gorillas are herbivorous, with a heavily foliage based diet, due to lack of available fruit in their habitats. They have smaller home ranges than western gorillas as foliage is more abundant than fruit. They are diurnal but the majority of foraging occurs in the morning and late afternoon. At night, they build nests by folding over vegetation, usually on the ground. Behavior Eastern gorillas live in stable, cohesive family groups, led by a dominant silverback male. Eastern gorillas tend to have larger group sizes than their western relatives, numbering up to 35 individuals. There is no distinct breeding season and females give birth only once every 3–4 years due to the long period of parental care and a gestation period of 8.5 months. Newborn gorillas have greyish-pink skin and can crawl after 9 weeks; they are not fully weaned until 3.5 years. Males defend their females and offspring using their large size in intimidating displays involving charging and chest-beating. Conservation status The eastern gorilla has become increasingly endangered since the 1990s, and the species was listed as critically endangered in September 2016 as its population continued to decrease. Primary threats to the eastern gorilla include habitat destruction for residential, commercial, and agricultural purposes, habitat fragmentation caused by transportation corridors and resource extraction, as well as disease. Between 1996 and 2016, the eastern gorilla lost more than 70 percent of its population, and by 2016 the total population was estimated to be less than 6,000. An exception to this declining trend is the mountain gorilla. According to the most recent estimates, there are approximately 1,004 mountain gorillas, and their numbers continue to grow. In some national parks, viewing mountain gorillas is a popular tourist attraction. These national parks include Volcanoes National Park in Rwanda, Virunga National Park in the Democratic Republic of the Congo, and Mgahinga Gorilla National Park and Bwindi Impenetrable National Park in Uganda. While ecotourism can benefit gorilla populations by generating revenue for conservation efforts, there is concern that increased exposure to humans will place gorillas at greater risk of contracting zoonotic diseases. Studies have shown that habituated eastern gorillas, that is, those that leave protected areas to forage in surrounding communities, have higher diseases rates than their unhabituated counterparts, with nearby humans and livestock as the likely sources of transmission. Unlike the western gorilla, there are few eastern gorillas in zoos. The Antwerp Zoo is the only