Ecological Archives A016-025-A1

John F. Lehmkuhl, Keith D. Kistler, James S. Begley, and John Boulanger. 2006. Demography of northern flying squirrels informs ecosystem management of western interior forests. Ecological Applications 16:584–600.

Appendix A. A priori biological and environmental hypotheses on northern flying squirrel demography used to estimate environmental and biological effects on capture probabilities (Step 1) and demography (Step 2) in Pradel demography model building process. Covariate abbreviations used in model selection tables are in parentheses.

Parameter 

Covariate 

Hypothesis 

Survivala  

weight (wt) 

Smaller squirrels may be more prone to mortality or dispersal. 

 

age 

Younger squirrels will show lower survival rates. 

 

sex 

Male squirrels may show a higher mortality rate or tendency to disperse. 

 

cover type (trt) 

Apparent survival should increase from open pine to young to mature cover types.  

 

weather
(snowmax)
(mindays)
 

Maximum snow-depth or days of freezing temperatures will decrease apparent survival rates. 

     

Recruitmentb 

weight 

Smaller squirrels may be more prone to immigrate into stands during dispersal events. 

 

age 

Younger squirrels may be more prone to immigrate into stands. 

 

sex 

Male squirrels may show a higher immigration rate into stands. 

 

cover type  

Birth rates should be lowest in open pine, intermediate in young, and highest in mature forest. Immigration should be high in open pine and young forests (sink habitats) vs. mature forest (source habitat).  

 

weather 

Birth and immigration events will be more likely during milder winter and springs. 

     

Recapture probability 

snow depth 

Higher snow depth results in reduction in recapture rate.  

 

weight 

Smaller squirrels may be more prone to capture. 

 

age 

Younger squirrels may be more prone to capture. 

 

understory cover 

High understory species cover will affect encounter rates with traps. 

 

cover type 

Recapture rates will increase from open pine to mature forest as spatial patchiness of vegetation and resources, and associated space use by squirrels, decreases.  

a Probability of remaining on site and surviving until the next sampling period.

b Rates of addition from births and immigration.



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