Reproduction - Mating Systems

      There are no actual seasons of chimpanzee reproduction. They mate throughout the year when the females are receptive. However, there are cycles where the females are infertile. Some of these cycles include the period of adolescent sterility, during pregnancy and early in the postpartum period. But that doesn’t stop the male chimps from mating with them. They’ll mate with them regardless of what kind of period the female is going through.    

       The female fertile period last about 36 days, which includes four main phases. The anogenital swelling increases when the hormone level increases in the female. The four main phases include “inflation,” “maximal tumescence,” detumescence,” and “flat.” Inflation is where the swelling increases. Maximal tumescence is where the sexual skin is fully distended. Detumescence is where the previously swollen skin looses all turgidity. And finally, flat is where there is no swelling in the anogenital area. Menstruation lasts about 3 days. It occurs nine days after detumescence. And lastly, on the last day of maximal tumescence, ovulation occurs.  

       Since the mother has to take care of her offspring, feed it milk and protect it, females don’t reproduce frequently. The intervals of interbirth vary from each community. The community usually decided they intervals of interbirth for the female chimps.  

      The average interbirth intervals include 3 to 6 years. The average days of the gestation period are about 230 days. A typical baby chimpanzee ways about 2kg and the weight often wouldn’t be any more than that because twins are rare. From 3 to 6 months, the baby is carried ventrally b the mother. After this period and the infants grow, they maybe carried on the back also until they are about 3.5 to 4.5 years old.  

      There is hardly any independence between chimpanzees. They are very social. Chimps that are just born can survive without their mothers and orphan chimps would be adopted by relative chimps that would take care of them like a mother. The young chimpanzees usually stick with their mothers until they hit puberty which about when they are 7 -10 years old. When females hit puberty, they are mostly interested in sex parties and when males hit puberty, they are interested in pride and dominance. The female chimps move into to neighbouring communities when they go through the period of adolescent sterility.

      Female chimpanzees usually give birth to their first offspring between the ages of 11 and 23 years. The age usually depends on where the chimpanzees come from. In Tanzania, the ages are 14.5 to 15 years. There even chimps in some communities that give birth at 7.5 years old.  

      Male chimps enter puberty at the same time as female chimps. But that does not mean they have sex after puberty. Male chimps mate anytime they copulate with a female, even at an infant stage. But it doesn’t lead to impregnation. Male chimpanzees mostly begin to ejaculate at the age of 9 and aren’t men until the age of 15.

      The ages of chimpanzees categorizes them. From o – 5 years, chimps are infants. From 5 – 7 years, chimpanzees are called juveniles. From 7 – 10 years (7 – 12 for males), chimps are called adolescents. From 10 – 13years, the female chimps are called sub-adults. Males are called sub-adults from 12 – 15 years. Females are fully grown adults at 13 years and males are fully grown at 15 years.