We all wish Kamba her own baby. Not only because she has had bad luck, but also because she is also so nice and loving towards both of the little ones in the pavilion.
Unfortunately, we can't reverse natural processes and the time is running out for her - Kamba turns 36 this
year. The fact is that after her miscarriage, the keepers observed only one attempt by Richard to mate her. All those
reasons and the hierarchy of the troop makes us call Kamba a "granny". However, she would most likely consider such a
label rather insulting, I guess.
The question is whether gorillas are affected by the process of hormonal change known in human females as perimenopause, which leads to the menopause or climacteric - an end of the menstrual cycle and a complete loss of fertility. The climacteric is perceived as a purely human phenomenon but it would be surprising if there were not an analogue in our close relatives.
They may not suffer from hot flushes, mood changes, or incapacitating migraines, but a research conducted in many zoological gardens across the United States showed that gorillas do undergo a menopause. The research was directed by primatologist Sylvia Atsalis from the Brookfield Zoo in Chicago. Conclusions of the study pointed to health problems of ageing gorilla females but also explained certain mechanisms behind the human climacteric, and indisputably proved a close relation between apes and humans.
The research started in 2002 and lasted more than three years. The primary reason for the research was the
behaviour of female gorilla Alpha from the Brookfield Zoo. She was born in 1961, her conception was undesirable, and
vets were not sure whether to prescribe contraceptive pills or not. Alpha continued to show strong interest in mating
with silver-backed male Ramar. Regularly once a month, she would sit before him ostentatiously, look at him
seductively and try to sit in his lap. However, the keepers feared she would not be able to care for a young properly
due to her age.
The first menstruation occurs in gorillas around age 6 but young gorillas remain infertile approximately for
another two years. The cycle takes 30 to 33 days and is accompanied by minor menorrhoea and inconspicuous signs of
ovulation. Gorillas can live in captivity for 50 or more years but a healthy baby from a mother after age 37 is rare.
The problem with Alpha inspired an experiment involving 30 elderly female gorillas in 17 zoos across the US. Scientists monitored their hormonal cycles - collected excrement samples for lab tests of progesterone levels, a hormone necessary for the reproductive cycle to function properly. The results showed that 24 % of the animals were in menopause, i.e. their menstrual cycles had died away. Another 32 % showed signs of perimenopause - on human scales, this is a period that women undergo 5 to 10 years before menopause, when hormonal changes start to manifest. At that time, Alpha still menstruated but showed signs of perimenopause. She was not prescribed contraception in the end because the probability of conception was very low.
Female gorillas, like women, lose fertility with age. Scientists were surprised to find clear parallels between gorillas and humans in this respect. The research helped them better understand physiological changes that accompany menopause as well as the diseases that may occur due to changes in hormonal levels. Climacteric in humans is largely unexplored and unpredictable. It is a period when people need to protect their health against the risk of osteoporosis and cardiovascular diseases. The main question regarding menopause is whether it provides the affected species with an evolutionary advantage or whether it is a secondary effect of longevity. There are few animal species that outlive their reproductive cycle. Besides some primates, we know of only one other species, the pilot whale, which is a relative of dauphins. All the species in which menopause occurs have very long childhood because they need to learn a lot. Gorillas become adult at age 7, orangutans even later (young orangutans stay with the mother for 8 to 10 years). Obviously, it takes humans the longest to rear their children (as long as they can stand!). One explanation is at hand - it might be a wise measure to ensure that even the last young has a strong, viable mother it needs and deserves. By the way, the aforementioned pilot whale fits the theory as well, because it breast feeds the young for a full two yours.
Don't forget to check the latest edition of The Revealed Plus from Thursday, August 7, which was called "Gorillas and Twigs".
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