Linking spatial and temporal patterns in resource availability, individual performance, & population dynamics.

Primary thesis objectives Determine how much individual detail is needed in models of population dynamics. Relate explicitly spatial and temporal variation in resource abundance to individual “success”.

For today…. Population level dynamics of red squirrels in Kluane valley Temporal/spatial variation in resource abundance and territory sizes Red Squirrel (Tamiasciuris hudsonicus)

Population dynamics

1. Population dynamics: –Holistic approach assumes: Habitat is homogeneous All individuals are identical –Reductionist approach assumes: individual level of detail is important Go with Holistic View - for now

Midden locations 60 m

SU KL

Female densities

Population models 4 competing models Density independent: N t+1 = N t e a Density dependent: N t+1 = N t e a+bNt Delayed density dependent: N t+1 = N t e a+bNt+cNt-1 Response Surface model: N t+1 = N t e a+bNt+cNt-1+dNt 2 +eNt-1 2 +fNtNt-1 AICc used to compare model fit to data

Population models: AICc results

Population models: Density dependence?? SU

What about food?? KL

Population summary Food and density effects appear to differ between these ‘populations’ KL - Density independent/Density dependent SU - Density dependent Habitat quality too???

Why are they different? Different birth rates, survival patterns? – λ-contribution analysis (λ=e r ) which life-history characteristic best-tracks changes in population growth-rate? »begin to tease apart what life-history is related to changes in the population growth rate (ie. fecundity, survival) »also, investigate spatial variation in this “key-factor” within each population, and relate to territory ‘quality’

CONES AND TERRITORY SIZE

Annual cone production White spruce - a masting species Cone index - count top 3m of tree Cone calibration - count all cones!! 3m Actual cone range: y=1.185*x r 2 =0.996

***** Spruce Cones

*****

Methods: - individual squirrels visually observed - territorial behaviours & locations noted % MCP 60 m 1994 and 2001 Territory size

Temporal patterns *****

*****

Linking food availability to reproductive output

Number of offspring per female per year. ANOVA P > 0.05 NS *****

Number of squirrels weaned per female per year. ANOVA P < *****

Number of squirrels born surviving to one year. ANOVA P < *****

Territory size decreases after a mast year, otherwise size appears mostly constant No significant effect of resource fluctuations on litter size, BUT significant effect on juvenile survival to weaning, 1-yr Territory Size - temporal summary

Recall: assumption of spatial homogeneity IS IT?

Spatial vegetation patterns Vegetation transects every 60m - 3 transects 120 0, 240 0, each transect 4m x 25m Kriged surfaces based on transects (10m 2 cell size) - ws density - ws density >5cm dbh, alive - bark beetle killed trees - aspen - willow

60 m Total white spruce density

60 m Midden placement (total ws den)

60 m White spruce (>5cm dbh, alive) density

60 m Bark beetle killed spruce density

60 m Aspen density

60 m Willow density

Spatial patterns in territory size

60 m White spruce (>5cm dbh, alive) density and August 2002 territories

60 m White spruce (>5cm dbh, alive) density, June and August territories

60 m Number of white spruce (>5cm dbh) and August territories

Spatial patterns in cone production IS IT SPATIALLY HOMOGENEOUS??? Additional cone count trees established in 2002 Modelling cone production - independent variables: dbh, density of surrounding trees, dbh of surrounding trees, location (r 2 = 0.38) plus.. slope, aspect, height, basal light class (r 2 = 0.60)

Cone Production 2002

Cone Production 2003

p<0.05 Change in June territory size

Goal - to map variation in habitat quality = c c c c c c +

Continuing Objectives Continue to develop cone production models Link spatial and temporal cone availabity and territory size to territory quality & “success” Investigate individual contributions to overall population dynamics

Long-Term Food Add Thoughts What happens to territory size when under constant high food conditions? Will females maintain high reproductive output under high food? What’s the key factor for recruitment? (What is the effect of lack of cues for increased cone production?)

Summer 2002 – field methods 1. Territory mapping

Population growth rate

NS paired t-test June and August 2002 territory sizes. (paired data only)

** Changes in an individual’s territory size