Wildlife Brett Johnson Urban Wildlife Biologist Texas Parks

Wildlife Brett Johnson Urban Wildlife Biologist Texas Parks and Wildlife

I. Definitions • Population - A group of organisms belonging to the same species occupying a particular area at the same time. • Community - An association of interacting populations, usually associated with a given habitat in which they live. • Ecosystem - The biological community of a given area and the physical environment with which it interacts.

I. Definitions • Niche - The sum total of all the interactions a species has within its community. Niche defines the role that organism plays within the community. • Habitat - The physical setting in which one usually finds a given species; its address. Usually characterized by a dominant plant association or physical setting, such as oakhickory forest or riparian habitat.

Ecosystems Understand how the pieces fit together

II. Ecosystem Characteristics Trophic Relationships • Producers - Autotrophs. Those organisms capable of producing their own food, primarily via photosynthesis. • Herbivores - Primary Consumers. Organisms obtain their energy directly from plants. • Primary Carnivores - Secondary consumers. Those organisms obtaining their energy from herbivores.

II. Ecosystem Characteristics • Secondary Carnivores - Tertiary consumers. Those organisms obtaining their energy from other carnivores. • Detritivores - Decomposers. Those organisms obtaining their energy from dead plants and animals.

Herbivore Food Chain Producers Organic Pool Energy Flow Inorganic Pool Detritivores Heat Sink Solar Radiation Generalized Scheme of Trophic Organization

Herbivore Food Chain Producers Organic Pool Matter Inorganic Pool Detritivores Heat Sink Solar Radiation Generalized Scheme of Trophic Organization

Food Chain Red Shouldered Hawk Coachwhip (snake) Whiptail (lizard) Common Toad Praying Mantis Field Mouse Cricket Prey to Predator Plants Mockingbird Scorpion Grasshopper

Food Web Red Shouldered Hawk Coachwhip (snake) Common Toad Field Mouse Whiptail (lizard) Praying Mantis Cricket Mockingbird Scorpion Grasshopper Plants Prey to Predator

Pyramid of Numbers General Observation: For a given unit of area, there are many more individual plants than herbivores, greater numbers of herbivores than carnivores, and only a few top carnivores.

Pyramid of Numbers (# individuals per 0. 1 hectare) C 2=1 90, 000 C 1 H 200, 000 P 1, 500, 000 Grassland (Summer)

Pyramid of Numbers (individuals per 0. 1 hectare) C 2=1 C 2 =2 90, 000 C 1 120, 000 H 200, 000 H 150, 000 P 1, 500, 000 P 200 Grassland (Summer) Temperate Forest (Summer)

Pyramid of Biomass In some habitats, there may be a partial inverted pyramid of numbers. However, when dry weight of each trophic level is calculated, it usually results in a pyramid of biomass.

Pyramid of Biomass (Grams dry weight/sq. meter) C 1 = 4 C 1 =. 01 C 1 = 11 H=1 H = 132 P 96 P 500 P 703 Wisconsin Lake Georgia Old-field Coral Reef

Pyramid of Energy While it is possible to have greater biomass at a higher tropic level than one below, you can NEVER have an inverted pyramid of energy. Over some unit of time, there is always less energy present in a higher trophic level than the one below it.

Pyramid of Energy (kcal/m 2/yr) C 2 = 21 C 1 383 H 3368 P 20, 810 Silver Springs, Florida

The 10% Rule Each succeeding trophic level has only 10% of the energy in the previous level C 2 = 10 C 1 =100 H=1, 000 P=10, 000

Energy Flow • The ultimate source of all energy used by organisms is the sun. • Only plants can convert solar energy into “food” (carbohydrates) via photosynthesis. • No organism is 100% efficient in obtaining energy, regardless of its source. • All living organisms continually lose energy in the form of heat. • Organisms must replenish lost energy, or die. • Energy flows through ecosystems, it is not recycled!

Ecological Efficiencies • Net Production Efficiency: The percent of energy fixed by plants in photosynthesis that is put into plant growth (25 -80%). • Harvest Efficiency: The percent of Plant Net Production ingested by Herbivores (5 -30%) • Assimilation Efficiency: The percent of ingested food that is assimilated by an animal (high in carnivores -60 -90%, low in herbivores- 30 -60%) • Tissue growth Efficiency: The percent of assimilated food converted to new tissue (high in ectotherms 20 -50%, low in endotherms- 1 -3% )

Ingested Energy 1000 cal (100%) 0 c n tio ila 0 =5 0% 5 x =10 0 20% Ax wth c Ax Gro I % (f 50 s ast 0 c e 0 w 5 g l a = E ec im s As Ix n o ti e) Meta 80% bolis = 40 m 0 c

II. Ecosystem Characteristics Nutrient Cycling • While energy flows through an ecosystem, nutrients are continually recycled. • Nutrient cycles, also known as biogeochemical cycles, usually have a primary reservoir in either the atmosphere or the lithosphere. Hence, they are referred to as either gaseous or sedimentary cycles.

Nitrogen Cycle Air Atmosphere is 79% Nitrogen N 2 Excretion Nitrogen Fixing Bacteria Decay Ammonia Soil or Water bes NO 2 Nitrite _ Microbes NO 3 Nitrate cr ob e Micro _ Mi NH 3 s (Microbes)

III. Population Dynamics • Population Density - The number of individuals of a given species per unit area. For example, 25 mice/acre. • Demography - The study of populations, their characteristics and how they change over time. • Natality - Production of new individuals either sexually or asexually • Mortality - Loss of individuals through death • Immigration - New individuals moving into population • Emigration - Residents moving out of population

III. Population Dynamics N(future) = N(current) + B + I - D - E N = Population B = Birth s D = Deaths I = Immigration E = Emigration If B + I > D + E, population grows exponentially

III. Population Dynamics • Intrinsic vs. Extrinsic Factors • Intrinsic Factors Influencing Rate of Growth or Decline • Sex and age distribution • Age-specific fecundity • Social Structure • Extrinsic Factors Influencing Rate of Growth or Decline • • Weather Predation, Competition, Hunting Disease, Pollution Carrying Capacity

III. Population Dynamics • Population Growth Models • Exponential Growth vs. Logistic Growth • Carrying Capacity - The maximum number of individuals of a given species that a habitat can sustain indefinitely.

Exponential Growth Number of Organisms K Carrying capacity Time

Logistic Growth Number of Organisms K Carrying capacity Optimal yield (1/2 K) Time

IV. Threatened and Endangered Species • Why Are Extinction Rates Increasing? • Loss of Habitat, Habitat Fragmentation • Increasing human population • Urban sprawl • Other Human Activities • Commercial hunting/fishing, predator/pest control, introduced aliens, pollution, exotic pet/plant trade • Which Organisms Are We Losing? • Animals at Top of Food Chains • Habitat Specialists

Regulated hunting hasn't caused a single species to become threatened or endangered.

Why are big, “fierce” animals so rare?

Predator – Prey Relationships “The only valid generalization about predation is that everyone is eaten by somebody, somehow. ” Jennifer Owen • Understand the concept • Based on life history information of listed species, be familiar with what role these species play in the relationship