Owl Pellet Dissection Lab

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IntroductIon Owl pellets are masses of bone, teeth, hair, feathers and exoskeletons of various animals preyed upon by raptors, or birds of prey. Pellets are produced and regurgitated not only by owls, but by hawks, eagles and other raptors that swallow their prey whole or in small pieces. Owls feed early in the evening and regurgitate a single pellet approximately 20 hours after eating.

Predatory mammals such as bobcats and wolves have teeth to grind up bones and claws, and, a digestive tract adapted to pass these ground parts. Owls, on the other hand, do not have teeth for grinding and cannot pass whole bone and claws through their digestive tract safely. The protein enzymes and strong acids that occur in the digestive tract of raptors do not digest the entire meal. The relatively weak stomach muscles of the bird form the undigested fur, bones, feather etc. into a bolus (or wet slimy pellet). Depending upon the prey eaten, the undigested portions may include beaks, claws, scales, or insect exoskeletons. This type of material has little nutritional value and must be passed from the body. In this process even the most fragile bones are usually preserved unbroken.

Owl Pellet Dissection Lab

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Scientists take advantage of this adaptation by collecting these pellets and examining their contents. Since owls are not very selective feeders, these pellets can be used to estimate the diversity of available prey. The contents are also a direct indicator of what an owl has fed on; information that is crucial for species management and protection.

The owl pellets that you will be examining in this lab have been collected and fumigated from common barn owls (Tyto alba). Owl pellets themselves are ecosystems, providing food and shelter for communities that may include clothes moths, carpet beetles and fungi. Clothes moth larvae are frequently abundant in pellets, feeding on fur and feathers. The black spheres about the size of periods (.) that are found in the pellets are the droppings of the caterpillars. The larvae metamorphose near the surface of a pellet in cocoons made of fur.

Owl Pellet Dissection Lab

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MaterIals: • owlpellet(wrappedinaluminumfoil)• brownglassspecimenjar(capoptional)• dishwashingdetergentorhandsoap• cheesecloth• forceps• 2dissectingmounts• dissectingprobe• dissectingpan/tray(locatedatstation)• severalsheetsofwhitepaper(recycled)• 2specimendishesand/orwatchglasses/petridishes• metricbalance• ruler• stereoscopicdissectingmicroscope• magnifyingglass• water• papertowel• desiccatingoven(hightemp.)• latexgloves(pairforeachpartner)

Owl Pellet Dissection Lab

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Procedure:

1.Unwrapandexaminetheoutsideoftheowlpellet.Putalldataandobservations ontheData,Observations,&Analysispage.Describetheexternal features.Measureandrecorditslengthandwidthincentimeters.Measure andrecordtheowlpelletmassingrams.

2.Toinvestigatetheinteriorofthepelletyoumustsoftenitbysoakingit inwater.Fillthespecimenjar3/4fullwithtapwater.Addadroportwo ofdishwashingliquidorhandsoapandthepellettothejar.Closethe jarwithacaporcoverwithyourglovedhandandshakegentlyforabout 30seconds.Letthejarstandforfiveminutesandshakeagainfor30 seconds.

3.Whenthepellethasfallenapart,haveyourpartnerholdthecheesecloth, andslowlypourthecontentsofthejaroverthecheesecloth.Becareful nottoallowanyanimalfragments,bone,orfurwashintothesink.

Lab Answer Sheet

Owl Pellet Dissection

Names:      

Pledge:

     

Authorized Aid means you worked TOGETHER to complete this lab – answers were discussed with one another before being typed, both of you participated in conducting the lab procedures. (28 total points)

Follow the procedures in the pdf and use this sheet for entering your data.

Observations

Length (cm):      

Width (cm):      

Mass (g):      

External features (any distinguishing characteristics):      

Data Table 1

Skulls

1

2

3

4

5

Total

Species

     

     

     

     

     

     

Bones Found

     

     

     

     

     

     

Likely Habitat

     

     

     

     

     

     

Likely Diet

     

     

     

     

     

     

Data Table 2

GROUPS

TOTAL

1

2

3

4

5

6

Number of Skulls

     

     

     

     

     

     

Species & Number found (goes in second, smaller column)

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

Total

     

     

     

     

     

     

     

GraphCreate a double bar graph that shows the number of each species found in the pellets. One bar will represent your group’s findings, another bar will cover the class findings (including yours). Set up is as follows:

· X axis = species found

· Y axis = number of individuals

· Title, Number and Date along top of the graph

· Key showing differences between group and class data

· Two bars (one for class; one for group)

Insert your graph here:

Graphic

Create a food web/chain based on your findings. Include the relationships between the different organisms you illustrate. Include all organisms that the class found during the lab. You may do this on a clean sheet of unlined paper or using a program like Inspiration on your computer.

Insert your graphic here:

Owl Pellet Prey Analysis Data Chart

After your biomass has been dried in the oven, record the total biomass and complete the following data analysis.

Prey

Habitat

Mean Mass (g)

Conversion Factor

Frequency Found

Percent of Diet

Biomass Units

Percent of Biomass

Redback Vole

Meadow

40

2

     

     

     

     

Meadow Vole

     

40

2

     

     

     

     

House Mouse

     

20

1

     

     

     

     

White-footed Mouse

     

20

1

     

     

     

     

Mole

     

55

2.75

     

     

     

     

Shrew

     

5

.25

     

     

     

     

Norway Rat

     

240

12

     

     

     

     

Small Bird

     

40

2

     

     

     

     

 

 

 

TOTALS

 

100%

 

100%

NOTE: Both team members need a completed copy of this lab in order to complete the lab homework.

dwheelerFile AttachmentOwl Pellet Dissection AS.doc

Owl Pellet Dissection Lab

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4.Placethecheeseclothonapieceofwhitepaper.Pickbones,teeth,insect parts,andanyotherpreyevidenceoutofthefurandplaceallpreyevidence (exceptskulls)inaspecimendishorwatchglass.Placetheskullsonasecond sheetofpaper.Useprobes,dissectingmounts,orforceps,asnecessary,but proceedcarefullytoavoidcrushinganysmallbones.Separatethefurand othersoftmatterasyousearchforbonesbyplacingtheminaseparate specimendishorwatchglass.

7.Usethelinksprovidedwiththedichotomouskeytofindthelikelyhabitatand dietofeachspeciesfoundinthepellet.Recordtheinformationonyouranswer sheet.

5.Labeltheskullsbynumber,andusethisdichotomouskeyto identifythem.Recordthespeciesofeachskullonyouranswersheet.

6.Trytomatchotherbonestoeachskull.Usethepreservedspecimens andthediagramsofanimalbonestructuresprovidedtoidentifyeach boneandrecorditsnameunderitsmatchingskullonyouranswer sheet.

Owl Pellet Lab

Dichotomous Key

Does the animal have....

Then...

1.   a)  3 or fewer teeth on each side of its upper jaw?

      b)  4 or more teeth on each side of its upper jaw?

go to 2.

go to 3.

2.   a)  2 biting teeth on its upper jaw?

      b)  4 biting teeth on its upper jaw?

go to 4.

it's a rabbit.

3.   a)  a skull length of 23 mm or less and brown teeth?

      b)  a skull length of more than 23mm and approx. 44 teeth

it's a shrew.

it's a mole.

4.   a)  the roof of its mouth extending past the last molar?

      b)  the roof of its mouth not extending past the last molar?

go to 5.

go to 6.

5.   a)  a skull length of 22 mm or less?

      b)  a skull length of more than 22 mm?

it's a house mouse.

it's a rat.

6.   a)  flat molars?

      b)  rounded molars?

it's a meadow vole.

it's a deer mouse.

 

Figure 2 (Rodent Skulls):

Adapted from: http://chs.carlsbadusd.k12.ca.us/DeCino/Webpage/APES/owldirections.htm

dwheelerFile AttachmentOwl Pellet Dichotomous Key.doc

Owl Pellet Dissection Lab

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8.Talkwithothergroupsandfindthetypesandnumberofspeciesfoundinallof thepellets.RecordthisinTable2.

9.Onceallboneshavebeenidentified,collectyourbonesinthespecimendish. Carefullydryasmanyasyoucanwithoneortwopiecesofpapertowel.Add theotherorganicmatter(i.e.furandsmallmiscellaneouspieces).Then,make asmallmarkonyourspecimendishtobeabletoidentifyit,andplaceyour entirespecimendishinahightemperatureovenfordrying.Checktheorganic matterafter24hourstorecordthebiomass.

10.CompletetheAnswerSheetandmakesurebothteammembers haveacopy.

11.CompletetheHomeworkforthislab.

Owl Pellet Lab

Homework

Name:     

Pledge:

     

Authorized Aid: You may discuss questions with classmates or other knowledgeable persons before composing your OWN answer or you may use a source and cite it appropriately.

You will need a copy of your team’s answer sheet to complete this assignment.

Analysis Questions

1. Is the owl pellet the “end” or termination of a food chain?        Explain.      

a. Is it the end or termination of a food web?        Explain with some detail and/or examples.      

2. How can the particular species within the pellet help you identify the location the pellet came from?  Based upon the species in your pellet hypothesize where it was collected.      

3. How many different animals did you find in your pellet?       

a. What were some of the difficulties you encountered in trying to identify them?      

4. What percent of the owl pellet’s original mass was its biomass (and not that of another organism)?      

5. Why are predators less abundant than their prey?      

6. Describe how evolution can affect predator-prey relationships.      

7. In the food web graphic you created, assume the owl represents 10,000 kcal of energy. Sketch and label a biomass pyramid and energy pyramid that include these organisms. Again, you may use a program like Inspiration or a piece of unlined paper.

Insert labeled graphic here:

dwheelerFile AttachmentOwlPelletLabHW.doc

Owl Pellet Dissection Lab

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references

“Alcorn/APEnvironmentalScienceOwlPelletDissection.”Dr.Decino’swebpage.CarlsbadHighSchool.27Oct.2008.

Gautschi,D.Tobias.“OwlPelletLab.”Mr.Gautschi’sHomePage.ElDoradoHighSchool.27Oct.2008..

Radcliffe,G.“HUMANBODYLab3:OwlPelletDissection.”HumanBodyUnit.CentrevilleMiddleSchool.27Oct.2008.

Owl Pellet Dissection Lab

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IMages

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Barnowlimages(bothadultandchicks)florinorfolk.“MagicOwls.”weblogpost.photorama.29may2008.flickr.27Oct.2008..

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