Marine Mammal Energetics and Social Systems

Flashcards for review of energetics, social behavior, and mating systems in marine mammals.

Energetics Definition

Energy is required for all biological functions; Enet = Eforage - Eallactivity; Natural selection should favor efficient foraging.

Consequences of Expenditure > Ingestion

Expenditure > ingestion results in negative energy balance, decreased body condition, and lower metabolic rate to compensate.

Types of Environmental Changes Affecting Energetics

Predictable changes (daily cycles, seasonality) and unpredictable changes (storms, natural disasters, anthropogenic disturbance).

Foraging Efficiency Strategies

Targeting energy-rich prey, optimizing time spent foraging vs resting, and using group foraging to increase prey detection.

Adjusting Metabolic Rates

Lower metabolic rates to conserve energy during food shortages.

Energy Storage and Use

Blubber/fat stores are critical, especially for capital breeders, allowing fasting during lactation or migration.

Heat Increment of Feeding (HIF)

The increase in metabolic rate that occurs after an animal eats, due to the energy cost of processing food.

Sea Otters and HIF

Using heat generated by ingestion as part of their thermoregulatory control.

Reproductive Strategies

Adapted to maximize energetic efficiency (capital breeders: fast; income breeders: forage during lactation).

Diving Physiology

Large oxygen storage and efficient use help conserve energy underwater.

Habitat and Seasonal Shifts

Migration to areas with predictable food.

Individual Consumption of Prey

Prey is colder than body temp, thermal mass prey absorbs heat from warmer stomach tissues, and the body has to expend energy to reheat the stomach contents.

Metabolic Energy

Usable energy from digestion used in maintenance (BMR, resting) + activity + storage + growth + reproduction.

Basal Metabolic Rate (BMR)

Minimum energy required to sustain life (adult, non-reproductive, resting, thermal neutral zone, post-absorbative).

Resting Metabolic Rate (RMR)

Less strict conditions than BMR, may or may not be: post-absorbative, complete rest and thermal neutral zone.

Field Metabolic Rate (FMR)

BMR/RMR + HIF + Activities over a 24 hour period.

Heat Increment of Feeding (HIF) Definition

Increase in metabolic rate that occurs after an animal eats, due to the energy cost of processing food.

Influence of HIF on Diving

Increased post feeding oxygen consumption, shorter diving durations, larger post-dive oxygen debt, helps maintain body temperature, and energetic costs of activities.

Direct Calorimetry

Measures heat production directly from the body.

Indirect Calorimetry

Estimates energy expenditure by measuring oxygen consumption or carbon dioxide production.

Time-Activity Budgets

Combines time spent in different behaviors/activities with known energy costs of those behaviors.

ODBA (Overall Dynamic Body Acceleration)

Accelerometers to measure body movement.

Heart Rate or Ventilation Rate

Heartbeats or breaths per minute to estimate metabolic rate.

Doubly-Labeled Water

Measures average daily energy expenditure over several days using deuterium and oxygen-18 isotopes.

Internal Investment

Increase in size (birth to maturity) + replenish reserves (restoration of energy reserves).

Energy Investment Varies Between Sexes

Varies between sexes (sexual dimorphism + differences in reproductive investment).

Male vs Female Reproductive Investment

Males: low investment in offspring, high energy costs (fight for female). Females: high investment in offspring.

Birth Mass vs Maternal Mass

Measure that looks at the size of the newborn relative to the size of the mother, key metric in analyzing maternal investment.

Milk Composition

Less water, higher fat composition overall (for capital breeders mainly).

Postnatal Energy Investment

Tied to milk composition and lactation strategy.

Lactation Interval

How long it takes offspring to transition from mother's milk to independence, relative to how large the mother is.

Lactation Interval Patterns

Capital breeders with rich milk have a fast transition; income breeders that feed while nursing have a slow transition.

Pinniped Reproductive Patterns

Phocids: capital breeders, single long trips, economical foraging; Otariids: income breeders, multiple short trips, high energy foraging.

Australian Sea Lion Exceptionally Long Lactation

Potentially related to low nutrient, stable environment.

Galapagos Fur Seal Exceptionally Long Lactation

Linked to low-productivity, unpredictable environment of the Galapagos

Mysticetes: Reproduction

Capital provisioner, short lactation, fasts while lactating, rapid calf growth.

Odontocetes: Reproduction

Income provisioner, long lactation, feeds while lactating, slow calf growth.

Sirenians, Odobenids, Otters & Bears Reproduction

Females accrue moderate resources before birth, income provisioners, lower rates of energy output during lactation.

Scaling up to Population Level

Population numbers and population composition.

Normal Energetic Balance

Prey availability and quality feed into prey acquisition; some energy is lost as fecal, urinary and heat output.

Energetic Balance Changes

Lower prey availability, higher cost of prey acquisition, less energy for growth, storage, reproduction, and repair.

Benefits and Costs of Group Living

Lower predation risk, higher prey detection/capture, and reproduction, but higher food sharing and competition.

Factors Influencing Sociality

Behavior and availability of prey and exposure to predators.

Odontocetes: Social System

Income breeders + 1 calf every 2-8 yr + high offspring dependency + lactation 1-3 yr + weaning 1-10+ yr

Mysticetes: Social System

Capital breeders + 1 calf every 1-3 yr + offspring dependency + lactation 6-8 months + weaning 6-8 months

Social Structures Within Groups

Varying number and stability of relationships within groups form the social structure.

Fission

A group splits apart into smaller subgroups to forage or avoid competition.

Fusion

Subgroups rejoin later, temporarily or for specific purposes (mating, socializing, protection)

Fission-Fusion System: Spinner Dolphins

Small groups rest in coastal bays, pods join together to feed pelagically, herds split up back into pods.

Transient Killer Whales

Specialize in hunting marine mammals, quiet and stealthy, smaller groups allow for reduction in competition.

Key Aspects of Sociality: Reproductive Pattens

long gestation, lactation + dependency

Alloparental care

Taking care of offspring other than your own

Teacup formation

Vulnerable animals in middle, dominant adults outside

Sperm whales

Matrilineal groups (around 10) - related females and their offspring form the core structure of the group

Matrilineal groups - Kin-based cooperative care

Older females may nurse and defend related young

Reversed sexual dimorphism

Females are larger than males

Mating strategy in Humpback Whales

males compete physically and behaviorally for females

Mating strategy in Right, Bowhead & Gray whales

High sperm production and multiple copulations, few male-male interactions

Pinnipeds social & mating systems

Females distribute according to resources & males map on to female locations

Polygyny

one male, many females

Polyandry

one female, many males

Monogamy

one male, one female

Fast Ice v Pack Ice (Lactation)

Fast ice has longer lactation periods, pack ice has lower lactation duration

Lekking

Males gather in a specific area (a lek) to perform courtship displays, and females visit solely to choose a male not for resources

Sea otters

Most common in California

Manatees

Form mating herds (1 female, 2-22 males).

Dugongs

mating herds (100s) & promiscuous, intense mating competition.