. La Canadian field-naturaliste. 22 Canadian Field-Naturalist 114 Le Vol. de frondes. Rizoma 10 cm Figure 1. D'encombrement d'un typique Dryopteris dilatata (synonyme de D. expansa ; Cody 1996) indiquant la position et taille relative de la fronde et rhizome. usines n'étaient pas détectés ou signalés dans leur alimentation. Dans une étude de l'écologie nutritionnelle des Cerfs à queue noire, nous avons soulevé-bouteille neuf cerfs et sevrés entre eux sur la végétation naturelle. Parce que nous avons pu observer ces liberté, et très-tractable animaux sur une période de deux ans, nous avons documenté l'utilisation intensive de rhizo

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. The Canadian field-naturalist. 22 The Canadian Field-Naturalist Vol. 114 FROND. RHIZOME 10 cm Figure 1. Scale drawing of a typical Dryopteris dilatata (synonymous with D. expansa; Cody 1996) plant indicating position and relative size of the frond and rhizome. plants were not detected or reported in their diets. In a study of the nutritional ecology of Black-tailed Deer, we bottle-raised nine deer and weaned them onto the natural vegetation. Because we were able to observe these free-ranging, highly-tractable animals over a continuous two-year period, we documented extensive use of the rhizomes of Dryopteris dilatata during winter (Gillingham et al. 1997; Parker et al. 1999). Here we report on the consequences of con- suming rhizomes on vegetative production during the following growing season. Methods As part of a larger foraging/bioenergetics study (Parker et al. 1993a, 1996, 1999), we conducted intensive field observations of hand-reared Black- tailed Deer on Channel Island 20 km southeast of Wrangell, Alaska (56°22'N, 132°10'W; see Parker et al. 1996 for details). Animals were completely dependent on their environment for their survival and allowed observers to follow within 1 m. Because they also allowed an observer to kneel next to them, we were able to make detailed observations of rhi- zome consumption. On 16 March 1990 we followed three animals while they were foraging for Dryopteris rhizomes. Because actual weights of the rhizomes could not be obtained before and after for- aging by deer, we estimated the percentage of each rhizome removed. This percentage was based on a visual estimate of the amount removed by the deer using an accurate bite-unit technique (Parker et al. 1993b) and our visual inspection of the amount of rhizome remaining in the ground after deer moved to another forage item. Although this estimation was subjective, we were confident that we could estimate rhizome removal to the nearest 25% (i.e., 1-25%, 26- 50%, 51-75% and 75-99%). An

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