Transcript 15_HabitatSelection

Announcements
Final Exam
May 11, 8-11 am.
kg meat/lion/day
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hunting group size
Caraco and Wolf
Packer
Why do humans use spices?
H1: They provide extra calories
But very little amounts are used
H2: They provide rare nutrients
Nutritional analyses say no
H3: They help to preserve food longer
Prediction 1: spices show antimicrobial properties
See also: Srinivasan K. Food Research International 38 (1): 77-86. 2005
H3: They help to preserve food longer
Prediction 2: spice use should be proportional
not to availability, but to risk of food spoilage
Spices are more commonly used in hot
climates where spoilage is more common.
Sherman PW , Billing J Source: BioScience 49: 453-463 1999
Habitat selection, dispersal and
territoriality
Spatial distribution of resources: random, clumped, dispersed
Ideal Free Distribution: Individuals should distribute
themselves among habitats so that every individual maximizes
its net rate of return
Homerange: area which an individual, pair, or group
occupies or regularly returns to
Core Area: area of heaviest use, may center on a
resource, i.e. nest, water source, food source
Territory: any defended area; area of more or less
fixed boundaries from which rival conspecifics are
excluded through Aggression (self-preservation,
protection of the young, or resource competition)
Lek: a communal mating area in which individuals
hold small territories solely for courtship and
copulation
Different estimators of home range
Kernel (95 and 50%)
95% Minimum Convex Polygon
Horned lizard home
ranges overlap with their
food - ant colonies
Dispersal: Ecological process affecting distribution.
leaving an area of birth or activity; largely a short range
effort but can also be long range
Genetic perspective - can affect geographic
differentiation and variation
Choice:
Stay in the safety of home (the tendency for offspring to
breed in their natal home range is referred to as
philopatry).
or
Disperse and take chances: high mortality but high
payoffs.
Juvenile dispersal:
Hatching juveniles or fledglings leave their natal area.
Mostly short range but can be long distance (migratory spp.)
birds - bird banding records have found juveniles settling
1000's of kilometers away from their natal area.
lizards - 1.5 km.
Given the length of a hatchling (2.5 cm), this amounts to
approximately 60,000 body lengths
the human equivalent of 120 km traveled in the first
week or two of life.
Long range dispersal:
Can occur naturally : e.g. Cattle egrets, rafting, storms
Cattle Egrets - original range in Africa
1880 - West Suriname
1930 - South America, North America
Long range dispersal:
Unintentional or intentional dispersal
by humans.
The Argentine ant
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The Argentine ant
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Distance (km)
1000
Definitions:
Introduced (non-native, exotic)
- species introduced deliberately or accidentally from
somewhere else
Domestic/Feral (released pets, livestock and game animals)
- can spread disease, compete with native species
Human commensal or subsidized (out of control natives)
- native species that benefit from our land use
(disturbance)
Invasive species
- species that spread subsequent to establishment
usually at some cost.
Invasive Species
Some introduced
deliberately:
•naturalization
societies
Some accidental:
•ballasts of ships
•unprocessed wood
•Shakespeare fans
•fruit shipments
•game animals
•domestic animals
•by-pass natural
barriers
Dispersal:
Can have incredible energetic costs.
A moving animal may be at great risk of predation.
How do you find right habitat?
abiotic cues
conspecific attraction
Outbreeding depression
Why do juveniles of most species tend to disperse
despite these costs?
Inbreeding avoidance
Reduce competition with relatives
Colonization of new habitat (ideal free distribution)
Sex-biased dispersal - kin avoidance mechanism
Because dispersal entails costs, both sexes of progeny need
not disperse to dramatically lower the probability of inbreeding.
Belding’s ground squirrels
One way to reduce costs of dispersal: hitch a ride!
Dispersal: typically associated with a once in a lifetime event - movement to a new habitat
Orientation: the use of external cues to move about the
environment (visual - landmarks)
Navigation: more involved - need to where you are in addition
to a “compass sense” (a sense of the appropriate direction in
which to move)
Migration: distinct from dispersal - migratory animals typically
move from one geographic region to another,without using the
intervening habitat. movements often associated with a
particular season, and tied to the reproductive cycle.
Who migrates?
birds
insects (e.g., Monarch butterflies)
mammals (caribou, wildebeests, whales)
amphibians (e.g., newts to their natal pond)
reptiles (e.g., sea turtles)
fish (salmon, eels)
Arctic terns
Monarchs take two generations to complete migration!
Cues used for migration:
Celestial compass (sun and polarized light)
Stars
Geomagnetic field
Visual (landmarks, shore lines)
Smell?
Cochran et al. 2004 Science
Territoriality:
Defending an area from conspecifics.
(territory - an area occupied and defended from
competitors)
Costs: time, energy, potentially harm
Benefits: resources (shelter, nest sites, food),
access to mates
Alternate strategies: sneakers, satellites.
Yarrow’s spiny lizard
Surgeon fish
Why do territorial holders usually win contests
when their territory is challenged?
The “dear enemy effect”
Neighbors may learn to recognize each other and
reduce aggression as a response.
- lower costs associated with maintaining territory
- gang up on foreign intruders.
Evidence in some birds and ants.