A BIOENERGETIC BUDGET FOR OVERWINTERING NEWTS (NOTOPHTHALMUS-VIRIDESCENS) FROM SOUTHERN OHIO - THEIR FAT RESERVES AND AEROBIC METABOLIC RATES IN WATER

1. Red-spotted newts (Notophthalmus viridescens) remain active throughout the winter. Locomotor costs and fat reserves of newts from southern Ohio were investigated to determine their energy balance under winter food shortage. 2. A magnetic rotating respirometer was devised to exercise the newts, acclimated at 5 or 25-degrees-C, at speeds of 0, 30, 60 and 90 cm/min and at 1, 5 and 25-degrees-C. 3. Our results suggest that this device is useful for studying the locomotor metabolism of small ectotherms. 4. The metabolic rates were incorporated into a total energy budget. 5. Fat reserves were determined for the newts before and after a 55% reduction of their body mass. 6. Oxygen consumption increased with speed at both 1 and 5-degrees-C, but differences among treatments were not significant. 7. Oxygen uptake at 25-degrees-C was significantly higher than that at 1 or 5-degrees-C. 8. Metabolic rates at 25-degrees-C increased to a plateau when the newts moved at 30 cm/min or higher speeds. 9. Transport costs for the newts decreased as locomotion speed increased. 10. Newts can store at least 85 mg fat prior to winter. This could support low levels of activity for a minimum of 78 days at low winter temperatures. 11. Red-spotted newts thus appear to be capable of remaining active and surviving winter without ingesting food.