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Sky Islands High School

Students: Sara Atkins, Trent Chollar, Miyah Dykeman, Oliver Frudko, Grayson Hart, Nadia Mehr, Kayshan Mouzet, Aden Rhody, Joel Ruiz, Max Speagle, Ty Wabaunsee, and Nechama White; Teachers: Allie Silber and Emily Rockey

Shedding the “Black” Light on Woodchip Mulch: Are Scorpions an Issue?

Background Information

Hypothesis

Methods and Experimental Design Results Conclusion

Picacho Peak Study

Special Thanks

Organic wood chip mulches benefit soil health and aid in plant establishment as well as resilience to stress. Inert rock or gravel ground covers are also popular, however they do not possess the same benefits. Some choose rock over wood chips (at least in part) due to concern that wood chip mulch "attracts" scorpions, although no known research supports the claim.

Arizona is home to many species of scorpions including the Bark Scorpion, Centruroides exilicauda, which has a venom that can be life threatening. Scorpion experts explain that Bark Scorpions prefer cool, moist areas and can be found in narrow crevices for coverage and protection.

Among those who promote wood chip mulch is Emily Rockey, currently employed by organic landscape material supplier Tank's Green Stuff in Tucson. Over several years, Rockey repeatedly responded to concerns from the public of potentially attracting scorpions via wood mulch. As a result, she consulted with scorpion experts, and approached Sky Islands High School (SIHS) to conduct a study. SIHS teacher Allie Silber recruited students to participate in collaboration with Emily Rockey in a three-part study from fall 2018 to fall 2019: 1) Seasonal scorpion hunt on SIHS property where wood chip mulch is utilized in the landscape, 2) In-classroom controlled experiment to determine if scorpions prefer wood chips over rock, wood shingles, or bare soil, and 3) a one-time site study near Picacho Peak.

If we use wood chip mulch, we will not find the scorpions in the wood chip mulch, because at Sky Islands we didn’t find any scorpions in the wood chips mulch.

1. Collect materials:● (4) 16” x 8” glass terrariums● 8 live bark scorpions● wood chip mulch(½” minus)● wood shingles (approx. 4”x4”x0.25”) ● sandy native soil (¼” minus)● small rocks (½” minus)● cardboard pieces

1. Put 1 inch of sandy soil in the bottom of each terrarium 2. Section off four 4x8in quadrants in each terrarium with

cardboard3. Fill top right quadrant with an inch of small rocks4. Fill top left quadrant with an inch of wood chip mulch5. Fill bottom left quadrant with 6-8 four-inch wood shingles6. Leave the bottom right quadrant alone, this is the control7. Remove cardboard from the buffer zone and make sure that

there is about a half inch of the sandy soil between every quadrant (repeat steps 4-8 for each terrarium)

8. Place 2 bark scorpions in the middle of each terrarium 9. Record which material each scorpion is in, twice a week for

6 weeks

Our results show that the scorpions prefered the wood shingles over any of the other materials.

In conclusion, our hypothesis was correct: the scorpions did not prefer the wood chips over the other materials. In fact, they preferred the wood shingles 96.8% of the time. They were only observed in the wood chip mulch 1.6% of the time and in the rocks for 1.6% of the time.

These results indicate that bark scorpions’ preferred habitat is in narrow protected spaces, and that wood chip mulch can be used in the landscape without fear of attracting scorpions.

We’d like to thank the following people for their help and support on this project:● Shari Popin, Director of Sky Islands High School.● Michael Bagesse, Scorpion Keeper, Teacher, Sky Islands

High School.● Lee Ingle, Ever Evolving Exotics, Supplied scorpion terraria.● Sam Rathke, UA Blankinship Lab, Host at Picacho Peak.● Joey Blankinship, Department of Environmental Science,

University of Arizona.● Sarah Toms-Bergquist, Picacho Peak Park Ranger,

Geologist● Charles Hofer, Arizona Game and Fish, Wildlife Biologist● Dr. Leslie Boyer, University of AZ VIPER Institute,

Experimental Advisor.● Dr. Howard Byrne, Curator of Herpetology, Arizona-Sonora

Desert Museum.● Eric Sophiea, Scorpion Collection Team.● Christopher Byrne, Scorpion Collection Team.● Craig Pearson, AZDEQ, Picacho Peak Study Site Access.● Alphagraphics Palo Verde, Poster Donation

At Picacho Peak, the SIHS students conducted a survey observing scorpions' activity and proximity to wood chip mulch that had been applied to a desert landscape. The site is host to an ongoing dust mitigation study by the UA Blankinship Lab which began in summer 2019. The nearby Interstate-10 is notorious for automobile accidents caused by dust which impares road visibility. The Blankinship Lab was comparing the use of wood chip mulch versus chemical soil stabilizer for dust control.

The students observed a total of only three scorpions in the wood chip plots, none in control plots, and over a dozen in the vegetation around the plots. Though these results are preliminary, they support the results found in the classroom: scorpions do not prefer wood chips.

QuestionVariables

Independent Variable: the types of materials in terrarium

Dependant Variable: the location of each scorpion

Control: the quadrant with bare soil

Constants: 1) type of scorpions; 2) amount and type of food; 3) amount of water; 4) amount of each material inside the terrariums; 5) temperature; 6) light; 7) and size of terrarium

Do bark scorpions prefer wood chip mulch over other materials?

Total Number of Scorpions Found in Each Material by Day

Wood Shingles Wood Chips Rocks Bare Soil

9/23 7

9/26 6 1

9/30 6 1

10/3 7

10/14 7

10/17 7

10/21 7

10/24 7

10/28 7