They studied chimpanzees, gorillas and orangutans respectively. Mammals include elephants, gorillas and hippopotamus. They determined that chimpanzees are more closely related to humans than gorillas. He saw similarities between this environment and the habitat of the chimpanzees and gorillas. Some propose that males were substantially larger than females similar to gorillas and orangutans. It walks on its front knuckles similar to gorillas and chimpanzees. The country is noted for its population of forest elephants and western lowland gorillas. Peter sees Amy with a troop of silverback gorillas and bids her goodbye. Except for gorillas and humans, hominoids are agile climbers of trees. She had created the fund to finance patrols against poachers seeking to kill mountain gorillas. The average weight of wild male western lowland gorillas is 146 kg. Infanticide is common in polygynous species such as gray langurs and gorillas. This behaviour has not been observed in eastern lowland gorillas. This species of gorillas exhibits pronounced sexual dimorphism. Infanticide by adult male gorillas has occasionally been observed in this subspecies.