Culverts and Fencing to Reduce Wildlife-Vehicle Collisions and Maintain Permeability

Culverts and Fencing to Reduce Wildlife-Vehicle Collisions and Maintain Permeability

Objectives: Identify culvert use by taxonomic groups Identify seasonal variation in culvert use Identify factors that contribute to culvert use

County-wide inventory of underpass structures Culvert Selection Criteria: Culvert type 24 CMP, 36 CMP, Concrete Box Road type 2-Lane, 4-Lane Vegetation community USDS, LSDS, SDG Land use - Natural Culvert modifications No Unique Modifications Presence of natural substrate No excessive human presence

2,354 culverts inventoried 146 culverts selected for monitoring 24 CMP (n = 45) 15 four-lane; 30 two-lane 36 CMP (n = 44) 18 four-lane; 26 two-lane Concrete Box Culvert (n = 57) 28 four-lane; 29 two-lane Each Culvert Monitored during 3 Sessions Summer and fall monitoring sessions completed Spring session underway Video review is on-going

Videography Road kill surveys Traffic volume Road Kill: 100 Meter Segment

1,691 Road Killed Animals Detected

Road Kill Detections 350 300 Seasonal Road Kill Detections Summer Fall 250 200 150 100 50 0

Road Kill Detections Road Kill Detections and Road Type 450 400 Two Lane Four Lane 350 300 250 200 150 100 50 0

3,679 events captured on video (to date) 1,098 documented use of culverts

Latin Name Common Name Guild 24CMP 36CMP BOX Canus latrans Coyote Meso-Carnivore X Lynx rufus Bobcat Meso-Carnivore X X Mephitis macroura Hooded Skunk Meso-Carnivore X X Urocyon cinereoargenteus Gray Fox Meso-Carnivore X Ammospermophilus harrisii Harris' Antelope Squirrel Small Mammal X X Chaetodipus sp. Pocket Mouse Small Mammal X X Dipodomys sp. Kangaroo Rat Small Mammal X X Neotoma albigula White-throated Woodrat Small Mammal X X X Peromyscus sp. Deer Mouse Small Mammal X X Spermophilus tereticaudus Round-tailed Ground Squirrel Small Mammal X X Sylvilagus audubonii Desert Cottontail Small Mammal X X X Pecari tajacu Javelina Ungulate X X

Latin Name Common Name Guild 24CMP 36CMP BOX Bufo alvarius Sonoran Desert Toad Amphibian X Aspidoscelis sp. Whiptail Lizard X X X Coleonyx variegatus Western Banded Gecko Lizard X Phrynosoma sp. Horned Lizard Lizard X Sceloporous magister Desert Spiny Lizard Lizard X X Sceloporous sp. Spiny Lizard Lizard X X X Urosaurus ornatus Ornate Tree Lizard Lizard X Uta stansburiana Side Blotched Lizard Lizard X Crotalus atrox Western Diamond-backed Rattlesnake Snake X Lampropelits getula Common Kingsnake Snake X Masticophis flagellum Coachwhip Snake X X Pituophis catenifer Gophersnake Snake X

Passage Rate = # Successful Crossings Total # of Approaches

Passage Rates by Structure Type 1.0 2 2 2 20 0.8 18 0.6 0.4 315 148 28 3 463 1,083 62 13 11 14 24 inch 36 inch 278 Box 0.2 0.0 0 1

Continue video review, species ID, and behavioral categorization Analyze the relationship between passage rates and: Vegetation Community Road Type Structural Characteristics Traffic Volume Road Kill Accumulation Rates Substrate Season Time of Day Human Activity

Objective: Test effectiveness of fence designs Rusticated steel flashing Concrete panel Concrete panel with overhang Guard rail

Guild Latin Name Common Name # of Trials Small Mammals Dipodomys merriami Merriam's Kangaroo Rat 23 Dipodomys spectabilis Banner-tailed Kangaroo Rat 10 Neotoma albigula White-throated Wood Rat 31 Sylvilagus audubonii Desert Cottontail 10 Large Mammals Mephitis mephitis Striped Skunk 10 Snakes Crotalus atrox Western Diamond-backed Rattlesnake 13 Crotalus cerastes Sidewinder 6 Crotalus scutulatus Mohave Rattlesnake 3 Lampropeltis getula Common Kingsnake (Desert Kingsnake) 1 Pituophis catenifer Gopher Snake 1 Lizards Aspidoscelis tigris Tiger Whiptail Lizard 4 Callisaurus draconoides Zebra-tailed Lizard 2 Sceloporus magister Desert Spiny Lizard 6 Amphibians Bufo alvarius Sonoran Desert Toad 32 Scaphiopus couchii Couch's Spadefoot Toad 48 Total Trials 200

Treatment (% successful crossings) Guild Steel Rail Cement Cement w/ Overhang Small Mammals 64.71 40.00 33.33 58.33 Large Mammals 75.00 100.00 100.00 trials pending Snakes 33.33 20.00 50.00 66.67 Lizards 0.00 0.00 0.00 0.00 Amphibians 0.00 0.00 0.00 n/a

Amphibians: Positive results with all 4 treatments 30 inch fencing is an effective barrier Should be buried 6 inches to prevent burrowing Kangaroo Rats: Positive results with all 4 treatments Maximum observed leap height = 12-14 inches Burrowing issues could be mitigated by burying the fence and/or installing a horizontal apron to prevent burrowing

White-throated Wood Rats: None of the treatments have been effective Maximum observed leap height = 24-26 inches Superior climbers Snakes: Barrier heights must be snake length to be effective May not be an issue in real world applications however Cottontails: No difficulty jumping over 30 inch treatments Maximum observed leap height = 37 inches Taller fencing will be necessary

Skunks: Excellent burrowers Did not scale 30 inch barrier treatments Burying the barrier deeper than 6 inches and/or installing an apron may inhibit burrowing

Continue trials with emphasis on lizards, snakes and large mammals to bolster sample sizes Analysis