Sodium content in plant and insect food resources consumed by chimpanzees (Pan troglodytes schweinfurthii) in Gombe National Park, Tanzania

Objectives

Many nonhuman primate diets are dominated by plant foods, yet plant tissues are often poor sources of sodium—a necessary mineral for metabolism and health. Among primates, chimpanzees (Pan troglodytes), which are ripe fruit specialists, consume diverse animal, and plant resources. Insects have been proposed as a source of dietary sodium for chimpanzees, yet published data on sodium values for specific foods are limited. We assayed plants and insects commonly eaten by chimpanzees to assess their relative value as sodium sources.

Materials and Methods

We used atomic absorption spectroscopy to determine sodium content of key plant foods and insects consumed by chimpanzees of Gombe National Park, Tanzania. Dietary contributions of plant and insect foods were calculated using feeding observational data.

Results

On a dry matter basis, mean sodium value of plant foods (n = 83 samples; mean = 86 ppm, SD = 92 ppm) was significantly lower than insects (n = 12; mean = 1549 ppm, SD = 807 ppm) (Wilcoxon rank sum test: W = 975, p < 0.001). All plant values were below the suggested sodium requirement (2000 ppm) for captive primates. While values of assayed insects were variable, sodium content of two commonly consumed insect prey for Gombe chimpanzees (Macrotermes soldiers and Dorylus ants) were four to five times greater than the highest plant values and likely meet requirements.

Discussion

We conclude that plant foods available to Gombe chimpanzees are generally poor sources of sodium while insects are important, perhaps critical, sources of sodium for this population.