Gorilla Family Formation
- Mountain gorillas form up groups in four major ways;
- Group fissioning
- Females transfer to solitary males
- Emmerger of immature males
- Disintegration of the group
Group fissioning
This refers to when the multi male family splits to form two families, this may be as a result of frequent fights in the family due to attempt of trying to overtake the dominant male by the subordinate males and also heterosexual families can also fission because within the family there are always females who are more close, friendly and loyal to the subordinate males hence giving room for sneaked mating thus creating a strong bond between the females and subordinate Silverbacks , this bonds can make the subordinate males to always feel comfortable and move away with those females hence splitting the family . This happened in 2002 in Bwindi impenetrable national Park when Habiyanja family split to form Rushegura family and interesting is that when these two groups meet they don’t engage themselves into fighting because they are related but also gives a chance for females to transfer from one family to another , females can repeatedly transfer and change families throughout their lifetime . Females in these two families have always been seen transferring from one to the other. In 2010 Nshongi family fissioned to form Mishaya family. Bweza family and Kahungye gorilla family has always been observed fissioning for even more than one month and rejoins again.
Transfer of female to the solitary males
This is a common habit among the sub adult females at the age of 6-8 years of age who are now sexually active and may be fearing to inbreed with their fathers so such females always transfer from one family to another and sometimes they transfer to the lonely males and these solitary males sometimes involve themselves into fights and the due course some females switch and join them hence forming up a group.
Emmerger of immature males
This always happens with the black backs and the young silverbacks between the age of 10- 12, and 13 -15 respectively. This happens majorly due to no tolerance from the dominant male of the family, so these young males may decide to leave their natal group and become solitary and in the due course they may join themselves hence forming up a all male group hence making it easy for them to engage in a fight with different families hence absorbing females to join them
Gorilla family Disintegrations
This always happens in a one male group when the silverback dies, the females and the infants may disintegrate hence joining the solitary males or even other groups with the silverbacks because after the death of the alpha male the females will be left with no defense for themselves and vulnerable which makes it easy for the family to disintegrate since females are in search for males to mate with and also for their protection and some females may join the solitary males hence forming up a family.
The average size of the mountain gorilla family is 12 gorillas but there are always a lot of variations, to the extent that the group size may range from 2 to 30 individuals or even more. The largest group size ever observed in Bwindi impenetrable national Park was Nshongi group with 36 members with 7 silverbacks which later in 2010 fissioned to form various groups and currently has only 13 individuals.
The mountain gorilla group always consists of the dominant silverback, adult females, and various immature offspring of various ages.
Infants from 0-3.5 Years of age
Infants are generally dependent on their mother’s breast milk for their survival but this way of survival keeps on declining as the infant gets older. The infants always keep constant physical contact with their mothers for approximately the first 9 month of their lives, after this period the contact between the infants and their mothers keeps on declining as the infant starts to feed on the vegetation. The infants are carried by their mothers regularly until they are about two years of age.
Initially they are carried on their mothers chest from the time of birth until when they are 9 month old then later shifted to the back when they are about to make one year of age. The infants share night nests with their mothers as they are not in position to make their own nests, when the infant is about to make three years they start to learn how to make their own nests, this mainly happens during the day when they are resting. The infants are generally curious and playful as they prefer swinging on plants, as one way of learning how to climb trees, this helps them to strengthen their body muscles. The mothers with unweaned infants prefer to keep close to the alpha male; this is majorly for safety and protection for their infants. The infants are nursed by their mothers until they are at the age of 3.5 years and sometimes up to four years when they turn to be juveniles then they get displaced and on certain occasions some of the infants even after becoming juveniles may continue being nursed, sleeping with their mothers until when they are displaced by the birth of the new born baby. The rare case was witnessed in Mgahinga gorilla national park in Nyakagezi gorilla family, where by both the infant and the juvenile, who are of the same mother, they were all breast feeding from their mother.
Juveniles from 3.5 to 6 years
Juveniles are immature gorillas that are still heavily dependent on their mothers but they can survive on their own in case the mother dies or the mother transfers to another family. This is because they have stopped nursing and they are capable of living their own life. Juveniles basically feed on vegetation for their survival and they are able to climb trees to look for food, they can construct their own nests for the night despite the fact that those whose mothers haven’t given birth yet can still share the night nest with their mothers. If the mother gives birth, the juveniles tend to be too close to their mothers and the newborn infants and as the infants grow, the juvenile will keep playing with that infant most of the time. Juveniles have also been observed helping their mothers to carry the babies mainly during the resting time when the family members are taking a rest
Sub Adults 6-8 years
These are immature gorillas that are fully independent from their mothers but they are not yet fully grown adults. At this stage the females get sexually active but they cannot conceive because in this period they undergo adolescents’ infertility whereby they can mate with the males but they can’t get pregnant. Females at this stage prefer to switch families or move away from their natal family mainly to avoid in- breeding . This happens when two different families meet; these immature females tend to utilize the chance to join another family. In a multi male family this stage is where there is a high rate of mating between the immature females and subordinate males. Subadults play much less compared to the juveniles and infants in the family.
Adult females 9 years and above
These are females who are reproductively mature, and even though they are yet to have their first off spring they can mate and conceive their first pregnancy. these females weigh approximately 100 kgs. An adult female is estimated to feed in between 10- 18 kgs of food on a daily basis. An adult female in her entire life is estimated to produce about 6 offspring. Female gorillas may live until their late 40’s or early 50’s but sometimes longer. An adult female is able to lead the family in case the alpha male has some illness, this was observed in mishaya family in 2020 where by the alpha male sustained Serious injuries and went missing for nearly two months and one of the alpha females led the family until when the alpha male returned to the family. So, these females are capable of the family leadership as well. In most cases females in the family are not related this is because they tend to switch families when they are getting sexually active but still sisters can all transfer to one family .in this stage is where some females can become solitary because one might have grown too old and fails to walk together with the rest of the family members as her pace tends to be so slow.
Black backs 8 – 12 years
These are males that have started the process of becoming mature males of the family, black backs always tend to be smaller as the size of an adult female but they continue to grow larger. They appear bigger than the adult females, as the black backs mature their hair starts to change slowly into silver hair and the head develops into a large sagittal Crest. At this age they are able to lead the family In case the alpha male dies but it depends on how brave and strong he is for example kabukoyo the current silverback of Rushegura family took over the leadership when he was still a black back in 2014 after the death of the dominant silverback (Mwirima) they are also sexually active as they will keep sneaking a way the females to mate with them, they also oftenly exercise mating with the subadult females who will also be sexually active. They help the alpha male to defend the family in case of an attack from another male. In most cases they are the ones who keep on fighting while the alpha male moves away with the females. Amongst gorillas it is at this stage that the males prefer to leave a natal group and live a solitary life. This happens mainly due to failure to tolerate the behavior of the alpha male besides it is one way of getting a chance to come back to challenge the alpha male over dominance of the family. It should be noted that not all males become alpha males as this will require one to be strong enough and intelligent to challenge the alpha. In this age the relationship between Blackback and the alpha male of the family is not always positive as the alpha male may always keep punishing them and this makes them to get scared of the alpha and end up leaving the family or come from behind the family or a side of the family but while maintaining the distance with the alpha male. Blackbacks weigh around 100- 150 kgs. Blackbacks are muscularly strong enough to defend themselves and their families against attack.
Silverback males at the age of 12 and above
These are adult males who are fully sexually active and are able to mate and reproduce when they mate with the females in the family and they are also able to take full responsibility of the family. All males by the age of 12-15 years tend to develop silver hair on their back hence the name silverback. The process of becoming a silverback takes a few years from the age of a black back and the males don’t attain their full body size until the age of 15years.
https://youtu.be/rh9PwFvMS0I?si=xqyo9XyAeeNdYtGB
Mature males are majorly characterized by large sagittal rest on their head and they can nearly double the size of the females and the silver hair on their back. It should be noted that not all males which develop silver hair will obtain families to lead, some may remain and live in their natal families and be subordinates to the alpha male of the family that they are born from or others can decide to opt to live a solitary life outside the natal family as a way of trying to develop their confidence to come back to challenge the alpha male of the natal family over the dominance of the family