Eastern gorilla (Gorilla beringei)
- Mountain gorilla (Gorilla beringei beringei)
- Eastern lowland gorilla (Gorilla beringei graueri)
Western gorilla (Gorilla gorilla)
- Western lowland gorilla (Gorilla gorilla gorilla)
- Cross river gorilla (Gorilla gorilla diehli)
When choosing the research topic for my Master's degree, I knew that I wanted to focus on a zoo animal that displayed behaviors in captivity which were not typically seen in wild conspecifics. Western lowland gorillas fulfilled these criteria, as they are the subspecies of gorilla that is most commonly kept in zoos. Some are also known to display several abnormal behaviors in captivity. These behaviors are considered abnormal because, thus far, field researchers have not observed gorillas displaying these behaviors in the wild. In other words, these behaviors are seen mainly in captive environments. The cause of abnormal behaviors in captivity is currently unclear, although research is beginning to shed light on nutrition, enclosure design, activity levels, and rearing history. I’ll discuss abnormal behaviors in more detail in my next blog post.
Gorillas are from African countries. Western lowland gorillas are found in Gabon, the Cabinda province of Angola, western Congo, southwestern Central African Republic, south central and southern Cameroon, and mainland Equatorial Guinea. They are regionally extinct from Democratic Republic of Congo. They mainly live in primary (old growth) and secondary (regenerating) forests as well as submontane, lowland areas, and even swamp forests. They are classified as Critically Endangered on the IUCN Red List of Threatened Species.
Western lowland gorillas consume a lot of fiber in their diet. Important foods include pith, leaves (browse), shoots, stems, invertebrates, and fruit. Fruit consumption is dependent on seasonal variability and availability. Western lowland gorillas consume greater amounts of fruit than the other subspecies of gorilla; however, the amount of fruit that they consume varies with the season and how much is available. For instance, they eat a lot of woody vegetation during the non-rainy season and switch to fleshy fruit during the rainy season when it is more abundant. Fibrous and vegetative matter, such as shoots, young leaves, and bark, are also eaten outside of the fruiting season. Western lowland gorillas have been described as “seasonal frugivores” and “fruit pursuers,” meaning that they will travel greater distances to find fruit when it is available. Wild gorillas have also been observed to spend from 50% - 70% of their day engaged in feeding behaviors.
These patterns are indicative of the importance of variability in the diets of western lowland gorillas; this can be difficult to replicate in captive environments. In the wild, these gorillas adjust to the changing seasons and change their eating patterns and daily ranges (how far they travel in a day) accordingly. This may mean that they do not consume too much of any one kind of food. It also could mean that they achieve their nutritive requirements through a range of different foods. In captivity, gorillas (like many captive animals) are fed by staff and do not forage for food the same way they would in the wild. Sometimes they are even fed food items that are very different from what they eat in the wild. These food items can be those that were cultivated for human tastes, like meat, milk, candy, potatoes, bread, and excessive amounts of any one type of food. This food is very different from what gorillas consume in the wild and it may be fed to them all year long, without any seasonal variability.
There are several threats that are currently harming their survival in the wild. Commercial hunting and the Ebola virus are two of the primary threats to western lowland gorillas in the wild. Mechanized logging has increased which has doubled regional timber production resulting in forest clearings. Gorilla habitats, which were once remote, are now more accessible to logging employees and commercial hunters. Disease outbreaks of Ebola (which is spread through its reservoir host, bats) results in high gorilla mortality rates. Out of all these threats, the human impact has been the highest to gorillas.
We can take proactive steps leading to encourage the survival of this beautiful species:
- Raise Awareness of the Western Lowland Gorillas' status!
a. They were classified as Critically Endangered in 2007 which means that in three generations their population has declined by 80%!
b. In 20 – 30 years, habitat loss and deforestation from agriculture, timber extraction and mining will continue to act as major threats of extinction.
c. Make conscious efforts to decrease your environmental impact by following the 3 Rs: Reducing the amount of items you waste; Reusing materials (i.e. writing on both sides of a piece of paper); Recycling (i.e. remember to recycle paper).
- Recycle your Cell Phones!
a. Coltan is a metallic ore used to produce an element called tantalum. This is a light-weight metal which can hold a very strong electrical charge. Therefore, it has become a vital element in creating capacitors that control electric flow inside miniature circuit boards. Tantalum capacitors are used in nearly all cell phones, laptops, and other electric devices.
b. Coltan is highly concentrated, and therefore most easily mined, in the rainforests of the former Republic of the Congo (Africa). Unfortunately, this is also prime lowland gorilla habitat!
c. Recycling our electronics (at specified collection organizations, like the Toronto Zoo’s EcoCell Program) means that the tantalum can be safely extracted and re-used in new electronics. Therefore, the demand to mine pure coltan in the Congo is decreased and we can lessen the stress on gorilla habitat and of course, the gorillas themselves.
What does that mean?
- Conspecific: Another organism of the same species
- Abnormal Behavior: Actions demonstrated by an individual which are statistically rare
- Enclosure Design: Planning a captive primate’s environment to meet its behavioral, social, and physical needs. This requires consideration of primate species’ natural histories and how these can be applied to captive management and environmental enrichment
- Rearing History: How one was cared for, during the early stages of life
- Browse: Leaves, twigs, and young shoots of trees or shrubs, which animals feed on
- Frugivores: An animal that feeds primarily on fruit
- Foraging: The act of looking for food or provisions