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The gross morphology of the body and gastrointestinal tract of genetically-similar tammar wallabies (Macropus eugenii) that had been introduced into two different nutritional environments on the North Island of New Zealand were compared using multivariate analysis. Tammar wallabies from Kawau Island had significantly lower body mass per unit body length than those from the Rotorua district where food was more abundant. Furthermore, wallabies from Kawau Island had longer small intestines and caecae relative to other gut regions than did those from the Rotorua district. This suggests that poor-quality food might reduce the efficiency of primary fermentation in the forestomach; similarly, the efficiency of digestion and absorption in the small intestine might be reduced. In addition, poor-quality food might promote secondary fermentation in the hindgut of grazing tammar wallabies.

The particle size distribution of stomach contents from 25 tammar wallabies (Macropus eugenii Desmarest) shot in the Okataina State Forest and adjoining farmland near Rotorua, New Zealand, were determined. There was a greater percentage of finer, and a smaller percentage of larger, particles than reported in the stomach contents of larger macropods. The chewing and biting activities of four free-ranging tammars fitted with radio-microphone collars were monitored. Chewing rates (chews per minute) were similar to those of other small herbivorous vertebrates. There were significantly lower rates of chewing and higher chew-to- bite ratios when browsing than when grazing. Observations of browsing by three captive tammars showed inefficient handling by mutually opposed palms and digitopalmar grip, resulting in low rates of ingestion. We suggest that tammars lower the time necessary for fermentation of food by reducing the size of food particles, and that their choice between graze and browse is influenced by food handling and chewing investment.

The temporal association between drinking and feeding in four captive tammar wallabies (Macropus eugenii Desmarest) maintained on various foods is examined. Tammars maintained on cubed carrots never drank. In tammars fed pellets food-associated drinking took place and 77.5% (7.4, s.e.) of drinking episodes commenced within 60 s of the beginning or end of a feeding event. Drinking events occurred singly, were of short duration and increased in frequency but not duration, when low-quality pellets were fed. Food- associated drinking in the tammar may result from the induction of drinking episodes of relatively fixed duration by an oropharyngeal reflex.

We explored the factors that govern the length, wet tissue weight and wet digesta content of the gut components of 100 tammar wallabies (Macropus eugenii Desmarest) shot on the same night, by multivariate (discriminant) analysis and by allometric analyses based on simple linear regression, and on reduced major axis regression. The slope coefficient of the regression describing variation of whole gut content with body weight was not significantly different from isometry. Similarly, stomach length, content and tissue weight scaled isometrically with body weight, as did small intestine tissue weight and content and colon content. Colon tissue weight scaled allometrically with body weight. Length of caecum scaled to body weight was similar to that of browsing species, shorter than that of gazing species and varied with body size like that of larger species. Length of small intestine scaled to body weight was shorter, and length of colon longer, than that of similar-sized grazing species. There was a sexual dimorphism in gut morphology, females having a relatively greater amount of tissue in the stomach and colon, and a relatively longer caecum and colon. There was a reciprocal variation in the weight of digesta in stomach and hindgut, suggesting that hindgut content was evacuated as feeding proceeded. It appears that the hindgut may contribute to overall digestive strategy under conditions when reduction in feeding rate brings about a relative emtpying of the stomach.

The feeding behaviour of four tammar wallabies (Macropus eugenii Desmarest) inhabiting a bush pasture ecotone in the Rotorua district of North Island, New Zealand, is described. Feeding activity, monitored by feeding sounds, was crepuscular. Mastication effort, as daily eating time corrected for metabolic body weight and weight-related change in tooth surface area, was similar to that of the red kangaroo, a species of greater equivalent dry-matter intake. Grazing events were significantly longer than browsing events, and feeding events longer than 100 sec comprised 66.5% of total feeding activity. Grazing on farm pasture took place only at night during fine weather in visits that averaged 6.5 h. The number of feeding events longer than 100 sec taking place within the forest were significantly increased at night and were reduced during periods of adverse weather. Overall, temporal spacing of feeding events did not differ significantly by day and night but there was a significant overall negative correlation between log-converted feeding-event duration and interfeed intervals for all animals, particularly with feed events of less than 100 sec duration. This differed from that obtained in laboratory studies and may be due to grouping of feeding events according to spatial distribution of food sources.

Four tammar wallabies, maintained in a fixed 12 : 12 light : dark cycle, were fed ad libitum, one of three foods, of differing nutrient density and fibre content, consecutively, each for a period of two weeks. During the second week, food consumption was assessed daily and the temporal feeding pattern was monitored by visible and infrared video recording. Apart from a short rest period around noon, feeding continued throughout the 24-hour cycle, peaking crepuscularly. Total daily feeding time corrected to metabolic body weight was significantly longer, but dry-matter intake corrected to metabolic body weight was significantly lower than that of larger macropod species, indicating greater investment in chewing. Feed-event duration, inter-feed-event interval, rate of feeding, and dry matter intake all increased significantly on pelleted foods of low nutritional density. Rate of feeding and feed-event duration increased significantly on diced carrot such that dry-matter intake was not significantly different to that on high-quality pelleted food. Survivorship curves of inter-feed-event intervals were predominantly linear. This and the consistently higher positive correlations between the duration of individual feed events and inter-feed-event intervals than between meals and inter-meal intervals, indicated a nibbling rather than a meal-based feeding strategy. Levels of correlation of feed-event duration with inter-feed-event interval were generally low but there was a significant increase in positive correlation when food of lower quality was given. The duration of successive feed events tended to increase on low-quality and decrease on high-quality food more consistently than did successive inter-feed-event intervals.