FRESH - Deer


            This is a system for evaluating habitat quality for black-tailed deer and moose on the basis of available food, its nutritional quality, and the nutritional requirements of the adult female segment of the population.  We focus on food because it clearly sets the potential upper limit on the number of animals a habitat can support.  Forage resources (vegetation and nutritional quality) can be measured in the field and can be manipulated by land management.  We focus on digestible energy and digestible protein, because they are the two most common nutritional limiting factors for wild ungulates, and their requirements are reasonably well known for black-tailed deer and moose.  We focus on adult females because they are the productive segment of the population, the animals that produce young.  Nutritional requirements vary seasonally and with reproductive status (e.g., maintenance versus lactation).  This system is suitable for any habitat and any species of deer (Cervidae) where the availability of forage, its nutritional quality, and the nutritional requirements of the deer are known.

           The analytical system provides a “snapshot” analysis at one, user-specified point of time.  It is assumed that all available vegetation is potential food, and there is no accounting for herbivore-plant dynamics (effects of overbrowsing).  This is not a simulation model.  Rather, it is a calculator:  given specific values of available forage biomass, nutritional quality, and animal requirements, it calculates the maximum number of “animal days” (one adult female for one day) that can be sustained by the forage resource. The animal-day values are best considered in a relative (comparative) sense, not as absolute values, because they are the maximum number of animal days (at one point in time) that can be supported by the food if all the suitable food were eaten then (no herbivore-plant feedback).  The instantaneous, food-basedcarrying capacity” of a habitat varies daily with marked changes in plant phenology  and animal metebolic requirements during summer and with variation in snowpack during winter.  Our snapshot values are valid for the point of measurement and analysis; they are not an annual, or even seasonal, average.  They are best used for comparing two or more habitats, or the same habitat(s) in two or more different states (times or post-manipulation, succession, etc.).  Additionally, a large scale, GIS application of the system is useful for comparing various landscapes or patterns within the same landscape – where size and spatial configuration of habitats are important considerations.

            The FRESH system includes linked databases of understory biomass and forage-specific nutritional data for a variety of habitats and forages.  The databases provide users examples or reference points (in the case of habitats) and ballpark-level default estimates (in the case of forages) for data that the user might not have.  Although field data directly from the user’s study area always are best, a user can use the FRESH system to explore habitat relations with estimates of habitat variables based on the examples and default values from the linked databases stored within the FRESH system.

Linear Programming Model

Factors Affecting Nutrition and Palatability

Carrying Capacity Models

Two calculators: (1) stand-level application and (2) landscape-level application

Two deer (Cervidae) species: (1)black-tailed deer and (2)moose

Current status and and future plans

Who we are