Specific dynamic action of a large carnivorous lizard, Varanus albigularis

Area of Science:

• Physiology
• Herpetology
• Ecology

Background:

• Varanus albigularis in Africa undergoes prolonged dry-season fasting and wet-season feeding.
• Sit-and-wait foraging snakes show large post-feeding metabolic increases due to gut up-regulation.
• This study investigates if V. albigularis exhibits similar metabolic responses to digestion.

Purpose of the Study:

• To measure pre- and post-prandial oxygen consumption rates (VO2) in adult V. albigularis.
• To determine if V. albigularis exhibits large metabolic responses to digestion.
• To compare these responses to those of sit-and-wait foraging snakes.

Main Methods:

• Adult V. albigularis were fed various meals (ground turkey/snails, eggs, juvenile rats).
• Oxygen consumption rates (VO2) were measured before and after feeding.
• Specific dynamic action (SDA) was calculated based on elevated VO2.

Main Results:

• V. albigularis VO2 peaked at 7-10 times pre-feeding levels within 24-27 hours.
• Elevated VO2 persisted for 60-90 hours, with SDA representing 24% of ingested energy for fully digested meals.
• Metabolic responses were comparable in magnitude to those of sit-and-wait foraging snakes.

Conclusions:

• V. albigularis exhibits significant post-prandial metabolic increases, similar to sit-and-wait snakes.
• This suggests V. albigularis may down-regulate gut function during fasting and up-regulate it during feeding.
• The high energetic cost of gut up-regulation is a key factor in their feeding strategy.