Week 14 - Behavioral Adaptations, Feeding Ecology

Torpor

dormancy, physiological state where energy expenditure is greatly reduced by decreasing body temp and rate of metabolism

Daily torpor

saves energy during the inactive period of the day, last a few hours

done by small mammals and small birds

Hibernation

winter seasonal torpor, Tb can be reduced within 1 degree of Ta

O2 consumption largely decreased, heart rate reduced, prolonged periods of breathing apnea

Who hibernates?

one bird species (common poorwill)

mammals (main group): carnivores, rodents, insectivores, smaller marsupials

What induces hibernation?

cold weather, photoperiod, low food supply, increased fat, increased serum magnesium levels, changes in respiratory control sensitivity to CO2

Entrance into hibernation

1. decrease in heart rate and breathing rate

2. decreased in O2 consumption

3. drop in body temp

estivation

summer/drought torpor

less severe depression of Tb and metabolic rate

seen in amphibians, lungfish, some rodents

Cryoprotectant

natural antifreeze inside cells

allows herps to be freeze tolerant

benefits of torpor

balance the energy budget in extreme environmental conditions

Costs of torpor

animal is helpless, little to no growth, reduced reproductive period

foraging cycle

cycle of search, pursue, attack, capture, handle

varies across vertebrates

Structural Feeding Adaptations - Fish

Different jaw shapes: Homologous bones have different shapes, sizes and functions

Major jaw and head movements (cranial kinesis): Various hinges in the mouth

Pharyngeal jaws: Second set of jaws located in the pharynx, Used for crush shells or grab and manipulate prey items once they're immobilized by the oral jaws (front, regular ones)

Structural Feeding Adaptations - Amphibians

Tongue projection of varying degrees (especially frogs): Folding out, adhesive pad is on the bottom of the tongue, Punching out

Ballistic tongues (plethodontid salamanders): Tongue retraction muscles of salamanders anchored to the pelvis!

Structural Feeding Adaptations - Reptiles

Tongue projection (chameleons)

Cranial kinesis

Snakes have jaws that 'unlock' / egg-eating snakes

Structural Feeding Adaptations - Birds

Beak shapes for different feeding modes

Feeding habits determine bill size and shape

Structural Feeding Adaptations - Mammals

Squamosal-dentary jaw articulation (associated with increased jaw musculature)

Heterodont dentition: Incisors (biting and cutting), Canines (seizing and piercing), Molars and premolars (grinding and crushing)

Mammary glands

Types of search

Active: or cruise, continuous search for prey while moving

Ambush: sit and wait

Saltatory: alternation between ambush and cruise modes, depends on habitat and conditions of the moment

Search image: perceptual screening, mechanism that improves the ability to locate specific food items

Pursuit

Places predator within striking distance of prey

Fast vs slow pursuit (coyote vs snake)

Luring vs stalking (frogfishes do both, 85/15%), Depends on distance from prey item and water clarity

Attack and capture

Some predators alter final attack behavior as a function of distance to prey (marlin spearing vs striking with sideways blow)

Handling

Larger prey or those with chemical or anatomical defenses require manipulation, disarticulation, dissection

Remove defense structures (seed coat, clam shell, etc.)

Reduces prey to size that can be swallowed

Optimal foraging theory (OFT)

Animals will forage in a way that maximizes the ratio of benefits to costs (profitability)

Benefits and costs of OFT

B: energy/nutrition obtained, growth increased

C: energy/time expended (searching, capturing, handling), exposure to possible injury

Components of OFT - optimal diet

Choice between food items

Food quantity and profitability determine choice: Prefer more profitable food items, Will be more selective when food items are abundant, Less selective when food is less abundant

Components of OFT - foraging efficiency

Choice between location (patches), marginal value theorem

Marginal Value Theorem

an animal should stay in a feeding patch until the expected net gain from staying declines and matches the expected net gain from traveling to and foraging in a new patch (stay as long as you can until it's no longer profitable)

length of stay depends on: Richness of food in patch, Time required to get to patch, Time required to extract the resource

Predictions of OFT

Forage in areas where food is abundant

Leave when searching is no longer rewarding

Select most profitable items first

Leave poor items until last

Travel no further than necessary to feed

Switches to risk-prone behavior if they are desperate