Methods of Morphological Diet Micro-Analysis in Rodents

Methods of microscopic diet analysis were examined and special emphasis was placed on the different methods applicable to granivorous and herbivorous diet of small rodents. No satisfactory method for direct measurement of food composition exists but volume estimates agree rather well with a known composition, when a minimum area is visually surveyed. Difficulties in interpretation of stomach volume composition arise due to hydration and dehydration. Different retention of various food components was quantitatively unimportant in the rodent Microtus agrestis but particles retained from earlier meals caused difficulties when frequency of occurrence evaluations were used. These accidental diet particles increase with increasing slide area, with magnification and when sampling from mouth to dropping. The orders of importance of diet items showed pronounced differences between volume estimates and estimates according to frequency of occurrence or relative occurrence. The use of conversion factors may be erroneous due to i.a. different fragmentation at different seasons.