However, given that mountain gorillas consume a much higher level of K than minimally required, alternative explanations are likely required to account for this behavior in mountain gorillas. In dairy cattle it has been suggested that high levels of K interfere with Ca absorption and lead to higher incidence of milk fever, though this interaction may be unique to foregut fermenters. Both mountain gorilla foods and their diets overall have a higher Ca:K ratio than recommended, but the direct implications of this ratio are unknown. It should also be noted that published R428 mineral requirements and ratios might be conservative because primates vary in body size, physiology and digestion, and foods vary in bioavailability. While we compared gorilla foods to recommended Hominidae requirements, the recommendations for adequate concentrations of minerals for nonhuman primates may be higher than what primates actually require. For example, the NRC suggests that primates need to consume a diet of 0.25% Na on a dry matter basis, but the diets of most wild primates are much lower, indicating that primates are able to survive on lower dietary concentrations of Na. Given that the mineral ratios do not always meet recommended target ratios when considered within the context of overall diet. The ratio of Ca to P ratio in gorilla feces is 4.04, higher than the ratio averaged across all staple foods suggested by this study but lower than that of the major dietary component, herbaceous leaves. The Ca:P ratio in feces, however, is lower than that observed in the daily diets of gorilla females, silverback males, and juveniles, which is considerably higher than the recommended ideal ratio for humans. This suggests that the high levels of Ca in the diet might inhibit the absorption of P, which occurs when Ca is consumed in excessive amounts. In addition to mineral interactions, the bioavailability of minerals can also be affected by plant physiology. Roots, for example, carry high percentages of the minerals abundant in the surrounding soil, and the single rock sample ingested by an individual at the site was found to be exceedingly high in Fe. The Fe in plant tissues tends to be predominantly unavailable for digestion, as it is usually bound to organic compounds in the plant structure that may past through animal digestive tracts. While little is known about the use and uptake of Fe in roots, the availability of Fe has been tested in legumes, where levels of Fe-binding polyphenols and the presence of phytate render most Fe unusable to animals, despite the high overall content of Fe found in these plant structures. Understanding patterns of bioavailability in Fe is especially crucial in primates, as captive primates have been shown to be highly vulnerable to hemosiderosis as a result of overconsumption of Fe.