Western lowland gorillas are endangered, but they remain far more common than their relatives, the mountain gorillas. They live in heavy rain forests, and it is difficult for scientists to accurately estimate how many survive in Cameroon, Central African Republic, Congo, Equatorial Guinea, Gabon, Angola, and the Democratic Republic of Congo.

A new tally of lowland gorillas has found massive and surprising numbers of these African primates alive and well in the Republic of Congo, Wildlife Conservation Society scientists announced.

The new census puts the number of western lowland gorillas (called great apes, along with chimpanzees, bonobos and orangutans) within two adjacent areas in the northern part of the Congo at 125,000 individuals, including infant gorillas.

Previous estimates from the 1980s placed the entire population of western lowland gorillas, which live in seven Central African nations, at fewer than 100,000 individuals. Since then, scientists thought the number would've at least halved due to hunting and disease but last year’s census was a surprise to many.Western lowland gorillas tend to be a bit smaller than their mountain cousins. They also have shorter hair and longer arms.

Western lowland gorillas are one of four recognized gorilla sub-species, along with mountain gorillas, eastern lowland gorillas and Cross River gorillas. While the eastern lowland gorilla is considered endangered by the International Union for Conservation of Nature (IUCN), the others are labeled "critically endangered," which means the group faces an extremely high risk of extinction in the wild.

Gorillas can climb trees, but are usually found on the ground in communities of up to 30 individuals. These troops are organized according to fascinating social structures. Troops are led by one dominant, older adult male, often called a silverback because of the swath of silver hair that adorns his otherwise dark fur. Troops also include several other young males, some females, and their offspring.

The leader organizes troop activities like eating, nesting in leaves, and moving about the group's three-quarter- to 16-square-mile (2- to 40-square-kilometer) home range.Those who challenge this alpha male are apt to be cowed by impressive shows of physical power. He may stand upright, throw things, make aggressive charges, and pound his huge chest while barking out powerful hoots or unleashing a frightening roar.

Despite these displays and the animals' obvious physical power, gorillas are generally calm and non-aggressive unless they are disturbed.Female gorillas give birth to one infant after a pregnancy of nearly nine months. Unlike their powerful parents, newborns are tiny—weighing four pounds (two kilograms)—and able only to cling to their mothers' fur. These infants ride on their mothers' backs from the age of four months through the first two or three years of their lives.

Young gorillas, from three to six years old, remind human observers of children. Much of their day is spent in play, climbing trees, chasing one another, and swinging from branches.In captivity, gorillas have displayed significant intelligence and have even learned simple human sign language.

In the wild, these primates are under siege. Forest loss is a twofold threat; it destroys gorilla habitat and brings hungry people who hunt gorillas for bush meat. Farming, grazing, and expanding human settlements are also shrinking the lowland gorilla's space.