Trees Squirrels: Narrators of Nature in Your Neighborhood By: Kristi Backe, Michelle Rabkin, and Steve Sullivan Engage: 1. Ask students to generate a list of animals they have observed in the schoolyard, and record the list on the board. 2. Focus the conversation on squirrels and ask students to share their observations of squirrel behavior in the schoolyard. What kinds of things have students seen squirrels doing? (If students had not listed squirrels in Step 1, prompt them by asking if they have observed squirrels in the schoolyard.) 3. Take students outside to look at their schoolyard and imagine it from the perspective of a squirrel. Can students identify certain areas in the schoolyard where squirrels might spend more time? Less time? What kinds of places would make squirrels feel safe? What kinds of places would make them feel unsafe? 4. Suggest to students that some scientists studying animal behaviors are interested in how animals behave in areas where they feel safe or threatened. One possible way to test this is to place food out for the animals in different locations and then analyze how much food the animals eat in each location. 5. Have students describe what they would expect to observe if they put food out for the squirrels in the schoolyard in an area that seemed safe for the squirrels. How might this differ from what they would expect to observe if they put food out in a place that seemed unsafe to the squirrels? Where do students think the squirrels would eat more? If necessary, present an analogy of a person’s response to food in places that seem safe or dangerous. For example, have students imagine they have access to one bowl of candy on the kitchen table and one bowl of candy in the middle of a busy street. Would they eat the same amount of candy from each bowl? 6. Inform students that scientists studying squirrels are addressing some of the same questions about squirrel behavior. In particular, some scientists have formed hypotheses about how the relative safety of a location for squirrels can impact how much food squirrels consume. These scientists are requesting help from citizen scientists around the United States who can submit data that helps the scientists to address their questions about squirrel behaviors on a larger scale. 7. Introduce students to Project Squirrel, and pull up the website (projectsquirrel.org) if possible. If web access is not available, give students an overview of Project Squirrel and how the citizen science component works, including what kinds of data any citizen scientist can submit. Highlight the importance of citizen science to students by explaining that because scientists like those involved in Project Squirrel can’t be in every city gathering data throughout the year, they rely on citizen scientists to help gather information. 8. Explain that just like the Project Squirrel scientists, students will use food consumption as a way to understand how squirrels feel about the schoolyard habitat and submit their data to Project Squirrel. Through their investigation, students will learn more about the behaviors of the squirrels in their schoolyard, which can provide clues about the interactions occurring between organisms in the area. These data may help scientists to understand why some neighborhoods have one species of squirrel, others have two, and some have none. Explore: Part 1 (before foraging patches are placed in the schoolyard) 1. Provide students with an overview of the investigation. (Students will select sites in the schoolyard that they think will be “safe” and “unsafe” for squirrels. Two foraging patches will be placed at each site, one at the base of a tree and one farther out from the tree (4m from the tree). Students will install one ear of corn at each foraging patch and allow foraging throughout the day. Students will then record how much the squirrels consume in each of the four locations.) 2. Explain that because Project Squirrel scientists are interested in using data from multiple sites across the country, it is important for participants to follow standardized procedures. When everyone does things the same way, their data can be compared more effectively. Introduce these guidelines, provided by Project Squirrel: Consider the trees around the school. Select a tree in a quiet part of the yard where students hypothesize squirrels will feel comfortable. Identify this as the “Safe site.” Select a second tree in a busier place where students hypothesize squirrels will feel uncomfortable. Identify this as the “Unsafe site.” For each site, one foraging patch will be placed at the base of the tree and one foraging patch will be placed 4m from the base of the tree. Both foraging patches at each site (“safe” and “unsafe”) should be at least 4m from other trees, fences, walls, or buildings. 3. Divide the students into four groups: Safe Site near tree; Safe Site 4m from tree; Unsafe Site near tree; Unsafe Site 4m from tree. 4. Pass out a Data Collection Sheet and a cob of feed corn to each group. Have students use a balance to find the initial mass of the corn cob (to the nearest gram) and record this value on the Data Collection Sheet. Each corn cob should then be placed in a resealable bag labeled with the group’s name (e.g. “Safe Site near tree) and the day of data collection. 5. Take students outside to locate their group’s patch location. 6. Pass one Habitat Information Sheet to the two groups at the safe site and one Habitat Information Sheet to the two groups at the unsafe site, and have the students record the indicated information about patch locations. As necessary, assist students with the Habitat Information Sheet. (See Background Information for resources.) Note to teacher: You will place the foraging patches in the schoolyard in the locations selected by the students each morning on the four data collection days. The patches should be out in the schoolyard for a minimum of six hours and should not be left out overnight. You will also need to collect the corn and patches at the end of each day. (Students could be involved in setting up and/or collecting the foraging patches and corn, depending on the school schedule.) See the Foraging Patch Assembly Instructions for information on how to assemble the patches, how to attach an ear of corn to each patch at the beginning of the day, and how to collect each patch at the end of the (minimum) six hour period. Part 2 (while foraging patches are in the schoolyard) 1. Explain that to collect more data about the squirrels in the schoolyard, students will observe the patches for a few moments and record the number of squirrels they observe in the school yard. 2. Go to the Project Squirrel website and introduce students to the two types of squirrels that make up the vast majority of tree squirrels in the United States, the gray squirrel and the fox squirrel. Introduce the major characteristics of each (belly color and tail markings) and make sure students can distinguish between species. (If it is not possible to pull up the website during class, print pictures of both species to show to students.) 3. Take students outside to observe the area around the foraging patches. Once outside, split the students into their four groups. Send the two groups who are monitoring the safe location and the two who are monitoring the unsafe location to observe the area around their sites for 1 to 5 minutes. 4. Have students count how many squirrels they see near their site during their observation. Using what they learned about the squirrel species, students should identify which squirrel species they are observing. This number of squirrels they see and the squirrel species should be recorded on the Data Collection Sheets. Part 3 (after foraging patches are removed from the schoolyard; refer to Foraging Patch Assembly Instructions for information on removing the foraging patches from the schoolyard ) 1. Divide students back into the four groups, and give each group the bag of corn collected from their foraging patch. 2. Introduce the terms “intact kernels,” “kernels with excised embryos,” and “small pieces of kernels.” Show pictures when appropriate. Explain that students will fill out the rest of the Data Collection Sheet, which should already have the foraging patch location, mass of corn cob before foraging, squirrel species observed and number of each species observed recorded. 3. Have students separate the corn into piles according to the categories listed on the Data Collection Sheet. 4. Have students weigh each pile and record the data on their Data Collection Sheet. 5. Have students calculate the mass of all of the corn kernel scraps left behind by the squirrels by adding the mass of kernels with excised embryos to the mass of small pieces of kernels (first data table). Note to teacher: “Corn kernel scraps” refers only to remaining parts of corn kernels that squirrels have eaten, not to whole kernels that squirrels have knocked off the cob. 6. Next, have students combine whole kernels left behind on the cob and whole kernels found loose on the foraging patch. Students should weigh this pile of all whole kernels left behind by squirrels and enter the mass onto the Data Collection Sheet. 7. Have students calculate how much corn was consumed by the squirrels using the initial mass of the cob and the information in the second data table. If necessary, assist students with the calculation. [“initial mass of corn before foraging (with kernels attached)” – “mass of cob with all kernels removed” - “total mass of all whole kernels left behind by squirrels” = amount of corn consumed] Note: The “kernels with excised embryos” and the “small pieces of kernels” are considered consumed by the squirrel, because the squirrel has removed the nutritious part of the kernel. (See Background Information) 8. On at least three additional days, repeat the procedure by placing foraging patches in the schoolyard, observing the patches, bringing in the patches, and collecting data about the remaining corn. The foraging patch locations should not change. Students should fill out a new Data Collection Sheet each day. Note to Teacher: Students will collect a range of data to manipulate in class. The teacher is responsible for compiling all of this data and submitting it to Project Squirrel at projectsquirrel.org. A Reporting Sheet is provided to aid the teacher in compiling the data, which will make data entry more straightforward. Part 4 (after four days of data collection) 1. Have each group find the average mass of corn kernel scraps and the average mass of corn consumed at their site over the four days of data collection. Use the Class Data Sheet to compile the data collected by all four groups. (Project the data sheet on the board if possible.) 2. Pass out a Data Analysis Sheet and a Graph Sheet to each student. Have students create 2 bar graphs (in the space provided) that present the data collected by the class at each of the four locations. (Provide guidance as necessary. One graph should include the average mass of corn kernel scraps left behind in the foraging patch for each of the four locations, and the other graph should include the average mass of corn consumed for each of the four locations. These calculations have already been compiled on the Class Data Sheet. If desired, have students also graph the data collected for each day.) 3. Have students analyze their graphs and the class data and respond to the questions on the Data Analysis Sheet. Note to teacher: To help students analyze data, you may wish to clarify that the two data calculations compiled on the Class Data Sheet are two possible ways of looking at how much corn the squirrels were interested in eating. Because squirrels don’t eat the whole corn kernel, they leave behind clues about how much they actually ate. Compare the corn kernel scraps left behind on the foraging patch to candy wrappers. If we put out a bowl of candy and look at the wrappers left behind, we can figure out approximately how much candy was eaten at a given location. When we measure the corn kernel scraps, we are doing the same thing with the squirrels. The corn consumed calculation tells us how much corn is actually missing from the foraging patch. The calculation takes the starting mass of the cob (including kernels) and subtracts all whole kernels of corn left behind in order to calculate how much is missing. Explain 1. As a class, discuss students’ conclusions about which location seemed most safe based on the data students collected. What factors can students identify that may have impacted the amount of food consumed by the squirrels? How does this compare with students’ initial ideas about features that might make a location seem safe or unsafe to squirrels? 2. What conclusions can students draw about squirrels’ willingness to venture away from trees in search of food? How can they use the data to support their conclusions? 3. Do the data from both graphs seem to suggest the same site as the most safe site? If not, what factors might be contributing to the differences? If so, what specific features of that site do students think are most important? Elaborate: 1. Place students in pairs or small groups. Explain that each pair of students will conclude where they think the ideal squirrel habitat is located in the schoolyard based on what they have learned from the data collection and analysis completed thus far. 2. Give the students time to discuss their ideas in their pairs or small groups, and have each group present their ideas to the class. Students should be encouraged to use data from the four days of data collection to support their choices. 3. To highlight the collaborative nature of science and the importance placed on questioning the ideas of others, encourage students to share their doubts about groups’ claims. Are there any data or other possibilities that the group has overlooked? 4. Remind students that the scientists at Project Squirrel are attempting to answer similar questions as they study the habitat preferences of squirrels throughout the country. The data that students collected will be submitted to Project Squirrel, and Project Squirrel scientists plan to use this data to see if trends emerge in the larger scale study regarding squirrel feeding habits. Evaluate: 1. Assess students’ ability to analyze similar situations and provide thoughtful responses about what behavior they would expect from squirrels. For example: Quiet alley with few humans but many other animals 1 x x 2 x x 3 x x Busy road with lots of car traffic o This is a map of a schoolyard. The numbered shapes represent trees. You place a corn foraging patch in each spot marked by an X on this map. Where would you expect squirrels to consume the most corn? Where would you expect squirrels to consume the least amount of corn? Support your answer. Extend: 1. To more closely monitor foraging behavior at the four foraging sites, have one or two students observe each site once per hour and record and share their observations. 2. Set up an investigation similar to the schoolyard experiment to study the foraging behaviors of squirrels in other locations or to study the foraging behaviors of another species. If students are testing other squirrel foraging locations, they may wish to use the same foraging experiment parameters. However, if students are designing an experiment to measure how much other animals eat in a given location, they must research the eating behaviors of the animal. Students should consider what type of food to provide and how and where it should be presented (on the ground, above ground, on a platform, covered or uncovered, etc.). Compare conclusions with those from the original squirrel investigation. Background Information Message to Instructors Thank you for your interest in Project Squirrel. Studying squirrels presents a range of fun and educational opportunities, and Project Squirrel activities can involve people of all ages and add a scientific purpose to backyard wildlife observation. These activities can also be used as real-life applications of science skills and as a foundation for a range of reading, writing, math, and geography exercises. Participation in this project will help you understand your neighborhood squirrels more clearly, and by contributing the data you collect, you will help to illuminate regional patterns of biodiversity, demographics, and ecology. Love them or hate them, squirrels are excellent organisms for documenting backyard wildlife, and it is our hope that this guide will encourage citizen scientists everywhere to develop their skills in observing and enjoying the interactions that are occurring in their neighborhoods while contributing to a focused, long-term data set that is illuminating the relationships between humans and our environments. We look forward to seeing your data sets over the coming seasons. Happy Squirreling! Foraging Patch Basics The exercises outlined in this lesson are based on the principle that when, where, and to what extent an animal forages for food can tell us a lot about how that individual perceives its environment. Imagine a scientist puts a bowl of your favorite candy on a table near your bedroom door. How much might you eat? Now if the bowl is moved near your neighbor’s bedroom, or the middle of the street, or under the kitchen sink, how much might you eat then? The amount of food left in the bowl (the foraging patch) when you are done foraging gives us insights into how you feel about different places. When the foraging patch is near your bedroom, where you feel comfortable, you will usually forage more than when the patch is near your neighbor’s bedroom or in the middle of the street where territorial conflicts, potential predators (like cars), or other dangers make you uncomfortable. Patch use theory is an important tool that helps us evaluate animal motivations and preferences. Patch use theory predicts that a foraging animal will cease using a patch when the costs of foraging are greater than the benefits. Costs may include the inability to watch for predators while handling food or the difficulty of separating the most nutritious parts of a corn kernel from the starchy parts. The relative costs and benefits may change with factors like the health and reproductive status of an individual. For example, a starving individual is likely to take more risks for food than one that has recently fed. How Squirrels Forage on Corn A corn kernel has two main parts, the endosperm (the starchy outside) and the embryo (the oily inside). When a corn kernel is planted in the soil, the embryo grows into a corn plant, and the endosperm feeds the plant until it forms leaves and begins to photosynthesize. endosperm embryo Background Information Because the oily embryo has many nutrients, it is preferred by squirrels over the endosperm. Squirrels often eat only the embryo from the middle of a corn kernel, leaving the endosperm behind. In this lesson, when a squirrel leaves an endosperm behind, it is referred to as a kernel with an excised (removed) embryo. Much in the same way that candy wrappers could be used to determine how much candy a person ate, kernels with excised (removed) embryos can be used to measure how much a squirrel ate. excised embryo excised embryo Sometimes, squirrels will eat very quickly and leave a pile of broken corn kernel scraps behind instead of leaving a kernel with the embryo neatly cut out. In this lesson, students record information about the amount of corn consumed by squirrels and the scraps left behind by squirrels. If squirrels do not forage from your patches, this is important data and should be reported. Since all data are useful data, please report the amount eaten by squirrels, even if it is 0 grams. The Foraging Patches The foraging patch assembly instructions included with this lesson are for creating simple, disposable patches. Instructions for creating more durable wood patches are available at projectsquirrel.org. The patches are baited with ears of dried feed corn. These ears may be missing kernels and may be different weights from one another. However, provided that the squirrels do not consume every kernel of corn from any of the corn cobs, differences in initial corn cob mass are not significant. The squirrels still have food available to them and have chosen to stop eating. (As an analogy, a person might only eat two hamburgers whether someone offers the person five hamburgers or ten hamburgers.) In this lesson, students will weigh each cob before their foraging patches are put outside, as they will use this information to calculate how much food is missing after the squirrels have foraged. Data Gathering and Entry Scientists at Project Squirrel will be comparing data from hundreds of sites each year. The data collected by your students will be used to make comparisons with data from across the country. To ensure accurate comparisons, the Project Squirrel data submission page (on projectsquirrel.org) will ask for habitat information about the sites that students have chosen. It may be useful to get to know the trees on your school’s property. Columbia University, the University of Maryland, and the Smithsonian Institution have developed a useful mobile tree identification application called Leafsnap, but you can also just keep an eye on the trees throughout the year to see what kind of propagules (seeds, nuts, downy fluff, etc.) they produce. The kind and amount of propagule can have a significant influence on squirrel Background Information populations. For example, squirrels love acorns and walnuts but don’t do as well on maple samaras, and they get almost no nutrition from cottonwood catkins. Acknowledgements Project Squirrel has been working with citizen scientists for more than a decade to learn about tree squirrels. The project was initiated in 1997 and has become a joint venture between the University of Illinois at Chicago (UIC), the members of the Brown Lab at UIC, the Chicago Academy of Sciences and its Peggy Notebaert Nature Museum, and all of the citizen scientists from all ages and walks of life, throughout the United States and in many other countries, who have contributed to Project Squirrel. Habitat Information Sheet Investigator Names: Hypothesized Habitat Type: (circle one) Safe Unsafe Approximate diameter of tree at breast height (DBH): _________________cm DBH To calculate the diameter at breast height: Use a flexible measuring tape (or a piece of string that you later measure) to find the circumference of the tree (in cm) at approximately chest height, which will vary slightly depending on the height of the person making the measurements. Divide the circumference by π (approximately 3.14). Kinds of trees within 20m of foraging site: Nut bearing (trees like walnut, oak, or hickory) Seed bearing (trees like maple, elm, or locust) Fruit bearing (trees like crabapple, gingko, or hawthorn) Cone bearing (trees like pine, fir, or spruce) Tiny seed bearing (trees like cottonwood, willow, or ash) Check off any of the following that are within 10m of the foraging patch: Building Fence Garbage cans or recycling bins Other trees Bird feeders Note: If any of the features listed above are within 4m of the foraging patch location, please select a new location. Habitat Information Sheet If the following are present, indicate how busy you think they are during the day: Not Usually Sometimes Regularly Very Busy Present Quiet Busy Busy Street Alley Sidewalk Playground Sports Field Note: If any of the features listed above are within 4m of the foraging patch location, please select a new location. How many of the following do you think are within one block of the schoolyard in one day? None 1-2 3-4 5+ Cats Dogs Hawks Coyotes How often do you see squirrels obtaining food from the following sources near your school? Never Seldom Often Always Bird feeders Human Handouts Garbage Trees and other plants What other animals do you see in your school yard? Corn Data Collection Sheet Investigator Names: Hypothesized Habitat Type: (circle one) Safe Unsafe Foraging Patch Location: (circle one) Near Tree 4m from Tree Date: ________________________________________ Day # _____ of data collection Time patch opened: ___________ a.m./p.m. Time patch closed: ___________ a.m./p.m. Squirrel species observed in the schoolyard today: Gray Squirrel Sciurus carolinensis Number_________________ Fox Squirrel Sciurus niger Number_________________ Other ____________________ Number_________________ Initial mass of corn cob (before foraging): ____________g Has feeding occurred today? (circle one) Yes / No ------------------------------------------------------------------------------------------------------------------------ If yes, use the corn cob and all corn kernels (whole or in pieces) collected from the cardboard foraging patch to continue: 1. Set the corn cob to the side. Do not remove any kernels from the cob at this time. 2. Split the remaining corn into three piles: whole kernels kernels with excised embryos small pieces of kernels 3. Kernels with excised embryos and small pieces of kernels are the scraps of kernels that were nibbled on by squirrels. Find the masses of these two piles, and use them to calculate the total mass of corn kernel scraps left behind on the foraging patch: Total mass of corn Mass of kernels with kernel scraps left excised embryos (not on Mass of small pieces of behind on foraging the cob): kernels (not on the cob): patch: g + g = g Corn Data Collection Sheet 4. The squirrels may also have left behind kernels that are still whole, either attached to the cob or loose on the foraging patch. Remove the whole kernels from the cob and combine them with the pile of whole kernels that were loose on the foraging patch (already set aside during step 2). 5. Find the mass of this new pile that is made up of all of the whole corn kernels left behind by squirrels, either loose on the foraging patch or removed from the cob by you. Then, find the mass of the cob with all of the kernels removed. Total mass of all whole corn kernels left behind by Total mass of the cob (with all squirrels: kernels removed): g g Use the data collected to determine the mass of all corn that was consumed by squirrels: Mass of corn consumed by squirrels: ___________g Class Data Sheet Location: safe; near tree Location: safe; 4 m from tree Total corn consumed: Total corn kernel scraps: Total corn consumed: Total corn kernel scraps: Day 1: g Day 1: g Day 1: g Day 1: g Day 2: g Day 2: g Day 2: g Day 2: g Day 3: g Day 3: g Day 3: g Day 3: g Day 4: g Day 4: g Day 4: g Day 4: g Average: g Average: g Average: g Average: g Location: unsafe; near tree Location: unsafe; 4 m from tree Total corn consumed: Total corn kernel scraps: Total corn consumed: Total corn kernel scraps: Day 1: g Day 1: g Day 1: g Day 1: g Day 2: g Day 2: g Day 2: g Day 2: g Day 3: g Day 3: g Day 3: g Day 3: g Day 4: g Day 4: g Day 4: g Day 4: g Average: g Average: g Average: g Average: g Data Analysis Sheet Name: ____________________ 1. Use the graphs you created to compare squirrel feeding behavior in the safe location and the unsafe location. In which location was more corn consumed? In which location did the squirrels leave behind more scraps? Explain. 2. Use the graphs you created to compare squirrel feeding behavior near a tree and 4m from a tree. In each location (safe; unsafe), where was more corn consumed, near the tree or 4m from the tree? What differences do you notice in the amount of scraps the squirrels left behind near the tree and 4m from the tree? 3. Based on the data collected, are your hypotheses about the relative safety of each location supported or refuted? Explain. 4. Are there any interesting data that were surprising? Explain. How do the “corn consumed” data compare to the “corn kernel scraps” data? Do the graphs look similar? Graph Sheet Name: __________________________ Corn Kernel Scraps Left Behind by Corn Consumed by Squirrels Squirrels NEAR FAR NEAR FAR NEAR FAR NEAR FAR SAFE UNSAFE SAFE UNSAFE Using the data from the Class Data Sheet, create a bar graph showing the average amounts of corn scraps left behind by squirrels and a bar graph showing the average amounts of corn consumed by squirrels from each of the four foraging patches. Be sure to label the y axis for each graph. Data Reporting Sheet – SAFE Location Day 1 Day 2 Day 3 Day 4 SAFE SAFE SAFE SAFE SAFE SAFE SAFE SAFE Near 4m from Near 4m from Near 4m from Near 4m from Tree Tree Tree Tree Tree Tree Tree Tree Date: Time patch opened: a.m. a.m. a.m. a.m. a.m. a.m. a.m. a.m. p.m. p.m. p.m. p.m. p.m. p.m. p.m. p.m. Time patch closed: a.m. a.m. a.m. a.m. a.m. a.m. a.m. a.m. p.m. p.m. p.m. p.m. p.m. p.m. p.m. p.m. For the following three rows, please provide an estimate of the number of squirrels in the schoolyard each day, based on the most common number of each species seen and recorded during students’ observations. These three rows will not appear in the Data Reporting Sheet for the unsafe location, as the numbers you record here are an estimate of the number of squirrels seen by students from any location in the schoolyard. # of gray squirrels observed: # of fox squirrels observed: # of other squirrels observed (note species): Did feeding occur? Yes or No Yes or No Yes or No Yes or No Yes or No Yes or No Yes or No Yes or No Initial mass of cob g g g g g g g g (before foraging): Mass of kernels with g g g g g g g g excised embryos: Mass of small pieces g g g g g g g g of kernels: Total mass of whole kernels left behind g g g g g g g g (loose or on cob): Use students’ completed Data Collection Sheets to compile information from each group before submitting the data to Project Squirrel. Data Reporting Sheet – UNSAFE Location Day 1 Day 2 Day 3 Day 4 UNSAFE UNSAFE UNSAFE UNSAFE UNSAFE UNSAFE UNSAFE UNSAFE Near 4m from Near 4m from Near 4m from Near 4m from Tree Tree Tree Tree Tree Tree Tree Tree Date: Time patch opened: a.m. a.m. a.m. a.m. a.m. a.m. a.m. a.m. p.m. p.m. p.m. p.m. p.m. p.m. p.m. p.m. Time patch closed: a.m. a.m. a.m. a.m. a.m. a.m. a.m. a.m. p.m. p.m. p.m. p.m. p.m. p.m. p.m. p.m. Did feeding occur? Yes or No Yes or No Yes or No Yes or No Yes or No Yes or No Yes or No Yes or No Initial mass of cob g g g g g g g g (before foraging): Mass of kernels with g g g g g g g g excised embryos: Mass of small pieces g g g g g g g g of kernels: Total mass of all whole kernels left g g g g g g g g behind (loose or on cob): Use students’ completed Data Collection Sheets to compile information from each group before submitting the data to Project Squirrel.
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