Anthropogenic supply of nutrients in a wildlife reserve may compromise conservation success

In nutrient-poor wildlife reserves it has become common-practice to provide supplemental mineral resources for wildlife. Yet, the impacts of anthropogenic mineral supplementation on large herbivore nutrition, behaviour, and subsequent impact on ecosystem processes have received little attention. Here, we examine the contribution of anthropogenic mineral lick provision to wildlife nutrient intake across a community of mammalian herbivores (>10 kg) in the southern Kalahari Desert. Based on predicted daily nutrient intake and a faecal nutrient assessment, many large herbivore species appear deficient in phosphorus (P), sodium (Na), or zinc (Zn). For these nutrients, anthropogenic salt and mineral licks constitute an important source of nutrient intake helping to reduce or overcome requirement deficits. Larger-bodied species disproportionately consumed licks, acquiring more nutritional benefits. A comprehensive assessment of animal body condition indicated that, in general, large herbivores display good health. However, bulk grazers, non-ruminants and females displayed poorer body condition. We discuss how provisioning of anthropogenic mineral licks may inflate large herbivore populations beyond the long-term carrying capacity of the reserve by decoupling wildlife fecundity from nutrient-related feedbacks on population growth. Over time, this could compromise ecosystem integrity through habitat degradation, modified species interactions and trophic cascades. Based on results presented here, it is clear that anthropogenic provisioning of mineral licks should be considered cautiously by wildlife managers aiming to conserve natural processes in landscapes.

Automated summary

In nutrient-poor wildlife reserves, providing supplemental mineral resources for wildlife is common practice. However, the impacts of anthropogenic mineral supplementation on large herbivore nutrition, behavior, and ecosystem processes have not been well studied. This study examined the contribution of anthropogenic mineral lick provision to wildlife nutrient intake in the southern Kalahari Desert. Results showed that many large herbivore species are deficient in phosphorus, sodium, or zinc, and anthropogenic salt and mineral licks are an important source of these nutrients. Provisioning of mineral licks may have negative long-term effects on ecosystem integrity and should be considered cautiously.