Gorillas are our close cousins in the animal kingdom, sharing over 90% of our DNA. As highly intelligent and social primates, their behaviors and physiology invite comparisons to our own. A question that often arises is – do gorillas menstruate and have periods like human females?
Read on as we take a comprehensive look at the reproductive health and cycles of our hairy relatives.
If you’re short on time, here’s a quick answer: Yes, female gorillas do have menstrual cycles and periods similar to human women lasting around 30 days. However, gorillas do not bleed as heavily as humans and instead reabsorb much of the uterine lining.
The Menstrual Cycle of Gorillas
Length and Regularity of Gorilla Periods
Female gorillas experience menstrual cycles that are similar in length to those of human females. On average, gorilla periods last around 28-30 days, though there can be some variation between individuals. The menstrual flow typically lasts between 3-8 days.
Gorillas tend to experience regular monthly menstrual cycles once they reach sexual maturity. Female gorillas become sexually mature a bit earlier than males, starting their periods around 8-10 years old. Their cycles continue until menopause, which occurs around age 40.
Bleeding and Discharge During Gorilla Menstruation
When gorillas are menstruating, they experience bleeding and discharge from the vagina, just like human females during their periods. The amount of bleeding can vary each cycle and between individual gorillas. Heavier flows are more common among mature, adult females.
Some observable signs that a gorilla is going through her menstrual period may include:
- Visible blood on the fur around her genital region
- Increased frequency of genital self-grooming
- Swollen or reddened genitals
- Changes in nesting behaviors, such as building fresh nests more frequently
Gorillas tend to be quite secretive about menstruation and will isolate themselves from social groups when menstruating. They often consume the bloody discharge rather than leaving evidence behind.
Tracking Reproductive Status and Fertility
For gorilla conservation efforts, researchers track the menstrual cycles of female gorillas to gather data about reproduction, fertility, and overall health. Cycle monitoring helps identify optimal mating periods and factors impacting fertility and fecundity in gorilla populations.
Some methods used to monitor gorilla reproductive status include:
- Direct visual inspection of menstruation
- Fecal hormone analysis to estimate ovarian cycle stage
- Observing physical and behavioral changes (e.g. sexual swelling, nesting habits)
- Keepers recording information on captive gorillas’ periods
Understanding gorilla reproductive physiology through menstrual cycle tracking allows for better management of mating, pregnancies, and overall gorilla health and welfare.
Gorilla Reproduction and Gestation
Mating Habits and Behaviors
Gorillas live in family groups led by a dominant silverback male. When a female gorilla reaches maturity at around 8-10 years old, the silverback will mount and mate with her to show his dominance. Mating occurs all year, with females giving birth around every 4 years.
Gorillas do not have “periods” or menstruation like humans, but they do experience estrous cycles where they are most fertile for mating.
During mating, the male gorilla will repeatedly mount the female over several days to ensure impregnation. Gorillas are mostly monogamous, with the one silverback male mating with several females in his harem group.
However, when a new silverback takes over a family, he may kill any existing infant gorillas to bring the females into estrous sooner so he can sire his own offspring.
Pregnancy and Gestation Period
The gestation period for gorillas is 8.5 months on average, which is similar to humans. Pregnancies are generally single births, with twins being rare. Towards the end of her pregnancy, the expectant gorilla mother may eat specific plants to help stimulate labor.
During pregnancy, the growing fetus and infant are well-protected in the mother’s womb. Gorilla mothers do not menstruate and the bloody discharge of a human period does not occur. Fun fact: Gorilla babies are about 1/900th the size of their mother when first born!
Birth and Infant Care
The mother gorilla gives birth in a nest she has built on the ground, in a seated, upright position that is unique among great apes. Other female gorillas may attend the birth to offer support. The newborn gorilla weighs about 4 pounds.
New gorilla mothers are very protective and affectionate with their infants. They cradle them to their chest using both arms for the first few months. Even as the infant grows and becomes more independent, the mother will still support it on her back and care for it for 3-4 years until the next baby arrives.
Menopause and Old Age in Gorilla Females
Declining Fertility and Hormonal Changes
Like human females, female gorillas experience a decline in fertility as they reach advanced age. According to research, the average age of menopause (the permanent end of menstruation and fertility) in gorillas is around 35-40 years old (Herndon, 2018).
This coincides with observable changes in behavior and group dynamics.
Leading up to menopause, older female gorillas go through perimenopause where hormone levels fluctuate. They may experience irregular cycles or amenorrhea (lack of menstruation) for months at a time. Dominant silverbacks tend to stop mating with perimenopausal females as they become less fertile (Sciencedaily, 2016).
However, even postmenopausal females have been observed mating, likely for social bonding purposes.
Role and Status of Post-Reproductive Females
Female gorillas who can no longer reproduce continue to play an important role in the troop. Post-reproductive females in matriarchal primate species seem to live longer, allowing them to contribute to group survival (Herndon & thorpe, 2003).
Their experience and knowledge help guide the group to food sources, protect infants, and mediate conflicts.
In fact, the presence of older females may improve the survival rates of infants! One study found that groups with at least one non-reproductive female had higher infant survival over a 15 year period compared to groups with no non-reproductive females (Herndon & thorpe, 2003).
These elders play a valuable advisory role in the complex social dynamics of gorilla troops.
Comparisons to Human Menopause
There are some notable similarities and differences between menopause in humans versus gorillas:
- On average, gorillas reach menopause about 10 years earlier than human females (late 30s vs late 40s).
- The reproductive period also starts earlier in gorillas, leading to a shorter overall reproductive lifespan.
- Postmenopausal female gorillas continue to engage in mating activity, while human females typically do not.
- Extended post-reproductive lifespan seems beneficial to both species in terms of passing on knowledge and caring for young.
| Measure | Gorillas | Humans |
|---|---|---|
| Average Age of Menopause Onset | 35-40 years | 45-55 years |
| Postmenopausal Lifespan | 10-15 years* | 30+ years |
While the menopausal transition looks somewhat different in gorillas, it marks a shift toward older age where females continue to valuably contribute through their experience and guidance!
Conclusion
In conclusion, female gorillas do indeed experience menstrual cycles and periodic bleeding similar to human women. However key differences exist including shorter, less heavy periods and the capacity for pregnancy into advanced age.
Understanding gorilla reproductive health provides insight into our own biology and reinforces our tight evolutionary bonds.
