WILD 170: Wildlife Nutrition and Carrying Capacity

A comprehensive vocabulary flashcard set covering nutritional energetics, digestive assays, vegetation sampling transects, carrying capacity models, and interspecific competition mechanisms from WILD 170.

Energy Balance Equation

The fundamental energetic relationship defined as $\text{Energy Balance} = \text{Energy Intake} - \text{Energy Expended}$, dictating whether an animal maintains energetic homeostasis or operates in deficit.

Energy Intake (Supply Side)

The acquisition of energy and nutrients via consumed food items, governed by food quality (such as digestible energy and digestible protein), quantity, and physical accessibility.

Energy Expenditure (Demand Side)

The total energy required by an animal to sustain its basal metabolic rate, thermoregulation, somatic growth, antler or horn development, reproduction, and seasonal fat storage.

Basal Metabolic Rate (BMR)

The minimal rate of energy expenditure by an animal at rest needed to maintain life-sustaining physiological processes, including cellular activity, circulation, and respiration.

Maintenance Energy Requirements

The baseline quantity of energy an animal must consume daily to support its basal metabolic rate, without which the organism dies.

Cellular Respiration

The metabolic process taking place inside cells where nutrients and glucose are broken down to generate adenosine triphosphate ($\text{ATP}$).

Thermoregulation

The physiological and behavioral maintenance of a stable core body temperature within a viable range suitable for supporting life processes under changing ambient temperatures.

Brown Adipose Tissue

A specialized adipose tissue catabolized by animals specifically to generate heat for thermoregulation rather than yielding cellular energy in the form of $\text{ATP}$.

Physiological Thermoregulation

Internal biological mechanisms used to shed or produce heat, such as shivering, increasing metabolic rate, metabolizing brown fat, sweating, and panting.

Behavioral Thermoregulation

Voluntary actions performed by an animal to alter heat exchange, including seeking shelter in burrows, dens, or tree canopies, huddling with conspecifics, or basking in direct sunlight.

Seasonal Fat Reserves

Excess energy and nutrient stores deposited as body fat during favorable conditions to sustain an animal through predictable seasonal periods of food limitation.

Reproductive Demand Timing

The evolutionary scheduling of peak reproductive nutrient demands (e.g., late gestation and lactation) to coincide with seasonal peaks of excess nutrient availability.

Growth Energy Demand

The energy intake required by young wildlife in excess of baseline maintenance needs to support somatic growth, bone elongation, and body mass accumulation.

Gross Energy (GE)

The total chemical energy inherently contained within ingested food or feed prior to any digestive or metabolic losses.

Digestible Energy (DE)

The portion of gross energy remaining after subtracting the energy lost through fecal excretion ($\text{DE} = \text{GE} - \text{fecal energy}$).

Metabolizable Energy (ME)

The portion of digestible energy retained after subtracting energy losses excreted in urine and combustible digestive gases ($\text{ME} = \text{DE} - \text{urinary and gas energy}$).

Net Energy (NE)

The usable energy remaining after subtracting the heat increment of feeding from metabolizable energy, directly supporting maintenance, growth, and lactation.

Net Energy for Maintenance ($NE_m$)

The fraction of net energy allocated solely toward sustaining basic physiological equilibrium and baseline tissue maintenance without body mass change.

Net Energy for Growth ($NE_g$)

The net energy fraction deposited directly into the synthesis of somatic tissues, muscle mass, and skeletal bone growth.

Net Energy for Lactation ($NE_l$)

The portion of net energy mobilized by female mammals to synthesize and produce milk for nourishing neonates.

Total Digestible Nutrients (TDN)

A standard expression of feed energy defined as digestible energy plus the energy derived from digestible protein ($\text{TDN} = \text{DE} + \text{energy from digestible protein}$).

TDN Energy Equivalence

The energetic conversion benchmark specifying that $1.0\,\text{pound of TDN}$ equals exactly $2.0\,\text{Mcal of DE}$.

Energy Partitioning Framework

The hierarchical accounting scheme detailing how gross feed energy is progressively partitioned into digestible, metabolizable, and net energy fractions as energy is lost via feces, urine, gas, and heat.

Kleiber's Law

The physiological allometric scaling principle stating that an animal's basal maintenance energy requirement scales with metabolic body weight, calculated as $BW^{0.75}$ (body weight in $\text{kg}$ raised to the power of $0.75$).

Baker et al. (1979) Mule Deer Fawns Finding

An empirical study establishing that mule deer fawns require $158\,\text{kcal}$ of metabolizable energy per $W_{\text{kg}}^{0.75}/\text{day}$.

Staudenmaier et al. (2022) Energy Tolerance Comparison

A comparative nutritional study showing that mule deer operate at lower daily maintenance energy requirements ($283.9\,\text{kJ/kg/day}$) than white-tailed deer ($358.0\,\text{kJ/kg/day}$).

Sandhill Crane Spring Migration DEI (Vanausdall et al.)

Measured digestible energy intake requirements for sandhill cranes during spring stopover: males require $553\,\text{kcal/day}$ (early), $566\,\text{kcal/day}$ (mid), and $562\,\text{kcal/day}$ (late), while females require $500$, $513$, and $522\,\text{kcal/day}$, respectively.

Sandhill Crane Barley Demand (Vanausdall et al.)

The daily mass of barley required per sandhill crane during spring migration: males require $0.156\,\text{kg}$ (early), $0.160\,\text{kg}$ (mid), and $0.159\,\text{kg}$ (late), whereas females require $0.141\,\text{kg}$, $0.145\,\text{kg}$, and $0.148\,\text{kg}$, respectively.

San Luis Valley Stopover Energetics Research

Research by Vanausdall, Kendall, and Collins evaluating the landscape-level agricultural energy supply relative to the migratory energy demands of sandhill cranes in Colorado.

Microhistological Diet Analysis

A traditional laboratory technique used to reconstruct herbivore diets by microscopically identifying undigested plant and animal cellular fragments in fecal samples.

DNA Metabarcoding

A modern genetic approach that determines wildlife diet composition by amplifying and high-throughput sequencing residual barcode DNA recovered from scat samples.

Camera Collars

Animal-borne tracking devices with integrated video cameras that document the specific forage species selected and consumed by free-ranging wildlife.

Direct Foraging Observations

Field methods that determine diet composition either by directly watching wild animals feed or by walking trained captive animals through habitats to record plant intake.

Dietary Carbohydrates

Plant-derived macronutrients analyzed in nutritional ecology to quantify digestible energy availability within individual plant species or composite diets.

Dietary Proteins

Nitrogenous macronutrients quantified in plant- and animal-based diets necessary for tissue maintenance, growth, antler development, and gestation.

Dietary Fats (Unsaturated vs. Saturated)

Lipid macronutrients categorized ecologically into unsaturated fats (found predominantly in plant-based forage) and saturated fats (found primarily in animal tissues).

Van Soest Method

A standard laboratory detergent procedure used to partition plant forage into digestible cell contents and fibrous, indigestible cell wall fractions.

Neutral Detergent Fiber (NDF)

The Van Soest residue isolating total plant cell wall components (cellulose, hemicellulose, and lignin), where lower values generally indicate higher-quality forage.

Acid Detergent Fiber (ADF)

The Van Soest residue isolating the indigestible and fibrous fraction of the plant cell wall, composed predominantly of cellulose and lignin.

Acid Detergent Lignin (ADL)

The isolated Van Soest fraction representing pure lignin, which is completely indigestible by animals.

In Vitro Digestibility Trial

A trial simulating digestion outside a living animal by incubating dried, ground plant samples in test tubes with rumen fluid and digestive enzymes to measure mass loss.

In Vivo Digestibility Trial

A live-animal feeding trial that quantifies digestible energy by precisely measuring total intake energy and subtracting energy eliminated in feces.

Fistulated Animal Digestion Technique

An in vivo method wherein plant samples enclosed in porous nylon bags are placed directly into the rumen of a cannulated animal to measure digestive disappearance over time.

Respiration-Metabolism Chamber System

An airtight animal enclosure system utilized to measure respiratory gas emissions, metabolic heat production, and nutrient digestibility in captive wildlife.

Kjeldahl Method

A chemistry-based analytical method that quantifies the total organic nitrogen content of diet samples to estimate crude protein.

Dumas Combustion Method

An automated, high-temperature combustion laboratory technique that converts sample nitrogen into gas to quantify total nitrogen content.

Crude Protein Multiplier ($6.25$)

The universal conversion factor applied to sample nitrogen concentration to calculate crude protein: $\text{Crude Protein} = \% \text{Nitrogen} \times 6.25$.

Digestible Protein

The portion of crude protein absorbed by an animal's digestive tract, calculated by subtracting fecal protein excretion from total protein ingested.

In Vitro Protein Digestion Assay

A laboratory procedure that combines Kjeldahl or Dumas crude protein estimates with enzyme incubation to measure residual undigested protein.

In Vivo Protein Digestion Approach

A live feeding trial method determining digestible protein by directly comparing the mass of protein ingested against total protein excreted in feces.

40-Meter Vegetation Transect

A standardized $40\,\text{m}$ linear survey used by habitat ecologists to record understory plant canopy cover and phenological stage proportions.

Plant Phenology

The recurring developmental lifecycle stages of plants (e.g., vegetative, flowering, fruiting, senescent) that dictate seasonal forage quality and digestibility.

Percent Ground Cover

The visual estimate of the proportional ground surface area covered by the foliage of a given plant species within a sampling plot.

Plot-Level Forage Biomass

The available dry mass of edible forage per unit area, determined by clipping, drying, and weighing vegetation, typically expressed in $\text{kg/ha}$.

Daubenmire Plot

A standardized rectangular quadrat frame deployed along field transects to estimate understory percent cover, species composition, and forage phenology.

Supply-Demand Nutritional Ecology Framework

A habitat assessment approach that evaluates landscape capability by comparing animal energy and protein requirements (demand) against dietary nutrient availability (supply).

Carrying Capacity (CC)

The approximate maximum number of animals of a given species that a specified landscape can support sustainably over time without habitat degradation.

Nutritional Carrying Capacity (NCC)

The specific number of animals that can be supported across a landscape determined by animal nutrient requirements relative to landscape-level nutrient availability.

Density-Dependent Demographic Response

The biological feedback mechanism where per capita reproductive success, recruitment, and survival decrease as a population nears or exceeds carrying capacity.

Logistic Growth Model

A mathematical population growth model depicting how per capita growth rate declines progressively as population size approaches environmental carrying capacity.

S-Shaped Logistic Growth Curve

The characteristic sigmoidal curve generated when a population transitions from an early slow growth phase to rapid exponential growth, followed by leveling off at carrying capacity.

Fast Growth Phase

The intermediate phase of the logistic growth curve where natality is drastically greater than mortality, producing rapid population increase.

Slow Growth Phase

The phase of logistic growth occurring at very low population sizes or near carrying capacity, where natality only slightly exceeds mortality.

Stable Equilibrium

The demographic balance met when population abundance aligns with carrying capacity, resulting in zero net population growth as natality equals mortality.

BIDE Population Accounting Equation

The fundamental demographic equation expressed as $N_{t+1} = N_t + B_t - D_t + I_t - E_t$, tracking population size via births, deaths, immigrants, and emigrants.

Immigrant ($I_t$)

An individual animal that moves into a defined resident wildlife population from outside the population boundaries during time interval $t$.

Emigrant ($E_t$)

An individual animal that moves out of a defined resident wildlife population during time interval $t$.

Exploitative Competition

An indirect competitive mechanism where one species consumes or depletes a shared resource (such as forage), leaving fewer resources available for another species.

Interference Competition

A direct competitive interaction where individuals of one species behaviorally exclude or prevent another species from accessing space or resources.

Apparent Competition

An indirect negative interaction where an abundant prey species supports an elevated predator population that disproportionately preys upon an alternate, less abundant prey species.

Mule Deer and Elk Population Divergence

A widespread demographic trend across the western United States where growing elk populations coincided with steep declines in mule deer numbers.

Habitat Succession Hypothesis for Mule Deer Decline

The hypothesis proposing that mule deer declines were driven by ecological succession as open, shrub-dominated habitats transitioned into dense, mature forests and grasslands.

Winter Range Interference Competition

A hypothesized mechanism where abundant elk physically displace mule deer from crucial low-elevation winter range forage resources.

Fawning Habitat Interference Competition

A proposed competitive interaction based on observations that elk presence displaces mule deer does from prime fawning habitat.

SAVANNA Model

A spatially explicit ecosystem modeling framework (Coughenour 1993, Weisberg et al. 2002) used by wildlife ecologists to simulate forage dynamics and calculate nutritional carrying capacity.