Giraffes breed all year round, although peak births have been observed in many populations including Nairobi N.P. in Kenya- August and September, Waza N.P. in Cameroon (November-January when acacia blooms, Serengeti N.P. (September ) and northern Namibia, December; Found at different times of the year in the same area (e.g. Kruger N. P.).
Calving peaks are often associated with rain in juvenile protein-rich acacias suggesting that differences in ecological conditions lead to variability in mating strategies. Captive giraffes also breed seasonally. Only one calf was born, although two twins were recorded.
The average gestation period is approximately 457 days or 15 months; One captive individual gave birth to consecutive pups just 420 days apart. The young weigh more in the wild (about 101 kg) than those in captivity (55 kg). The average birth size is 1.8 m and 1.9 m.
Juveniles are almost double in size in the first year, i.e.this will likely serve as a strategy against predation, as juveniles are extremely vulnerable to predation.
Giraffe milk is high in fat 13 to 17% and protein 6%, despite the concentration of lactose that male and female calves suckle at the same rhythm. The timing of weaning varies: exceptionally up to two years, but usually between 9 and 12 months, although calves may begin eating solid food by the third or fourth week and begin hatching between three and four months.
Calving intervals are 19 to 20 months. Rates are similar in captivity, ranging from 14 to 38 months. The time between delivery and conception is usually 4 to 9 months. The first conception was at 50 months in Serengeti N.P. and 56 months in Southern Africa. In captivity, the mean age at first calving was 57 months.
Sex ratios between adults have been documented in Serengeti N.P., Nairobi N.P., Katavi N.P. were more females., Luangwa N.P. and in Niger, while in Tsavo East N.P..In northern Namibia, male to female ratios differed between subpopulations, although they were the same in the general population The sex ratio at birth is 1:1.
Limited research limits any true assessment of such variation. Between 54% and 62% of a given population is over the age of 4. Mortality rates are mostly based on Lion Panthera and are strongly influenced by depression, particularly in newborns. In Serengeti National Park, 58% of young giraffes died in their first year of life, while only 2% died by the age of four.
The maximum lifespan of male giraffes, based on individuals from Luangwa Valley, is shorter in males (22 years) compared with females (28 years); maximum longevity in captivity is recorded at 39 years.