Reproductive biology

Reproductive cycles are often closely linked to the annual rainfall pattern so that, in regions with distinct rainy and dry seasons, births often peak in or near the rains. However, several species show no marked seasonal peak in breeding, for example, the Arabian oryx and the beisa oryx produce calves in any month, while roan produce a calf about every 10.5 months.

All Hippotraginae species bear single offspring, although waterbuck occasionally have twins. Estrus lasts for a day in territorial species and several days or more in non-territorial species. Gestation is 8-9 months in larger species and 6.5-8 months in the smaller species, but the gray rhebok has a nine-month gestation period.

In most species, the female leaves the herd or family group to give birth. Most species produce relatively helpless young that lie hidden for a period varying from only 1-2 days (impala) to two months or more (reedbucks). However, female wildebeest bear calves within the herd and the young can run a few minutes after birth. Young tsessebe (Damaliscus l. luna-tus) are also able to keep up with the herd from shortly after birth.

Females return to hidden calves to suckle them. In herding species, calves associate together when they rejoin the herd, returning to the mother for nursing and in emergen-

A common reedbuck (Redunca arundinum). (Photo by © Image Ideas, Inc./PictureQuest. Reproduced by permission.)

cies. In most species, weaning takes place at 6-8 months, but blesbok, topi (Damaliscus lunatus jimela), and black wildebeest are weaned at four months. Addax and scimitar-horned oryx, which live in very arid environments where water is at a premium, wean their young at only 3.5 months. In contrast, young Lichtenstein's hartebeest are not weaned until they are 12 months old.

In most species, females begin breeding when 1-2 years old. Males may be sexually mature at 18 months to 2 years, but often have to wait for several more years before they can occupy a territory; they do not breed until 4-6 years of age. Longevity varies with species, being about 10 years in some (e.g., reedbuck) and reaching 20 years in the black wildebeest, scimitar-horned oryx, and Lichtenstein's hartebeest.

Pregnancy And Childbirth

Pregnancy And Childbirth

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