Foraging Patterns and Their Multiplier Effects on Productivity of Northern Ungulates

In most of their arctic and subarctic ranges reindeer, caribou and muskoxen adopt generalist foraging strategies; they consume a wide variety of plants even though they feed selectively. This paper analyses some aspects of selective feeding behavior and its possible influence on animal production. Selective feeding that makes only small changes in quality or amount of food intake may cause a greatly enhanced, or multiplier, effect on animal production. In an example for reindeer grazing in arctic coastal tundra during summer, selective grazing increased digestibility by 14% and dry matter intake by 27%, which combined to give a 268% increase in projected daily weight gain. Weight gain may then influence populations through control over conception rate and survival during winter. An increase by 14% in bodyweight of young female reindeer during summer results in a 35% increase in the probability of conception in autumn. Winter range conditions can affect birth weight, milk production and calf growth rates, all of which affect future reproduction and survival and provide additional avenues for multiplier effects.