Wildlife Management Midterm 2 Study Set

Population

Group of organisms of a single species that interact and interbreed in a common place (Particular area)

• Have to be able to interbreed

• Boundaries usually arbitrary

Population Characteristics:

• Abundance

• Distribution

• Composition

Abundance

# of individuals

• Density - # of individuals per unit area

Distribution

Spread or scatter

• Pattern — e.g. clumped?

Composition

Sex Ratio

• The ratio of males:females

Age Structure

• The relative proportions of various age groups in a population

Demography

• Intrinsic factors that contribute to a population’s growth or decline

• “BIDE” Factors

BIDE Factors

• Birth Rate (Natality)

• Death Rate (Mortality)

• Immigration

• Emigration

Birth Rate (Natality)

Proportion of a population newly born in a unit of time.

Death Rate (Mortality)

Proportion of a population dying in a unit of time

Immigration

Movement into a given area

Emigration

Movement out of a given area

“Closed Population”

Population where no immigration or emigration occurs

Population change = _____

Births (B) - Deaths (D) + Immigrants (I) - Emigrants (E)

Birth Rate Terms

• Fecundity

  • Fertility

• Recruitment

Fecundity

Actual number of organisms produced

• Fertility: The POTENTIAL capability of an organism to produce young

Recruitment

Increment of new individuals added to a wildlife population by natural reproduction, immigration, or stocking

Rates

• Finite rate = discrete intervals (birth pulse)

• Instantaneous rate = time interval very short (continuous) (birth flow)

• Finite rate = e^{instantaneous rate}

  • 𝜆 = e^r

• Instantaneous rate = log_e finite rate

  • r = ln 𝜆

Discrete Difference Equations

• Models for populations at a specific point in time

  • Non-overlapping generations/discrete intervals

  • Birth-pulse

  • Finite Rates: 𝜆

Continuous Differential Equation

• Models that allow for continuous time change in populations

  • Overlapping generations

  • Population growth is a smooth curve

  • Instantaneous Rates: r

Density-Independent Growth

• Multiplication Rate Density Independent

  • Constant

• Exponetnial Growth (“Geometric” Growth)

N

Size of population

N_t

# of individuals at time t

N_t+1

# of individuals at time t+1

• 1 time interval later (usually years)

Equilibrium

B + I = D + E

N_o

Starting # of individuals in a population at time 0

N_t+1 = N_t(𝜆*𝜆)

Difference equation

• use when working step-by-step with consecutive time periods

N_t = 𝜆^tN_o OR N_t = N_oe^rt

Recursion equation

• use when projecting far into the future or working directly with an initial population

• predicting a future population size

dN/dt

Change in per capita population over change in time

dN/dt = rN

Differential equation

• use when modeling continuous exponential population growth under ideal, unlimited environmental conditions

• finding the growth rate/speed of change

(ln2)/r = t_double

Doubling time equation

• use when asked “how long will it take for the population to double?”

Population Growth: r vs 𝜆

Continuous/r:

• Population Increase: r > 0

• Population Static: r = 0

• Population Decline: r < 0

Discrete/𝜆:

• Population Increase: 𝜆 > 1

• Population Static: 𝜆 = 1

• Population Decline: 0 < 𝜆 < 1

Exponential Growth Model Assumptions

• No I or E

• Constant b and d

• No genetic structure

• No age or size structure

r = _____ on a graph

slope

Death (Two broad categories)

1) Intrinsic (internal)

2) Extrinsic (external)

Intrinsic Death Examples

Genetic factors, organ failure, senescence

Extrinsic Death Examples

Predation, starvation, weather, disease

Density independent

Population processes NOT affected by population size

Density dependent

Population processes affected by population size

• Positive or Negative

Population density is at equilibrium only when _______

per capita birth rate = per capita death rate

Environmental carrying capacity (K)

Capacity of the environment to “carry” a population.

Logistic Growth Model Assumptions

• No I or E

• No genetic structure

• No age or size structure

• Constant carrying capacity

• Linear density dependence

dN/dt = rN(K-N/K) OR rN(1 - N/K)

Logistic growth equation

• used to model population growth when resources are limited

Infraspecific variation in mortality rate (it’s not constant!)

• Seasonality: mortality rate is much higher during harsh times of the year

• Sex difference: males often more vulnerable to predation, females to starvation or predation while birthing or caring for young

• Experience: some individuals will be better at avoiding risks

• Age: very young and old animals are often most vulnerable, but this varies greatly between species.

Life Table

A table of population data based on a sample of the population showing the age at which each member died

• Mortality Schedule

• Fecundity Schedule

x

age (time interval)

f_x

number alive at age x

l_x

proportion surviving from the start of the life table to the beginning of age x

• = f_x/f_o

d_x

proportion of original cohort dying during the age interval x to x+1

• = l_x - l_{x + 1}

Type I Species

Most individuals die late in life

Type II Species

Uniform rate of decline

Type III Species

Huge decline in young

r-selected species (fast)

• Boom and bust

• Higher r

• Type III survivorship

• Low parental care

  • Example: Rabbits, many insects

K-selected species (slow)

• Conservative

• Lower r

• Type I survivorship

• High parental care

  • Example: Elephants

m_x

Average number of offspring born per unit time to an individual female of a particular age/Reproductive outlook at age x

• Fecundity related

• = b_x/f_x

b_x

Number of female offspring produced per age group

Net Reproductive Rate (R₀)

mean number of offspring produced per female over her lifetime

• Per capita growth rate per generation

• R₀ = ∑(lx)(mx)

  • Sums of l_xm_x

• If survivorship 100%, R₀ = ∑(mx)

Generation time (G)

Average length of time between when an individual is born and the birth of it’s offspring

• Average time for a population to increase by a factor equal to R₀

r ≈ (lnR0)/G

If know R₀ and generation time, can estimate r

Dynamic Life Table

• “Cohort” “Generation” “Horizontal”

• Follow cohort of organisms over time

Time-Specific Life Table

• “Static” “Stationary” “Current” “Vertical”

• Sample of individuals from each age class

  • Cross-section of population at a specific time

Things that can be gathered from life tables

• Survivorship directly observed

• Age at death observed

• Age structure directly observed

Welfare factors

Necessary aspects for survival

Components of habitat

• Food

• Water

• Cover

• Space

• Oxygen

Decimating factors

Those that kill directly

• Predation

• Hunting

• Disease

• Accidents

• Starvation

Welfare Factor — Food

• Nutrition: process animals use to procure and process portions of their external environment for the continued functioning of internal metabolism

• Forage: Browse and herbage, which is available and may provide food for grazing animals or be harvested for feeding

• Food habits: diet of wildlife

Matter

• Materials that occur in the physical environment of Earth and its atmosphere

• Plants and animals composed of it

• Recycled

Energy

• Required for growth and all metabolic processes

• Not recycled

2nd Law of Thermodynamics

• Transformation of energy not 100% efficient

• Two consequences:

  • Less energy at successive levels (10%)

  • Length of food chain limitied

Rule of 10

Only ~10% passes to the next level. Therefore, ~90% of energy is LOST at each trophic level.

Maintenance Requirements

Intake at which animal’s weight remains constant and the animal remains healthy.

Vitamins

Organic compounds, which occur in food in minute amounts and cannot be synthesized by animals, and are essential for normal life and functioning.

• Coprophagy - consumption of feces

Minerals

Essential inorganic elements

• Macroelements and trace elements

• Geophagy - eating earth/rocks

• Salt licks

Function of digestion

Break up large and complex molecules to sizes that may be absorbed and used for metabolism

Two types of stomachs:

• Monogastric stomach (humans)

• Digastric stomachs (ruminants, multichambered, etc. cows)

Foregut Fermentation

Ruminants

• More efficiently digests cell wall

• Microorganisms provide nutrients & help detoxify tissues

• Processing time slower (70-100 hrs); eat less overall but get more out it

Hindgut Fermentation

Nonruminants

• Less efficient type of fermentation

• Rapid processing time (30-50 hrs)

Cover

Vegetative and topographic features that provide shelter from weather or concealment from or for pedators

Succession

The orderly progression through time of changes in community composition

Pioneer

The first species or community in succession

Climax

The oldest stage given no disturbance. “ultimate expression” of vegetational development under prevailing local or regional conditions.

Home Range

Area included in the daily, seasonal, and annual travels of an individual

Territory

Part of home range that is actively defended

How is Water Obtained?

1. Free water

2. Preformed — acquire the water via the diet (vegetation or prey)

3. Metabolic — Water is a product of respiration (converting sugar to carbon dioxide and water)

Winterkill

• Lakes freeze over, snow falls on top

• Eliminates light to plants

• Plants and animals exhaust oxygen.

• Likely when:

  • Water shallow

  • Prolonged periods of ice cover, snow

  • Decaying organic material (algae, aquatic plants, etc)

Summerkill

• Upper layer — photosynthetically active

• Lower layer — decomposition, less oxygen

• Summer — algae grows

• Water temp increases, holds less oxygen

• Likely when:

  • Algal bloom, decaying

  • Evenings, cloudy days

  • Lake is stratified and abrupt mixing occurs