Eating Behavior

After observing the gorillas at the San Diego Zoo, I became more curious about the eating behavior of these large creatures.  I noticed that when the gorillas were thrown large lettuce leaves for lunch time, they were very picky about which parts of the leaf they ate; it seemed like they actually ended up leaving most of the lettuce on the ground.  I wanted to really investigate their eating habits because it seems like such giant animals would need huge amounts of protein and calories to survive, and that eating half of a salad for every meal just wouldn't cut it.  Here is what I found...

It turns out that gorillas' diets really do consist mainly of plants! Although there are slight diet variations depending on the type of gorilla.  Western lowland gorillas' diet consists of 67% fruit, 17% leaves, seeds, and stems, and 3% termites and caterpillars.  The diet of Mountain gorillas, on the other hand, consists of 86% leaves, shoots, and stems, 7% roots, 3% flowers, 2% fruit, and 2% ants and snails.  The lack of fruit that the Mountain gorilla consumes compared to the Western lowland gorilla is due to the scarce amount of fruits that grow at the high altitudes of their mountain habitats.

Gorillas are, in fact, able to survive on only fruits, leaves, trees, and other plants.  However, in order for them to obtain all of the energy and nutrients that they need, gorillas must consume a large amount of this vegetation, which, luckily, is available to them year round in their natural habitats.  Adult male gorillas consume more than 40 pounds of vegetation every day! Now that's a lot of salad.

Here is a cool video where you can see gorillas eating up close.

Gorillas use their strength to break apart plants.  They are also very selective foragers, in that they like to only eat certain parts of plants (which is what I had noticed at the zoo!).  This helps so that they don't overexploit an area for food.  They crop the vegetation in a manner that allows for quick replenishment to  occur.  This system is very important because this is their only diet, so they need a constant, abundant source if they are to survive.

sources:
http://www.youtube.com/watch?v=Q4Gm_lzn0iI
http://www.seaworld.org/animal-info/info-books/gorilla/diet.htm
http://en.wikipedia.org/wiki/Gorilla#Food_and_foraging

Adventures at the San Diego Zoo!

This picture shows the comparison between the baby ("Frank the Tank") and the large silverback that is clearly in charge at the zoo.

 This gorilla liked to cause a little bit of trouble, and tried taking food from the littlest one, Frank the Tank, and the Silverback and him got in a little fight.

 The gorillas were expecting food but I was amazed at how the gorillas held their hands up in the air waiting for the food to be tossed to them, caught the lettuce heads, and then continued waving, signaling that they wanted more food.

 Watching the Silverback eat was interesting because he examined each piece of lettuce before eating it and was pretty picky about the parts he ate. He preferred the crunchy roots and threw the leafy part of the lettuce to his feet.

 I just took a picture of his foot because I couldn't believe how big it was! Also he was sitting very human-like while eating his lettuce, leaning against the glass window with his knees bent.

   Bridget, the Silverback and me!

 The Silverback was looking over all of the leafy remains and showing it to the younger gorilla.

Eating and relaxing, what a life!

The Silverback gets mad and chases the other gorilla!

Gorilla Senses!

Sound
Although gorillas' hearing capabilities are probably not any better than ours, they do need to be extra sensitive to sounds because they live in dense forests which conceal visibility of potential predators.  So hearing is important to gorillas for locating one another and for detecting danger.  For this reason, gorillas often respond to strange noises that they aren't used to.

Sight
Gorillas see mostly as well as we do.  Their eyesight is used for finding and identifying food, as well as looking out for danger.  Because gorillas are herbivores that search for food in the daytime, they probably have color vision which is useful for detecting the difference between ripened and unripened fruits.  Like humans, gorillas also have both eyes facing forward, instead of one on each side of the head. This binocular vision allows them to accurately assess distances and depth.  Gorillas and humans both have a specialized area of the eye called a fovea, which contains condensed light-sensitive cells that aid in good visual acuity.

Smell
Gorillas probably have a better sense of smell than humans do.  They are able to detect strong odors in the environment, like human sweat and the scent of an unfamiliar gorilla.  Males use females' odors to determine their reproductive statuses.  Also, Silverbacks emit a scent from their armpits when they sense strangers around them.

Touch
Gorillas probably have a less sensitive sense of touch than humans do, and they are less tactile than other primates.  The hands and feet of gorillas are protected by hair and very thick skin so that they can pick up nettles (a plant covered with stinging hairs) and be stung by wasps without being hurt.  One of the main reasons gorillas use their sense of touch is for grooming.  Mutual grooming often takes place between mothers and offspring, and sometimes females groom Silverback.  This grooming keeps the thick hair free from dirt and parasites, and also reinforces social bonds.

Taste
Gorillas most likely have the same tasting abilities as humans do.  Their tasting capabilities are important so that they can learn the differences between poisonous and non-poisonous plants.

Sources
http://gorillacd.org/2007/11/30/how-mountain-gorillas-see-hear-touch-smell-and-taste/
http://www.seaworld.org/animal-info/info-books/gorilla/senses.htm
http://www.inmagine.com/x139/bxp40906-photo
http://mountaingorillas.gorillacd.org/
http://www.digitalapoptosis.com/archives/animals/002024.html

Koko and Gorilla Intelligence!

Gorillas are extremely intelligent creatures, and the Gorilla Language Project (also known as Project Koko) proves it. This project began in 1972, when Koko the Gorilla was only one year old. After being in the study for about 40 years, Koko has surpassed any other non-human in her ability to communicate with sign language. She has a vocabulary of approximately 1,000 signs and can about 2,000 words of English when she’s spoken to. Koko also initiates many of her conversations with humans, and even tested between a 70 and 95 on the IQ scale. Not only can she understand basic human conversation, but the study has consisted of “spontaneous gorilla language use including invention of new signs and compound words, simultaneous signing, reference to time and emotional states, metaphorical word use, humor, definition, argument, threat, fantasy play, storytelling and moral judgment” along with many other aspects of human behavior.

Intelligence is defined as the capacity of the mind to be aware of what is occurring around us, and not only acquiring knowledge, but also putting it into practice. By testing self-awareness by using a “mirror test,” then gorillas are self-aware because Koko could recognize herself. Gorillas also use tools to solve problems, and even in the wild, they have figured out how to use medicinal plants to help cure their sicknesses.

Koko is also emotionally intelligent, as you can see in this clip by clicking on the following link.  She played and cared for this little kitten, and even named him All Ball, because he reminded her of a ball. This shows the innate motherly side of her, but also the fact that she named the kitten shows her understanding of the human relationship between a mother and child, or even of a human and their pet. After All Ball tragically died, Koko responded like a human and grieved the loss of her kitten.

http://www.youtube.com/watch?v=XqTUG8MPmGg

Sources:

http://www.koko.org/world/

http://www.tropical-rainforest-animals.com/Koko-the-Gorilla.html

http://www.streetdirectory.com/travel_guide/29693/pets/patterns_of_gorilla_intelligence.html

Pictures:

https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjY03LtxxsBa7tP73ukDNh9o3TDmQQ28_QWzCn7N2rylKnHK2iZz3n_Ub7ijRyPl2JEle2tPijYDvlRDZs3UwzCYx5lCA5DYgl0B2PFxWyDpJIuj1iRQ8ezhACpKhLfXGtajAkbkVxriQRt/s1600/Koko+with+her+kitten.jpg

https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjr9YG4bdYqvyEt-ooQ6FC2UVceavbOfSdeTWIu2_lruSSNsv8Pyfvm6PEkT_6qrYufzsCCmnFHkr0oUFCNlBALPlssvXTYOWcaLxNbh2my0m5w273vmBOjgTx6orIZhl0wDMQgiOJVa_KR/s1600/koko.jpg

http://dingo.care2.com/pictures/c2c/share/44/444/473/444732_370.jpg

Baby Gorillas Are Just Like Us!

Being that gorillas share about 98% of the same genes as humans, it is not surprising that they develop and mature in a very similar manner as we do! For instance, the gestation period for gorillas is around 8 1/2 months, which is very close to our average nine-month period.  Gorilla mothers usually wait about three to four years before having another baby because that is usually how long the infant stays with them.  Also, mothers usually only have about three offspring during their lifetimes, which is very similar to the average of about 2 children per human mother.  Similar to human babies, gorilla babies also love to cling to their mothers, horse around with their fathers, and make a mess when they eat.  Also like humans, gorillas use a wide variety of nonverbal communication with their young, such as animated facial expressions, eye gaze, and tactile signals like grooming and cuddling.

Although human and baby gorillas are indeed very similar in their development stages, it is interesting to note that gorillas do tend to mature more quickly than humans do.  For example, gorillas usually learn to crawl at about two months and learn to walk at nine months, while humans are still learning to sit up at around 6 months and then walking at about 1 year.  Also, female gorillas reach "puberty" between the ages of 10 and 12, and male gorillas reach this maturity between 11 and 13 years, while for humans it can range from ages 10 to 18.  

All in all, baby gorillas are very similar to human babies in most aspects.  They are also just as cute! Here is a video that is kind of cheesy but has some great footage and insight about how the gorilla mother cares for her baby.

Sources:

http://www.environmentalgraffiti.com/animals/news-baby-gorillas-are-just-we-were-only-cuter-and-smarter

http://www.enchantedlearning.com/subjects/apes/gorilla/

http://www.youtube.com/watch?v=3HzfLJA_CrY

Analysis of Klailova, Hodgkinson, and Lee (2010) Article

Klailova, Hodgkinson, and Lee (2010) recently studied the correlation between human tourism and aggression in gorillas.  Before this study, it had been suggested that human tourism may negatively affect wild gorillas because of potentially lowering gorilla's immunity and making them more susceptible to contracting human diseases.  So, Klailova, Hodgkinson, and Lee wanted to evaluate the impact of tourist presence, human observer numbers, and human observer distance on the behavior of a group of Western Lowland Gorillas at Bai Hokou, in the Central African Republic.  The results showed that although tourist numbers had no significant effect on human-directed aggression, close observer-gorilla proximity correlated with a decrease in feeding rates and an increase in human observation.  For instance, the silver-back (dominant male) of the group directed less aggression toward observers when they stood more than 10 meters away, but his aggression was greater when observers stood anywhere from 6 to 10 meters away.  Furthermore, the human-directed aggression was eliminated when observers stood greater than 18 meters away.  From this observation, Klailova, Hodgkinson, and Lee suggest that the current 7 meter distance limit governing gorilla tourism be increased to anything greater than 10 meters in order to increase the gorillas' well-being and decrease their aggression towards humans.  The researchers also recommend decreasing observer group sizes and restricting tourist access to one visit per day.  These recommendations are important to consider because although observation of gorillas can be very educational and useful (and interesting!), we want to make sure that by learning about these great creatures we are not harming them in any way.  This is especially true of observation of gorillas in the wild, where we are guests in their natural habitat.  So, we should treat them with respect now if we want keep them safe and healthy so that we can continue learning about them in the future.

To read the abstract of this article, you can go to http://onlinelibrary.wiley.com/doi/10.1002/ajp.20829/abstract, but to read the full-text you'll need to sign in via a university library or create an account for Wiley Online Library.

Sources:

 Klailova, M., Kodgkinson, C., & Lee, P.C. (2010). Behavioral responses of one western lowland gorilla (Gorilla gorilla gorilla ) group at Bai Hokou, Central African Republic, to tourists, researchers, and trackers. American Journal of Primatology. 72 (10), 897 - 906. 

http://wwf.panda.org/who_we_are/history/50_years_of_achievements/myworld/imagecredits2/

Predatory Behavior

Gorillas’ main food source consists of plants, fruits, and ants. Therefore, Gorillas aren’t really known as predators. However, the Silverbacks in the troop are usually more aggressive, as their role is to protect the rest of the group. Silverbacks need to gain experience before they can fully protect their troops, and tend to live by themselves for a few years before developing and securing a group of their own. They tend to be the dominant male and group leader. If there is a threatening situation, the Silverbacks will beat their chest, make loud sounds, and produce a powerful odor that can be smelt from 25 miles away by both humans and animals. Although this is 99% meant as a threat, if needed the Silverbacks will follow through with an attack.

Gorillas have few animal predators in the wild, other than leopards and possibly crocodiles for the lowland gorillas. The real threat to these magnificent animals are humans. In western Africa, gorillas are hunted for meat or “in retaliation for crop raiding,” by poachers, while on the opposite coast, they sometimes accidentally get caught in antelope snares or traps meant for other animals. Sometimes, entire family groups are killed by poachers, who are trying to take the infants for zoos. Although gorillas rarely attack humans, they could easily overtake a person, and in this type of situation, them fighting back is no match for the poachers’ guns.

Gorillas are generally calm animals and not threatened by other primates. They are even unbothered if chimpanzees wander through their troops.

Sources:

http://www.outtoafrica.nl/animals/enggorilla.html?zenden=2&subsoort_id=1&bestemming_id=1

http://www.seaworld.org/animal-info/info-books/gorilla/behavior.htm

http://pin.primate.wisc.edu/factsheets/entry/gorilla

Pictures:

http://rlv.zcache.com/silverback_gorilla_beating_chest_card-p137348553357367299z85g9_400.jpg

https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjP2swEcoxLNrNojlfoh5kJR-9qwlsYdmoNXXwVyXpcSwZpZ2CpDUlKhhQ6AyJS2MC4iLA6MUufSPFyeNInYsHFoUq0dLKHSN6Qz_3Pp9hbOyjnD2WjRdgjyJfpGUbGTHTcVFCKbgRF13M/s1600/leopard_3.jpg

http://www.gorillatrails.co.uk/Images/Silverback.jpg