Camera collars reveal macronutrient balancing in free-rangingmale moose during summer

Abstract

Understanding how the nutritional properties of food resources drive foraging choicesis important for the management and conservation of wildlife populations. For moose(Alces alces), recent experimental and observational studies during the winter haveshown macronutrient balancing between available protein (AP) and highly metaboliz-able macronutrients (total non-structural carbohydrates [TNC] and lipids). Here, wecombined the use of continuous-recording camera collars with plant nutrient analysesand forage availability measurements to obtain a detailed insight into the food andnutritional choices of three wild moose in Norway over a 5-day period in summer. Wefound that moose derived their macronutrient energy primarily from carbohydrates(74.2%), followed by protein (13.1%), and lipids (12.7%). Diets were dominated bydeciduous tree browse (71%). Willows (Salix spp.) were selected for and constituted51% of the average diet. Moose consumed 25 different food items during the studyperiod of which 9 comprised 95% of the diet. Moose tightly regulated their intake ofprotein to highly metabolizable macronutrients (AP:TNC + lipids) to a ratio of 1:2.7(0.37 ± 0.002SD). They did this by feeding on foods that most closely matched thetarget macronutrient ratio such as Salix spp., or by combining nutritionally imbalancedfoods (complementary feeding) in a non-random manner that minimized deviationsfrom the intake target. The observed patterns of macronutrient balancing alignedwell with the findings of winter studies. Differential feeding on nutritionally balanceddowny birch (Betula pubescens) leaves versus imbalanced twigs+leaves across mooseindividuals indicated that macronutrient balancing may occur on as fine a scale asforaging bites on a single plant species. Utilized forages generally met the suggestedrequirement thresholds for the minerals calcium, phosphorus, copper, molybdenum,and magnesium but tended to be low in sodium. Our findings offer new insights intothe foraging behavior of a model species in ungulate nutritional ecology and contrib-ute to informed decision-making in wildlife and forest management. cervid, deer, large herbivore, macronutrient balancing, nutritional ecology