The Giant Nests of the African Stink Ant Paltothyreus tarsatus (Formicidae, Ponerinae) Author(s): Ulrich Braun, Christian Peeters and Bert Holldobler Source: Biotropica, Vol. 26, No. 3 (Sep., 1994), pp. 308-311 Published by: The Association for Tropical Biology and Conservation Stable URL: http://www.jstor.org/stable/2388852 . Accessed: 28/11/2013 01:48 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 This content downloaded from 134.157.146.58 on Thu, 28 Nov 2013 01:48:10 AM All use subject to JSTOR Terms and Conditions BIOTROPICA 26(3): 308-311 1994 The Giant Nests of the AfricanStink Ant Paltothyreustarsatus (Formicidae, Ponerinae)1 UlrichBraun, Christian Peeters2, and Bert Holidobler Theodor-Boveri-Institut,Lehrstuhl Verhaltensphysiologie und Soziobiologie der Universitat,Am Hubland, D-97074 Wurzburg,Germany ABSTRACT Fourteennests of the ponerineant Paltothyreustarsatus were excavated in Kenya and in the IvoryCoast. All colonies containedonly one mated queen. The workerpopulation varied markedlybetween colonies, reaching 2444 adults in one case. Nests consistedof manychambers located 30 cm to morethan 150 cm belowthe surface. The construction and arrangementof the chamberswere not particularlyelaborate, but the associatedhorizontal tunnel system (5-15 cm below the surface)was mostremarkable. In one nest,over 130 m of shallowsubterranean tunnels were uncovered. An area of 1200 m2 was coveredby the tunnelsystem of anothernest. Through multiple tunnel exits the ants are able to reachalmost any spot in theirforaging area. In some nestswe founda secondhorizontal tunnel system, 50- 80 cm below the surface,which connected nest chambers several meters apart. Keywords: ants;foraging; monogyny; nests; Paltothyreus; Ponerinae; polydomy; queen; reproduction. PALTOTHYREUS TARSATUS, a memberof the ant sub- galleriesby gentledigging with a trowel.A consid- familyPonerinae, is widelydistributed throughout erableamount of clearing was oftenrequired in order Africasouth of the Sahara (Wheeler 1922). It is a to proceed;branches and rootswere cut and ground hunterand a scavenger.Although the workers for- litterwas removed.Once large concentrationsof age individually,they can recruitnestmates with workerswere found, vertical digging proceeded. The chemicalsignals when retrieving large or more abun- excavatedtunnels were leftuncovered, and over- dant preyitems (H6lldobler 1984). The nestsof nightdigging activity by the ants led to thedetection P. tarsatusare built in thesoil. As notedin previous of many side tunnels.The lengthsof the tunnels fieldstudies, they have multipleentrances, and ma- weremeasured between intersections. The number turecolonies occupy rather large surface areas (Le- and locationof exitholes were not recordedin this vieux 1965; Kalule-Sabiiti& Banage 1977; H611- colony.Another ten colonieswere collectedin the dobler 1980, 1984; Dejean et al. 1993). In the National Park of the Comoe in the Ivory Coast courseof continuing ecological investigations of Pal- duringAugust 1992 and February-May1993. tothyreuswe have found that theirnests can be substantiallybigger in areaand morepopulous than previouslythought. RESULTS Paltothyreustarsatus colonies nest primarily in for- MATERIALS AND METHODS estedareas, but also in the transitionzone between forestand savanna.Our mostdetailed data on nest We excavateda total of 14 nests. Four colonies structurewere obtained from two colonies in Kenya. werecollected in the Shimba Hills Reserve(Kwale In one colony (August 1978), we especiallyex- district,south of Mombasa, Kenya); threeduring aminedthe tunnel system in the "core area" where July-August1978 and one duringMay 1991. The most of the brood and the queen were collected latterin particularwas verythoroughly dug out by (Figs. 1 and 2). There were about 25 exit holes two personsover 4 days (>40 man-hours)and leadingeither to tunnels5-15 cm belowthe surface, unexploredtunnels still remained. We began at an or directlyto the inhabitedchambers. The latter activeentrance, and followedthe shallowforaging werealso connectedtogether by subterraneangal- leries(Fig. 2). The core area could be recognized by the crater-shapednest entrancesand the con- I Received 19 March 1993, revisionaccepted 4 October 1993. spicuousmounds of soil and refusepiles (containing preyand cocoonremains); this was not the case in 2 Presentaddress: CNRS URA 667, Laboratoired'Etho- logie Experimentaleet Comparee,Universite Paris Nord, all colonies.The majorityof thenest chambers were F-93430 Villetaneuse,France. located 30-150 cm below the surface.The larger 308 This content downloaded from 134.157.146.58 on Thu, 28 Nov 2013 01:48:10 AM All use subject to JSTOR Terms and Conditions The Giant Nests of the AfricanStink Ant 309 Im FIGURE 2. Verticalsection through the central cham- bersand connecting galleries of a P. tarsatusnest (Kenya; August1978). This drawing is basedon numerousfield 1m sketchesand photographs taken during the excavation. FIGURE 1. Corearea of a P. tarsatus nest(Kenya; This mayexplain why so fewbrood were collected, August1978), showing the funnel-shaped entrances sur- roundedby mounds of soil and refusepiles. The under- especiallycocoons (although one cocoonwas carried groundtunnels leading to theforaging grounds are also bya workeralong a foraginggallery, indicating that indicated,together with exit holes. theywere present at thistime of the year). Two additionalnests excavated in July 1978 also yieldedonly one inseminatedqueen foreach chambers,measuring approximately 25 x 5 x 5 colony;the numbers of workerswere 392 and 446, cm, were foundcloser to the surface(ca 30-100 respectively.In both cases, however,we were not cm depth),the smallerchambers (4 x 3 x 1 cm) yetfamiliar with the complexity of the architecture weremostly located at a depthof 100-150 cm. In ofPaltothyreus nests, and it is thereforepossible that thisparticular nest we identifiedmore than 40 in- we did not uncoverother major parts of the nests. habitedchambers. We collectedfrom those cham- Our excavationsof ten P. tarsatusnests in the bers,from adjacent galleries and on the surface,a IvoryCoast (1992 and 1993) revealeda similar totalof 1 dealate queen, 916 workers,82 larvae, organizationas foundin Kenya.The sizeof thenest 45 pupae, 4 males, and 1 alate queen. We con- populationsvaried greatly (Table 1), suggestingthat firmedby dissectionthat the dealate queen was some colonieswere younger, while others may have inseminated.Despite our intensiveefforts we prob- been collectedincompletely. One colonyexcavated ably did not uncoverall nest chambers,missing especiallymore alate queens and males. As previ- ouslynoted (H6lldobler 1980, 1984) an extensive systemof shallowtunnels led fromthe nestcham- .~~~~ bersto the surroundingforaging grounds (Fig. 1). In a second colonyfrom Shimba Hills (May 1991), we aimed to revealthe entirenetwork of shallowtunnels (Fig. 3). The excavationstarted in an open, grassyarea, but the galleriessoon led to twodifferent forested areas. Over 130 m offoraging gallerieswere uncovered.This excavationrevealed thatone colonycan be distributedinto several nest- ing sites,labelled A, E, and F (Fig. 3). In A, where Sm chambersreached deeper than elsewhere,we col- lected518 workers,20 larvae,6 eggs,and I dealate queen (also inseminated);there were 208 workers FIGURE 3. The subterraneantunnel system of a P. tarsatus tunnels and 2 larvaein and 77 workersin F. In addition nest(Kenya; May 1991). Onlyshallow E, are indicated(5-10 cm belowthe surface). The arrow we caught 102 workerswalking along the uncov- indicatesthe spot where the excavation began. A, F, and eredforaging galleries. Thus a totalof 905 workers E arethe locations of deep chambers where workers and werecollected throughout the rangeof thiscolony. broodwere collected. Many workers were also found above Howeverwe wereunable to followall the foraging groundaround B and C. Stippledareas indicate forest and thicketvegetation; clear area represents grassland. galleries,or to excavatedeep chamberscompletely. This content downloaded from 134.157.146.58 on Thu, 28 Nov 2013 01:48:10 AM All use subject to JSTOR Terms and Conditions 310 Braun, Peeters, and Holidobler TABLE 1. Demographicdata from10 nestsof Paltothyreustarsatus excavated in theIvory Coast. Dealate Alate Nest queen queens Males Workers Cocoons Larvae Eggs Aug. 1992 1 0 0 385 499 458 218 Aug. 1992 1 0 0 157 120 7 35 Aug. 1992 1 59 0 247 68 91 19 Aug. 1992 1 73 5 688 764 241 0 Aug. 1992 1 36 0 377 30 164 0 Feb. 1993 1 0 0 1552 94 1376 208 Feb. 1993 1 466 696 1191 444 129 945 Feb. 1993 1 408 131 1522 166 2016 139 April 1993 0 0 0 2444 1118 2789 177 May 1993 0 0 0 692 580 915 163 in April1993 wasconsiderably larger (numbers of specialcase of polydomy.Based on thesenew find- adultworkers, cocoons and larvae).In all colonies, ings,we have to considerthe possibilitythat some however,we foundonly one dealate queen. In four of the nests(10 to 20 m apart) whichH6lldobler