Meeting Abstract

141.5  Monday, Jan. 7  Jirds living in a hypercapnic environment incur energetic costs, but don’t appear to care. DOWNS, C.J.*; BRICKNER-BRAUN, I.; VATNICK, I.; PINSHOW, B.; Ben-Gurion Univ., of the Negev, Midreshet Ben-Gurion, Israel; Ben-Gurion Univ., of the Negev, Midreshet Ben-Gurion, Israel; Widener Univ., Chester, PA; Ben-Gurion Univ. of the Negev, Midreshet Ben-Gurion, Israel downsc@gmail.com

Animals use burrows to avoid predation, find protection from adverse environmental conditions, raise young, and hoard food. But, burrow dwellers are isolated from atmospheric sources and sinks for exchange of respiratory gases and if CO₂ accumulates in burrows of animals with high metabolic demands, the question is: are these animals physiologically and behaviorally adapted to high inspired FCO₂? We investigated how exposure to high FCO₂ (0.07) affected total evaporative water loss (TEWL), metabolic rate (MR), respiratory rate (f), and activity patterns of the Sundevall’s jird (Meriones crassus), a semi-fossorial desert rodent. Assuming that breathing CO₂-rich air is stressful, we hypothesized that the above variables all increase under hypercapnic conditions. We found that jirds breathing high FCO₂ had higher resting and daily MR and higher f than jirds breathing CO₂-free air; the jirds were also more active and slept less. However, average TEWL did not differ between treatments. We concluded that living in a hypercapnic environment is energetically costly, but does not increase TEWL, and therefore hypothesized that Sundevall’s jirds should prefer environments with atmospheric FCO₂ to hypercapnic surroundings. To test this hypothesis, we did a choice experiment, but found no difference in the time jirds spent in fresh or CO₂-rich air. Thus, despite the energetic cost of inhabiting a hypercapnic environment, jirds did not leave it. This suggests that the costs to fitness of leaving a burrow with high FCO₂ (e.g., risk of predation, thermoregulating in the desert) may be greater than the physiological costs of staying in the hypercapnic environment.