Title

Digestive physiology and food preferences of nectarivorous and frugivorous bats in the neotropical family Phyllostomidae

Date of Award

1997

Availability

Article

Degree Name

Doctor of Philosophy (Ph.D.)

Department

Biology

First Committee Member

Theodore H. Fleming, Committee Chair

Abstract

In this study I compared the digestive processing of nectar sugars and pollen between specialized and occasional flower-visiting bats (Phyllostomidae) and examined the ecological and physiological correlates of nectar sugar preferences of these bats.Digestion efficiency of sucrose, glucose and fructose solutions was very high (94-96.7%) in two species of nectarivorous bats, Leptonycteris curasoae and Anoura geoffroyi, and was slightly lower (87.8-92.7%) in one species of frugivorous bat, Artibeus jamaicensis. There were no significant differences in the efficiency of digestion among the three types of sugar in any species of bat. Blood glucose in bats kept in small cages and given individual solutions of the three sugars increased 1.5-4.5 times above baseline levels in the first 10-20 minutes and decreased to pre-dose levels in less than 60-90 minutes. High sugar digestion efficiency and rapid absorption of glucose probably allow flower-visiting bats to meet their energetic requirements with a nectar-based diet.In general, nectarivorous bats had higher extraction efficiencies (46-90%) of the contents of three types of pollen (Hylocereus undatus, Pseudobombax ellipticum and an unidentified columnar cactus) than frugivorous bats (32-68%) although their gastrointestinal tracts (GI) processed pollen at the same rate. In these animals, the GI apparently functions as a continuous stirred-tank reactor (CSTR) in series with a plug-flow reactor (PFR) represented by the stomach and intestine, respectively, with longitudinal mixing in the PFR. Differences among species of bats in pollen digestion efficiency was not explained by time spent in the GI by pollen grains.Frugivorous and nectarivorous bats consistently preferred sucrose over glucose, fructose, or a mixture of glucose and fructose. This pattern in sugar preference is not consistent with predictions based on the sugar composition of fruits and nectars ingested by these bats in the wild and cannot be explained by the efficiency with which the animals digest each of these sugars. I hypothesize that sucrose preference may be explained by pre- and post-digestive events.My results indicate that the GI tract of nectarivorous bats is physiologically specialized to process nectar and pollen, and that the nectar sugar preferences of these bats cannot be explained by ecological or digestive factors.

Keywords

Biology, Ecology; Biology, Animal Physiology; Biology, Zoology

Link to Full Text

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