Population Reproduction, births, natality (B) Mortality, death (D) Emigration (E) Immigration (I)...
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Transcript of Population Reproduction, births, natality (B) Mortality, death (D) Emigration (E) Immigration (I)...
Population
Reproduction, births, natality (B)
Mortality, death (D)
Emigration (E)Immigration (I)
Population growth
Adult survival, juvenile survival, and fecundity are what we need to estimate λ, the intrinsic population growth rate.
Winter Wren
Reserve Changing Developed
La
mb
da
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
Sink / declining
Stable population
Source/ growing populations
Landscape Species Fecundity var Adult se Juv se λ Upper λ *Developed American Robin 0.59 0.08 0.4 0.15 0.13 0.08 0.5416 0.962
Bewick's Wren 0.92 0.88 0.29 0.14 0.08 0.05 0.4526 0.9243Dark-eyed Junco 1.37 0.15 0.5 0.17 ** 0.7543 1.158Song Sparrow 1.13 0.46 0.54 0.03 0.21 0.04 0.827 1.022Spotted Towhee 0.57 0.12 0.5 0.06 0.18 0.05 0.6563 0.8795Swainson's Thrush 0.40 0.07 0.46 0.07 0.16 0.05 0.5719 0.7886Winter Wren 1.23 0.08 0.35 0.19 0.11 0.08 0.5823 1.207
Changing American Robin 0.89 0.16 0.55 0.12 0.18 0.08 0.7606 1.102Bewick's Wren 0.78 1.33 0.32 0.08 0.08 0.03 0.4566 0.7325Dark-eyed Junco 1.10 0.38 0.47 0.09 0.14 0.05 0.6924 0.9812Song Sparrow 1.23 0.21 0.54 0.02 0.18 0.03 0.8125 0.9273Spotted Towhee 0.82 0.46 0.55 0.03 0.18 0.03 0.7475 0.9013Swainson's Thrush 0.40 0.07 0.53 0.04 0.17 0.04 0.6368 0.7744Winter Wren 0.61 0.33 0.38 0.08 0.1 0.03 0.5016 0.7522
Reserve American Robin 0.80 0.13 0.71 0.22 0.31 0.23 0.9666 1.443Bewick's Wren 0.84 0.16 0.14 0.06 0.03 0.02 0.2435 0.4885Dark-eyed Junco 0.55 0.50 0.5 0.17 0.15 0.09 0.6308 1.176Song Sparrow 0.81 0.37 0.51 0.06 0.16 0.04 0.6962 0.9349Spotted Towhee 0.74 0.15 0.54 0.06 0.18 0.04 0.724 0.9245Swainson's Thrush 0.50 0.06 0.59 0.1 0.21 0.08 0.7332 0.9873Winter Wren 0.61 0.09 0.54 0.12 0.18 0.08 0.6974 1.057
* Upper 95% CI Limit of parameters used for calculating λ
** Changing Juv survival estimate used in calculating λ
Apparent Survival
From Oleyar et al. (in prep)
No obvious response in growth rate by landscape.
Spotted Towhee
Reserve Changing Developed
La
mb
da
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
Song Sparrow
Reserve Changing Developed
La
mbd
a
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
Declining λ outside of reserves?American Robin
Reserve Changing Developed
La
mb
da
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
Swainson's Thrush
Reserve Changing Developed
La
mb
da
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
Winter Wren
Reserve Changing Developed
La
mb
da
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
Possible sink during development for some species followed by recovery as subdivision ages?
Dark-eyed Junco
Reserve Changing Developed
La
mb
da
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
Bewick's Wren
Reserve Changing Developed
La
mb
da
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
Num
ber
dete
cted
with
in
50m
dur
ing
10m
ins
0.0
0.5
1.0
1.5
2.0 Winter WrenAmerican RobinSwainson's Thrush
Num
ber
det
ect
ed
with
in
50
m d
uri
ng
10
min
s
0.0
0.5
1.0
1.5
2.0
1999 2000 2001 2002 2003 2004 2005 2006 2007
Num
ber
det
ect
ed
with
in
50
m d
uri
ng
10
min
s
0.0
0.5
1.0
1.5
2.0
Year
Reserves
Developed
Changing
How do these projections match up with what we see out there?
•Winter Wren numbers high and ‘stable’ in reserves, low and/or declining elsewhere
•Robin numbers ‘stable’ but low in reserves, highest in developed residential areas
•Are developed landscapes ecological traps for Robins?
Populations fluctuate due to
• Density dependent factors– Ex: Predation, competition, habitat availability
– change population growth in predictable ways
– N is driven by population density
• Density independent factors– Random or Stochastic events
– Ex. Weather, accidents
– Breeding
14 aug 2007
time
# ofAnimals
(N)
Definitions
• Population regulation: the tendency of population sizes to stay within a certain range
time
# ofAnimals
(N)
k
Carrying capacity (k): the number of organisms that can be supported by a given area; the actual number of organisms fluctuates near this
Carrying capacity
Population fluctuationsCarrying capacity (k)
Classic growth curve,unlimited resources
Classic growth curve,limited resources (k)
time time
N N
k
Example of unlimited growth:Australian rabbit (European hare)
• 1859: 24 hares introduced (for human food?)• 1865: over 20,000 hares were harvested, actual population much greater.• Mid-1800’s to mid-1900’s: major problem with too many hares; caused habitat destruction and reduction in native mammals• 2000: still present, local problems
Population fluctuations
No rabbitsRabbits exceeded k
Rabbit-proof fence
Carrying capacity
High food addition
Low food addition
No food added
Shaded area is winter
Townsend’s vole
Population regulation: food
Population cycles: Ex. peaks in lynx populations show time lag behind peaks in snowshoe hare populations
Pop
ulat
ion
size Snowshoe hare
Lynx
Time (years)
Population regulation: food
Population regulation: climate
• Competition – demand by 2 or more individuals of the same or different species for a common resource
• Between 2 individuals of same species: Intraspecific• Between 2 individuals of different species: Interspecific
• Limited supply of resource: Exploitation• Not limited but interaction detrimental: Interference
Population regulation: competition
Inter- or Intraspecific competition?Exploitation or Interference competition?
Population regulation: competition
Niche: an n-dimensional hypervolume which includes the range of biological and physical conditions under which an organism can exist, including the resources that an animal must exploit for growth and reproduction
A portion of the feeding niche of the Blue-gray Gnatcatcher (Smith & Smith 1998)
Prey length (mm)
Fo
rag
ing
he
igh
t (m
)
Niche
• Food sources (both what and where)
• Nest or Den sites• Interspecific competition can
lead to resource partitioning, and expression of a ‘realized niche’ versus a species ecological niche.
Interspecific Competition
Predator-Prey Relationships
What are predators?
• Animals that kill and eat other animals (prey)• At or near the top of the trophic pyramid
Major predators of the Arctic NWR
Polar Bear Grizzly Bear
Wolf
Ermine
Arctic fox Snowy Owl
Predation in Natural Communities
Almost all animals have significant predators- exceptions are:
Herbivores: Top predators:
Bison Grizzly bear
Elephant Lions
Rhinoceros Polar bear
Hippopotamus Killer Whale
Human Attitudes and Predators
• Human perspectives– Little Red Riding Hood
– The Three Little Pigs
• Human persecution
Why?
• Domestication of animals• Protection• Entertainment
Overcoming History
• Old attitudes die hard
• Urban residents and predators
Predator-Prey RelationshipsResponse to Prey
Functional Response• Tendency of the predator to eat more of a prey
species as the prey become more abundant
Predator-Prey Relationships
Functional Response
0
20
40
60
80
0 20 40 60
Prey Density
# P
rey
Att
ac
ke
d
0
20
40
60
80
0 20 40 60
Prey Density
# P
rey
Att
ac
ke
d
Predator-Prey RelationshipsResponse to Prey
Numerical Response• Number of predators increases with an increase in the
density of prey animals
Predator-Prey RelationshipsNumerical Response
(Buckner and Turnock 1965)
High Density
(N/km2)
Low Density
(N/km2)
Sawfly Juveniles 5,280,000 98,800
Sawfly adults 507,500 11,600
Birds 58.1 31.1
Annual cycle of a prey populationPerc
en
tag
e o
f Pop
ula
tion
Energy shortages
Accidents
Disease
Predation
Predation
Disease
Accidents
Energy shortages
J F M A M J J A S O N D
100
Population Cycles
Population Cycles
Adaptations to cyclical prey cycle?
Dispersal Prey switchReproduction
Isle Royale
Isle Royale
• Size: 45 miles long x 9 miles wide• Protection: National Park established in 1940
Wilderness designation in 1976
National Biosphere Reserve 1980• A location of a long term study of the relationships
between the moose and gray wolf
Historically, two large ungulates occupied Isle Royale:
Woodland Caribou Moose
Isle Royale
Settlers arrived in late 19th centuryResponsible for fire and forest cutting
Moose cross ice from Minnesota and establish early 20th century
Fires change old-growth coniferous forests to younger deciduous forests
Moose outcompete woodland caribouCaribou became extinct on the island
Wolves arrive 1950 by crossing ice
Wolf Response to Moose
Functional Response: lots of moose• Possible because wolves are cooperative hunters
Numerical Response: lots of moose• wolves reproduce well
• Immigration is unlikely since it depends on Lake Superior freezing (uncommon)
Moose Response to the Wolf
• Most vulnerable moose are the very young and the old (infirm)
• Most killed moose show signs of malnutrition and disease (i.e. they are more vulnerable)
• Males most vulnerable: go into winter in relatively poor shape because of rut
Wolf Population
Three major factors that control the wolf population:
1. Moose numbers
2. Linear dominance hierarchy in wolf population
3. Genetic diversity (inbreeding effects)