The development of feeding behaviour in wild western lowland gorillas (Gorilla gorilla gorilla)

Before being weaned, young primates must learn which plant species are suitable to eat, and how to process and combine them to meet their nutritional needs. This study provides a detailed investigation of the development of feeding behaviour in a wild population of western lowland gorillas observed in a bai habitat. The behaviour of 56 known immature individuals aged between 0 and 8 years was recorded at Mbeli Bai, Republic of Congo, using focal, scan and all-occurrence sampling over a period of 16 months. Results indicated that independent feeding skills were acquired by the end of infancy and did not undergo significant change beyond this point. However, suckling continued into the juvenile period, suggesting that some continued investment by the mother was necessary until the strength and skills of immatures developed, perhaps to enable self-sufficiency through periods of succulent fruit (assumed to be the most suitable weaning food) scarcity. This was supported by observations of an increase in feeding-related behaviour with age, particularly during infancy. Additionally, age-related differences in the species and plant parts selected by different age classes, as well as in levels of food processing, were apparent. Play feeding, suggested to be a precursor to independent feeding, was most prevalent in infancy, decreasing as feeding skills developed. Thus, it would appear, given that food transfer also occurs (Nowell & Fletcher, 2006), that feeding skills in western lowland gorillas are learned by a combination of exposure to and manipulation of food items, and probably also through the observation of conspecifics. Observations in a forest habitat are needed to improve our understanding of feeding development in this subspecies.