Interactions between ungulates, forests, and supplementary feeding: the role of nutritional balancing in determining outcomes

Abstract

People provide wild ungulates with large quantities of supplementary feed to improve their health and survival and reduce forest damage. Whereas supplementary feeding can positively affect the winter survival of ungulates and short-term hunting success, some of the feeds provided may actually reduce ungulate health and increase forest damage. Here, we highlight how recent advances in ungulate nutritional ecology can help explain why supplementary feeding can lead to undesirable outcomes. Using Europe's largest cervid, the moose (Alces alces), as a model species, and Sweden, as the socio-ecological context, we explain the concept of nutritional balancing and its relevance to supplementary feeding. Nutritional balancing refers to how animals alter their food intake to achieve a specific nutritional target balance in their diet, by selecting balanced food items or by combining items with nutritional compositions that are complimentary. As the most common supplementary feeds used contain higher concentrations of non-structural carbohydrates than the ungulates' normal winter diet, the consumption of such feeds may cause animals to increase their intake of woody browse, and thereby exacerbate forest damage. We also explain how animal health may be negatively affected by large intakes of such feed if complementary browse items are not available. We therefore suggest that the use of inappropriate feed is an additional means by which supplementary feeding may result in negative outcomes for hunters, forest owners, and wild animals.

Varied diets, including broadleaved forage, are important for a large herbivore species inhabiting highly modified landscapes

“…This phase of the forest rotation period (ca 0-15 yrs since clear cutting and regeneration) represents the habitat type with the highest concentrations of tree browse within browsing height 7,29 . Our results thus support the hypothesis 30 that variation in landscape scale winter food composition and quantity is one explanatory factor behind regional differences in body mass in Scandinavian moose 31 . This result has wide implications, as body conditions early in life can affect many aspects of adulthood, creating long-lasting effects on demographics 22 .…”

“…These crops are common supplementary foods in the region 28 , meaning that the root crops (stripped of leaves) are deliberately placed into the environment with the aim of regulating the availability of food for the wild animals 41 . These root crops have been cultivated for enhanced energy content and have nutritional compositions that are highly inconsistent with the natural winter diet of moose 30 . Large intakes of such items can increase the risk for ruminal acidosis 42 , and teeth deterioration, if items are high in sucrose (e.g.…”

“…Concerns regarding supplementary feeding are not limited to Sweden 30 , as these practices have been associated with adverse impacts on the health 41 and ecology 45 of free-ranging ungulates internationally, even though positive effects of supplementary feeding on ungulate survival and reproduction also have been observed 45 . Due to covariance in our data-set between the intake of supplementary foods with diet diversity and ungulate population density, a clear interpretation of these particular linkages is not possible in our study.…”

Challenges and science-based implications for modern management and conservation of European ungulate populations

“…The feeding of wild ungulates often has unintended effects, which are typically complex (Milner et al 2014). These may involve changes to vegetation composition and structure with consequent cascading effects on other trophic levels (Mathisen and Skarpe 2011), as well as exacerbating within-and between-species disease persistence and transmission risks (Sorensen et al 2014), browsing damage and competition between ungulate species (Felton et al 2017). We urge managers to consider both the costs and benefits of supplementary and diversionary feeding before deciding whether to feed ungulates or not.…”

Human activities might influence oncogenic processes in wild animal populations

“…A recent review on nutritional effects of supplementary food on wildlife demonstrated that nearly half of the studies (42%) found negative effects of provisioning on protein or micronutrient deficiencies 44 . In addition, higher sugar content and lower fibre content often describes anthropogenic food provided for animals 52 . All of these dietary characteristics have been associated with different types of cancer in humans [53][54][55][56] .…”