Table 13 — The species with the highest and lowest mean values for 13 minerals and nutrients (from appendix B) 



Exceptional value (high or low) 

 Nutrient High value Low value from special plant parts 





Percent 





Percent 





Percent 



Moisture 



74.18 



{Opuntia erinacea) 



17.55 



(Erioneuron pilosum) 







Nitrogen 



2.63 



{Atriplex canescens) 



1.12 



(Aristida purpurea) 



2.93 



(Eriogonum inf latum, leaves) 



Protein 



16.44 



{Atriplex canescens) 



7.12 



(Aristida purpurea) 



18.31 



(Eriogonum inflatum, leaves) 



Phosphorus 



0.20 



(Erodium cicutarium) 



0.07 



(Erioneuron pilosum) 



0.30 



(Sphaeralcea ambigua, flowers) 



Potassium 



4.19 



{Atriplex canescens) 



0.42 



(Aristida purpurea) 







Zing 



23.28 



(Erodium cicutarium) 



9.91 



(Ephedra nevadensis) 



25.32 



(Sphaeralcea ambigua, flowers) 



Iron 



1.561.62 



{Plantago patagonica) 



116.02 



(Ephedra nevadensis) 



98.08 



(Opuntia erinacea, fruits) 



Manganese 



95.46 



(Opuntia basilaris) 



19.02 



(Eriogonum fasciculatum) 



133.44 



(Opuntia erinacea, fruits) 



Sulfur 



0.98 



(Atriplex canescens) 



0.17 



(Eriogonum fasciculatum) 







Sodium 



0.043 



(Krameria parvi folia) 



0.003 



(Hymenoclea salsola and 















Stipa hymenoides) 







ADPi 



46.73 



(Erioneuron pilosum and 



17.87 



(Atriplex canescens) 











Plantago patagonica) 











TNC2 



15.26 



(Eriogonum fasciculatum) 



5.11 



(Ceratoides lanata) 







Fat 



18.23 



(Hymenoclea salsola) 



5.24 



(Plantago patagonica) 







'Acid detergent fiber. 



^Total nonstructural carbohydrates. 



Table 13 shows the species with the highest and low- 

 est mean values for 13 minerals and nutrients. 



Fat and protein (total organic nitrogen) had a sig- 

 nificant (P < 0.05) positive correlation; protein and 

 ADF, and TNC and ADF were negatively correlated. 

 There were no significant correlations between pro- 

 tein and TNC or fat and ADF (fig. 2; appendix B). 



For four species we sampled different plant parts 

 (appendix B). The regular samples for Eriogonum 

 inflatum consisted of leaves and small twigs; separate 

 collections were made for flowers and flowering stems, 

 for large flowering stalks, and for small inflorescences 

 and flowers. Leaves and twigs were higher in many 

 measured parameters than the large flowering stalks. 

 Those parameters include moisture content, nitrogen, 

 phosphorus, potassium, iron, manganese, calcium, 

 magnesium, and TNC; ADF was lower. Flowers and 

 flowering stems were lower than the large flowering 

 stalks in potassium, calcium, and (especially during 

 the spring) sodium. 



We sampled Sphaeralcea ambigua flowers and flow- 

 ering stems, as well as leaves and tv^rigs. Flowers and 

 flowering stems were higher in nitrogen, phosphorus, 

 potassium, zinc, iron, copper, and calcium than were 

 leaves and twigs. We sampled flowers and fruits of 

 Ceratoides lanata as well as leaves. The two kinds of 

 samples differed little, but potassium was up slightly 

 for the samples of flowers and fruit; water content, cal- 

 cium, and TNC were dovm slightly. We sampled fruits 

 as well as the pads of Opuntia basilaris. The fruits 

 were lower than the pads in respect to moisture con- 

 tent, calcium, and magnesium, but were higher in 

 nitrogen, phosphorus, potassium, and fat. 



These samples of separate plant parts suggest some 

 differences, usually not dramatic, for the measured 



parameters. Our regular samples were of leaves and 

 closely attached stems— the material most likely to 

 be foraged. One spring during the course of our col- 

 lections we saw a large desert tortoise with its beak 

 stained purple fi-om the Krameria flowers it had eaten. 

 Tortoises, like other herbivores, can be selective in eat- 

 ing plant parts. On another occasion, we noted a tor- 

 toise in a patch of Erodium. This tortoise voraciously 

 consumed several whole Erodium plants. Esque and 

 others (1991) have meticulously documented feeding 

 preferences and habits of tortoises at City Creek and 

 Littlefield. They found that tortoises fed mostly (up 

 to 80 percent) on the plentiful ephemerals, Bromus, 

 Erodium, and Schismus, but that they also consumed 

 a wide array of grasses, forbs, and shrubs. Perhaps 

 desert tortoises fare well on exotic plants as does the 

 Townsend's ground squirrel (Sperophilus townsendii) 

 in southwestern Idaho (Yensen and Quinney 1992). 



Woodbury and Hardy (1948) and Hansen and others 

 (1976) suggested that the desert tortoise's preferred 

 foods were perennial grasses, especially Muhlenbergia 

 porteri. Our analyses do not show a nutritional advan- 

 tage for perennial grasses; rather annual grasses, an- 

 nual forbs, and shrubs appear better when nitrogen, 

 phosphorus, and TNC are considered (table 4). Suc- 

 culents have favorable moisture content, potassium, 

 calcium, magnesium, and ADF. Perennial grasses do 

 have the advantage of consistent production. Among 

 the perennial grasses we studied, nutrient and min- 

 eral values were quite similar. However, high values 

 for the following parameters are of note: moisture con- 

 tent (Hilaria rigida and Muhlenbergia porteri), potas- 

 sium (Stipa hymenoides, Hilaria rigida, and Muhlen- 

 bergia porteri), iron (Erioneuron pilosum and Aristida 

 purpurea), manganese, magnesium, and sodium 



13 



