DECOMPOSITION of RAPTOR PELLETS by Jamesr

Home , Little owl, Monopis weaverella, Pellet (ornithology), Trox

DECOMPOSITION OF RAPTOR PELLETS by JamesR. Philips and Daniel L. Dindal Departmentof ForestZoology StateUniversity of New York Collegeof EnvironmentalScience and Forestry Syracuse,New York 139•10

Abstract Deco•nposingpellets from Great Horned Owls were studiedduring the summer and fall of 1973. After four months,pellets weighed 38-89 percent of their initial dry weight. Thirteen speciesof fimgi were isolatedfrom the pellets. Funnel extraction yielded3,665 invertebratesfrom 75 pellets.The most importantinvertebrates in pellet decompositionappear to be the trogid beetlesand the tineid moths.Raptor pellets serve as a feeding,breeding, and sheltersite for many invertebrates,including predators,parasites, fi•ngivores, and saprovores.

Introduction Indigestiblematerial is quite commonly regurgitatedby birds in the form of roughlyoval to cylindricalpellets. Such regurgitation is known to occur in 330 species in more than 60 families,according to a surveymade by The InternationalBird Pellet Study Group (Glue 1973). Among them are suchbirds as jays, flycatchersand thrushes,as well as hawks and owls (Simmons1973, Tucker 1944). Raptor pellets generallyconsist of fur, feathers,bone, scales, chitin, and other prey remains,densely packedand held togetherby mucussecreted from the digestivetract which driesand hardenssoon after egestion.In somecases, pellets of wax (HoneyBuzzard, Perhis api- vorus,Meinertzhagen 1959) or even soil (Kestrel,Falco tinnunculus,Davis 1975) may be found.Pellets are alsoejected by other vertebrates,including some mammals, rep- tiles, and amphibians(Hanson pers. comm., Dobroruka 1973). Pelletsprovide data on avian foodhabits and prey populations,but many other as- pects are of interestas well. Smith and Richmond(1972), Duke et al. (1973, 1975, 1976),and othershave examinedthe physiologyof pellet formationand regurgitation. Dobrokhotovand Litvin (1971)studied time-related dynamics of Kestrelpellet forma- tion by measuringpellet radioactivity after the raptoringested mice containing p32. Raptor pelletsmay alsoplay a role in the spreadof diseasessuch as sylvaticplague, since they are temporarilyinfective if diseasedprey has been eaten (Jellison1939). Plagueantigens can be detectedmuch longerthan the plaguemicrobe itself in pellets, and pellet analysishas been proposedas one of the best methodsof detecting epizooticplague infestations (Lobachev et al. 1971, Lobachevand Shenbrot1974). Pellet decompositionhas been given very little attention.Some authorshave reported that pelletsmay remainintact for many years(Brooks 1929, Presttand Wag- staffe 1973). Others have found that pellets are broken down in weeks or months (Wilson1938, Marti 1974).Warling (1962, 1963) studiedfungal succession on Kestrel

102 RaptorResearch 13(4):102-111 Winter 1979 Philips& Dindal--RaptorPellets 103

(Falcotinnunculus) pellets and isolated51 speciesof fungi and one alga. Hub•ilek (1974)isolated many fungalspecies from owl pellets.The invertebratefauna reported from pelletsis limited to a few insects(table 1). Therefore,the objectiveof this re- searchwas to elucidatethe invertebratemicrocommunity associated with decomposition of owl pellets.The conceptof microcommunityas presentedby Dindal (1973a) wasassumed in the study.

Table 1. Insect Fauna of Raptor Pellets

Order References Family

Coleoptera DermestidaeCarpet beetles Wallace, 1948 Dermestesspp. Simmons, 1971 SilphidaeCarrion beetles Hanson, pers. comm. TrogidaeSkin beetles Petersen, 1960 Trox erinaceousJ. Lec. Davis, 1909 Troxfoveicollis Harold Vaurie, 1955 Troxplicatus Robinson Vaurie, 1955 Trox scaber(L.) Davis, 1909 Troxspinulosus simi Robinson Vaurie, 1955 Trox striatus Mels. Vaurie, 1955 Trox variolatus Mels. Dillon and Dillon, 1972; Vaurie, 1955 Diptera AnthomyiidaeAnthomyid or latrine flies Fannia aerea (Zetterstedt) Aubrook, 1939 Itydrotaeaocculta (Meigen) Aubrook, 1939 ScatophagidaeManure-feeding flies Scatophagasqualida Meigen Aubrook, 1939 ScenopinidaeWindow flies Scenopinussp. de Joannis,1899 Hymenoptera BraconidaeBraconid parasitoid wasps Phaenocarparuficeps (yon Es.) Aubrook, 1939 Lepidoptera Tineidae Clothes moths Morton et al., 1977; Vernon, 1972 Monopisferruginella (Hubher) Hinton, 1956 Monopisrusticella (Clerck) Nurse, 1906; Buxton, 1914; Elton, 1966 Monopisweaverella Scott Elton, 1966 Tineapellionella (L.) de Joannis,1899 Tincolabisselliela (Hummel) de Joannis,1899 Trichophagasp. Moon, 1940 Trichophagatapetzella (L.) de Joannis,1899; Forbes, 1923; Baer, 1924;Davis (citedby Lutz, 1948)

Methods Rats (Rattus norvegicus)were fed to five Great Horned Owls (Bubo virginianus). Pellets and pellet fragmentswere collectedas soonas possibleafter regurgitation. They were dried in an oven at 60øC for 24 hours.Dry weight and volume were 104 RAPTOR RESEARCH Vol. 13 No. 4 measured.The dry pelletswere placedin 6-mm meshnylon bagsand frozen. On 3 July 1973, 90 "pellet bags"were set out in a maple-oakstand at our College'sForest Experiment Station, Lafayette Road, Syracuse,New York. The pellets varied in weight from 3.08 to 11.47 g (av. 6.06); lengthranged from 33 to 86 mm (av. 49.71) and width, from 20 to 34 mm (av. 25.11). Six pelletswere removedevery 8 daysfor 4 months.Five pelletswere placedin modifiedTullgren funnels for extractionof invertebrates.As the pelletsair-dried, des- iccationdrove out the invertebrates,which fell into a collectingjar containingan al- coholand glycerinsolution placed at the baseof the funnel.The remainingpellet was used for culturingof fungi and invertebrates.Portions of the pellet were in- cubated on moist filter paper in a petri dish in the dark at 25øC. When insects hatched,they were preservedin alcohol.As fungalgrowth became evident, pieces of the pellet were transferredonto mycobioticagar. The other half of the pellet was usedfor culturingof fungi by meansof the soil-dilutionagar plate method(Menzies 1965). Dilutions from 10-4 to 10-6 were used with preparationsof mycobioticand malt agars.

Results and Discussion After 4 months'exposure to field conditions,pellets weighed from 38.03 to 89.53 percent of their initial dry weight, averaging62.87 percent (fig. 1). Decomposition rates were highly variable because of differencesin size, composition,micro- environment,and faunaland floral colonizationof pellets. PhysicalFactors. Weather is a major factor in pellet decomposition.Rain flattens the pellet, dissolvesthe mucus,washes hair away from bonesnear the surfaceof the pellet, and helpscreate entry holesfor invertebrates.Freezing and thawingare also important(Wilson 1938). Faunal Microcommunity.Fresh moist pellets attract flies, suchas Calliphoridaeand Anthomyiidae,which deposittheir eggson the pellets.Such flies do not appearto be attractedto dried or older pellets.Other flies may be foundon older, moistpellets; however,pellets may at times representislands of moistureon the soil litter surface and attract cryptozoans,such as sowbugsand earthworms.Snails and slugscan also be found on pellets,and the large slugLimax maximusoften leavesa trail of mucus on pellets it has visited nocturnally.Various transientspecies, such as ants, centi- pedes,millipedes, and spiders,also visit pellets,as well as occasionalhungry mammals (Wilson 1938, Fleay 1968) and industriouspack rats (Griffin 1976, Long and Kerfoot 1963). Pelletssupport large populationsof protozoaand nematodes,and even tardigradesmay be present. Pelletsserve as habitat for beetlessuch as Leptodiridaeand Staphylinidae.Various parasiticwasps find pelletsto be a sourceof hosts.Predatory, parasitic, fungivorous, and saprophagousmites all were found.Akimov and Shehur(1972) have shownthat the acarid mites Tyrophagusputrescentiae (Schrank), Glycyphagus domesticus (Deg.), and Rhizoglyphusechinopus (Fum. et Rob.)cannot digest keratin but feed on the lip- ids associatedwith keratinoussubstances such as feathers.However, other possible food sourcesare present,on feathersand pellets.Also, we have often found larvae, nymphs,and adultsof T. putrescentiae,on pellets,with alimentarytracts filled with hyphaeand fungal spores. The two mostimportant pellet invertebratedecomposers are the tineid mothsand Winter 1979 Philips& Dindal--RaptorPellets 105 the trogid beetles.The larvae of the Tineidae, or clothesmoths (fig. 2), eat hair and feathers,and we have foundover 60 of them in a singlepellet. Pelletssometimes ap- pear to be coveredventrally with a centimeteror more of debris.Actually this is a thin layer of soil and moth excretacovering many casesof silk constructedby the larvae.These cases range from 7 to 18 mm long by 2 mm wide, and the larvae feed and pupatewithin them. The open end of the caseis in the pellet and the casere- semblesa small "sock"sticking out of the pellet. In decomposedpellets, the silken network of thesemoth casesmay be all that holdsthe remainingbones together. Fly larvaeof the genusScenopinus prey on tineld larvae in pellets(de Joannis1899). The trogid beetlesalso feed on hair and feathers,and their larvae burrow into the soil beneaththe pellet. The burrowsmay be 30 mm deep by 2 mm wide, and they may be lined with hair for the upper 20 mm. Trogidbeetles also serve as transporta- tion for uropodineand macrochelidmites (Sixl 1971). Many mites attach themselves to insectsfor transportationfrom one site to another.This relationshipis known as phoresy.A mesostigmaticmite Macrochelespenicilliger (B.) hasbeen reported phoretic on Trox scaberin owl nestsin England(fig. 3). We have found it on Trox variolatus in pelletsand rat carrionin central New York. In additionwe have foundnema- todes that are also phoretic on the phoretic Macrochelesmite (fig. 3). There are severalother publishedrecords of this type of nematodephoresy (Dindal 1973b, Ramsay1970). Funnel extractiondata for both tineid moths and trogid beetleswas found to be unreliablebecause their casesprovide considerableprotection againstdesiccation. The trogid beetlesare often foundbeneath the pellets-adultsin the litter, and larvae in the soil. Millipedes,sowbugs, and earthwormswere alsoobserved on pelletsmore frequentlythan the extractiondata indicates(table 2). Perhapsthe most surprisingfind was a specimenof Radfordia. This prostigmatic mite is a smallmammal ectoparasite which feedsin the basesof hair follicles(Krantz 1971).The specimenwas in goodcondition but was probablydead and accidentally fell into the collectingjar duringextraction. However, another specimen was obtain- ed in an extractionof fresh Great Horned Owl pellets. These findingsbring up the questionof whetherectoparasites may occasionallysurvive in the environmentof a raptor'sstomach long enoughto be regurgitatedalive in a pellet. Chmielewski(1970) studiedthe passageof astigmaticmites throughthe alimentarycanal of mice, spar- rows,and hens.Survival rates of somespecies varied from 1-7 percent.Survivors in- cludedindividuals of all stagesalthough eggs and restingstages were more resistant. Other parasitesmay alsooccasionally be foundin pellets.Bond (1940) reported Great Horned Owl pelletsin Nevada containingchicken ticks, Argas persicus(Oken); for example,one pellet containeda gopherskull and 42 ticks.Also, roundwormssuch as Porrocaecumand Ascaridiaare sometimesegested with pellets(Cooper 1972). In ad- dition to vertebrateparasites, we have periodicallyfound insect and acarineparasites of other invertebrateson pellets. PelletFlora. Thirteenspecies of fungi were isolatedfrom the pellets(table 3). Oth- er speciesof fungi were observedon the pellets,but culture attemptsfailed. The mostimportant species (as judged by visiblegrowth) are Trichodermasp. and Chry- sosporiumtropicurn Carmichael. Large greenpatches of Trichodermaat timescovered up to 20 percentof the pellet surface.Most pelletshad somesurface growth of Chry- sosporium,and someappeared extremely white as the fungustook over as much as 106 RAPTOR RESEARCH Vol. 13 No. 4

Table 2. Invertebrates from Great Horned Owl Pellets

no. no. of max. no. pellets specimens on one (75) pellet

Prostigmata 73 1,840 156 Collembola 55 884 84 Oribatei 63 369 57 Mesostigmata 53 241 42 Lepidoptera 43 194 22 Astigmata 18 27 6 Coleoptera 14 26 9 Hymenoptera 9 17 6 Gastropoda 9 13 2 Diptera 7 12 2 Isopoda 9 11 2 Homoptera 8 8 1 Araneida 7 8 2 Chilopoda 3 4 2 Thysanoptera 2 4 3 Psocoptera 3 3 1 Diplopoda 1 1 1 Oligochaeta 1 1 1 Pauropoda 1 1 1 Symphyla 1 1 1 Total 3,665

Av. no./pellet 48.87 Mites 67.59% Av. no./g dry wt 9.25 Insects 31.32% Max. no./g dry wt Others 1.09% on one pellet 48.00

Table 3. Fungi from Great Horned Owl Pellets

Alternaria sp. *Aspergillusflayus Link Aspergillusfumigatus Fresenius *Aspergillusniger Van Tieghem Aspergillussp. Chaetomiumsp. Chrysosporiumtropicurn Carmichael * Fusarium roseurn section Paecilomycessp. Rhizopussp. Sporotrichumsp. Trichodermasp.

* speciesnot previouslyreported from pellets Winter 1979 Philips& Dindal--RaptorPellets 107

75 percentof the surface(fig. 4). Chrysosporiumis a keratinophilicfungus which at- tackshair with the aid of penetratingbodies (Carmichael 1962). This genus is com- monon bird feathersand in their nests(Pugh 1966, 1972;Pugh and Evans1970; Ot- cen•igeket al. 1967;Rees 1967; Hub•dek 1974. While Aspergillus fumigatus, the cause of aspergillosisin birds, was found, its occurrencein pelletsdoes not appearto be an unusualsource of infectionsince the fungusis sowidespread.

Summary Pelletsmay serve as a siteof breeding,feeding, and shelter for manyinvertebrates and as a substratefor growthof a varietyof fungi. Someinvertel)rates consume vari- ouspellet componentssuch as the lipidsof hair and featherswhile othersfeed on the fungi.Still otherpredatory or parasitoidinvertebrates are attractedto pelletswhere they afflict someof the "pioneer"invertebrates. Pelletsmay be foundin manyhabitats. They are producedby manyavian and other vertebratespecies, and they differ widely in compositiondepending upon the prey species.For thesereasons pellets are excellentinstructional tools since they illustrate so manyaspects of ecology.Much remains to be learnedabout pellets as habitatsfor microbe and invertebrate microcommunities.

Acknowledgments We thank Jack Gray for allowingus to use two of the owls of the Burnet Park Zoo, Syracuse,and Dr. A. A. Padhyeof the Center for DiseaseControl, Atlanta, Georgia,for identifyingthe fungi.Also, Dr. Roy A. Nortongraciously aided in the identificationof the mite specieswe collected.

Literature Cited Akimov,E. A., and L. E. Shehur.1972. Features of the nutritionof the grainmites Glycyphagusdomesticus (Deg.) and Tyrophagusputrescentiae (Schr.) and the root mite Rhizoglyphusechinopus (Fum. et Rob.)on someproteinoids. (In Rus- sian,English summary). Vestnik Zool. 6(6):45-48. Aubrook,E. W. 1939.Insects bred from owl pellets.Entomol. Mon. Mag. 75:88. Baer, W. 1924. BiologischeBeobachtungen an Kleidermotten.Naturw. Korresp. 2:122-123. Bond,R. M. 1940. Food habitsof hornedowls in the PahranagatValley, Nevada. Condor42(3): 164-165. Brooks,A. 1929. On pelletsof hawksand owls.Condor 31:222-223. Buxton, P. A. 1914. Habit of Tinea rusticella. Entomol. Rec. 26:143. Carmichael,J. W. 1962.Chrysosporium and some other aleuriosporic hyphomycetes. Canadian J. Bot. 40:1137-1174. Chmielewski,W. 1970.The passageof mitesthrough the alimentarycanal of vertebrates.Ekol. Pol. Ser.A. 18(35):741-756. Cooper,J. E. 1972. Hawksand parasites.Hawk Chalk11:31-35. Davis,T. A. W. 1975. Food of the kestrelin winter and early spring.Bird Study 22(2):85-91. Davis,W. T. 1909.Owl pelletsand insects. J. New YorkEntomol. Soc. 17(2):49-51. Dillon,E. S., andL. S. Dillon.1961. A manualof commonbeetles of EasternNorth America.Dover Publications,New York.2 vols.894 pp. 108 RAPTOR RESEARCH Vol. 13 No. 4

Dindal, D. L. 1973a.Microcommunities defined. Pages 2-6 in D. L. Dindal (ed.),Soil Microcommunities I, Proc. First Conf. Nat. Tech. Information Serv. USAEC. CONF-711076,Springfield, Virginia. Dindal, D. L. 1973b. Review of symbioticrelationships in soil invertebrates.Pages 227-256 in D. L. Dindal (ed.), Soil MicrocommunitiesI., Proc. First Conf. Nat. Tech. InformationServ. USAEC. CONF-711076, Springfield,Virginia. Dobrokhotov,B. P., and V. Yu. Litvin. 1971. Radioactivityof pelletsof Falco tinnunculus L. after feeding on mice containingp32. (In Russian,English summary). Zool. Zh. 50:1591-1592. Dobroruka,L. J. 1973. Pellet formationin the Japanesegiant salamander.Int. Zoo. Yrbk. 13:158. Duke, G. E., J. C. Ciganek,and O. A. Evanson.1973. Food consumption and energy, water and nitrogenbudgets in captive Great Horned Owls (Bubovirginianus). Comp.Biochem. Physiol. 44(A):283-292. Duke, G. E., O. A. Evanson,and A. Jegers.1976. Meal to pellet intervalsin 14 speciesof captiveraptors. Comp. Biochem. Physiol. 53(A):1-6. Duke, G. E., A. A. Jegers,G. Loft, and O. A. Evanson.1975. Gastricdigestion in someraptors. Comp. Biochem. Physiol. 50(A):649-656. Elton, C. S. 1966. Thepattern of animal communities.Wiley, New York. 432 pp. Fleay,D. 1968.Nightwatchmen of bushand plain. Taplinger,New York. 163 pp. Forbes,W. T. M. 1923. The Lepidopteraof New York and neighboringstates. Primi- tive forms, Microlepidoptera,Pyraloids, Bombyces. Mem. Cornell Agric. Exp. Sta. No. 68. 729 pp. Glue, D. E. 1973. Owl pellets. Pages193-197 in J. A. Burton (ed.), Owls of the world. E. P. Dutton, New York. Griffin, C. R. 1976. A preliminarycomparison of Texasand ArizonaHarris' Hawks (Parabuteounicinctus) populations. Raptor Res. 10(2):50-54. Hinton, H. E. 1956. The larvae of the speciesof Tineidaeof economicimportance. Bull. Entomol. Res. 47:251-346. Hub51ek,Z. 1974. The distributionpatterns of fungi in free-livingbirds. Acta Sc.Nat. Brno 8(9):1-51. Jellison,W. L. 1939.Sylvatic plague: Studies of predatoryand scavengerbirds in re- lation to its epidemiology.U.S. Public Health Service.Public Health Reports 54:792-798. Joannis,j. de. 1899. Note sur quelquesMicrolepidopt•res dont les chenillesse nour- issentde poilsd'animaux. Bull. Soc.Entomol. Fr. 1899:248-250. Krantz, G. W. 1971. A manual of acarology.Oregon State Univ. Book Stores,Inc., Corvallis,Oregon. 335 pp. Lobachev,V. S., M. E. Levi, and M. M. Levschitz.1971. The preservationof a spe- cific antigenof a plague-causingagent in the foodpellets of predatorybirds. (In Russian,English summary). Zool. Zh. 50:1593-1595. Lobachev, V. S., and G. Shenbrot. 1974. Food of the Little Owl in the North Aral Seaarea. (In Russian).Ornitologiya 11:382-390. Long, C. A., and W. C. Kerfoot.1963. Mammalianremains from owl-pelletsin east- ern Wyoming.]. Mammal. 44(1):129-131. Lutz, F. E. 1948. Field bookof insects.G. P. Putnam'sSons, New York. 510 pp. Marti, C. D. 1974. Feedingecology of four sympatricowls. Condor 76(1):45-61. Winter 1979 Philipsand Dindal--RaptorPellets 109

Meinertzhagen,R. 1959.Pirates and predators.Oliver and Boyd,London. 230 pp. Menzies,J. D. 1965. Fungi. Pages1502-1505 in C. A. Black (ed.), Methodsof soil analysis.Part 2. Am. Soc.Agronomy Inc., Madison,Wisconsin. Moon, E. L. 1940. Noteson hawk and owl pellet formationand identification.Trans. Kansas Acad. Sci. 43:457-466. Morton, S. R., M. Happold, A. K. Lee, and R. E. MacMillan. 1977. The diet of the barn owl, Tyto alba, in southwesternQueensland. Australian Wildl. Res. 4:91-97. Nurse,C. G. 1906. Food of Monopisrusticella. Entomologist 39:160. Otcenfigek,M., K. Hudec, Z. Hub•ilek,and J. Dvor•ik. 1967. Keratinophilicfungi from the nests of birds in Czechoslovakia. Sabouradia 5:350-354. Peterson,A. 1960. Larvae of insects.Part 2. EdwardsBros., Ann Arbor, Michigan. 416 pp. Prestt,I., and R. Wagstaffe.1973. Barn and bay owls. Pages42-60 in J. A. Burton, (ed.), Owls of the world. E. P. Dutton, New York. Pugh, G. J. F. 1966. Associationsbetween birds' nests,their pH, and keratinophilic fungi. Sabouradia5:49-53. __. 1972. The contaminationof birds' feathersby fungi. Ibis 114:172-177. Pugh, G. J. F., and M. D. Evans.1970. Keratinophilicfungi associatedwith birds. I. Fungi isolated from feathers, nests, and soils. Trans. British Mycol. Soc. 54(2):233-240. Ramsay, G. W. 1970. Mites with phoretic nematodes. New Zealand Entomol. 4(4):91-92. Rees,R. G. 1967. Keratinophilicfungi from Queensland.II. Isolationfrom feathersof wild birds. Sabouradia 6:14-18. Simmons,G. E. 1971. Patternsof life in woodlandcommunities. 8. Bird pellets.Quar- terly J. Forestry.65:224-231. 1973. The studyof bird pellets.Country Side 22:116-122. Sixl, W. 1971. Ein Beitrag zur Kenntnisder Phoresie.Mitt. naturwiss.Ver. Steiero mark. 100:405-406. Smith,C. R., and M. E. Richmond.1972. Factorsinfluencing pellet egestionand gas- tric pH in the Barn Owl. WilsonBull. 84:179-186. Tucker,B. W. 1944. The ejectionof pelletsby passerineand otherbirds. British Birds 38:50-52. Vaurie, P. 1955. A revisionof the genusTrox in North America (Coleoptera,Scara- baeidae).Bull. AmericanMus. Nat. Hist. 106(1):1-89. Vernon,C. J. 1972. An analysisof owl pelletscollected in southernAfrica. Ostrich 43:109-124. Wallace, G. J. 1948. The Barn Owl in Michigan.Its distribution,natural historyand foodhabits. Michigan State Coil. Agric. Exp. Sta. Tech. Bull. 208.61 pp. Watling, R. 1962.Fungal succession on kestrelpellets. Naturalist 41-43. Watling, R. 1963. The fungal successionon hawk pellets.Trans. British Mycol. Soc. 46(1):81-90. Wilson,K. A. 1938. Owl studiesat Ann Arbor, Michigan.Auk 55:187-197. 110 RAPTOR RESEARCH Vol. 13 No. 4

DECOMPOColTION R.ATE$ o/' GREATNOR. NED OWL PELLET9

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Figure 1. Decompositionrate of Oreat HornedOwl pellets.

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Fibre [. La•a 0½clothes moth, Ti•eidae (headcapsule •dicat• by arrow). Winter 1979 Philipsand Dindal--RaptorPellets 111

Figure3. Phoreticnematodes (indicated by arrows)attached to mesostigmaticmite Macrochelespenicilli- g•'.

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Figure4. Growthof the white keratinophilicfungus, Chrysosporium tropicurn, on surfaceof decomposing Great HornedOwl pellet.