A tail of two scorpions

Ashlee & Matt Rowe

Ashlee and Matt Rowe at the Santa Rita Experimental Range in Arizona

The activities are as follows:

Animals have many ways to defend against predators. Many species use camouflage to avoid being seen. Others rely on speed to escape. Some species avoid capture by hiding in a safe place. Other animals use painful and venomous bites or stings to try to prevent attacks or to make capture more difficult. Anyone who has been stung by a bumblebee understands how stinging could be a great way to keep predators away! However, there is little research that shows painful stings or bites deter predators.

The grasshopper mouse lives at the base of the Santa Rita Mountains in Arizona. Scientists Ashlee and Matt have been studying this mouse for many years, and wanted to know what the mouse ate. In the mountains, there are two scorpions that make a great food source for the mice. One of the scorpion species has a painful sting. The other species is slightly larger, but its sting is not painful. Ashlee and Matt thought that painful, venomous stings would prevent predator attacks, and that the painless species would be attacked and eaten more often.

The Santa Rita foothills - habitat for the grasshopper mouse and scorpions

The Santa Rita foothills – habitat for the grasshopper mouse and scorpions

The scientists collected six grasshopper mice from the wild. Once back in the lab, they trained the mice to expect a food reward when they tipped over a small cup containing live prey. Once trained, the mice were used in an experiment. The mice were presented with two cups to choose from. One contained the scorpion species that has a painful sting. The other cup contained the scorpion species that has a painless sting. Ashlee and Matt collected data on which cup the mice chose to approach, inspect, or pursue (by tipping over the cup). They also recorded if the mice attacked or consumed the painless or painful species of scorpion. Each trial ended when the mouse finished consuming one of the scorpions. If painful stings prevent a predator from attacking, they predicted the mice would choose to eat the scorpion species with the painless sting more often.

Watch a video of one of the experimental trials:

Mouse Trial

Watch three additional videos on the grasshopper mouse and scorpions:

Images of the southern grasshopper mouse (Onychomys torridus) capturing and eating the painful species of scorpion (Centruroides sculpturatus).

Ot vs Cs 4

Ot vs Cs 1

Ot vs Cs 2

Size differences of the two scorpions used in the experiments (painful Arizona bark scorpion, Centruroides sculpturatus is on the left; painless stripe-tailed scorpion, Hoffmannius spinigerus on the right)size comparison 1 (1 of 1)

Featured scientists: Ashlee and Matt Rowe from Michigan State University

Undergraduate researchers also involved with the project: Travis Tate and Crystal Niermann from SHSU; Rolando Barajas, Hope White, and Amber Suto from Michigan State University

Flesch–Kincaid Reading Grade Level = 7.1

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  1. Mr. LeBlond says:

    My students are going through the data nuggets and had a question about the data collected in the “Tail of Two Scorpions.” Why does the chart only show the approach, tip, attack, and consume data for the Painful variety of scorpion and not the painless?

    • Thank you for your question! We actually had a version of this activity before where we gave both tables – we had a table showing the data for the painful scorpion, and a table for the painless. The table for the painless is in this case just the reverse of the painful. For example, if the mice chose painful species 1/6 times, this means that they chose the painless species 5/6 times. We presented it to teachers and they thought it was repetitive to have both tables so we took the second out. Let us know if you think it would be better to have both tables in instead!

      • Don Walthers says:

        Students that might benefit from reading level 2 will likely struggle with how the data is presented. Presenting only “1/2” of an either/or result (painful sting or not) at this level will be confusing for many students. Perhaps a double bar graph or a stacked bar graph (good way to introduce this type of graph!) that displays all data would be more interpretable. Students will also struggle with the related concepts of proportion and percentage – many students are explicitly taught that frequency or proportion is the decimal value of solving the fraction, whereas percentage is multiplying that number by 100. The DV unit is percentage but the values are proportion (or frequency).


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