In light of Endangered Species Day, I found an interesting study involving one of my favorite endangered species, the Bornean orangutan (Pongo pygmaeus) that resonated with me. When I was younger, I was a picky child; new foods were scrutinized and judged by smell, appearance, and if I was bold enough—taste and texture. One day, after eating some new type of cereal, my mouth had an inky taste and upon looking in a mirror, my mouth was filled with blue ink. I had unintentionally consumed the toy, but from then on, exceptionally crunchy foods became linked in my head with ink and a blue mouth. It was a little jarring and I thought I was going to die at the time (in typical melodramatic fashion), but nothing really happened. Eventually, I got over this as I became more social and attempted new foods recommended to me by friends and sharing.
Unlike my younger self, it turns out orangutans are not hesitant to attempt to try new foods too. In a study performed by Gustafsson, Krief, and Saint Jalme (2011), four captive orangutans (including the famous, Nénette–who was removed halfway through the study for surgery) were given 11 fresh plants and 4 infused plants in a beverage (containing marjoram, thyme, savory, and pellitory-of-the-wall) to determine the individual and group learning methods of trying new foods. The four orangutans were kept in solitary conditions and then group conditions to measure rates of attempting new foods.
There were four behaviors investigated in conjunction with the consumption of the plant: holding, sniffing, tasting, and ingestion. To the researchers, tasting was defined as “licked, nibbled, or at least held to mouth” (or, in the 4 infused plants case, <100 ml of liquid) whereas ingestion was “a significant amount of the plant eaten” (or >100 ml of liquid) (Gustafsson, Krief, and Saint Jalme 2011). Interestingly, while holding was a common behavior for the first sessions in both group and individual settings, tasting and ingestion were especially high in the infused plants in the first session with the marjoram infusion, the first of the experiments. It is also curious that thyme was also consumed in large amounts when it was strongly infused in the first experiments. In the second experiments, the marjoram remained the same, but increased in thyme. Whereas, savory and pellitory-of-the-wall were low for tasting and ingestion in both sessions, suggesting orangutans might have a preference for certain tastes.
Orangutans consumed 9 out of the 11 fresh plants presented between the first individual and group sessions, indicating low neophobia. Given that food availability fluctuates in areas where orangutans are endemic due to seasonality and potential climate change, being flexible in food consumption may be necessary to survive times when fruits and other preferred foods are unavailable (Knott 1998; Felton et al. 2003). Assuming this trait is found in non-captive orangutans as well, dietary plasticity can increase survivability by falling back on newer foods.
Furthermore, as orangutans experience habitat loss and get removed from the pet trade and placed into rehabilitation centers, the potential for disease transmission increases as more individuals come into closer contact with one another. In these situations, malaria parasites are measured to increase as individuals have more contact than they normally would in non-captive/semi-captive settings (Wolfe et al. 2003). As this occurs, it is possible that the flexibility in trying new foods will lead to more consumption of medicinal plants that would reduce morbidity effects.
Although testing orangutans’ flexibility in trying new foods seems superficial on first glance, it has great significance for conservation purposes for both potential food availability and zoopharmacognosy. Given that orangutans are an endangered species, it is warranted to study the willingness to attempt new foods for captive/semi-captive conditions and also fallback foods when preferred fruiting trees are removed due to logging.
Edit: Because it’s so good and really worth sharing, Barbara J. King also wrote about this study too. I really enjoy her take on it and if you’re reading this, it’s well worth your time to read hers. This study is just too good to not read about and get different perspectives on.
Felton, A.M., Engstrom, L.M., Felton, A., & Knott, C.D. (2003). Orangutan population density, forest structure, and fruit availability in hand-logged and unlogged peat swamp forests in West Kalimantan, Indonesia. Biol Conserv, 114(1): 91-101.
Gustafsson E, Krief S, & Saint Jalme M (2011). Neophobia and Learning Mechanisms: How Captive Orangutans Discover Medicinal Plants. Folia primatologica; international journal of primatology, 82 (1), 45-55 PMID: 21525772
Knott, C.D. (1998). Changes in orangutan caloric intake, energy balance, and ketones in response to fluctuating fruit availability. Int J Primatol, 19(6): 1061-1079.
Wolfe, N.D., Karesh, W.B., Kilbourn, A.M., Cox-Singh, J., Bosi, E.J., Rahman, H.A., Tassy Prosser, A., Singh, B., Andau, M., & Spielman, A. (2002). The impact of ecological conditions on the prevalence of malaria among orangutans. Vector Borne Zoo Dis, 2(2): 97-103.