Laurie,W. A.

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JOURNAL
OF THE EAST AFRICA NATURAL HISTORY
SOCIETY AND NATIONAL MUSEUM
VOL. 28 10thAUGUST 1971 No. 125
THE FOOD OF THE BARN OWL IN THE SERENGETI NATIONAL PARK,
TANZANIA,
by
W. A. LAURIE
INTRODUCTION
The objectof this studywasto obtaininformationaboutthepreyof theBarn
Owl (Tyto alba, Scopoli),by identificationof skullsin theirregurgitatedpelletsand
tocomparethepreytakenin differenthabitats.Differencesin thecontentsofthepellets
fromvarioushabitatsmaybe dueto differencesin abundanceof thepreyspeciesor
differencesin selectionbythepredator.The lattercouldbedueto differentvegetation
coveror differenthuntingmethodsor a combinationof both.Attemptsweremadeto
determineanypreyselectionby comparingthepelletcontentswitha smallnumberof
trappingrecords.Neithertrappingnorpelletcollectionprovideanunselectivesampling
methodbutcomparisonof thetwocangivesomeideaof thetypeof selectiontaking
place.Otherpredatorselectin differentways;a numberof droppingsof theGenet
(Genettagenetta,Linnaeus)werealsoexaminedforcomparisonwiththeowlpelletdata.
Methods
The workwasdonein someof mysparetimeasa fieldassistantin theSerengeti
ResearchInstituteof the SerengetiNationalPark, Tanzania.Collectionsof pellets
weremadein thelargegraniteoutcropsorkopjesnearSeronera,betweenlIth Mayand
31stJuly 1969-averydryperiod.All pelletswerefromroostingsitesatwhichBarn
Owlshadbeenseen.Therewerethreemainsitesof collection:-
SiteNo. I: Oloserian,the site of the SerengetiResearchInstitutebuildings
3.219km (twomiles)fromSeronera.At leastonepairof BarnOwls
wereresidentin a largerockoutcropsduringthestudyperiodbut
no newpelletswerefoundafterthebeginningof July. The group
of rockoutcropsandbuildingsaresituatedinsparseacaciawoodland
eastof Seronera.
SiteNo. z: MasaiKopjes,a largegroupof thicklyvegetatedoutcrops8.047kIn
(five miles)south-eastof Seroneraon theborderof theopenplains
andthewoodlands.BarnOwlsweredisturbedonfourdifferentroosts
andnewpelletswerefoundunderoneormoreofthemateachcollec-
tion.
Site NO.3: SimbaKopjes,anothergroupof largerock outcrops,32.187kIn
(twentymiles)south-south-eastof Seronerain theopenplains.The
vegetationis verylike thatof MasaiKopjesbut slightlysparser.
Two definiteBarnOwl roostswerefoundhere.The similarityto
Page2
SiteNo.2 meansthatthesetwocanbe comparedjointlyasplains
siteswithSiteNo. I, awoodlandsite.
439pellets,togetherwitha quantityof disintegratedpelletmaterialwerecollected
from thesethreelocalitiesandall lowerjawsandskullspresentweredissectedout.
Thesewereidentifiedto generawiththeaid of "Keys to theGeneraof Insectivora,
Chiroptera ndRodentiaof EastAfrica"by J. B. FosterandA. Duff-Mackay,and
bysubsequentcomparisonwithspecimensattheBritishMuseum,Londonin December
1969.The birdskullswerenotidentified,norweretheonlyreptileremains-alizard's
lowerjaw.
The wingandbodycasesof beetleswerepresentin manypellets.Thesewerenot
identified,nor wasit possibleto estimatethenumbersof beetlescontributingto the
remainspresentin anyone pellet.However,eachpelletwasrecordedas containing
ornotcontainingbeetleremainsandtheresultsof thisanalysisareshownbelow.
GenetdroppingswerecollectedonseveraloccasionsfromalargerocknearOloserian.
The skullsin thesedroppingswerebrokenup to a considerabledegreeandnotmany
reliableidentificationscouldbemade.Lowerjaws,however,werefoundintactandtheir
identificationasfarastheordersInsectivorandRodentiawaspossible.
A littlemammaltrappingwasdoneat Oloserianwith Longworthtraps.These
weredeliberatelyplacedto attempto catcha largevarietyof species;consequently
numbersof thosetrappedby no meansreflecttherelativeabundancesof thesmall
nocturnalmammalswhichwouldbeavailabletotheowls.
Results
SiteNo.1SiteNo.2SiteNO.3
Olosman
MasaiimbaTotal
No.
%Tot.N ..
RODENTIA: Arvicanthis
246.81457.82220·41915 1
Mastomys
581 .1 19·7Saccostomus 36
·67·55·6038.2
Steato ys
2303 784 6
Zelo m
I0· 1 130
Mus
.21 1
Th ll ys
3.8 2·9
P l mys
6 Io I 00
tera
00
hyor ctes
I3 I
IN ECTIVORA: Crocidura
18152·46372 8 46
ElephantulusCHIROPTERA Tadaridaap zou
IO
BIRDS
82.2
REPTILES
0
TOTALS
460387.0
BEETLES
373 0 80B E LES 73
6 8.4 6
TOTALS
10 61 . 9.
Page3
Notes:Specieswereidentifiedasfollows:-
Mus minutoides(Smith)
M. hufo(Thomas)
Crocidurahieolor(Bocage)
Elephaatulusrufe.eens(peters)
Tadaridaaegyptiaca(E. Geoffroy)
Taphozous(Liponyeteris)nudiventris(Cretzschmar)
Trappingresults:The followingwerecapturedin a total of 70 trap daysin the rock
outcropsat Oloserian.
Aeomysspp. 20
Arvieanthisspp. 16
Mastomysspp. 13
Lemniseomysspp. 1
GTaphiurusspp. I
Crociduraspp. 4
Genetdroppings:Few positiveidentificationscouldbemade;thenumbersof insectivores
arecomparedwith thenumberof rodents(lowerjaws),from 43 droppings.
Rodentia: 23 (inc.Arvieanthis,SteatomysandMastomysspp.)
lnsectivora: 3 (probablyCrociduraspp.)
Discussion
Various significantdifferencescan be seenbetweenthe contentsof pelletsfrom
differentsites.The mostobviousarebetweenthosefrom Oloserianand the othertwo
sites.Oloserianhasa significantlylowerpercentageof Arvieanthisandhigherpercentages
ofMastomys,SaceostomusandSteatomys.Oloserianalsohasaverymuchlowerpercentage
of pelletscontainingbeetleremains.Somegeneraarecompletelyabsentin the samples
from a particularlocality;for example,Taterais presentonly in the smallersampleof
Simba,andElephantuluswasfound only at Oloserian.
As statedearlier thesedifferencescould be causedby a differencein the small
mammalpopulationsor by differencesin samplingor by a combinationof both. The
habitatdifferencesbetweensites2 and 3 areslightandthis is reflectedin the similarity
of the pellet contents from these sites. The details of the way in which the
habitatdifferencesaffectthe smallmammalpopulationsrequirean extensiveknowledge
of the habitatpreferencesof the animalsinvolved.Differencesin samplingby the owls
couldresultfrom the longergrassandthickertreecoverroundtherock outcropsin the
woodlandand the presenceof humanhabitationat Oloseriancould also be involved.
From thetrappingresults,it canbe seenthattheidentificationof owl pelletremains
gavenotruepictureof thesmallmammalpopulation:threegeneraweretrappedfor which
no remainswerefound in pelletsat anysite.Aeomys,thespinymouse,hasthe posterior
dorsalhairs modifiedinto rigid spineswhich could discourageowls (andgenets)from
eatingor capturingthem..GTaphiurus,the dormouse,is presumablyprotectedby its
arborealhabits.Arvieanthisfeaturesprominentlyin trap dataandtheywereoftenseen
during daytimein the areaalthoughoccuringas rathera low percentagein the pellets
from Oloserian.Possiblytheyareprotectedfrom owl predationby their largelydiurnal
habits.
The very high proportionof insectivoresin the owl pelletscomparedwith their
almostnon-existencein thegenetdroppingsis noteworthy.Many carnivores(domestic
cats,foxesandjackals)areknownto dislikeshrewsbut it seemsthatowlshaveno such
dislike.
Page4
Acknowledgements
I wouldliketo thankall thosewhohavemadethisstudypossibleandespecially
Dr. H. F. Lampreyfor theopportunityof workingin theSerengetiResearchInstitute,
to A. Duff-Mackayfor somepreliminary identificationsat the NationalMuseum,
Nairobi,to Dr. Corbettfor permissionto usethereferencecollectionsof mammalsat
theBritishMuseum(NaturalHistory)andto Miss InglesandMr. Hill. (bothalsoof
theBritishMuseum)for theirhelpin identification.I wouldlike to thankDr. H.
Kruuk for hisadvicethroughoutandfor readingandcommentingonthemanuscript.
REFERENCES
ANDERSON& LONG,C. A., (1961).Smallmammalsin pelletsof BarnOwls fromMinaca,Chihuahua.
Am.Mus.Novit.No.2052.
FOSTER,J. B. & DUFF-MACKAY,A., (1966).Keys to the Generaof Insectivora,Chiropteraand
Rodentiaof EastMrica. Jl E. Africanat.Hut. Soc.Vol. 25.NO.3.
MISONNE,X. &VERSCHUREN,J. (1965).Les rongeurset lagomorphesdela regiondu PareNational
du Serengeti,Tanzania.Mammalia.
UTTENDORFER,0., (1952).Neue Ergebnissetiberdie Erniihrungder Greifvogelund Eulea. Ulmer,
Stuttgard.
VERSCHUREN,J., (1965).Contribution a l'etudedes cheiropteresdu Pare National du Serengeti
(Tanzanie).Rev.Zool.Bot.afr.,71.
(Received4thJanuary,1971).


The Food of the barn owl in the Serengeti National Park, Tanzania

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The Food of the barn owl in the Serengeti National Park, Tanzania

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