular mass was positi vely allometric relative to testicular length and mass. In contrast, t esticular length and mass of breeding old seals were not correlated si gnificantly with bacular size, length of body, or age. In breeding old seals, testes averaged 10.1 cm in length (range = 7.4-13.2 cm, CV = 1 0.9%) and 128 g in mass (range = 60.6-204 g, CV = 24.9%), and testicul ar length averaged 5.7% of length of body. Variation in bacular and te sticular size suggests that males have variable reproductive strategie s. Comparative analyses on phocid species with known mating systems ar e needed to test this interpretation.