Behavioral Ecology: Movement & Orientation

Behavioral Ecology:Movement & Orientation • Why move? • Types of movement • Metapopulations • Local Distribution • Home Range • Territoriality • Migration - Mass movements • Breeding • Over-wintering • Movements of juveniles - Dispersal • Homing/Orientation

I. Why move? Reasons to move: • Mortality can be high when individuals move from one habitat to another

A. General types of movement • Herps are not distributed randomly! Some places are better than others… • Station keeping: movements directly related to the acquisition of resources within a home range • Ranging behavior: exploring new habitats or resource patches • Dispersal: juveniles leaving their parent’s home range to find their own

B. Metapopulations – populations of populations • Spatially subdivided populations

II. Local distribution of individuals • Home ranges = area which individuals move within & do not defend from conspecifics • Association between body size & home range • Resources • Food, shelter, thermoregulation sites, escape routes • Social activities • Finding mates • Calculating home range – minimum polygon method

Minimum polygon method of calculating home ranges – • Measure the area that encompasses all of the outer points within which an individual occurs. • Most widely used method • Good for species living in 2D habitats • Does not take into consideration amount of time or relative frequency with which an individual might use different parts of the home range

Anolis transversalis -

Home range can vary through time/space • Terrestrial amphibians, during non-breeding season have small home ranges away from water • Pond breeding species, home range breaks down during breeding events • Microhabitat specificity a factor • Vary w/sex & reproductive state

Resource dispersion & home range • Habitat = resource patches • Depleted / not depleted • How rapidly will resources be replenished? • Abundant resources = limited home range • Resources renewed slowly = wider home range

Herbivores – wider food sources, but abundant… Masticophis (whiptail) – has to go where the food is…

Iguana iguana Dermochelys coriacea Hoplocephalus bungaroides

B. Territoriality • Territory = area within the home range which is defended against conspecifics & other species • Usually has some sort of defendable resource • Defense results in exclusivity • Most often males defend territory • Direct combat • Threats • Avoidance • Selection favors those that control & use resources in a way that positively influences their reproductive success

Amphibians exhibiting territoriality: Dendrobates pumilio Plethodon cinereus

III. Migration - Mass movements A. Breeding migrations • Amphibians - Triggered by rainfall & temp, usually starting at night – but continuing through day • Mass movements – explosive breeders, i.e. Ambystoma & Bufo move en masse to and from breeding ponds • Reptiles – Vipera, Kinosternon, Chelydra, Crocodylus, Iguana, Sea turtles

Loggerhead turtle –movement monitored via satellite

B. Over-wintering movement Seeking more hospitable climate • Flowing water of streams vs. frozen water of lakes/ponds

IV. Dispersal • usually refers to juveniles leaving home ranges of parents to find a home of their own, reasons to disperse: • Costs =

V. Homing Behavior • Ability of displaced individuals to return to their original location – animals must be able to sense the direction they are moving

ORIENTATION Pilotage - orientation with respect to fixed landmarks home

Mechanisms of orientation • Local environmental cues (landmarks) • Smells, visual cues • Compass orientation • X-Y axis orientation • Depends on sunny conditions • Must have built in sense of daily changes in the sun’s position (internal clock) • Celestial orientation • Magnetic orientation

Navigation - orientation without fixed landmarks

Behavioral Ecology: Movement & Orientation