Animal's Common Name: Chimpanzee
Genus & species: Pan Troglodytes
The specific behavior (describe):
Chimpanzees exhibit differences in feeding behavior in a single day. The chimpanzees show more consumption of the leaves from Pterygota mildbraedii and Celtis Africana in the afternoon compared to the morning (Carlson, Rothman and Mitani 344). This is categorized as diurnal variation in feeding behavior.
Is this behavior shown only in certain behavioral contexts, such as in communication, getting food, competition, social behavior, attracting mates, mating behavior, parental behavior, or some other area of activity?
This behavior occurs only in a specific context namely the foraging (getting food) behavior, as well as specific time in a single day. Geographically, this behavior exists in all chimpanzee communities in Ngogo, Kibale National Park Uganda.
Is this behavior stereotypic of the species? (I.e. typically by all similar members of the species, similar by sex or age or reproductive status.)
This behavior is not stereotypic of the species. Diurnal variations in feeding behavior are also observed in Atlantic Cod (Reubens, Rijcke and Degraer 218) and in domestic animals such as dairy heifers (Greter, Keyserlingk and DeVries 16). However, there are differences in trigger mechanisms for such behavior in different species.
Observed in natural population YES or in lab situation YES
There has been evidence that feeding behavior is associated with cognitive capabilities of the chimpanzee species. There are similarities in resting and feeding behavior in wild and captive populations of chimpanzee (Yamanashi and Hayashi 1234).
PROXIMATE CAUSES
1. Mechanism (Causation)
Is this behavior a Fixed Action Pattern?
This behavior is a fixed action pattern that occurs daily in wild chimpanzee population in Ngogo, Kibale National Park Uganda.
If so, what is the releaser (the stimulus or innate releasing mechanism)?
This behavior is facilitated by the ability of chimpanzee to recognize the nutrients in these two plants. Pterygota mildbraedii shows increased hemicellulose, cellulose and lignin in the afternoon. Similarly, Celtis Africana shows increased sugar contents in the afternoon (Carlson, Rothman and Mitani 344). Chimpanzee has the ability to recognize the daily variations in the nutrient contents of these plants, therefore, it can be concluded that the daily variations of nutrient contents (hemicellulose, cellulose, lignin and sugar) in these two plant species trigger the diurnal foraging behavior of the chimpanzees.
Through what sensory system is this releaser received?
They employ several sensory mechanisms such as external and internal sensory mechanisms consisting of vision, touch, texture, taste, and smell, to detect these properties as fruits ripen and leaves mature (Dominy, Lucas and Osorio 171).
Does the behavior you are describing directly involve genetic/molecular mechanisms?
This behavior involves molecular mechanisms such as recognition of characteristic molecules of hemicellulose, cellulose, lignin and sugar (glucose). The recognition of these molecules triggers signaling system (through nerve and neurotransmitter systems) to the brain. Consequently, this mechanism establishes the brain-behavior mechanism for the diurnal foraging behavior exhibited by the chimpanzees.
What is known about the genetic/molecular mechanisms of this behavior?
The genetic and molecular mechanisms of this behavior seem to be shared commonly among the chimpanzee species. Almost all individual chimpanzee exhibits the behavior. From evolutionary point of view, this behavior increases the fitness, as the animals will be able to optimally absorb nutrients from the food plants.
Is any type of learning involved in this behavior? If so, what specific type of learning: operant conditioning, observational learning, insight learning?
There are possibilities of observational and insight learning in this behavior. Insight learning may be more dominant in this behavior, as the main mechanism responsible for this behavior is the molecular or genetic mechanism to recognize specific substances and daily variations of these substances in the feed plants.
Is imprinting involved in this behavior? Describe how.
Imprinting is not involved in this behavior.
2. Ontogeny (Development)
Over the course of the individual's lifespan, when is this behavior exhibited?
It is likely that this behavior is exhibited after the weaning period. After this period, an individual chimpanzee no longer relies on milk from the mother and must forage in order to fulfill daily nutritional requirements. It is also likely that there is learning mechanism from mother to child in the development of this behavior.
Shown by males, females, or both?
This behavior is shown by both males and females.
Shown only in certain behavioral contexts which are age dependent? If so, describe the behavioral context.
The behavior is age-dependent, for it is exhibited by individuals after weaning period (e.g., individual foraging behavior).
ULTIMATE CAUSES
3. Adaptation (Function)
How is this behavior adaptive? This actually is answered by asking 3 different questions (for which there may be different answers).
Does this behavior lead to higher reproductive fitness for the individual showing the behavior? Explain how.
This behavior allows optimal absorption of nutrition in relevance with daily variation of nutritional concentration in the two plant species. Optimal nutrition intake contributes to the increase in reproductive fitness of the individual.
Does it also lead to this individual’s longer survival? Explain how
This behavior also leads to individual’s survival. The optimal intake of nutrients (especially glucose) ensures the availability of energy for the individual’s survival. Energy is required in all metabolic processes and also required to sustain daily activities.
Does it contribute to the survival of this individual’s offspring? Explain how
This behavior also contributes to the survival of individual’s offspring. This contribution is prominent in female chimpanzee that feeds her offspring (breastfeeding). The quality of the milk that the mother provides to the young is directly influenced by the quality of the nutrients absorbed from the food plants.
What aspects of the environment explain why this behavior is adaptive?
The environmental aspects such as sunlight, soil nutrients, water, etc. influence the production of hemicellulose, cellulose, lignin and sugar in the two plant species. Considering these environmental aspects and the nutrients of the plants, the behavior is adaptive due to the ability of chimpanzees to adapt to the daily changes in the nutritional contents of the plants.
4. Phylogeny (Evolution)
What speculations can be made about the origin of this behavior evolutionarily?
This behavior may be originated from two evolutionary advances of the species. The first aspect is the improvement of external (touch, sights, smell) and internal (textures, taste, nutrient absorption) mechanisms of chimpanzee. The second aspect is the improvement of brain capacity to increase cognitive ability, learn and adapt to the best possible scenario for nutrient intake.
In your opinion was it more likely to have been "pushed" by natural selection, sexual selection, kin selection, or genetic drift? Explain why you think so.
Considering the wide spread of this behavior, this behavior may have been the result of natural selection. Individuals with the ability to adapt to the daily nutrient variations in the food plants are selected for. These individuals may have been able to obtain better nutrition intake and may have provided them with physiological and reproductive advantages. Consequently, since the trait is passed on through generations, it is maintained in the existing population.
If the behavior is not stereotypic in the species, but does have a high genetic contribution, it may be rare because it has been selected against (gene frequency decreasing in the population) or rare because it is new and slowly becoming more common (gene frequency increasing in the population). If you think either of these conditions apply for this behavior, please explain why.
Most (if not all) of the chimpanzee population in the study area in Ngogo, Kibale National Park shows this behavior. Since this behavior is associated with the genes for external and internal sensory mechanisms, as well as for cognitive capability, the fact implies that the frequencies of the genes are high, as the genes are becoming more frequent among the existing chimpanzee population. Therefore, the gene frequency also implies that the genes are increasing (selected for) in the natural selection process.
If possible, discuss whether this behavior is also exhibited in closely related species.
Foraging behaviors and the adaptation to the environmental conditions (e.g., habitat types and plant availability) are also observed in Bonobo (Pan paniscus) populations (Stanford 339) and other great apes populations (Parker 623). This indicates that feeding and foraging behavior is crucial for the survival of primates.
Works Cited
Carlson, Bryce A, Jessica M Rothman and John C Mitani. "Diurnal Variation in Nutrients and Chimpanzee Foraging Behavior." American Journal of Primatology 75 (2013): 342-349. Print.
Dominy, Nathaniel J, et al. "The Sensory Ecology of Primate Food Perception." Evolutionary Anthropology 10 (2001): 171-186. Print.
Greter, Angela M, Marina A G von Keyserlingk and Trevor J DeVries. "Ration composition affects short-term diurnal feeding patterns of dairy heifers." Applied Animal Behavior Science 140(1-2) (2012): 16-24. Print.
Parker, Sue Taylor. "Object manipulation, tool use and sensorimotor intelligence as feeding adaptations in cebus monkeys and great apes." Journal of Human Evolution 6(7) (1977): 623–641. Print.
Reubens, Jan T, et al. "Diel variation in feeding and movement patterns of juvenile Atlantic cod at offshore wind farms." Journal of Sea Research 85 (2014): 214–221. Print.
Stanford, Craig B. "The social behavior of Chimapzees and Bonobos." Current Anthropology 39(4) (1998): 339-420. Print.
Yamanashi, Yumi and Misato Hayashi. "Assessing the Effects of Cognitive Experiments on the Welfare of Captive Chimpanzees (Pan troglodytes) by Direct Comparison of Activity Budget Between Wild and Captive Chimpanzees." American Journal of Primatology 73: (2011): 1231–1238. Print.
