Nattium for porcupine

a great amount of absorption. However, the high concentration of the other minerals in the colon indicated there was little absorption of potassium, calcium and phosphorus. In all hindgut fermenters, high levels of Na+, K+ and P++ are maintained throughout the cecum and colon, and are absorbed in the distal colon (Staaland, et al., 1995), which is true for the porcupine, as well. High levels of minerals in the cecum are important for fermentation. In most species, sodium concentrations remained approximately the same or increased through the small intestine, which is not the case with porcupines. Roze (1989) suggested that the higher concentration of sodium in the cecum might give evidence that porcupines have a sodium storage mechanism analogous to that found in the rumen fluid of moose at Isle Royale, as reported by Belovsky and Jordan (1981). This mechanism could be an adaptation to sodium-depleted environments, particularly in the winter, or as a way to offset the deleterious effects of excess potassium in the spring diet.

4. The porcupine's ability to masticate food into small particles may contribute to digestion, by increasing the surface area and further exposing particles to fermentation (Felicetti, et al., 2000).

5. Vispo and Hume (1995) suggested that the large distal colon in the porcupine was beneficial in water and possibly electrolyte resorption. This would be an ideal adaptation for a diet low in minerals, such as sodium, in order to maintain the necessary physiologic balance.

6. Metabolic fecal nitrogen (MFN) in herbivores ranges from 1-9 g. N/ kg dry matter intake (DMI) (Robbins, 1993), and is generally on the high end in animals consuming forage and high fiber. The MFN for porcupines is on the low end of normal (2.8g. N/ kg. DMI) (Felicetti, et al., 2000), but is consistent with that of leaf-eating marsupials consuming diets high in tannins (2.3 – 5.9g. N/kg. DMI) (Robbins, 1993). The ability to reduce MFN lowers the amount of protein required to meet metabolic needs, so is a benefit for animals on a low-protein diet.

One unique difference in the digestive tract of porcupines, not found in most other rodents, is the presence of a sixth lobe of the liver. A major function of the liver is detoxification. Porcupines also lack a gall bladder, although adults do possess a bile duct (Dodge, 1982). The adaptive importance of these modifications is unknown.

DIETARY PROTEIN, FAT AND FIBER

The winter diet is very low in protein and high in indigestible fiber. Feeding on the most nutritious plants or plant parts may ultimately determine survival until the more nutritious spring vegetation emerges. Gill and Cordes (1972) analyzed the crude protein and fiber content of Limber pine (Pinus flexilis), Lodgepole pine (Pinus contorta), Douglas fir (Pseudotsuga menziesii) and White spruce (Picea glauca) in their study site. Limber pine, which was the preferred food item, had the highest crude protein (CP) level (3.2%) and lowest fiber content (9.7%). Lodgepole pine, the least preferred species, had the lowest CP level (1.9%) and highest fiber content (24.3%). Limber pine also had a higher percentage of crude fat than the other species (12.7%). The conclusion was that porcupines exploited species with the highest protein and fat, and lowest fiber content available.

Stricklan, et al. (1995) compared nutrients of Gambel Oak (Quercus gambelii), white fir (Abies concolor) and Douglas fir (Pseudotsuga menziesii) in Utah. Gambel oak was preferred over the conifer species, even though the tannin level, which binds protein, was higher in oak. The conclusion was that even though the fiber content in oak was higher, it had a higher protein level