Food Resources of Anteaters (Edentata: Myrmecophagidae) I. A Year's Census of Arboreal Nests of Ants and Termites on Barro Colorado Island, Panama Canal Zone Author(s): Yael D. Lubin, G. Gene Montgomery and Orrey P. Young Reviewed work(s): Source: Biotropica, Vol. 9, No. 1 (Mar., 1977), pp. 26-34 Published by: The Association for Tropical Biology and Conservation Stable URL: http://www.jstor.org/stable/2387856 . Accessed: 30/09/2012 22:16 Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at . http://www.jstor.org/page/info/about/policies/terms.jsp . JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact [email protected]. The Association for Tropical Biology and Conservation is collaborating with JSTOR to digitize, preserve and extend access to Biotropica. http://www.jstor.org Food Resources of Anteaters (Edentata: Myrmecophagidae) 1. A Year's Census of Arboreal Nests of Ants and Termites on Barro Colorado Island, Panama Canal Zone Yael D. Lubin Smithsonian Tropical Research Institute, P. 0. Box 2072, Balboa, Canal Zone G. Gene Montgomery' National Zoological Park, Smithsonian Institution,Washington, D.C. 20009, U.S.A. and Orrey P. Young Department of Zoology, Universityof Maryland, College Park, Maryland 20742, U.S.A. ABSTRACT Arboreal carton nests of four speces of termites(Nasutitermes corniger, N. columbicus, N. nigriceps,and Microcero- termes exiguus) and of ants (genus Azteca) were monitoredperiodically for one year on Barro Colorado Island, Pan- ama Canal Zone. The nests were examined for signs of damage, new growth,and nest abandonment.Nest damage was attributableto predation by anteaters (Tamandua tetradactyla),to nestingactivities of birds, or to unknown causes. Nest damage due to anteaterpredation occurred frequently, but rarelyresulted in destructionof the nest. Small nestsof Micro- cerotermestermites were most prone to anteater damage, while large nestsof Nasutitermestermites suffered more dam- age from nestingbirds. Azteca ant nests were attackedby anteaters,but not by nestingbirds. Fewer Azteca neststhan ter- mite nests showed signs of predation during the year's census, with 37 percent of the ant nests damaged as compared with 91 percentof the termitenests. There were few instancesof multipledamage to ant nests,while 60 percentof ter- mite nests were damaged two or more times. No Azteca ant nestswere abandoned during the census, but 16 percentof termitenests were; most abandonmentsfollowed tree or nest-falls.The significanceof predationon nests by anteaters and of nest damage by nestingbirds is discussedin relation to seasonality,nest longevity,nest defense,and anteaterfeed- ing behavior. The census data and estimatesof the daily attack rates of anteaterson termiteand Azteca ant nests are used to estimate the impact of anteaterson these nests, and population densitiesof anteaters. SEVERAL SPECIES of arboreallynesting termites, and griceps (Haldeman), and Microcerotermesexiguus antsof the genusAzteca (Dolichoderinae),may be (Hagen). All fourspecies were utilized as preyby importantfood resources for banded anteaters(Ta- bandedanteaters. Sixteen of thesixty-one nests cen- mranduatetradct-yla) in lowlandmonsoon forest on susedwere not identifiedto speciesbecause samples BarroColorado Island, Panama (BCI). Arborealnests of thetermites were not obtained. of bothtermites and Aztecaants which wild, radio- Nasutitermesnests (table 1) were all arboreal markedanteaters encountered on BCI wereattacked and were medium-to-largesize (over 20 cm diam- infrequently,although insects in such nests could eter), while those of Mlicroceroternizeswere pre- providean abundantand nutritionallyimportant food dominandysmall (under 20 cm diameter), and were source (Montgomeryand Lubin,in press). When at ground level or relatively low on stumps or attacksoccurred, damage to nestsranged from very branches (fig. 1 ). Both typesof nests are within the slightto severe,but in no instancewas a nestcom- verticalforaging range of banded anteaters.N. corni- pletelydestroyed. The censusreported here was de- ger and AM.exiguus were the most common species in signedto monitordamage to a sampleof Aztecaand the census. Nests of M. exiguus rarely grow larger termitenests in an area of the forestused by ant- than 30-40 cm diameter.Small nests of N. corniger eaters.Other gross morphological changes in nests, must surely exist, but, because nests of this species suchas new growthand repairsor abandonmentof are generallyfound higher in the trees,small nests nests,were also monitored. may have been overlooked.All nests were composed of "carton,"a substance derived from chewed wood THE NESTS mixed with fecal material. Microcerotermes nests, to include some clay TERMITES: We censusednests of fourspecies of ter- however,sometimes appeared mitesof thefamily Termitidae: Nasutitermes corniger and were harder and more dense than Nasutitermes (Motschulsky),N. columbicus(Holmgren), N. ni- nests. ANTS (Azteca spp.): All Azteca nestscensused were l Presentaddress: SmithsonianTropical Research Institute, P.O. Box 2072, Balboa, Canal Zone. arboreal, and composed of a papery substance de- 26 BIOTROPICA 9(1): 26-34 1977 rived fromchewed wood. The cartonmaterial of of Azteca rangedfrom 1-20 metersabove ground Azteca nestsis lightcolored, soft on the outsideof (mean 7.9 m, n 19). The nestswere from 30 thenest, and morecompact toward the center. Nests cm to 2 meterslong, eitherconical in shape and hangingfrom a limbor trunk(fig. 2), or flattened 8I againstthe side of a verticaltree-trunk. Nests were oftenclumped, and bothconical and flattenednests 6 Nosutitermescorniger could be foundwithin a singleclump. Azteca are 16nests. 'I 7.4 meters difficultto identifyto species,so specimensfrom eachnest are deposited with the senior author (Y. L.) for futureidentification. 0t METHODS 0- 3- 6- 9- 12- 15- CENSUSING TECHNIQUES: Thirty-fivetermite nests 3 6 9 12 15 18 and fifteennests of Aztecaants were mapped on 31 March 1974 on BCI, and examinedapproximately everytwo weeksuntil 23 April 1975. A finalcheck of the nestswas made in July1975. New nests,or that notbeen noticed previously, were later w nests had z 14- included.Other nests that became obscured by vege- tationor thatfell and were abandonedduring the 0 12 6 Microcerotermesexzguus courseof thecensus were omitted, so thatthe num- ber of nestsmonitored varied from census to census. 61O 22 nests. : 2.2 meters The nestswere located along a 1.8 km circularroute throuighthe forest,and were generallywithin 20 z metersof thepath. Not all nestsalong this route were includedin the census,because many were obsctured 6- by treesand lianas.The nestswere checked for signs of recentdamage (holes, scrapes,or missingsec- 4- tions),and forpatches of new growthor rep-airsto 82 3 6 5 1 the nest.Termite nests that fell duringthe census 2 periodwere monitoreduntil the occupantsdied or vacated the nest. All termitenests were checked 0- occasionallyto determineif thenests were still active, 0- 3- 6- 9- 12- 15- usuallyby breakingtrails which led to thenest. Ac- tivityof Aztecanests was gaugedby the numbersof 3 6 9 12 15 18 ants movingup and down the tree-trunks. The censusmethod was non-destructive,and pro- METERS ABOVE GROUND vided informationon major morphologicalchanges FIGURE 1. Frequencydistribution of heights of censused occurringin a sampleof nestsduring one year.The nests of Nasutitermescorniger and Microcero- accuracyof censusingdiffered for ant and termite termesexigmus. nests.Damage to Aztecanests was conspicuous,and TABLE 1. List of termitespecies censused and some characteristicsof theirnests. Nests sizes are: S = small (less than 20 cm diameter); M medium (20-50 cm diameter); and, L = large (greater than 50 cm diameter). No. Species nests S M L Nest type Nasutitermescorniger 16 0 37.5 62.5 arboreal, carton,hard surface N. columbicus 3 0 66.6 33.3 arboreal, carton,hard surface N. nigriceps 2 0 0 100 arboreal, carton, thin papery surface,hard inside Nasutitermessp. 1 0 0 100 arboreal, carton Microcerotermesexiguus 23 78.3 21.7 0 tree bases or arboreal,carton (+ clay), surface with papillae-like extensions Food Resources of Anteaters 27 could not distinguishholes made by trogonsfrom thosemade by puffbirdsand parakeets.In the analy- sis theseare groupedtogether under the categoryof bird damage.The birdsmay begin several holes and abandonthem before settling in a good nestingsite. Because of this habit,more termitenests may be dcamagedthan are used for nests.It is sometimes possibleto distinguishbird nest-holesfrom anteater damageto a nest,since completed holes are circular, 8-12 cm in diameter,and extenddeep intothe nest. Smallcavities or scrapemarks, however, could be due to eitherexploratory digging by birdsor small-scale attacksby anteaters. All damageto Azteca nests,ranging from small scrapesto destructionof one-thirdof the nest,was includedin the categoryof anteaterdamage. Only thoseincidents of damageto termitenests that were dearlydue to anteaters,such as visibleclaw marks or large irregularpieces of the nestremoved, were includedin thiscategory. Thus, nest damage by ant- eatersmay have been underestimatedfor term,ite nests. Euglossinebees (Apidae) also burrowin termite nests (Zucchi,et al. 1969), makingholes which are