How Do Gorillas Mate? Gorilla Breeding Guide
How do Gorillas Mate, Courtship and Reproduce
Today the largest living ape in the world is the Gorilla and these live within the verdant forests of Central as well as Eastern Africa. These largely herbivorous forest giants share approximately 98% of their DNA with man making them the closest living relative humans. There are two main species of the Gorilla (the Eastern gorilla and the Western gorilla) and each of these is comprised of two subspecies that is to say: the mountain gorillas and eastern lowland gorillas that make up the eastern gorillas, and then the cross river gorilla and the western lowland gorilla that make up the western gorilla. For more information about the types of Gorillas, you can check out article on Types of Gorillas in the world
Gorilla Groups and Family hierarchy
A typical gorilla group comprises of different family members that include infants, juveniles, adult males and females and then a dominant male who leads and guides the family/ group on what to do and where to go. They normally live in groups of about thirty (30) individuals, and it is worth mentioning that gorilla families are generally peaceful with just a few internal conflicts. Interactions among various gorilla groups are extremely rare despite the fact that these have been recorded among the western lowland subspecies. This explains why you cannot see all the gorillas in one park during your gorilla trekking experience. You can visit one gorilla family at a time. External confrontations by lone males or other groups may occur and these are generally very violent however with the help of other mature male gorillas in the group, the silverback is able to defend his family.
Breeding in Gorillas
According to the gorilla breeding customs, the females in a gorilla group are all breaded by the dominant male gorilla known as the silverback. Mating can happen all year around a process that is normally initiated by the females irrespective of whether they are in estrus or not. the western and the eastern gorillas are both known to mate while facing the same side however, instances of then doing it while facing each other have also been observed especially among the mountain gorillas.
When do Gorillas become Sexually Mature / Reproductive?
There are a number of factors that determine the mating habits of gorillas however, the best way to understanding this is by first comprehending the reproductive cycle of these forest giants. Between the age of 10 and 12, the female gorillas attain sexual maturity with the ovulation cycle beginning earlier at about six (6) years, however, the female stays infertile until 10 years when they are eventually mature. Interestingly a number of females leave their father’s group to prevent inbreeding, while those that don’t leave the group try as much as possible to avoid mating with their father. In fact they would to a certain extent mate with less subordinate males as research has proven.
On the other hand, because it’s the silverback that mates the females, once the males attain maturity, majority of them leave the group and go to become loners or group up with other bachelor gorillas and later begin stealing females from other groups.
Despite the fact that the dominant silverback creates very strong bonds with the females in his group, as he grows very old and his reproductive cycle is soon coming to an end, the female in the group begin leaving him to join other groups. The few that are loyal to him will stay however once that silverback dies they join other groups. In fact the females can change groups multiple times as way of protecting their off-springs especially in case of a new dominant silverback taking over.
How do Gorillas Mate?
Well this is a question that leaves many wildlife enthusiasts scratching their heads. Well as earlier mentioned mating can be done all year round with the dominant male silverback mating all the females while they are ovulating. The mating processing is normally initiated by the female when it is sexually active however there are instances when the dominant silverback male also imitates this process. He does so by advancing towards the female and then he touches her or makes a display with a sound. When the female doesn’t respond positively, he may not take that rejection well and instead charge while slapping the female as he forces her to accept.
Mating is done while both gorillas are on the ground with the female (which is normally smaller than the dominant silverback) appearing to kneel on the ground while the male is on top throughout the copulation. However as earlier mentioned a number of gorilla subspecies like the mountain gorilla and the lowland gorillas have on several occasions been observed mating while the male and female are facing each other a technique once believed to be unique among the human species and the bonobos (also known as the pygmy chimpanzee).
How to know that a female gorilla is ready to mate
Unlike their counterparts the chimpanzees, when it comes to female gorillas there is no physical body change to show that it is ready to mate. Normally, once the female is ready, it initiates the process of mating by gently approaching the male through pressing her lips together and making prolonged eye contact with him. during instances when the male does not respond to her advances, she then goes ahead to slap the ground as she moves towards the male as a way of attracting his attention. It should be noted that there are some moments when the male doesn’t respond positively to her or is too busy to attend to her, and then she is compelled to mate with less subordinate males within her gorilla group.
According to a study conducted in 1982, it was revealed that because of the aggression that a silverback exhibited towards a specific female, that female was compelled to initiate the mating process even when not in estrus.
Do Gorillas only Mate to Reproduce?
Generally speaking, besides reproduction, it is very unusual for Gorillas to mate / have sex for leisure or for competition among themselves. However, the females normally mate to win favor before the dominant silverback as well as to prevent him from mating with other female gorillas in the group. In fact instances of expectant female gorillas mating with the dominant silverback have been recorded and it’s alleged that they do so to prohibit the male from impregnating other adult females that are ready for mating. Amusingly in all subspecies of gorillas, the silverbacks prefer mating with the adult experienced females; while the interest and focus a dominant silverback gives to an ovulating female provokes competition among other female gorillas within that group. On the other hand, the male silverbacks within the western gorilla species have been observed to mate with females where they are ovulating or not, although the rest will have sex only with the sexually ready females.
Reproduction / Giving Birth and Parenthood
Once the mating is successful and the female conceives, she will experience an 8.5 month gestation period and only give birth again after approximately four (4) years. During the pregnancy, she will have a slight increase in breast size and also develop a bump on her tummy that is not very pronounced. They normally give birth in the morning hours and this is preceded by her appearing uneasy with continuous babies and only stretching and loss of appetite. Throughout her life, a female gorilla may give birth to only 6 to 8 babies but just a few of these will be able to survive to maturity as caretaking is totally done by the females. The Silverback male on the other hand has a major role of making sure that the babies are accepted within the gorilla group and not bullied by other group members and for that reason for the first 5 months of the mother lives close to him for protection.
Breastfeeding and Weaning among Gorillas
For the first four (4) months, the infant is carried around by the mother in her hands as he/she suckles directly every three (3) hours on the mother’s breasts. by the fifth (5) month, the infants have begun gaining confidence among the group members so they ride on the mother’s back and occasionally lay on the ground close by to their mothers. By 12 months (one year), the baby gorilla has attained enough confidence to move as far as five (5) meters away from the mother during brief intervals. By the second birth – date, he/she can spend some time away from the mother while further away but still return to the mother. Weaning among the gorillas normally takes place when the baby is about 2.5 years (30 months) old. Nonetheless, the baby gorilla will continue to breastfeed (nurse) until they are about four (4) years old, however, when they stop doing so, they begin making their own nests and live independent of the mother, while the mother starts all over again to ovulate.
Mortality in Infant Gorillas
Although the gorilla species is generally considered to be endangered internationally, its sad to say that the mortality rate among the infant gorillas is high with nearly half of them not making it to adulthood.
Causes of High Mortality Rate in Gorillas
There are a number of reasons for this high mortality ass highlighted below.
Since the baby gorillas greatly depend on the mothers for a long time, any change in group leadership especially takeover by a new silverback will lead to the death of all nursing infants. the new silverback normally does this to create opportunities of successful mating with the females in that group.
Trauma is believed to lead to 56% of all infant mortality
Respiratory Infections; these are alleged to lead to the death of nearly 15% infants
Different illnesses especially among the mountain gorillas are said to be another major contributor to infant mortality such as hepatic Capillariasis, gastrointestinal parasitism and lymphoid disease.