Pacific Science (1982), vol. 36, no. 4 © 1983 by the University of Hawaii Press. All rights reserved Status and Distribution of Ants In The Crater District of Haleakala National Park! JOAN H. FELLERS 2 and GARY M. FELLERS 3 ABSTRACT: The Crater District ofHaleakala National Park was surveyed for ants. Three species were found. Argentine ants (Iridomyrmex humilis) occurred only within I km of the park headquarters and the nearby research facility. Hypoponera opaciceps was found in small numbers throughout the Crater District. Cardiocondyla emeryi was present only at the head of Kaupo Gap. Possible impacts ofthese ant species on the endemic, flightless insects ofthe park are discussed. THREE SPECIES OF ANTS have become estab­ populations now established in Africa, Aus­ lished in the Crater District of Haleakala tralia, Europe, South America, and North National Park: Iridomyrmex humilis (Mayr) America. The ants became established on (the Argentine ant), Hypoponera opaciceps Oahu, Hawaii, in 1940 (Zimmerman 1941), (Mayr), and Cardiocondyla emeryi (Forel). and by 1950 they had begun to invade other The Argentine ant and H. opaciceps were islands. By the early 1960s the Argentine ant known previously from the park (Beardsley had been reported on all of the six main 1980). The presence of C. emeryi, however, is islands except Molokai. (See review of per­ first reported in this paper. tinent literature by Wilson and Taylor 1967.) The primary purpose of this study was to Argentine ants are voracious feeders and determine the range of the Argentine ant consume a wide range of foods including within the Crater District of the park and honeydew, carrion, and other insects. They to assess the potential impact of this species can be very effective predators on small in­ on the endemic, flightless insects inhabiting sects, particularly those with low mobility. In the crater (e.g., flightless carabid beetles, lace­ addition, by monopolizing a high proportion wings, moths, and flies; see Beardsley 1980). of suitable cover objects (rocks, logs, etc.), During this survey, information was also the ants may prevent other insects from using gathered on the distributions of Hypoponera these items for refuge and thus may have a opaciceps and Cardiocondyla emeryi. The pos­ significant negative impact on invertebrate sible threat posed by these ant species to the populations. In the Solomon Islands another endemic insects was evaluated. species ofIridomyrmex (I. cordatus Fr. Smith) The Argentine ant is native to Argentina. has been shown to eliminate all potential prey, With the inadvertent assistance of humans, i.e., other insects and invertebrates, from the Argentine ants have spread throughout the immediate vicinity of their colony (Green­ northern and southern temperate zones, with slade 1972). The Argentine ant may have a similar effect, although this has not been ade- quately documented. The Argentine ant reaches extremely high I The research reported herein was supported by National Park Service Contract No. CX-8000-0-0005 and densities in many areas (Heer 1892 in Wheeler is Contribution No. CPSUjUH-036, Technical Report 1910, Tremper 1975). The high population 40. Manuscript accepted 10 June 1982. density of Argentine ants, as well as their 2 Sonoma State University, Department of Biological very aggressive nature towards other inverte­ Sciences, Rohnert Park, California 94928. Send reprint requests to Gary M. Fellers. brates, makes them exceedingly effective com- 3 Point Reyes National Seashore, Point Reyes, petitors. Where Argentine ants are abundant California 94956. they monopolize food sources, foraging areas, 427 428 PACIFIC SCIENCE, Volume 36, October 1982 and nest sites, and may eliminate all other ants cover-item transect consisted of 50 rocks that from the area. This replacement has been well­ appeared to provide suitable cover. When documented in Hawaii (Fluker and Beardsley ants were located under a rock, we recorded 1970), Bermuda (Haskins and Haskins 1965; whether only a few workers or a colony were Crowell 1968; Lieberburg, Kranz, and Seip present. If there was a colony, we also noted 1975), and California (Tremper 1975). the presence of any reproductives or brood. The inadvertent introduction ofthe Argen­ The second census method involved a com­ tine ant into Haleakala National Park has bination of bait transects and cover rocks. serious implications for the native inverte­ The baiting was designed primarily to locate brate fauna ofthe park. The endemic flightless workers and to estimate their density. At each insects found in the crater region ofHaleakala bait location a small portion of honey and are particularly vulnerable to predation and liver pate was placed on a white file card cut displacement by Argentine ants. IfArgentine to approximately 6.5 x 7.5 em. The use of ants become well-established in the crater, file cards does not interfere with ant activity they could conceivably cause the extinction (Fellers 1977) and greatly facilitates the re­ of these unique forms (Beardsley 1980: 7-9). location ofbaits and the counting of ants. Dense populations of the Argentine ant now Bait transects consisted of50 baits set out in occur in the vicinity ofthe park headquarters. two parallel rows of25 each. Baits were placed This paper reports the extent of the ant's approximately 2 m apart. Baits were left in range within the park and evaluates the threat place for 40 min after which we collected them posed to endemic insects living in the crater and recorded the number of ants present. itself. At each baiting locality we also turned The habits of the other two ant species 25 suitable cover objects. This additional found in the park, H. opaciceps and C. emeryi, census technique provided a means of direct are less well known than those of the Argen­ comparison between bait and cover-item tine ant. Hypoponera opaciceps is a very wide­ transects. spread species occurring on many islands Ateach locality (sampled by either method) of the South Pacific including the six main we recorded air temperature in the shade, Hawaiian Islands. The species probably origi­ ground temperature in both the sun and the nated in the New World where it is common shade, general vegetation type, major plant from the southern United States to Uruguay species present, general soil description, qual­ (Wilson and Taylor 1967). itative description ofsoil moisture, slope, and Cardiocondyla emeryi is native to India relative abundance of suitable cover items. (Wilson and Taylor 1967) but has been widely For a more detailed description ofthe tran­ distributed by human commerce and is now sect methods, see Fellers and Fellers (1981). found on many islands in the Pacific region. In Hawaii C. emeryi has been reported from Transect Placement the six largest islands where it is abundant at lower elevations with relatively little rainfall During the study 56 transects were con­ (Huddleston and Fluker 1968). The species ducted, 32 cover-item transects (R-I-R-32) was not known previously from Haleakala and 24 bait transects (1-24), for a total cover­ National Park. age of2200 rocks and 1200 baits (Figure 1). Twenty-one of the bait transects were con­ ducted along or near Haleakala Highway (Route 378). Transects were conducted at METHODS 200-foot intervals along the road, in eleva­ Transect Methods tions from 6800 up to 8200 ft. Above 8200 ft transects were spaced at 400-ft intervals up to We employed two techniques to census 9800 ft. Three additional roadside localities ants: (1) turning cover items to locate colo­ (2, 5, and 6) were added later in areas ofparti­ nies and (2) using baits to attract workers. A cular interest. Bait transects were also con- ;l> ::l fZ S' :I: Pl ii" Pl HALEAKALA NATIONAL PARK :>;" Pl CRATER DISTRICT S; I "T:I m t'" ~~;t~:' .~.~-_. Wolk~u t'" \ - -., ,,- "_. Cobin m ; ~ :>:l ./;' ./ ••r.......",,-<?i. ·..-'.....i en . ". II f (:>"r'--..,. \ ~~"n l 15 .. ' .• > ~ ~'C'~ oZ • ,.. ".~\'" '--~7~--- .," ,,~ ~.'~,,' ~~, ) "T:I '7 .• 1. '-'r: ... ,._ "~ ~~,~ ~, m f. ",~ ~ ".""0 , r•• __ __--:;->-,, ~ " "'~d' 'KOIO o(~ "\.--. ...;;::"~!~~ObOO 7200~,'" ,f,. '" ,\ .../".... ",- Mlqqnu\,>/, !:l '~.:. en "'\ -""', Poliku CO.b on " ~~:~{,~I.f+j;"~7. r"~~;:'J:(2·5""''''''',,·------~t·I·;~..r~f~)"-'W>! , ~Q, \ '(?""', '" , """" 'l,0\ ....~ o r /"""""1,,'_,__..,' .!----' of'," --------"'1~__ \,.y --'" .,~.~f~Vl _J.L--i;-~i-----~~! '\ ... • .r ~~5600• <P ~~/.ii~'V:-1'- \1\\".,l ... L·..-....... ,. ~- '. • --~~c,~_J( ._ ,Ill, ' ~';;" ""'s..~_=~"~---"""-'-" ~.-,_.v-~'1:~/--" ~ ,-_. .- .~ .-.r-~.-r:;:..~I'-_-' 0 • 1100 ~ir,·--~ 6400 '=-~ 400 ,_ .' 1200 FIGURE I. Map ofHaleakala National Park showing locations oftransects. The inset is an enlargement ofthe area around the park headquarters (labeled Ranger Station). Circles 1-24 indicate locations ofbait transects. Squares 1-32 indicate localities for cover-item transects (referred to as localities R-I through R-32 in the text). ~ 430 PACIFIC SCIENCE, Volume 36, October 1982 TABLE I ARGENTINE ANTS FOUND AT BAIT TRANSECTS ELEVATION NO. %BAITS %ROCKS LOCALITY (ft) ANTS OCCUPIED OCCUPIED REPRODUCTIVE INDEX· I 6800 2315 100 56 50 2 6900 2980 100 84 19 3 6960 1062 96 16 25 4 7000 2750 100 84 57 5 7080 2430 100 80 50 6 7140 17 16 8 0 7 6700 6085 100 68 24 8-24 6600-9800 0 0 0 0 • Percentage ofrocks that harbored Argentine ants where reproductives and/or brood were present. ducted at the three cabins within the crater: TABLE 2 Kapalaoa, Paliku, and Holua. ARGENTINE ANTS FOUND AT COVER-ITEM TRANSECTS Cover-item transects were carried out at 18 sites within the crater. We spaced these tran­ ELEVATION %ROCKS REPRODUCTIVE sects fairly evenly through habitat with at LOCALITY (ft) OCCUPIED INDEX· least some vegetation and appropriate cover. Fourteen cover-item transects were also con­ R-19 6780 70 40 R-20 6760 2 0 ducted near Hosmer Grove and on the lower R-24 6430 52 27 slope ofHaleakala below the park boundary.