Week 11 - Spatial Patterns, Seasonal Migration, Disperal

Home range (HR)

area over which a group or individual travels during normal daily movements

HR characteristics

not defended, linear/2D/3D, both individuals and groups can have HR, commonly overlap but still avoid each other

HR predictions

larger animal larger HR, migratory species have seasonal HR

Benefits of HR

familiarity (aids in gathering food, shelter, avoiding predators, knowing neighbors)

ultimate benefit: increase fitness

Factors affect HR size

age, repro state, pop density, body mass, seasonality, producivity of resources, diet, elevation, latitude

Territory

defense of an area around a high priority, limited resource from which competitors are excluded

Terr. characteristics

don't overlap, actively defended, displays involved (sound, visual, smell)

Why have a terr.

access to limited resources (food, mates, sleeping/nesting/display sites)

What is defendable in terr.

feeding area, refuge, mates, nests

Who is territorial

basically everyone (across taxa, individuals or groups, one/both sexes, common in verts)

How to defend a terr.

chemical markings, fighting (last resort), visual displays, auditory displays

Seasonal migration

round trip, occurs across taxa, affects ecosystems

half of birds living in north america migrate (6 billion)

costs of seasonal migration

HUGE energy demands, predators love exhausted prey, exposes individuals to new climatic events or new pathogens, time spent traveling means less time for reproduction

benefits of seasonal migration

avoid harsh climate, exploit favorable seasonal resources and locations for repro (outweigh the costs)

Flyways

migratory routes

N. America - two coastal, MS, rockies, most N/S some E/W

Oceanic - long distances over water, N/S some E/W

Arctic tern

breed in arctic, winter in antarctic (technically 'summer' climate for each location)

Hit both times of plenty

Anadromous fish

from sea to natal stream

hatch in freshwater, live in marine, return to fresh to breed/eggs/die

ex. salmon

Catadromous fish

from freshwater to sea

hatch in sea, live in freshwater, migrate back to sea to breed/eggs/die

ex. atlantic eel

How do animals navigate?

plotting uses familiar landmarks, compass orientation refers to ability to go in a particular compass direction

Dispersal

one-way change of locations, not round trip, no seasonal return

Natal dispersal

most commonly young animals leaving natal HR/territory to find their own

costs of dispersal

mortality high (lack of familiarity, increased locomotion, more susceptible to local disease)

outbreeding depression

benefits of dispersal

avoidance of inbreeding, avoid local crowding, decrease competition with secondary kin, potential to locate uninhabited areas and gain access to important resources