Heat or Estrus Period Elephant seal（热或发情周期象海豹）.pdfVIP

Everything you wanted to know about Northern Elephant Seals reproduction but refused to ask. Heat or Estrus Period It is not clear how males detect estrus in females. It doesn’t appear that scent is involved. For research purposes, and since there are no visible signs, scientists define estrus as the time between the first and last mating of the season. Depending on the female this is usually the last week of nursing 1,2,3, and more than one male may be involved 4 . Note that mating means actual copulation, not attempted matings that may occur at any time the female is on the beach 2 . Breeding Typically females are sexually mature at 2 years of age; the most common age for a first birth is four.5 Males do not court or investigate the perineal area of the female prior to mounting; they seem to be testing the receptivity of the female. They mount from one side without any preliminaries and seemingly attempt to overpower the female. Males use the great bulk and weight of their forequarters, a fore-flipper clasp, and a neck bite to restrain the animal. They mount pregnant females, those giving birth, females soon after birth, and females in estrus. Only the frequency not the form of these mating attempts varies with estrus. A mount may end in copulation; by the mounter being repulsed by an alpha; or simply because the male ceases the attempt.4 Females respond to male mounts by active protest or passive acceptance. A female protests by issuing a virtually continuous train of vocal threats and by whipping her hindquarters vigorously from side to side. Because of their relative positions her rear flippers often strike near the males penile opening. She may also flip sand directly at the males head and face, nip his neck, or struggle to get away. Alternatively the female may remain passive throughout the mount or may facilitate by spreading her hind flippers. Females were