Terrestrial Passage Assessment Protocol Scoring Proposal

I.     Animal groupings for scores 

 

1. Small mammals (mice, voles, shrews, squirrels, weasels) and squamates (snakes and lizards) 
2. Medium mammals (rabbits, hares, porcupines, skunks, fishers, foxes, martens) and box turtles
3. Bobcat, lynx 
4. Bear, coyote, cougar, wolf 
5. Deer 
6. Moose 

II.     Variables for the score 

Each crossing score will be based on six variables:  

1. Openness (of largest structure at a crossing) (USES AQUATIC DATA) 
2. Height of structure (minimum height of largest structure at a crossing)  
3. Length of structure  
4. Clear line of sight through structure (yes, partially obscured, no) 
5. Dry passage  
6. Barriers to accessing crossing 

III.     Scoring each variable 

Variable 1: Openness of structure

Parameterization (units = meters)

Animal group	Asymptote	Midpoint	Steepness
Small mammals and squamates	1	0.05	-20
Medium mammals	1	0.1	-10
Bobcat, lynx	1	0.4	-6.0
Bear, coyote, cougar, wolf	1	1	-3.0
Deer	1	0.75	-5.0
Moose	1	1.2	-4.0

Variable 2: Height of structure 

Parameterization (units = feet)

Animal group	Asymptote	Midpoint	Steepness
Small mammals and squamates	1	2	-1.8
Medium mammals	1	4	-1.8
Bobcat, lynx	1	5	-1.8
Bear, coyote, cougar, wolf	1	7	-0.8
Deer	1	6	-1.5
Moose	1	9	-0.9

Variable 3: Length of structure

Parameterization (units = feet) 

Animal group	Asymptote	Midpoint	Steepness
Small mammals and squamates	1	50	0.06
Medium mammals	1	120	0.02
Bobcat, lynx	1	120	0.04
Bear, coyote, cougar, wolf	1	120	0.04
Deer	1	120	0.04
Moose	1	120	0.04

Variable 4: Clear line of sight through structure 

Animal group	No	Partial	Yes
Small mammals and squamates	0.1	.5	1.0
Medium mammals	0.1	.4	1.0
Bobcat, lynx	0.1	.3	1.0
Bear, coyote, cougar, wolf	0.1	.2	1.0
Deer	0.1	.3	1.0
Moose	0.1	.3	1.0

Variable 5: Dry passage – scoring is the same for all animal groups

Dry passage	Score
No dry passage	0
Inadequate dry passage	0.2
Moderately useable dry passage	0.5
Good dry passage	0.8
Excellent dry passage	1.0

 Variable 6: Barriers to accessing crossing – scoring is the same for all animal groups

Barriers	Score
Total barrier	0
Severe barrier	0.2
Moderate barrier	0.5
Minor barrier	0.8
No barriers	1.0

IV.     Combining variables for a final score 

Weighting of variables for composite score

Animal group	Openness	Height	Length	Clear line of sight	Dry passage	Barriers
Small mammals and squamates	1	1	3	2	3	2
Medium mammals	1	2	2	2	2	2
Bobcat, lynx	1.5	2	1	3	3	2
Bear, coyote, cougar, wolf	3	2	1	3	2	2
Deer	2	2	1	3	2	2
Moose	2	2	1	3	1	2

 Limiting variables for each animal group

Animal group	Openness	Height	Length	Clear line of sight	Dry passage	Barriers
Small mammals and squamates			X		X	X
Medium mammals						X
Bobcat, lynx		X		X	X	X
Bear, coyote, cougar, wolf		X		X		X
Deer		X		X		X
Moose		X		X		X

Each crossing will have a score for each animal group and an average score of the six animal group scores. 

Graph for Variable 1: Openness of structure

Parameterization (units = meters): 

 

Graph for Variable 2: Height of structure 

Parameterization (units = feet):