The western lowland gorilla ( Gorilla gorilla gorilla) is the smallest of the four gorilla subspecies and is commonly found in zoos. This article delves into the specifics of their diet and feeding habits, highlighting their adaptability and crucial role in their ecosystem.
General Overview
Western lowland gorillas are primarily herbivorous primates, consuming a variety of vegetation. They are diurnal animals, being most active in the morning and late afternoon, dedicating a significant portion of their day to foraging and eating.
Habitat and Distribution
Western lowland gorillas inhabit the rainforests of western and central Africa, specifically in countries like Gabon, the Republic of Congo, the Central African Republic, Equatorial Guinea, Angola, and Cameroon. They thrive in the tall, lush tropical forests where ample light reaches the forest floor, promoting the growth of herbs, shrubs, and vines that constitute their diet.
Physical Characteristics
Western gorillas can be distinguished from other gorilla subspecies by their brownish-gray hair, auburn-colored crests and overall smaller size. Eastern gorillas tend to be black in color and larger in size. In all gorillas, males develop silver coloration along their backs as they mature. Western lowland gorillas have a more pronounced brow ridge and ears that appear small in relation to their heads. Adult male gorillas' heads look conical due to the large bony crests on the top and back of the skull. These crests anchor the massive muscles used to support and operate their large jaws and teeth. In comparison to the mountain gorilla, the western lowland gorilla has a wider and larger skull, and their big toe is spread apart more from the alignment of the other four toes.
Diet and Foraging Behavior
The diet of western lowland gorillas is primarily herbivorous, consisting mainly of leaves, stems, shoots, roots, and flowers. They also consume fruits when in season. They also get some protein from invertebrates found on leaves and fruits. An adult western lowland gorilla can eat up to 18 kilograms of food in a day.
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Gorillas are very selective foragers, often consuming only specific parts of a plant, such as the leaves, pith, stalk, or roots. They utilize their incredible strength to break apart vegetation, accessing the nutritious parts. They are also known to use tools like sticks to check the depth of water or branches to extract termites and ants from holes. Gorillas do not overexploit an area for food.
Feeding Habits in Captivity
In zoological settings like the Smithsonian's National Zoo and Zoo Atlanta, western lowland gorillas are fed a variety of fruits and vegetables, including apples, oranges, bananas, raisins, sweet potatoes, cabbage, collards, and primate chow. Food is typically scattered around the habitat to encourage foraging behavior. To provide enrichment, zookeepers may also offer forage items such as popcorn, sunflower seeds, peanuts, beans, and diced fruits and vegetables. Fresh tree trimmings are also given daily.
Social Structure and Feeding
Western lowland gorillas live in family groups called troops, typically consisting of about five individuals but can range from 5 to 30 individuals. These groups are led by a dominant silverback male, along with several adult females and their offspring. Unlike other gorilla subspecies, Western lowland gorillas show more tolerance towards non-relatives and gorillas from other groups. The silverback dictates the group's activities, including feeding times and locations.
Communication
Gorillas communicate using auditory signals, visual signals and odors. They are generally quiet animals but they may also scream, bark and roar. Gorillas exhibit complex and dynamic relationships. They interact using grooming behaviors, although less than most other primates. Affiliation may also be shown through physical proximity. Perhaps the most recognizable behavior performed by gorillas is chest-beating. It is primarily done by male gorillas at the end of a display meant to intimidate intruding males or predators. The sound can be heard for long distances. Females will chest-beat infrequently; they will typically beat their hands against the insides of their thighs. Chest-beating can also indicate playful behavior, however, especially in the young.
Conservation Status and Threats
Western lowland gorillas are classified as critically endangered due to several factors, including commercial hunting, deforestation, and disease. Habitat loss, largely due to mining activities, also poses a significant threat. Other threats include global warming, leopards (rarely), crocodiles (occasionally while crossing rivers) and diseases like Ebola.
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Conservation Efforts
Various organizations are dedicated to the conservation of western lowland gorillas and their habitat. These include the Wildlife Conservation Society (WCS), World Wide Fund for Nature (WWF), and the Dian Fossey Gorilla Fund International (DFGFI). These organizations work to promote conservation activities, enforce laws against poaching, support gorilla tracking programs, and promote sustainable development.
Unique Behaviors
There are three feeding behaviors sometimes observed in gorillas in human care that can bother visitors. These behaviors are natural, though not to humans. They are regurgitation and reingestion, coprophagy (eating feces) and urine drinking.
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