By : Zadani Nabila Ashari ( )

In the figure shows that distinguishing male and female sex in whales can be seen from their external reproductive organs. as if in a female, there is a vaginal opening and a mammary gland. Several species have female- biased sexual dimorphism, with the females being larger than the males.

 The female reproductive organs in the whales generally consist of a pair of parent eggs where to produce eggs and various hormones, a pair of Fallopian tubes (oviduct) which serve as a channel from the first egg to the largest or called uteri (the embryo develops), the vagina as the gate the outside of the body, and the cervix where as connecting the uterus and vagina.

 Cetacean corpora albicantia are thus unusual as in most other mammals they are gradually resorbed. It has been suggested that corpus albicans regression slows during active pregnancy because of the effects of hormones, although it is not clear why these structures fail to regress fully as in other mammals. Accessory corpora lutea may be found in the ovary ipsilateral to pregnancy. Ovaries may also contain other structures such as corpora atretica, corpora aberrantia, and cystic follicles, as well as cysts of unknown aetiology.

 Males typically mate with multiple females every year, but females only mate every two to three years.  Sexual activity occurs between pairs and in boisterous groups of several males and one or two females. Breeding season is observed from March through August; conception is believed to occur primarily in March when song activity is at its highest.  Reproduction can begin when a whale is 10 to 15 years old. The gestation period is 13–14 months with females producing a calf once every three to four years.[19] Lactation typically lasts about a year. To survive in the cold water immediately after birth, calves are born with a thick layer of blubber. Within 30 minutes of birth, bowhead calves are able to swim on their own. A newborn calf is typically 4– 4.5 m (13–15 ft) long, weighs approximately 1,000 kg (2,200 lb), and grows to 8.2 m (27 ft) within the first year.

 Lactation in cetaceans may be an extended process. Cetacean mammary glands are elongate narrow flat organs extending in the subcutaneous connective tissue on either side of the ventral midline. Offspring are suckled at two mammary slits positioned ventrally on either side of the midline just forward of the vulva, each of which contains a nipple. Cetacean milk is thick and creamy, may appear yellowish and has a high fat content ranging from 14 to 53% (Lockyer, 1984a, 1987a, 1993). Lactation and suckling together will suppress oestrus in cetaceans.