Paleoecology of “Fossilized” Owl Pellets Tonya Van Leuvan Goals: Students will learn: 1. Students will learn how differences in anatomy can be used to identify species. 2. Students will learn how a species environmental preferences allow us to reconstruct probable past environments. Objectives: Students will be able to: 1. Separate skeletal elements by type. 2. Use a dichotomous key to identify which species are being eaten by the owls. 3. Discern the minimum number of prey predated upon. 4. Use data about the climatic conditions of the prey to discern the climatic conditions of the predator. Background: Paleoecology: Paleoecology is the study of past environments and the relationships that took place within them. Things we observe today are assumed to have worked relatively the same way in the past. An owl today that morphologically resembles a set of fossilized owl bones is thought to be descendant of that owl species. If we know the habits of the owl today, and how it differs from other owls we can assume that within reason its ancestor shared some of these traits. For the purpose of this exercise we are assuming the ancestral owl is nocturnal (like today’s barn owls), predates from 1 to 3 miles from its nest (as do today’s barn owls) and we also assume that the “fossilized” rodents, birds, shrews and moles lived in areas with roughly the same rainfall and temperature as do their descendants today. Barn Owls: Barn Owls are nocturnal, which means they awake and prey only at night. They nest in one area and fly from 1 to 3 miles in search of food. They swallow most of the small animals they prey upon whole. Their stomach acids are not as acidic as many other birds of prey and this allows the bones and fur from their prey to remain relatively intact through digestion. Fossils: fossils are formed when inorganic matter is leached out of bone, wood, etc., and inorganic matter takes it’s place. Amber, and coprolites are other examples of fossils. Coprolites are fossilized animal droppings. They provide information about what an animals was eating. If an animal was eating tropical plants, one can assume that the landscape was tropical for that time period for example. If they ate a desert animal like a javelina, one can assume the landscape was fairly dry. Materials: Owl Pellet kit Tweezers Skull and Mandible Key (attached) Temperature/Rainfall chart and questions (attached) Procedure: Preparation Dissect several owl pellets yourself and prepare a placard with the mandible and skull of each rodent taxon, for the students to refer to. Birds, Moles and Shrews are pictured in the Owl Pellet Kit packet, and attached as well. The taxa the students will most need to see mandibles and skulls of are the rodents – the Vole, Mouse and Gopher. Activity 1. Divide students according to how many owl pellets are available. Ideally students should work in groups of 2 ‐4 with at least 2 owl pellets between them (3 is better). Some pellets only have one animal, if it is a large animal, like a gopher, and it is impossible to get the point of this exercise with only one animal type. Alternately, two groups could dissect separately, but share information, as is often done in this type of science. 2. Tell the students that they are digging fossils and they found owl pellets where they never knew owls lived before. Based on owls in the area there are several options for which owl they may have – A, B, C, all, none, or two of them are candidates. 3. Instruct students to carefully dissect the owl pellet. The bones are fragile and gentleness is key. Tweezers may be used if necessary. 4. After all bones are removed from fur and dirt, you may or may not choose to have students identify all body parts (see extensions). For this lesson students need to separate out skulls and mandibles/jaws. 5. Students should then identify to which animal each skull or mandible belongs. This can be assisted by the key provided and by the placard made up by the teacher ahead of time. 6. Students should also determine the minimum number of individuals (MNI). This can be done by first dividing all mandibles and skulls into taxon. Within each taxon, one skull and two mandible halves equals one individual. If only one element is present this equals one individual. If three mandibular halves are present, students must look at which side each half is anatomically – right or left. It is possible that three mandibular halves equal two or three individuals. (See “MNI” excel sheet attached for examples of how the same amount of jaw bones can tell you increasingly more about how many animals were eaten by the owl). 7. Students should use the temperature rainfall table to answer questions and determine the climatic conditions of their owl. 8. Based on the climatic condition and the species present in the owl pellets, students should be able to determine which owl (A, B, or C) left the pellets. Grade Level: 6‐7 Duration: About 2 class periods. Dissection: 25 minutes Identification of animals and minimum number of individuals: 30 minutes Worksheet: May be done at home. If not 20 minutes. Science Standards: Strand 1: Inquiry Process Concept 2: Scientific Testing (Investigating and Modeling) Design and conduct controlled investigations. PO 5. Keep a record of observations, notes, sketches, questions, and ideas using tools such as written and/or computer logs. Concept 3: Analysis and Conclusions Analyze and interpret data to explain correlations and results; formulate new questions. PO 1. Analyze data obtained in a scientific investigation to identify trends. PO 5. Formulate a conclusion based on data analysis. Extensions: This lesson in designed to be taught in conjunction with the pre‐established owl pellet lesson. It is strongly suggested that students either do the owl pellet lesson and save their bones in a baggy for this lesson, or do this lesson first and the owl pellet lesson second.