Fecal nitrogen as an index of dietary nitrogen in two sika deer Cervus nippon populations

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We tested the reliability of fecal nitrogen (FN) to predict dietary nitrogen (DN) in two sika deer Cervus nippon Heude, 1884 populations with greatly differing habitats. One was near the village of Nishiokoppe (area A) and the other was on Nakanoshima Island (area B) in Hokkaido, Japan. To estimate FN, we washed feces through a sieve, and diet was identified based on rumen-content analysis. The diet in area A was mostly composed of grass and legumes of agricultural origin, with browse being only a minor component. In contrast, browse such as deciduous foliage was the main component of the diet in area B. Dietary nitrogen was significantly regressed by FN within specific areas. On the other hand, the DN-FN-relationship had a similar slope but significantly different intercepts between areas. DN-FN-relationships differed between diets with and without an agricultural component, irrespective of browse. Thus, the difference in the DN-FN-relationship between areas was explained by differences in dietary composition. We therefore conclude that FN may be useful in predicting DN in diverse dietary situations regardless of the ratio of browse in the diet of free-ranging ungulates, but that dependence on agricultural pastures may hinder the utility of FN as an index of DN.