Group2ODD

WOLF, DEER, FLOWER, WEED, AND BEES MODEL

PURPOSE

This model was designed to represent a dynamic equilibrium among a hierarchy of organisms on a simplified landscape in Wisconsin. Wolves feed on deer, deer feed on wildflowers, bees drink the nectar of flowers and pollinate them, and an invasive weed (i.e., garlic mustard) competes for space.

ENTITIES, STATE VARIABLES, AND SCALES Our landscape patches are characterized by their color: -yellow: full sun -light green: shade

Global Variables: -Initial number of wildflowers -Initial number of garlic mustard plants -Initial number of bees -Max food for wolf to grow in new pack -Base_energy of wolf pack: reserve energy a wolf pack has before starvation reduces its numbers

Landscape specifications: -Number of clumps of shade

Carrying Capacity -Number of garlic-mustard plants per patch -Number of wildflowers per patch -Number of bees per patch

The model has 5 agents - wolf packs, deer, wildflowers, garlic mustard, and honey bees. 1. Wolf packs are characterized by their energy level, hunger level (eatcount), pack size, and territory defense status (stationary). 2. Deer are characterized by their energy level and age (lifetime). 3. Garlic mustards are characterized by their color and location. 4. Wildflowers are characterized by their location and color. 5. Honey bees are characterized by their location, energy level and a variable that holds the number of time steps since it found the last wildflower.

The simulation lasts until wolves or deer die out or until it is ended by the user.

PROCESS OVERVIEW AND SCHEDULING

On each time step, the deer move, reproduce if they have enough energy, search to find and eat nearby wildflowers, age, and die if they run out of energy or grow too old.

On each time step wolf packs potentially fight for territory with a nearby pack where some pack members die, and if hungry, search for deer to eat, reproduce if energy needs are met, and potentially die out if all members die.

On each time step each bee also moves once and thereby loses energy. If a wildflower is on the new location the bee drinks nectar from it and thereby gains energy. It reproduces if its energy reaches a certain level and dies if the energy level drops to zero.

On each time step, each garlic mustard plant spreads once. Each garlic mustard plant will update their health.

Afterwards, each wildflower updates their health once. If a new garlic mustard plant is on the location, the wildflower dies. Every wildflower that was fed on by a bee closes and it reopens at a certain rate. The wildflower is also pollinated and reproduces at a certain rate.

DESIGN CONCEPTS

The model is driven by energy needs and life history of the different organisms and their ability to meet those needs in a diverse landscape. It is based upon a wolf-deer system in Wisconsin with the difference of wolves being the only predator of deer. Wolves operate as packs and eat at a much less frequent interval than deer. This is a typical behavior of a predator compared to its herbivorous prey. Both wolf and deer reproduction is driven by energy requirements and wolves absorb the energy of the deer they consume. Deer gain energy from the wildflowers and can gain energy from the weeds(garlic-mustard plants), but it is much less nutritious.

The sub models of plants and bees revolve around the interaction between garlic mustard plants, wildflowers, bees and the corresponding landscape. Wildflowers and bees are dependent on each other for feeding and reproduction. Garlic mustard grows well in the shade, and is not commonly found in sunny habitats. Garlic mustard is a rapidly spreading woodland weed that displaces native woodland wildflowers in Wisconsin. (Source: Wisconsin DNR)

INITIALIZATION

The landscape is randomly initialized with patches of full sun and shade. A number of healthy garlic mustard plants, wildflowers and bees are placed randomly on the landscape. Wolves and deer are also randomly generated and placed across the map.

INPUT DATA

There is no input data.

SUBMODELS

Deer submodel - Move: move randomly across the landscape. - Deer-repro: reproduce if pregnant, will set to pregnancy period if reaching certain energy. - Deer-eat-wildflower: deer eat wildflowers and increase energy based on the energy of the wildflower - Eat-weeds: deer eat the weed (garlic-mustard) and increase energy based on the energy of the weed (garlic-mustard) - Death: if no energy or reaching a certain age, then die.

Wolves submodel - Fight: a wolf pack will fight with another wolf pack that is close by. The winning side gains control of a territory in which it can hunt and will become stationary. Both wolf packs will decrease in size (losing side suffers more and is displaced). - Pack-eat: once the hunger level reaches a certain level, the pack will search for deer in its territory to eat. If a pack with a territory cannot find food for several time steps, it becomes mobile to search for new territory. Packs without territory cannot hunt. - Pack-grow: pack size will grow if the pack reaches a specified energy level. Packs that reach a specified size will split into two packs. One pack stays on the territory, and the other pack is displaced to find another territory. If the energy level of a pack decreases past a specified level, the pack looses a member. - Pack-death: the wolf pack will die out if all of the wolves in it die.

Bees Submodels - Search: Check the number of time steps since the last wildflower was found. If it is smaller or equal to 20 bee continues to search in the neighborhood, if not it searches in wide sweeps. - Drink Nectar: Check whether a wildflower is on the patch. If true bee gains 20 units of energy and wildflower closes (i.e. changes color). - Reproduce: Check if energy level is above 50. If true hatch one new bee. The new bee has energy level 40, the parent bee loses 50 units of energy. - Check for Death: Check if the energy level equals zero. If true then bee dies.

Garlic Mustard Submodels - Spread: randomly select 1 neighbor. Create and add a healthy garlic mustard agent to it. - Update health (garlic mustard): if a garlic mustard plant is in a sun patch, its health will decrease until it dies. This is specified by increasing the color value of the orange garlic mustard plant by one each tick it lies in the sun patch. When the color value reaches the lightest orange the garlic mustard will die.

Wildflowers Submodels -Update health (wildflower): if patch contains both a wildflower and a garlic mustard agent, wildflower dies. - Reopen-flower: Check the color of the wildflower. If red (i.e. closed) reopen with a certain probability. - Reproduce-wildflowers: Check color of wildflower. If red (i.e. closed and therefore pollinated) reproduce with a certain probability.