The Role of Minerals in Food Selection in a Black Howler Monkey (Alouatta Pigra) Population in Belize Following a Major Hurricane

Abstract

As plants may contain low levels of some minerals including sodium, copper, and phosphorous, herbivores may become deficient in these nutrients. In 2001, Hurricane Iris hit the Monkey River Forest in Belize causing substantial damage to the food supply of the black howler monkey population (Alouatta pigra) living there. This included an 18-month absence in fruit production and a complete loss of figs that are high in calcium. In this article, we describe the post-hurricane diet of this monkey population and compare the mineral content of food items to each other and to recommendations for non-human primates [NRC 2003]. We also investigate food selection in relation to potentially limiting minerals. Behavioral data from four groups of howlers (2002-2006) and samples of all ingested food items were collected and a sample of 99 plant from 18 food species was analyzed for mineral content. Unexpectedly, the post-hurricane diet contained more mature leaves than new leaves despite the availability of new leaves. Leaves contained higher amounts of minerals than reproductive parts and with the exception of Cecropia peltata stems, plant parts were low in sodium. Cecropia peltata is a pioneer species that grows following habitat disturbance thus the ingestion of these stems may be a potential mechanism to avoid sodium deficiency in this damaged forest. Calcium and zinc were found above recommended values in most food items; however, both positively predicted food selection, which may reflect a difference between their abundance and their bioavailability. However, as mature leaves contained more calcium than other plant parts, their high post-hurricane consumption may also be a response to the absence of figs and the need to find an alternate calcium source. This study highlights how habitat disturbance may affect mineral abundance and the dietary choices of primates.

Minerals in the Foods Eaten by Mountain Gorillas (Gorilla beringei)

“…The fruits analyzed in this study were low in their mineral content. The low mineral quality of fruits is well documented [11] (an exception being figs, which act as an important source of Ca for many primate species [9], [41]). The mineral content of mountain gorilla food items was similar to the foods consumed by western lowland gorillas in Cameroon ([16]; Table 4 ).…”

“…As suggested by Milton [42], this strategy of selecting a diversity of food items, each item high in particular minerals, may allow primates to achieve optimal micronutrient nutrition in habitats that are typically mineral-poor [7], [8], [9], [10]. The relationship between dietary diversity and likelihood of obtaining an adequate complement of nutrients has been observed across animals in general [43], [43], [44,45].…”

“…Much debate exists in the current literature as to the importance of minerals in driving food selection [7], [9], [10], [15], [17], [18], [28], [42], [49]. The consumption of certain foods that are low in macronutrients, like wood and roots, is likely explainable by their mineral composition.…”

“…Despite its importance, our understanding of the mineral intake and requirements of wild primates is limited [2], [7]. Few studies have investigated the dietary minerals of primates [7], [8], [9], [10], [11], [12], [13], [14], and particularly of apes [15], [16], [17], [18], [19].…”

“…Given the variety of dietary types and digestive systems within the primate order, taxa may differ greatly in their mineral requirements and strategies to acquire mineral nutrients. For example, howler monkeys rely heavily on figs in their diets, a fruit that is high in Ca [9], and thus may not seek to otherwise supplement their diet with Ca, and colobines that host foregut microbes may have a lower need for certain minerals (similar to ruminants) [22], [23]. When staple foods do not provide sufficient minerals, primates can meet their mineral needs by supplementing their typical diet.…”