390 



G. O. Batzli et al. 



a> 

 to 



0] 



O) 



o 



k_ 

 CL 



8o^ 



- 



Q 60- 



o 



c 40|- 



I 20h 





 80 

 60 

 40 

 20 



Lemmus 



S Summer 

 D Winter 



Rangifer 



Ml. 



I 







®Dry Maner(D) 

 DEnergy (E) 



E=33 



n D=3I 



Dicot 

 Graminoids Moss 



80 

 60 

 40 

 20 

 

 80 

 60 

 40 

 20 



Summer Only 



m Caribou (C) 

 □ Reindeer (R) 



I 



Dicot Lichen 



Graminoids Moss Dead 



Material 



FIGURE 10-18. The composition and digestibility of diet for lemmings 

 and caribou. The horizontal lines represent mean digestibilities for the 

 overall diet. (After White et al. 1975, Batzli and Cole 1979.) 



most available in the vegetation type. These include the graminoids Erio- 

 phorum angustifolium, Carex aquatilis and Dupontiafisheri, and several 

 willows — Salix pulchra, S. arctica, S. ovalifolia and 5. lanata. This gen- 

 eralized feeding was modified slightly by preferences for a few species of 

 herbaceous dicotyledons and lichens (White et al. 1975). Dicotyledons 

 made up a slightly higher percentage of the diet of caribou than did 

 graminoids. Vascular plants contributed 92% of the diet (Figure 10-18). 

 Mosses were eaten in such small amounts that intake may have been ac- 

 cidental. 



Estimates of in vitro dry matter digestibility of hand-picked plant 

 samples were used to calculate the mean digestibihty of dietary compon- 

 ents (Person 1975, White et al. 1975, Person et al. 1980, White and Tru- 

 dell 1980). Rumen inoculum was obtained from caribou and rumen- 

 fistulated reindeer while they were grazing on tundra. The ranges in di- 

 gestibility of individual species were large for graminoids (52 to 79%) 

 and shrubby dicotyledons (21 to 71%), but the mean ± 1 SE digestibility 

 of graminoids (54 ±3% to 64 ±3%, depending on species mixture) was 

 not significantly different from shrubs (45 ±5%). Forb and lichen 

 digestibility was similar to that of graminoids, but mosses had very low 

 digestibility (Figure 10-18). Based on the relative occurrence of these 

 dietary components mean summer estimates of digestibilities of all for- 

 age consumed were 57% for caribou and 49% for reindeer. The lower di- 



