Contents — Continued 



Page 



Age at Sexual Maturity 179 



Males 179 



Females 181 



Annual Reproductive Cycle 182 



Testis cycle 182 



Ovarian cycle 188 



Time of mating 191 



Breeding Behavior 192 



Pregnancy 194 



Time of implantation 195 



Growth of fetus 197 



Fetal sex ratio 199 



Time of birth 199 



Newborn Calf and Its Environment 201 



Physical conditions 201 



Maternal-Neonatal behavior 201 



Postpartum Involution of Uterus and Corpus Luteum 204 



Reproductive Performance 204 



Rate of ovulation 204 



Fecundity 209 



Morbidity and Mortality 211 



Fetal and Calf Mortality 213 



Predation 214 



Polar bear 214 



Killer whale 216 



Harvests by man 220 



Intraspecific Traumatization 223 



Damages caused by tusk strikes 224 



Mortality due to trampling 226 



Parasitism 228 



Ectoparasites 228 



Endoparasites 229 



Microbiological Infections 230 



Dermatomycosis 230 



Pulpitis of the tusks 231 



Conjunctivitis 233 



Urethritis 233 



Pleuritis 233 



Pneumonia-Pneumonitis 233 



Subdermal bullae 234 



Leptospirosis and San Miguel sea lion virus 234 



Miscellaneous Nonspecific Conditions 235 



Aneurysm 235 



Uterine tumors 235 



Cystic ovaries 237 



iv 



