Atmospheric carbon dioxide (CO₂) and tropospheric ozone (O₃) can impact plant physiology, and may reduce food quality for herbivores. Individual performance of herbivores is often determined by the nutritional quality of food. If herbivores cannot compensate for reductions in food quality, there may be detrimental fitness consequences. To test the hypothesis that global atmospheric change will negatively impact small mammal fitness through reduced plant quality, we measured daily body mass of just-weaned prairie voles (Microtus ochrogaster) fed equal amounts of uncultivated Solidago canadensis and Taraxacum officinale plants grown in control, enriched CO₂ and enriched O₃ rings at Aspen FACE near Rhinelander, Wisconsin. Growth measurements were taken for 8 days following a 2-day treatment-diet acclimation period.  Non-structural carbohydrates, cellulose, lignin, C/N and crude protein content were determined for both plant species.

Results/Conclusions

Results show that feeding on elevated CO₂ reduced vole growth, compared to ambient-grown plants. Voles on the enriched CO₂ diet grew 23% less than voles on the control diet (F_2,15 = 6.78, P = 0.03). Females, but not males, grew significantly less  (36%) on the enriched O₃ diet (F_2,15 = 5.97, P = 0.01). The reduced growth of females under enriched O₃ may result from a 40% increase in C/N (F_2,6 = 7.52, P = 0.02) and 26% decrease in crude protein (F_2,6 = 4.75 , P = 0.06). Plant quality between CO₂ and control treatments, however, did not differ. The reduction of growth on the CO₂ diet may be due to an increase in plant defense compounds. Further analysis along this line is ongoing. Global atmospheric change has the potential to affect the survival and reproductive success of voles through reductions in growth rate.