Movement Ecology Flashcards
diel vertical migration
diel separation of modal depths where diel distributions are not significantly overlapping and are of similar variance
diel activity pattern
diel distributions have different shapes (variances) but overlap
-ex: dive from surface to >100 m and back during day but stay at surface at night
Why is using diel mean depth not give full picture?
doesn’t account for variance or full distribution
-not high resolution
What are the potential evolutionary drivers of dispersal?
- kin competition
- inbreeding
- resource competition
- environmental stochasticity
dispersal
any movement between habitat patches
habitat patch
area of suitable habitat separates in space from other such areas
ultimate causes of dispersal
- kin interactions/selection (reduce competition)
- inbreeding avoidance
- habitat variability
proximate causes of dispersal
- variation in fitness between patches can select for dispersal
- gene for plasticity in dispersal selected for
- emigration
- inter-patch movement
- immigration
What may cause variation in individual dispersal?
- sex (variation in life history strategies between sexes)
- developmental stage
- body size or condition (smaller individuals may disperse because outcompeted OR larger individuals may disperse because they are in better condition to do so)
Why might predators use fronts/eddies?
- migratory cue
- enhanced foraging opportunities
- preferred thermal habitat
Why can/do blue sharks use mesoscale anticyclonic eddies?
anomalously warm temperature at depth allow these predators to deep-dive to forage on abundant fish community they normally couldn’t reach
What can habitat suitability modeling be use for?
help assess the efficacy of spatial management strategies, determine proportion of protection/vulnerability to fishing, inform conservation/management plans for HMS
What environmental variables may impact shark occurrence?
-bathymetry, bathymetric slope, chlorophyll a, SST, surface current
Maximum Entropy Model
habitat suitability model based on environmental variables and presence-only data
-can be used to project habitat suitability under climate change scenarios and levels of protection
partial migration
when only some individuals from a population migrate
ultimate causes of partial migration
- reproduction
- feeding/diet
- predation
- body size and physiology
- competitive release
Describe the evolutionary maintenance of partial migration.
- stable state - the two strategies (migrate and don’t migrate) have equal fitness at equilibrium
- best strategy dependent upon the individuals phenotype
What are the consequences of partial migration?
- ecological (nutrient transport and trophic effects)
- evolutionary (divergence of populations if partial migration is related to breeding)
Why are migratory species more vulnerable to population declines?
they rely on multiple habitats to complete their life cycle
differential migration
distance traveled or timing differs between portions of the population
What are the hypotheses for differential migration?
- body size (effect temperature tolerance, fasting tolerance)
- dominance (subordinate animals forced away)
- arrival-time (distance migrated may affect arrival time at breeding site. Early arrival may increased breeding)
obligate migration
must always migrate
facultative migration
only migrate in a proximate response to current deterioration of local conditions
nomadism
migration does not follow a regular pattern but links temporary breeding sites that are located where conditions are ephemerally favorable
irruption (migration)
occasional, irregular movements of a significant proportion of a population beyond its usual breeding or non-breeding area
Describe migration vs foraging behavior characteristics.
Foraging is slow meandering, changing directions, small spatial scales. Migration is directed, undistracted (don’t stop or change direction), large spatial scales
How does internal state influence movement?
- high body condition facilitates efficiency of foraging, dispersal, migration
- dispersal decision can also be stimulated by decreased condition (stress hormones) telling individual to leave
Describe how scale impacts animal habitat selection from large to small.
- geographical range
- level where animals conduct their activities (home range)
- level of specific sites or specific components within their home range (breeding ground, feeding ground, pupping ground)
- according to how they will procure resources within the micro-sites
habitat
resources and condition present in an area that produce occupancy by a given organism
habitat use
way and animal uses a collection of physical and biological components (i.e., resources in a habitat)
habitat selection
hierarchical process (series of innate and learned behavioral decisions) by which an animal chooses which habitat components to use
habitat preference
consequence of habitat selection process resulting in the disproportional use of some resources over others
habitat availability
accessibility and procurability of physical and biological components of a habitat by animals
abundance
amount of a resource in a habitat regardless of the organisms present
habitat quality
the ability of the environment to provide conditions appropriate for individual population persistence
-not based on population density or abundance
Why might “suitable habitat” be inappropriate to use?
if an organism occupies and area that supports at least some of its needs, then it is habitat
critical habitat
high-quality habitat
-an area’s ability to provide resources for population persistance
Why are PSAT location data inaccurate?
error associated with natural variability in light levels
- light attenuation with depth
- turbidity
- clock error
- shark diving behavior
What are methods for improving PSAT tracks?
- filtering outliers
- smoothing procedures (moving averages)
- processing raw estimates of location using state-space movement models (Kalman filter or particle filter)
- matching SST from tags with remotely sensed SSTs
How to finmount satellite tags determine location?
Doppler-shift calculations made by Argos when satellite receives 2+ signals from tag
What might cause tag failure?
saltwater switch malfunction due to biofouling
-switch to copper switch may reduce biofouling
What is the limitation of most shark movement studies?
They can only describe the “what” rather than the “why” aspects of shark behavior and ecology
What are ecotourism and fisher concerns about shark tags?
- animal welfare and behavior
- unsightly in photos
- too many tagged
- exposes fishing locations
- data used against fishers
- change quality of animal meat
What is reducing impact of tagging studies on policy?
-lack of communication between managers and researchers on needs and outcomes
How can tracking data benefit policy?
- bycatch mitigation measures
- MPAs
- time/area closures
- defining stocks
- assess abundance
- quantify mortality
- identify essential fish habitat
- identify overlap with human activities
- dynamic ocean management (real-time)
What are the 4 main components that contribute to movement?
- internal state
- external factors (abiotic and biotic)
- motion capacity (ability to move)
- navigation capacity (orient and navigate)
hotspots
spatiotemporal patterns of areas of high fishing density that overlap with animal habitat
spatiotemporal modeling
estimates species distribution and density in unsampled areas by imputation over space and time
-reduces biases caused by spatial and temporal heterogeneity of both fish and fisheries
preferred habitat
locations where the predicted catch rate is greater than the mean value
home range
an area with a defined probability (50%, 95%) of occurrence of an animal during a specified period
What is the problem with minimum convex polygon and flat kernels?
assume uniform space use within range
- unlikely for most animals
- probalistic methods are more useful
utilization distribution
probability distribution that maps an individual’s relative use of space
-kernal method provides an estimate of the UD
What is the benefit and con of traditional kernel method?
- pro: provides estimate of the utilization distribution (spatial probability)
- con: assumes statistical independence of observations (transmission are usually also temporally autocorrelated, which can cause UD to be biased)
time kernel method
- preferrable to traditional kernel method
- considers both spatial and temporal aggregation of observations
- calculates utilization distribution by standard kernel method BUT gives less weight to temporally close observations
- can also determine weight based on spatiotemporal variant of the time kernel (keeps high weight for fast long-distance movements that are important)
- highest UD values given to areas where the animal repeatedly returned to after being elsewhere for a while
How does ecology and evolution impact dispersal?
- ecology - abiotic factors and local adaptation to environment
- evolution - intra- and inter-specific interactions and dispersal capacity (inbreeding prevention, kin selection, dispersal capacity all genetic)
What does the success of spatial closures depend on?
- size/shape of closure
- fishing pressure outside of closed area
- no take vs no entry
- time period of closure
- life stages that use closed area
- fish movement rates
What might drive pronounced activity at crepuscular periods?
May aid in orientation and navigation
-sun angles and geomagnetic or electrical fields
When do animals use Levy flight vs Brownian movement?
- Levy flight when resources are scarce and patchily distributed
- Brownian movement when resources are abundance
When did international fleets targeting large, epipelagic fishes spread into the high seas?
1950s
-prior to this, high seas were a spatial refuge
What percentage of worldwide shark catches are large pelagic sharks?
~52%
Describe overlap between porbeagle habitat and fishing zones.
- 47% mean monthly overlap between porbeagle habitat and fishing on global scale
- 52% mean monthly overlap between porbeagle habitat and fishing in N Atlantic
- Porbeagle occurred in the highest risk zone in the N Atlantic
abundant center hypothesis
assumption that species are most abundant in the center of their range and decline in abundance toward the range edges
What are drivers of population distribution range boundaries and species responses to climate change?
- extreme environmental heterogeneity
- organisms adapt differently to heterogeneous conditions at different parts of their range
- variation in population demographics across the rang (birth, death, immigration, emigration)
- variation in species interactions across range
- variation between range edges
- variation in anthropogenic impacts
dynamic range models
statistically estimate both range dynamics and the underlying environmental response of demographic rates from species distribution data
-how spatiotemporal variation in population growth and dispersal determine spatiotemporal distribution of local population size
Hutchinsonian niche
set of environmental conditions under which a species can “exist indefinitely”
- intrinsic population growth rate (r) is positive
- can be dynamic to describe how birth and death rates vary with environmental conditions
What is the dilemma of estimating niche?
to have unbiased niche estimate you have to quantify range dynamics
-requires knowledge of how demographic rates respond to environmental variation
demographic response model
how spatiotemporal variation in environment translates into spatiotemporal variation in birth, death, dispersal
Allee effects
positive density-dependence of population growth at low desnities
FAIR (framework to promote biologging data standardization)
Findable, Accessible, Interoperable, Reusable
TRUST (framework to promote biologging data standardization)
Transparency, Responsibility, User focus, Sustainability, Technology
What are causes of individual variation in animal movement?
- intra-specific interactions (competition, mating)
- inter-specific interactions (prey and predation, competition)
- abiotic factors
- individual traits (genotype, internal state, perception of external factors, sex, life stage)
What are consequences of individual variation in animal movement?
- individual (cost/benefits in terms of growth, survival, reproduction)
- population (genetic structure, population connectivity, demographic rates)
- community/ecosystem (competition, predator-prey interactions, nutrient inputs across ecosystems)
How is individual variation in animal movement maintained?
- genetics (individual movement differences may to due to different genotypes)
- maintained by balance of genetic drift, immigration/emigration, mutation, selection
How do PSATs estimate longitude?
comparing the time of local midnight or midday with that of UTC time
How do PSATs estimate latitude?
estimates of day length based on timing of sunrise and sunset time based on light level
Why do sharks show regular diving oscillation throughout the day?
- searching for prey (diving most efficient way to sample olfactory sources)
- DVM - prey tracking of vertically migrating populations
How do we infer habitat selection of sharks based on tag data?
by comparing the habitat types where sharks are location to the types of other (presumably) equally available habitats where they are NOT located at a given time
-compare the amount of time spent (or prey encountered) in each habitat as a function of the movement track observed, compared with the predicted values for that individual based on random walks though the same environment
How much lower are daily energy costs by using “hunt warm, rest cool” strategy?
~3-4%
-adds up over lifetime
What factors effect home range size?
- metabolic rate and energy availability
- locomotion strategy
- foraging dimension (2D or 3D)
- trophic guild
- prey size
- BODY SIZE
How is thermoregulation expected to impact home range size?
expected to have larger home range because of higher MR, higher energetic needs, and larger area needed to find prey to meet those needs
- but this relationship was not found
- home range most impacted by body size
kernel density function
- where there is a high concentration of points (presence locations) the kernel estimate has a higher density than where there are fewer points
- non-parametric
What is a state space model?
Hierarchical models that accommodates the modeling of 2 time series:
- a state, or process, time series that is unobserved and attempts to reflect the true, but hidden, state of nature (i.e., behavioral state)
- an observation time series that consists of observations of or measurements related to the state of the time series
What are the assumptions of state space models?
- state time series evolves as a Markov process (incorporates temporal dependence of states)
- observations are independent of one another once we account for their dependence on the states (any marginal dependence between observations is the result of the dependence between hidden states)
first difference correlated random walk
- one of first SSM for animal movement
- developed for Argos doppler shift location data
- time series of N observed Argos locations at irregular time intervals
- time series of T true locations of the animal at regular time intervals
- process equation assumes that the animal location is not only dependent on the previous location, but also on the animals previous movement in each coordinate
- interpolates true location based on the proportion of time between observations compared to regular interval
continuous-time correlated random walk
-SSM where process equation is in terms of how changes in velocity through time affect the location of animal
hidden Markov model (HMM)
- class of SSM where the states are discrete (generally categorical with a finite number of possible values) rather than continuous
- used to model and animal that switches between distinct behavioral modes
- Markov chain - probability of being in each mode at time t depends only on the state value at the previous time step
Why is sampling frequency important in modeling distinct behavior modes?
-must sample the movement track at high enough frequency so that multiple locations are recorded in each movement bout
Why is there often migration between distinct residency regions in sharks?
in response to maintaining optimal thermal envelopes
- seeking high prey availability
- areas for reproduction
phenology
timing of life events
environmental envelope
the set of environments within which it is believed that a species can persist
- where its environmental requirements can be met
- mapping these envelopes in space delineates potential range
How can we overestimate or underestimate potential range using environmental envelopes?
- overestimate - if parts of potential range represent combos of parameters which are collectively unsuitable even though individual parameter values for those parts are within the observed ranges
- underestimate - if the records of observation do not fully span the environmental envelope
area-restricted search behavior
a predator in a patchy prey-field will spend more time and search more intensively in rich foraging areas than in sparse areas
What are traditional techniques for generating pseudo-absence points?
generate points at random across range (but outside the species known distribution, in unsuitable habitat), often failing to include biological knowledge about the species-habitat relationship
habitat envelopes
ecological representation of a species or species features (i.e., nest) observed distribution (realized niche) based on a single attribute or the spatial intersection of multiple attributes
-generates pseudo absence points from WITHIN the species distribution (excluding its known presence areas)
