Test 3 - OCS 4001

Ppts: Environmental Influences, Vertical Migration

What are some environmental influences on migration?

• Temperature

• Salinity

• Water levels

• Prey availability

• Habitat

• Dissolved oxygen

Temperature: Many marine animals move or migrate in anticipation of, or in response to, changes in water/air temperatures. Why?

• To maintain a more consistent temperature regime “Eternal summer” - birds do this too

• To maximize foraging and growth potential

Cold fronts are major drivers of movements/migration in who?

• Estuarine organisms

• Waterfowl, raptors

Describe the characteristics of a cold front

• Preceded by warm southerly winds

• Storms at the frontal boundary

• Followed by cold dry air and strong northerly winds

• In the U.S. fronts typically move south and east

Why are cold fronts important to migratory species?

• Winds

• Water levels

• Temperature

How do cold fronts affect migratory birds?

Birds

• Favorable winds for migrations south behind a front

• Sudden change in air temperature

• Generally poor conditions for migration preceding a front

How do cold fronts affect aquatic animals?

• Sudden drop in water temperature

• Drastically reduced water levels in estuaries - temporary loss of habitat

• Can signal beginning of large migrations

• Also triggers movements to localized overwintering locations for taxa

What are some consequences of not migrating?

Fish kill

Low water level - cold stunned sea turtles

Ex. Florida Manatees. Where do they migrate? Why might it be beneficial?

• Migrate north during summer

• Migrate to Florida during winter

• Move inshore into freshwater areas during winter

• Spring water is stable and warmer

Use of rivers as overwinter habitat for estuarine/coastal organisms. Lower portions of river systems may provide thermal refuge during winter, why?

• Protection from wind – so less impacts of water level

• Depth – deeper habitats are warmer

• Less temperature fluctuation

What environmental factor is often tied to prey availability in the the Gulf of Mexico?

Why do predators migrate throughout the year?

• Often tied to temperature

• Seasonal availability of prey in the northern Gulf of Mexico

  • Several migratory species converge on this area during late summer

• Migratory Coupling

• Predators may migrate to maintain optimal foraging throughout the year

• Many highly migratory species (billfishes, tunas, sharks)

• Some whales migrate for prey availability and mating/calving

What is migratory coupling?

The migration of predators aligning with prey availability

Some animals migrate for Habitat reasons, why?

• Ontogenetic migrations

• Preferred spawning or nesting habitats

• Ex. Humpback whales migrate to mating/rearing areas off the coast of Hawaii to seek ideal habitat

Where is hypoxia common and how does it affect marine animals?

• Common in backwater areas of estuaries

• Hypoxic zone in the Gulf of Mexico Mobile vertebrates and invertebrates

  • Horizontal displacement

  • Vertical displacement

What are some changes that affect movement and migration?

• Habitat change

• Climate change

• By-products of coastal development

  • Light

  • Sound

  • Pollution

Specialists vs. Generalists - We would anticipate that generalists will be less impacted by habitat change than specialists. Why?

Generalists are more likely to find alternative sites or habitats to exploit

Ex. Juvenile red drum in estuaries

How does habitat change impact migration/movement? - Habitat change

• Destruction of stopover sites

• Arctic shorebirds (extreme migrations)

• Depend on a few sites containing intertidal mudflats with extremely high abundance of invertebrate prey – fuel for migration

• Ex. Red knots

  • Migration between Australia/New Zealand to breeding grounds in Asia

  • 45% of the population stops at one site (20 km of coastline)

  • Much of the coastline is being destroyed through land reclamation (walls, industrial areas)

How does habitat change impact migration/movement? - Dams and salmon migration

• Historical – 175-250 thousand tons of salmon migrated up rivers of Pacific Northwest

• Current – 13-15 thousand tons

• 6-7% of marine derived nitrogen and phosphorus compared to prior levels

• Many different ecological effects

• Dams are bad

Climate change also has many different potential effects, many of which we do not know yet. What are the most well-known effects?

• Shifts in timing of migration

  • Evidence suggests that many animals have altered their time schedule for migration as response to a changing climate

• Also evidence of animal shifting migrations further north during summer and less migrants moving as far south during winter

Ex. European flounder

• Migration to spawning areas

• Migration occurred earlier (1- 2 months) during years that were up to 2 degrees cooler

• Flounder also migrated more rapidly

  • Cold years (arrive on spawning grounds 2-6 days)

  • Warmer years (arrive on spawning grounds over 12-15 days)

  • More synchronous migration during colder years?

What are some changes that affect movement and migration? - Light

• Artificial light

  • Nocturnal migration in birds

  • Foraging behavior in fish

  • Concentrates prey items and influences distribution of aquatic predators

What are some changes that affect movement and migration? - Sound

• Sound

  • Marine mammals

  • Oil and gas industry

  • Military testing

Most attention in migration ecology given to horizontal movements…but in marine systems many animals migrate vertically. Why?

• For many of the same reasons that animals migrate horizontally

• Suitable habitat

  • Food resources / bioenergetics

  • Temperature / thermal refuge

  • Avoid predation

• In contrast, vertical migration may also be affected by animals seeking optimal conditions influenced by

  • Light

  • Currents / tides

What are the different types of vertical migration?

Diel – daily migrations between deeper habitats and the upper water column (ex. Plankton, marine fish)

Diving/Foraging – shorter duration migrations/movements specifically for feeding purposes (ex. Whales, seals, turtles, birds, some sharks and fish)

Seasonal – seasonal shift in distribution from upper water column to lower water column – less common (ex. some marine fish and invertebrates)

To enhance horizontal transport

What are some challenges with vertical migration for mammals?

Pressure

Oxygen consumption

Temperature

Buoyancy

How is pressure a challenge with vertical migration?

• Pressure increases by one atmosphere for every 10 m of depth

  • At surface (sea level) we experience 1 atmosphere of pressure (101,325 pascals, or 14.7 lbs per square inch)

• Affects air filled spaces in the body

• Lungs, middle ear cavity, air sinuses in head

• Many marine mammals can collapse their lungs

• Remove air from lungs prior to diving

How is oxygen consumption a challenge with vertical migration? How do animals overcome not being able to breath underwater?

Oxygen storage in blood – marine mammals, diving birds have high blood to body volume ratios, higher percentage of red blood cells, higher concentration of hemoglobin (blood) and myoglobin (muscles)

Lower heart rate - Weddell seals heart rate as low as 4 beats per minute

The deep ocean is a cold environment. Global average temperature below 200 m is 4 degrees (Celsius). How do animals overcome this?

• Marine mammals tend to be large and have low surface areas to volume ratio (“sausage shaped”).

• High blood to volume ratios

• Mammals have thick layer of fat – blubber

• Fur (seals, otters)

• Feathers (penguins)

Mammals and birds float. So…how do they overcome buoyancy?

• Behavior

  • Deep diving mammals exhale before

  • Removing oxygen from the lungs makes animals slightly negatively buoyant • Plunging birds (gannets)

• Morphology

  • Diving birds are typically heavier than other birds – bones filled with marrow, greater muscle mass in legs, heavier plumage (waterproof with oils)

  • Shorter wings (penguins)

  • Fish? swim bladder

  • Sharks?? Lift

Dive duration for mammals, birds, turtles - All need to breath air, so….how long can they stay down?

• Thick billed murres – up to 100 meters (between 3-4 minutes)

• Elephant seals - > 1500 meters, over 60 min

• Leatherback sea turtles - > 1200 meters (85 minutes)

• Emperor penguins – up to 565 meters (up to 22 minutes)

• Sperm whales – up to 2032 meters (90 minutes)

• Cuvier’s beaked whales – up to 2992 meters (138 minutes)

What is diel migration?

• Occurs over a daily cycle

• Common in zooplankton, fish, and invertebrates

• Why?

  • Avoid predation

  • Maximize foraging opportunities (more food in surface waters)

What are the types of diel migration?

Type I – animals move up in the water column at dusk and down at dawn (more common)

Type II – animals move up in the water column during daylight and down at night (less common)

Why is Type I diel migration more common?

Driven by bioenergritcs/food

What does it mean “driven by bioenergetics/food”?

• Foraging opportunities at surface (phytoplankton)

• Sometimes foraging at depth (e.g. tunas)

• Both (swordfish)

Conditional migration - Migration is conditional on

• Physiology, sensory capability, and genetic capacity

• Habitat quality and resource availability

• Size, maturity, gender

• Social interactions – population density, learning, tradition, and personality

Migration is not necessarily as simple as a genetic trait nor is it directly determined by environment – rather it is influenced by interacting propensities.

How are we discovering individuality in animal movements?

• The advent of electronic tagging – greater resolution and insight into individual movement patterns.

• Genetics

• Behavior

Why would it be hard to discern individuality from tracking data? (What are some biases?)

• Many tagging studies have small sample sizes

• Unexpected behaviors can be discarded as “bad data”

• Increasing recognition of individual variation in movement patterns, migration patterns and timing – important implication for population ecology

• Example: determining survival in acoustic telemetry studies

• Individuals thought to be dead due to inactivity were in fact alive and non-migrants

What is partial migration?

Coexistence of two or more life cycles within the same population. Partial migration traditionally considers concurrence of migratory and sedentary life cycles.

What are some individuality seen in Arctic charr?

• Found throughout arctic 3 distinct ecomorphs, reoccur throughout the species range

• Dwarf resident – matures early and higher proportion of males

• Large resident – matures later and occupies a different trophic niche

• Migratory – Anadromous, ocean going, higher proportion of large females

• Both genetic and phenotypic plasticity play a role

• Adults of each ectomorph produced all three types, but were more likely to produce similar offspring

• Early rearing condition had a stronger influence, with higher food levels associated with resident behavior

• Also determined that migration behaviors were reversible

Partial migration cont’

• Often manifests as two or more ecomorphological types, which occupy differing trophic niches

• Early rearing conditions carry over into lifetime differences in migration behaviors

• Contingents are not genetically discrete, but their occurrence and relative frequency are heritable

• Migration behaviors covary with maturation rates and reproductive success

• Contingent behaviors are not necessarily permanent – they can reverse themselves over an individual’s lifespan

Multimodel partial migration response

1. Fast-growth juveniles mature early and remain resident

2. Intermediate-growth juveniles remain resident for a short period of time and migrate early in life

3. Slow growth juveniles remain resident for a longer period and migrate later in life

What are the 3 dominant types of partial migration?

1. Non -natal divergence

2. Natal divergence

3. Differential migration

What is Non-natal divergence?

• One contingent stays put in the natal habitat, another contingent disembarks but returns for spawning

• Classic type of partial migration for which the threshold model applies

• Extremes are either migratory or resident, while partial migration is predicted across a range of intermediate pheotypes

What is a threshold model?

continuously distributed liability trait is divided into discrete phenotypic outcomes. The liability trait is linked to a suite of other traits that determine migration outcomes (e.g. restlessness, early growth, size , dominance). This trait is represented by its propensity to cause an individual to undertake one of several discrete behaviors

What is Natal Divergence?

• Resident and migratory contingents comingle during nonbreeding seasons but originate from separate natal habitats (populations). Mixing between migratory contingent of one population and nonmigratory contingent of another.

• Exs. Shared shelf habitat for inshore and coastal spawning cod, Atlantic herring aggregations where migratory contingent comingles with resident contingent on feeding and wintering grounds

What is Differential Migration?

• Migration within a population conditionally dependent on size, age, sex, or other attribute

• Ex. Sexual segregation by mako sharks to avoid sexual harassment, decreased range with size for Pacific bluefin tuna, range extension with size for black drum

What is Switching?

• Midlife abrupt shifts in migration behaviors, more typical in moderately long-lived species

• Ex. Arctic charr, some eels, white perch

What is Skipped spawning?

• Animals disembark from natal habitat but only a portion of adults undertake natal migrations each year

• Ex. Common in marine fish, sturgeons, perhaps southern flounder

What is straying?

• A portion of the migratory contingent reproduces in nonnatal habitats. An amended type of nonnatal divergence. Straying propensity often varies by size and sex

• Ex. European plaice, pink salmon

What is Irruptive migration?

• Wholesale shifts in distribution caused by self-reinforcement of the migratory contingent’s behavior, evacuation is considered a type of irruptive migration when it occurs as a result of catastrophic environmental change

• Ex. Temporary evacuation of white sturgeon after Mt. St. Helen’s eruption, invasion of Indo-Pacific lionfish, rapid range expansion of Japanese sardines into north-central Pacific

Vertical migration (partial migration)

• Only a fraction of the population exhibits diel or other recurrent vertical movements. Could be considered a commuting or ranging behavior, but often occurs over seasons/years

• Ex. Juvenile plaice separate into migratory and nonmigratory individuals on the basis of their vertical behaviors

Classes of Partial Migration - draw all of them!

How does Animal personality affect migration?

• Individual differences in behavior that may lead to differences in movement or migration propensities (temperament, coping style, behavioral type)

• It’s a growing field – linking animal personality to movement/migration

• Tracking of individual birds (black browed albatross) showed that ”bolder” more risk prone birds foraged closer to the colony (high competition), while birds that were more risk-adverse made longer foraging trips further away from the colony

What are factors that may influence migratory behavior?

• Aggression – are more aggressive animals more likely to migrate?

• Sociality – do animals that are more/less social migrate further/shorter?

Animal tracking data analysis what?

• Residency

• Movement metrics

• Space use

• Relating movement/space use to variables of interest

What is residency?

In its most simple context….Residency is the length of time that an animal remains in an area of interest (e.g. reef, breeding location, other habitat, etc.)

What movement metrics?

• Distance

  • How far the animal has traveled from previous position, this is also referred to as step length

  • Total distance = summation of each step length

• Speed

  • Distance divided by time elapsed, how fast the animal is moving

• Turn angle

  • The angle at which the animal changes direction in movement path

• Tortuosity or straightness

  • Does the animal move in a relatively straight line or is are there many turns?

• Displacement

  • How far does the animal move from the original tagging location?

• Random Walk

  • a movement pattern where an animal's path is unpredictable and lacks a clear directional bias

What is space use and how would you analyze it?

• Home range

  • Space use over broader scales

• Minimum convex polygon (MCP)

• Kernel Density

  • Brownian Bridge Movement Models

• Niche partitioning

• Joint space use

What are Minimum convex polygon (MCP)?

The minimum bounding polygon around the relocations of the animal

Simple technique to broadly define the area of use or home range

Sometimes depicted as % of points (50%, 95%)

What is Kernel Density?

a statistical technique used to estimate the probability density function of a dataset

What do Brownian Bridge Movement Models do?

Identify corridors

More specific to locations

Think movement vs. space use

What is niche partitioning?

the process by which competing species use the environment differently to coexist

What variable of interest might influence animal movement or space use?

• Environment

  • Temperature, salinity, dissolved oxygen, currents, wind

• Temporal

  • Time, Month, Year, Day vs. Night

• Biological

  • Prey, other individuals of same species, influence of competing species, influence of predators

What are Seascape patterns?

The spatial and temporal distribution of physical and biological drivers (on the seafloor and in the water column) that influence species distribution (Costa et al. 2013)

What are the Spatial patterns in seascapes?

Patterns may be 2-D or 3-D (or even 4-D)

2-D patterns - horizontal

3-D patterns - vertical

4-D patterns - those 2 dimensions across time

What are Spatial patterns?

Patterns that are constant in time but change across space

Dependent on scale

What are Temporal patterns?

Patterns that are constant in space but change in time

Dependent on scale

What are Spatio-temporal patterns?

Patterns that change in both time and space
Dependent on scale

Seascape patterns depend on what?

the scale at which they are observed and analyzed

Scale can refer to both the

resolution (or grain) and the extent of a dataset or pattern. Resolution and extent can vary

Data scales

Spatially

Temporally

Thematically

What are the process scales?

• Ecological – scale at which ecological pattern or process occur

• Observational – resolution and extent at which a physical or biological process or pattern was observed

• Analytical – the scale at which spatial and temporal patterns are characterized

• Data scales are nested within process scales

What are passive sensors?

map seascape by receiving and recording energy that reflects the earth’s surface (map 2-D patterns)

What are active sensors?

map the seascape by emitting energy (radio waves, light, or sound) and receiving and recording the returned energy (can map 3D patterns) • RADAR, LiDAR, SONAR

What are some uncertainties in seascape maps?

• Introduced when observing, characterizing, and applying seascape maps.

• Measurement error, processing/classification error during making of maps, application error introduced when choosing scales and analytical techniques can combine and interact in unknown ways

• Could lead to inaccurate conclusions about ecological relationships

Natal divergence

Partial migration

Only one sex migrates

Differential migration

Shortstopping

Whooping cranes

Cold fronts

Major driver of migrations in U.S. during fall

Passive sensor

multispectral satellite imagery

Active sensor

SONAR

Homing

Return to birthplace

50% KDE

Core use area

Diving

Type of vertical migration

Lower heart rate

Reduced oxygen consumption

A metric to characterize when an animal remains in a habitat with limited movement for a period of time

residency

Which of the following is an example of differential migration?

males migrate and females do not

A ______is used to define home range by creating a bounding polygon around the outermost animal relocations.

minimum convex polygon

Papastamatiou et al. (2021) used a suite of biologging technologies to evaluate hunting behavior and ______ in white sharks

social dynamics

Mesoscale oceanographic feature also referred to as a cold cored eddy and associated with upwelling

cyclonic

Partial migration often manifests as two ecomorphs often described as ______ and _____ contingents.

resident, migratory

A midlife abrupt shift in migratory behavior is referred to as

switching

Which type of animal is likely to make the deepest dive?

elephant seal

A warm core eddy is characterized by

anticyclonic rotation, cyclonic rotation

Marine mammals often release most of the air from their lungs prior to diving to overcome

pressure change, buoyancy

Brownian bridge movement models may be preferred over traditional kernel density estimation to

identify corridors of movement

A metric that measures the length or proportion of time an animal spends in an area of interest

Residency

Taxonomic grouping with the deepest recorded diving behavior

toothed whales

Weather surveillance radar can be used to quantify migration intensity of

birds

Movement paths of animals are often compared to a _____,to determine if the movement path is more linear or tortuous than would be expected

random walk