Foraging behaviour, food selection and diet digestion of Babyrousa babyrussa (Suidae, Mammalia)

Abstract

A population of 79 babirusa distributed over 19 zoos in Europe and the United States were the subject of a study of the foraging behaviour, food selection, and digestion of the babirusa (Babyrousa babyrussa). Stomachs of six adult babirusa and one twelve month old animal were collected from zoological gardens. Gross anatomical and microscopic examination revealed the large size of the stomach (approximately 3000cm2 for adults) and the very large area covered by its cardiac glands (more than 70% of the total stomach's mucosal surface area compared to about 33% in the domestic pig (Sus scrofa)). Mucus was produced in the cardiac glands and micro-organisms were found both in the mucus-gel adhering to the stomach surface and within the stomach lumen. The pH in the lumen of the cardiac gland area of the stomach was between 5.3 and 6.4 which is suitable for the survival of microorganisms. Gastric glands were confined to a small region occupying the distal end of the corpus ventriculi which was named the "gastric unit". A comparative study of the digestibility of the dry matter, organic matter and fibre in a basal barley-soya diet supplemented with different amounts of dried grass was carried out with eight babirusa, eight Large White x Landrace and eight Chinese Meishan pigs using the chromic oxide indicator ratio technique. The digestibility of the Acid Detergent Fibre (= cellulose + lignin) component of grass was less in the babirusa than in the domestic pigs. However, babirusa were able to digest Neutral Detergent Fibre (= hemicellulose + cellulose + lignin) and Organic Matter from the total diet better than the domestic pigs. The foraging and other behaviour of a male and female babirusa when given access to a semi-natural enclosure was recorded using one-minute time scans for six hours per day during five consecutive days. Foraging mainly took the form of walking around with the nose close to or on the ground surface while sniffing. Rooting only took place in that part of the enclosure with very loose sand and was never observed in regions with more compact soil. The two most important food items consumed by the babirusa (in addition to the food that was offered to them by the zoo staff)were bramble leaves and cherry fruits. The animals also demonstrated their ability to carefully select certain plant parts when eating herbs and grasses. The results of these three studies suggested that the babirusa was a nonruminant foregut fermenting frugivore/concentrate selector, specialised in the fermentation of plant solubles and more easily digestible fibres and was able to select those plants and plant parts which are more easily digestible. Information on the diet being fed to babirusa in the 19 zoos indicated that fruits were the items most favoured in captivity. The animals also readily consumed a wide variety of leaves, buds and twigs from branches. The range between zoos in the amounts of total food, dry matter, crude protein, fat, fibre and digestible energy being fed was extremely large. Using prediction equations for domestic pig breeds the energy requirements for the babirusa were estimated to be 11.3 MJ/day for males and 8.5 MJ/day for females and the protein requirements were estimated to be 88g CP/day for males and 59g CP/day for females. These results together with other information gathered from the literature support the view that the main items in the diet of wild babirusa are likely to be fruits and leaves supplemented with smaller amounts of herbs, grass, roots and animal matter