Lec 14: Nutritional Ecology

energetics

the flow of energy and its changes from one form to another

energy

The ability to do work or cause change; necessary to undergo simple body functions (activity, growth, warmth, etc.)

basal metabolism (BMR)

the energy used when animals are laying down, calm, fasted, and thermally stable; baseline amount of energy required for an animal to survive

relationship between metabolic rate and body size

small body size corresponds with high metabolic rate, and large body size corresponds with lower metabolic rate

thermoregulation

cold and hot environments increase energy demand

Piloerection

raising feather or fur coat to cause insulation; combat thermoregulation

shivering

response to cold; body shakes, constricting muscles, to turn energy from food into body heat

torpor

period of dormancy; lowers metabolism to the point of not needing to eat frequently, persist off of stored nutrients

Countercurrent heat exchange

arteries and veins close together; cold venous blood warmed by arterial blood before going to body core

regional heterothermia

core body temperature is maintained, but not rest of body

daily torpor

in small mammals and birds, daily lowering of metabolism that allows them to survive on stored energy

shallow hibernation

body temperature regulated within 10 degrees C of normal. Also known as winter lethargy; short arousal periods

profound hibernation

marked reduction in temperature, heart rate, respiratory rate. Temperature may fall to within 1 degree C of ambient temperature; no arousal period

avoidance

avoid heat; remain inactive during periods of high temperatures

tolerance

the ability to physiologically cope with increases in body temperature

heterothermic

species that experiences wide fluctuations in body temperature

homeothermic

species that experience a stable body temperature

endothermic

produces heat within the body

ectothermic

absorb heat from outside the body

reverse countercurrent heat exchange

cycles cool blood around areas like the brain

energetics of reproduction in females

costs for reproductive females are relatively higher for small species than larger ones

energetics of reproduction in mammals

costs in mammals increase exponentially during fetal development; the most energetically costly mechanism in mammals is lactation

energetics or reproduction in males

costs mainly comes in the form of male-male competition for access to females (fighting one another or defending territories)

energetics of productivity

young individuals experience peak energy demands during periods of high growth

activity budgets

defines categorical behaviors and documents how much time an individual spends doing those behaviors; doesn't provide an exact energy requirement, but gives a basic idea

energy budgets

have data on activity budgets while also having an idea of how much energy each activity requires; this is when lab based research is integrated within field/ecological research

when is energy released?

when large food molecules are broken apart into different components

patterns of energy requirements

endotherms require more energy than ectotherms (ex: in mammals 91% of their energy goes into survival, while in fish only 50% of their energy goes into survival; the remaining percentages goes toward reproduction)

proteins

- major constituent of the animal body

- contain nitrogen; cause nitrogenous waste products (ammonia compounds)

- protein requirements peak for individuals during peak of growth (maximum cell division)

- highest in females during lactation for mammals, and egg production in birds

- amino acids are based on proteins

- proteins are not abundant in vegetative plant parts; concentrated in seeds

minerals and vitamins

required by all wildlife

vitamins

complex molecules that function as enzymes in the body; most wild diets are complete, but occasionally natural deficiencies occur (start to see wildlife do things like eating soil or feces to supplement vitamins in their diets)

macronutrients

several mineral and dissolved ions (electrolytes, phosphorus, calcium, etc.)

micronutrients

present in tissue in minute quantities; knowledge incomplete (cobalt, iodine, fluorine, silicon, etc.; can be very toxic with high enough quantities)

fats

consists of carbon and hydrogen atoms, and fewer oxygen atoms than carbohydrates

fats: energy

more than 2x the energy of carbohydrates, but extracted at a slower rate (this is why fats are used as stored energy)

breakdown of fats

broken down by bile produced in lover, stored in gall bladder, and secreted into small intestines

carbohydrates

cellulose, starches and sugars

simple sugars

metabolized quickly; source of incredibly quick energy (sugar rush)

wood

abundant calories in wood only available to a few species (beavers, porcupines, and some lagomorphs)

water

most essential nutrient for life

water requirement based on size

smaller animals need more water for metabolic activity

heat capacity of water

high heat capacity; takes a lot of change in temperature in order to change the temperature of water

why high heat capacity is important

water in the body acts as a thermal buffer; organisms are not immediately subject to temperature changes in an ecosystem

water as a solvent

universal solvent; alters chemical state of a large number of substances, breaks substances down to make nutrients available, and alters carrying capacity of substances and nutrients

food intake: availability and quantity

- as abundance of food increases, food intake per unit time usually increases

- kill rates by predators change with prey density (carnivores left with 3 options; eat something else, move, or decline)

- physical and physiological factors limit food intake

- highest voluntary food intake typically associated with highest nutrient demands

food intake: quality

- varies with plant and animal parts and changes with season (killer whales eating only the liver of great white sharks)

- protein (animals) or nitrogen (plants) content on a dry matter basis; dry out the parts and measure the contents

- digestibility; fiber, and plant secondary metabolites (PSMs)

fibers

high fiber = low digestibility; more energy to digest, but still important to digestion

plant secondary metabolites (PSMs)

defensive compounds of plants; comes from sedentary nature (range from highly toxic to reproductive or digestive inhibitors)

optimal foraging theory

theoretical framework to consider the trade-offs associated with different modes of foraging

foraging decisions

should it be a specialist or generalist? how should it acquire the food item?

currency

what is being maximized; energy spent vs energy gain

biological limitations

can't eat what you don't have the equipment to break down and extract the nutrients from; is the animal built for what it is trying to consume

marginal foraging theorys

- focused on feeding site decisions; food is not distributed equally throughout a habitat

- when should an animal make the decision to leave a patch of food for another; based on size of patch and distances between patches

food hoarding/caching

common in seasonal environments; gathering more food than can be consumed at one time and storing it for times of poor conditions

what order is food hoarding most common in?

Rodentia; studied frequently with squirrels (squirrels only end up re-visiting a small percentage of their caches)

food hoarding in Carnivora

- canids bury prey in shallow surface depressions

- felids and ursids rake soil and leaf litter over prey

- mustelids cache prey in dens or bury like canids

- Hyenas submerge prey in water to suppress smell

body condition

the level of energy stores and results from the integration of nutrient requirements and food intake; looks at body fat, protein, and mass

body condition consequences for reproduction and population dynamics

in ungulates, summer resources influence body condition for mating seasons and winter resources influence survival into the summer

capital breeders

animals that store energy and nutrients; eat excess of what they need

income breeders

animals that have to forage during the breeding season