348
BIOTROPICA 34(3): 348?356 2002
Seasonal Foraging Activity and Bait Preferences of Ants
on Barro Colorado Island, Panama1
Daniel A. Hahn2
Interdisciplinary Program in Insect Science, University of Arizona, Tucson, Arizona 85721, U.S.A.
and
Diana E. Wheeler
Department of Entomology, University of Arizona, Tucson, Arizona 85721, U.S.A.
ABSTRACT
A yearlong arboreal baiting survey of ants was conducted during 1983 on Barro Colorado Island, Panama. Because
of a severe El Nin?o event, the 1983 dry season in Panama was exceptionally long and dry with a distinct boundary
between the dry and wet seasons. Baits, located on tree trunks, attracted both terrestrial and arboreal ants, allowing
comparisons between the two groups. Species composition at baits changed dramatically with season. Baits were
primarily occupied by arboreal species during the dry season, while wet season baits were occupied mostly by terrestrial
species. Arboreal and terrestrial ants differed markedly in their preferences for protein- or carbohydrate-based baits;
arboreal ants preferred protein-based baits and terrestrial ants preferred carbohydrate-based baits. Foraging preference
for protein suggests that protein resources were limiting for arboreal ants, particularly during the dry season, and that
carbohydrate resources were limiting for terrestrial ants. Fundamental differences in arboreal and terrestrial habitats
may promote the differences in foraging strategies observed during an annual cycle in a seasonal tropical forest.
RESUMEN
Durante el an?o de 1983 se realizo? un estudio mirmecolo?gico en la isla de Barro Colorado, Panama?. Debido a que
el feno?meno``El Nin?o'' fue muy severo ese an?o, la estacio?n seca fue excepcionalmente intensa y larga; adema?s, se
observo? una diferencia marcada entre la estacio?n seca y la hu?meda. Se colocaron cebos en los troncos de los a?rboles
que atrajeron hormigas terrestres y arbo?reas, lo que permitio? la comparacio?n de estos dos grupos. La composicio?n
de las especies atraidas por los cebos vario? notablemente de acuerdo a la temporada; durante la estacio?n seca
predominaron las especies arbo?reas, mientras que en la hu?meda predominaron las terrestres. Las hormigas arbo?reas
y las terrestres di?rieron notablemente en su preferencias por cebos preparados con proteinas o carbohidratos. Las
hormigas arbo?reas pre?rieron las proteinas, mientras que las terrestres pre?rieron los carbohidratos. La inclinacio?n
por proteinas sugiere que e?stas son un recurso limitante para las hormigas arbo?reas, particularmente durante la
estacio?n seca; mientras que los carbohidratos lo son para las hormigas terrestres. Las diferencias fundamentales entre
los ambientes arbo?reo y terrestre puede promover diferencias en las estrategias de forrajeo observadas durante el
ciclo anual del bosque tropical.
Key words: ants; bait preferences; Barro Colorado Island; El Nin?o; foraging; forest canopy; Panama; seasonality.
ANTS ARE A MAJOR COMPONENT OF TROPICAL FORESTS
and play an important role in structuring biotic
interactions (Ho?lldobler & Wilson 1990, Tobin
1991, Davidson 1997). Tropical ant communities
can be divided into arboreal and terrestrial assem-
blages. The arboreal habitat, dominated by tree
crowns, and the terrestrial habitat, dominated by
leaf litter, differ markedly in their physical structure
and local climates (Andersen 2000, Yanoviak &
Kaspari 2000).
Tropical litter ant assemblages are generally
1 Received 24 May 2001; revision accepted 27 February
2002.
2 Corresponding author; e-mail: dhahn@u.arizona.edu
made up of many opportunistic, behaviorally sub-
ordinate species with small- to medium-sized col-
onies (Levings & Trainello 1981, Levings 1983,
Jackson 1984, Andersen 2000, Yanoviak & Kaspari
2000). In the Neotropics, mortality during dis-
persal and abiotic factors such as desiccation stress
and disturbance appear to have the greatest effect
on terrestrial ant assemblages, with competition
and dominance interactions playing a lesser role
(Majer 1976a, b, c; Leston 1978; Levings and Trai-
nello 1981; Levings 1983; Jackson 1984; Kaspari
1993; Byrne 1994; Andersen 2000).
Conversely, canopy ant communities are pop-
ulated by aggressive, numerically dominant species
that from a mosaic of territories (Room 1971; Les-
Ant Foraging Activity 349
ton 1978; Majer 1976a, b, c; Levings & Trainello
1981; Jackson 1984; Longino & Nadkarni 1990;
Andersen 2000; Yanoviak & Kaspari 2000). Thus,
competition is a major force structuring canopy ant
communities, and abiotic factors are less important
in structuring canopy assemblages than those in the
litter assemblage (Andersen 2000, Yanoviak & Kas-
pari 2000).
We studied the activity of ants at carbohydrate-
and protein-based baits on Barro Colorado Island
(BCI), Panama, through one seasonal cycle during
1982?1983. BCI is a tropical moist forest island
located in the Lake Gatun portion of the Panama
Canal (Holdridge et al. 1971). Rainfall patterns on
BCI have a strongly seasonal component with most
rain falling during an annual wet season, usually
from May to December (Rand & Rand 1982). The
phenology of many species of plants and animals
on BCI have been documented and seem to rely
closely on a number of biotic and abiotic factors
associated with these seasons (Leigh et al. 1982).
Our ?rst goal was to determine if the foraging
activity of arboreal and terrestrial assemblages on
tree trunks changed between the dry and wet sea-
sons. Microclimate, particularly moisture and tem-
perature, has been identi?ed as the main abiotic
force governing ant activity patterns in habitats
ranging from deserts to tropical rain forests (Hunt
1974, Schumacher & Whitford 1974, Briese &
Macauley 1980, Levings 1983, Levings & Windsor
1982, Kaspari 1993, Andersen 2000, Kaspari &
Weiser 2000). Speci?cally, Levings (1983) and Kas-
pari and Weiser (2000) have shown that ant activ-
ity at baits in a variety of locations on BCI (in-
cluding the litter surface, shrubby vegetation, and
tree trunks) is signi?cantly higher during the wet
season than during the dry season. In addition,
study of natural moisture gradients and watering
experiments have shown that foraging activity is
positively related to moisture within each season
(Levings 1983, Levings & Windsor 1982, Kaspari
1993, Kaspari & Weiser 2000).
In addition to desiccation risk, moisture is as-
sociated with resource availability. The availability
of insect prey and exudates, the primary dietary
components of most ant species, is greater in the
canopy, the litter, and understory shrubs during the
wet season than in the dry season (Jones 1987,
Wolda 1988, Basset 1991, van Schaik et al. 1993).
Within a single season, wet patches also support a
higher density of small arthropod prey than dry
patches (Levings & Windsor 1982). Thus, patterns
of resource availability associated with moisture
and desiccation risk drive the positive relationship
between moisture and activity in litter ants. Con-
sidering these factors, we expected the activity of
terrestrial ants to be highest on baits during the
wet season.
Moisture and resource availability, combined
with differences in the role of competition in struc-
turing canopy communities, may lead to different
patterns of foraging activity in arboreal ants. Due
to greater solar radiation and less moisture avail-
ability, the tropical canopy is probably a more abi-
otically challenging habitat for ants than the litter
throughout the year. These challenges would likely
be at their greatest during the dry season when
solar radiance is high and precipitation and exudate
availability are low (Dietrich et al. 1982, Rand &
Rand 1982, Jones 1987, Wolda 1988); however, a
comparative study of arboreal and ground-nesting
ants in the Temperate Zone has shown that arbo-
real ants are much more resistant to desiccation
stress than terrestrial ants (Hood & Tschinkel
1990). Thus, tropical arboreal ants may be less af-
fected by abiotic stresses than litter ants. An ex-
amination of foraging patterns over the two seasons
allowed us to narrow the range of factors affecting
the activity levels in the two assemblages.
Our second goal was to determine if ants from
the two assemblages differed in their preferences for
baits representing carbohydrate or protein resourc-
es. Plant-based food webs, such as the tropical for-
est canopy, are more nitrogen-limited than detritus-
based food webs, such as leaf litter (Swift et al.
1979, Mattson 1980, Pimm 1982, Vitousek 1982).
The difference in nitrogen richness is based on the
relatively low nitrogen to carbohydrate ratios in
plants relative to litter-decomposing microorgan-
isms (1:40 vs. 1:10). Given this difference, arboreal
ants should be nitrogen-limited, and terrestrial ants
should be relatively more carbohydrate-limited
(Tobin 1994, Davidson 1997, Yanoviak & Kaspari
2000, Kaspari & Yanoviak 2001). This led to the
prediction that canopy-foraging ants would show a
preference for protein baits and litter-foraging ants
would prefer carbohydrate baits. The studies of
both Yanoviak and Kaspari (2000) and Kaspari and
Yanoviak (2001) compared the foraging preferences
of ants attracted to bait stations containing protein,
carbohydrate, and water in the canopy and on the
litter surface on BCI during the beginning of the
dry season. They showed that protein-based baits
in the canopy attracted many more foragers than
protein baits in the litter. There was no signi?cant
difference in accumulation at carbohydrate baits
between the two habitats. We determined if arbo-
real ants foraging on tree trunks also display a pref-
350 Hahn and Wheeler
FIGURE 1. Weekly rainfall totals for Barro Colorado
Island, Panama, during the sampling period (16 Novem-
ber 1982?17 November 1983).
erence for nitrogen-rich protein baits and if pref-
erences were stable through time.
METHODS
SITE AND TRANSECTS. This study was conducted
on Barro Colorado Island (BCI) from 16 Novem-
ber 1982 through 17 November 1983. Three tran-
sects were chosen (each 500 m in length) that fol-
lowed trails in the Hubbell?Foster permanent tree
monitoring plot. One transect followed the Dray-
ton trail, and the other two followed the Armour
trail. Each transect consisted of 50 individually
marked trees ca 10 m apart along the trail. Each
tree was identi?ed to species using the Hubbell?
Foster database. Identities of individual trees in this
study are available from the authors by request.
The 1982?1983 dry season was the most se-
vere, beginning earlier, lasting the longest, and hav-
ing the least rain since 1929, when the Panama
Canal Commission began keeping records. Using
rainfall records, we de?ned the dry season as be-
ginning in mid-November 1982 (corresponding
with day 1 of this study, 16 November 1982) and
lasting 22 weeks (corresponding approximately
with day 155 of this study, 21 April 1983; Fig. 1).
The remainder of this study was carried out during
the wet season (day 156, 22 April 1983) through
the last sampling day in this study (day 364, 17
November 1983).
BAITING. On each sampling day, 50 trees in a sin-
gle transect were baited by using twine to attach
one 15 ml clear plastic conical centrifuge tube con-
taining a blended mixture of honey and bananas
and another 15 ml tube containing tuna ca 15 cm
apart on the trunk at breast height. This is a con-
venient location because ants from both arboreal
and terrestrial assemblages will forage low on tree
trunks (Longino & Colwell 1997). Morning trials
were run between 0630 and 0830 h and evening
trials between 1830 and 2030 h. The three tran-
sects were sequentially sampled on different days,
alternating between morning and evening in each
block so that morning and evening samples were
evenly dispersed throughout the year; i.e., the ?rst
three sampling dates were morning samples of tran-
sects 1, 2, and 3, respectively and the second three
sampling dates were evening samples of transects
1, 2, and 3, respectively. This pattern was repeated
throughout the study to yield a total of 33 trials.
Of these 33, 6 morning and 6 evening trials were
conducted during the wet season, and 12 morning
and 9 evening trials were done during the dry sea-
son. During the trials, tubes were left on the trees
for approximately two hours, after which they were
capped and brought back to the lab.
IDENTIFICATION AND CLASSIFICATION. The number
and species of ants contained in the tubes were
determined. Voucher specimens of all species have
been deposited in the ant collection at Harvard
University's Museum of Comparative Zoology.
Species were classi?ed as arboreal or terrestrial by
observing the approach and departure directions of
foragers at the baits during the study. Ants were
considered arboreal if they nested in and foraged
primarily on trees or in the canopy as revealed by
following recruitment trails. Only two ground-
nesting ants, Ectatomma tuberculatum and Parapo-
nera clavata, foraged primarily in the canopy and
were classi?ed as arboreal. Ants were designated as
terrestrial if they nested and foraged primarily on
the ground.
Individual species that occurred on ten or more
baits during the duration of the study were placed
in one of three preference categories based on bait
occupancy (protein, carbohydrate, or equal prefer-
ences). A binomial test with a null model of equal
preferences (probability of occurring on a protein
bait 5 probability of occurring on a carbohydrate
bait 5 0.5) was used to evaluate if a species showed
a distinct preference for one type of bait. A P-value
of less than 0.05 was taken as evidence for a pref-
erence. P-values and the proportion of carbohy-
drate baits occupied throughout the study can be
found in Appendix 1 for all species that occurred
on ten or more baits during the duration of the
study.
Ant Foraging Activity 351
FIGURE 2. Occupancy of baits by arboreal ants was
highest during the dry season and dropped precipitously
at the onset of the wet season. Terrestrial ant activity was
not signi?cantly different between the seasons.
STATISTICAL ANALYSIS. Exploratory data analysis
showed no effects of transect, time of day, or tree
species on bait occupancy rates; these variables were
not considered in subsequent analyses. To deter-
mine whether or not there were differences in bait
occupancy by arboreal or ground-foraging ants
during each of the two seasons, we used two-way
analysis of variance (ANOVA) with season (wet or
dry) and assemblage (arboreal or terrestrial) as fac-
tors and a season 3 assemblage interaction term.
Tukey's HSD correction for multiple comparisons
was used to test for signi?cant differences between
groups within the two-way ANOVA. Because over-
all bait preferences within an assemblage did not
differ between the two seasons, Student's t-tests
were used to determine if mean bait occupancy dif-
fered between carbohydrate- and protein-based
baits for ants of both assemblages over the entire
year. Pearson's chi-square test was used to deter-
mine if the distribution of species bait preferences
differed among species in the two assemblages.
Some authors have suggested that chi-square tests
are not appropriate if any of the cells contains less
than ?ve observations, as in this case; however, Yar-
nold (1970) has shown that 2 3 3 cell chi-square
tests are robust as long as the average expected cell
frequency is not lower than a certain critical value.
Yarnold's (1970) critical value for 2 3 3 cell chi-
square tests is calculated as [5(no. of expected cells
, 5)/(no. of rows) (no. of columns)]. In our case,
the average expected value was 4.67 and Yarnold's
(1970) critical value was 3.33. All analyses were
performed using the JMP IN (SAS 1996) statistical
package.
RESULTS
ASSEMBLAGE BASED PATTERNS IN FORAGING ACTIVI-
TY. Fifty-eight of the 59 species collected at baits
could be designated as either primarily arboreal or
terrestrial. Ants from both assemblages foraged on
tree trunk baits throughout the year (Fig. 2). To
investigate seasonal effects on foraging, the mean
number of baits occupied per sampling day by ar-
boreal and terrestrial ants was compared between
the two seasons (two-way ANOVA, full model, F3, 62
5 27.97, P , 0.001). Bait occupancy differed sig-
ni?cantly between the two assemblages (F1, 62 5
7.80, P 5 0.007), and between the two seasons
(F1, 62 5 24.78, P , 0.001); there was a signi?cant
interaction between assemblage and season (F1, 62
5 58.58, P , 0.001). Comparing activity between
seasons within an assemblage, arboreal ants occu-
pied signi?cantly more baits per sampling event
during the dry season than the wet (Tukey's HSD
test, P , 0.05, mean no. of baits 6 SE; dry 5
36.8 6 2.13 and wet 5 13.0 6 1.61). There was
no difference in bait occupancy by terrestrial ants
during the two seasons (Tukey's HSD test, P .
0.05, mean no. of baits 6 SE; dry 5 17.1 6 2.13
and wet 5 22.1 6 1.61). Comparing activity be-
tween assemblages within a season, arboreal ants
occupied signi?cantly more baits per sampling day
than terrestrial ants during the dry season (Tukey's
HSD test, P , 0.05, mean no. of baits 6 SE;
arboreal 5 36.8 6 2.13, and terrestrial 5 17.1 6
2.13). Conversely, terrestrial ants occupied signi?-
cantly more baits per sampling day than arboreal
ants during the wet season (Tukey's HSD test, P
, 0.05, mean no. of baits 6 SE; arboreal 5 13.0
6 1.61 and terrestrial 5 22.1 6 1.61).
BAIT PREFERENCES. Because within-assemblage bait
preferences did not differ between the wet and dry
seasons, the data for both seasons were combined.
Overall, arboreal ants occupied signi?cantly more
352 Hahn and Wheeler
FIGURE 3. Arboreal ants preferred protein baits (tuna)
over carbohydrate baits (honey 1 banana) (t 5 2.33, P
5 0.023, df 5 63). Terrestrial ants preferred carbohydrate
baits over protein baits (t 5 3.97, P 5 0.002, df 5 64).
Vertical bars 5 1 SE. N 5 33 sampling events over the
course of the study.
tuna baits than honey baits per sampling date,
whereas the reverse was true for terrestrial ants (Fig.
3).
Arboreal and terrestrial species that were col-
lected on at least ten baits throughout the study
were classi?ed by their preferences using a binomial
test (protein preference, carbohydrate preference,
or equal preferences; Appendix 1). A greater per-
centage of arboreal species preferred protein baits
(26.3% protein preference vs. 5.3% carbohydrate
and 68.4% equal preferences for 19 species) and a
greater percentage of terrestrial species preferred
carbohydrate baits (33.3% carbohydrate preference
vs. 0% protein and 66.7% equal preferences for 9
species). A Pearson's chi-square analysis revealed
that there was a marginally signi?cant difference in
the distributions of preference between arboreal
and ground ants (x2 5 5.740, df 5 2, P 5
0.0567).
DISCUSSION
Two patterns were apparent in this study. First, the
foraging activity of arboreal and terrestrial ants as
measured by baits on tree trunks differed between
the two seasons. Second, at the assemblage level,
arboreal ants preferred protein baits whereas terres-
trial ants preferred carbohydrate baits.
FORAGING ACTIVITY. Terrestrial ants occurred on
baits at moderate levels throughout the study, oc-
cupying slightly (but not signi?cantly) more baits
during the wet season. This pattern agrees with the
activity patterns of the terrestrial assemblage pre-
viously established on BCI. Levings (1983) and
Kaspari and Weiser (2000) both found that terres-
trial ant assemblages respond to desiccation stress
between seasons and among sites within a season
by reducing activity. Levings and Windsor (1984)
suggested that terrestrial ants probably reduced
their activity levels in response to a combination of
resource limitation and increased desiccation risk
because the density of most litter arthropods is pos-
itively correlated with soil moisture both between
seasons and years. Interestingly, a study of litter
arthropods on BCI by Wheeler and Levings (1988)
during the same 1982?1983 El Nin?o event as this
study showed that terrestrial ants followed the same
moisture-correlated pattern of activity reported
during previous dry seasons. With the onset of the
wet season, however, all ant activity increased more
quickly than expected, based on estimates from sev-
eral years' data. Extreme deviations in climate pat-
terns can result in nonlinear effects on seasonal ac-
tivity patterns of tropical ants. Our data, in agree-
ment with previous studies, suggest that moisture
is correlated with foraging activity in terrestrial
tropical ants; however, our results do not allow us
to determine what factors (i.e., microclimate, re-
source availability, or competition) are responsible
for the observed differences in activity. Because ter-
restrial assemblages are generally made up of many
opportunistic species with small- to medium-sized
colonies that are often behaviorally subordinate, it
is likely that the risk of desiccation and depressed
resource availability combine to decrease terrestrial
ant activity in the dry season (Levings & Trainello
1981, Levings 1983, Jackson 1984, Andersen
2000, Yanoviak & Kaspari 2000, Kaspari & Weiser
2000).
In our study, arboreal ants occupied baits on
tree trunks with greater frequency than did terres-
trial ants during the dry season, with a precipitous
drop in activity at the onset of the wet season. Bait
occupancy by arboreal ants during the wet season
was ca 65 percent lower than during the dry season.
This is in contrast to the pattern seen by Kaspari
and Weiser (2000), who found that total ant activ-
ity on baits placed at breast height on trees during
the wet season was 20 percent higher than during
the dry season.
There are several possible explanations as to
why our results do not agree with those of Kaspari
Ant Foraging Activity 353
and Weiser (2000). The difference in activity on
tree trunks in their study was due to species they
classi?ed as habitat generalists, species found in sev-
eral locations (including the litter and foraging on
low shrubs) rather than arboreal specialists. In our
study, most of their habitat generalists would be
classi?ed as terrestrial. In agreement with Kaspari
and Weiser (2000), our data showed a 29 percent
increase in bait occupancy by terrestrial ants during
the wet season, although this difference was not
statistically signi?cant. Explanations for the absence
of an increase in arboreal ant activity during the
dry season in Kaspari and Weiser's (2000) study
may include preference for the ingredients used in
our baits (tuna and a mixture of honey and banan-
as vs. peanut butter) and the duration of baiting
(2 hours in our study vs. 1 hour). Another expla-
nation may be differences in sampling. Kaspari and
Weiser (2000) took their dry season samples only
during two weeks in early December, whereas our
dry season samples were taken throughout the en-
tire dry season from mid-November until mid-
April. In addition, our samples were taken contig-
uously throughout the course of a single year,
whereas their wet and dry season samples were tak-
en in different years (1994 wet, 1997 dry). Lastly,
because the 1982?1983 dry season was extremely
dry due to an El Nin?o event, the patterns observed
in our study may be not representative of an av-
erage dry?wet season cycle.
The high level of arboreal ant activity on tree
trunks in this study suggests that they extend their
ranges and increase foraging intensity during the
dry season. This expansion coincides with a drop
in abundance of most canopy prey insect groups
during the dry season (Jones 1987, Wolda 1988,
Basset 1991). In addition, carbohydrate-rich re-
sources such as homopteran exudates, nectar, and
fruits also drop in abundance from wet season lev-
els (Wolda 1988, van Schaik et al. 1993). Like
many other animals, arboreal ants may extend their
foraging ranges when resource levels decline
(Schoener 1983, Davies & Houston 1984). Be-
cause arboreal ants increase their activity on tree
trunks during the dry season when desiccation risk
is high, desiccation stress is probably less important
in regulating the activity of arboreal ants relative to
terrestrial ants. This may be the result of several
physiological mechanisms utilized by arboreal ants
to resist desiccation stress more effectively than ter-
restrial ants (Hood & Tschinkel 1990). Canopy ant
communities are populated by aggressive, numeri-
cally dominant species that form a mosaic of ter-
ritories (Room 1971; Leston 1978; Majer 1976a,
b, c; Levings & Trainello 1981; Jackson 1984; Lon-
gino & Nadkarni 1990; Yanoviak & Kaspari
2000). Arboreal ants may not be able to afford a
reduction in activity levels during the dry season
due to the risk of losing territory. Therefore, re-
source limitation and competition in the canopy
environment may necessitate the year-round main-
tenance of territories among arboreal species, allow-
ing them to harvest adequate amounts of nitrogen.
Further studies of resource distributions and ant
responses to resource addition and removal are
needed to distinguish between these hypotheses.
BAIT PREFERENCES. In addition to differences in
seasonal activity patterns between the two assem-
blages, arboreal ants preferred tuna baits to honey
baits, particularly during the dry season, while ter-
restrial ants slightly preferred honey to tuna baits
throughout the year. When species were classi?ed
according to their preferences, a greater proportion
of arboreal species preferred protein baits and a
greater proportion of terrestrial species preferred
carbohydrate baits. If ants choose baits based on
the current needs of the colony (Ho?lldobler & Wil-
son 1990, Kaspari 1993), ants should prefer a cer-
tain type of bait when the nutrients represented in
that bait are most limiting in the environment.
Thus, our results suggest that arboreal ants are pro-
tein-limited, particularly during the dry season, and
terrestrial ants are carbohydrate-limited.
Our results agreed with the predictions of To-
bin (1994) and Davidson (1997), and with the
?ndings of Yanoviak and Kaspari (2000) and Kas-
pari and Yanoviak (2001); we found the same pat-
terns of preference on tree trunks as they found in
the canopy and litter. Therefore, assemblage-based
preferences for protein and carbohydrates are gen-
eral and occur throughout the foraging range of
each assemblage.
While our data agree with the hypothesis that
habit-based nutrient availability plays a central role
in structuring ant assemblages, the importance of
nutrient limitation remains to be tested. Without
a well-resolved phylogenetic framework, broad
comparisons of assemblages are dif?cult to inter-
pret. Habitat-based factors may cause the observed
differences in species activity patterns or preferenc-
es, or these characteristics may have been present
in species before they colonized the two habitats.
The two hypotheses are not mutually exclusive, and
some combination of them seems likely. It is in-
teresting to note that similar patterns of commu-
nity structure have been observed between arboreal
354 Hahn and Wheeler
and ground assemblages in both the Old and New
World tropics (Andersen 2000).
ACKNOWLEDGMENTS
We would like to thank Steve Paton and the Terrestrial
Environmental Sciences Program of the Smithsonian
Tropical Research Institute for providing unpublished
weather data. The Smithsonian Institution and the Mu-
seum of Comparative Zoology at Harvard University pro-
vided support to DEW. James Trager and John Longino
graciously identi?ed several species of ants. Betsy Arnold
was kind enough to help with the translation of the ab-
stract. We are especially grateful to Judith Bronstein, Mi-
chael Kaspari, John Longino, Jennifer Weeks, and two
reviewers who provided key comments to improve this
manuscript.
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APPENDIX 1.
Species
Foraging
location
Total
baits
occupied
% Total
baits
occupied
in
evening
% Total
baits
occupied
carbohy-
drate
Binomial
P-value Bait preference
Subfamily Dolichoderinae
Azteca aurita
Azteca sp. 1
Azteca sp. 2
Azteca sp. 3
Azteca sp. 4
Azteca sp. 5
Azteca sp. 6
Azteca sp. 7
Azteca sp. 8
Dolichoderus debilis
Tapinoma fulvum
Arboreal
Arboreal
Arboreal
Arboreal
Arboreal
Arboreal
Arboreal
Arboreal
Arboreal
Arboreal
Arboreal
15
84
11
24
14
8
15
12
1
7
53
40
48
9
33
57
88
33
25
100
14
100
40
37
27
38
50
25
27
25
0
14
49
0.607
0.021
0.227
0.308
1
0.119
0.146
1
Equal
Protein
Equal
Equal
Equal
Equal
Equal
Equal
Subfamily Formicinae
Brachymyrmex sp. 1
Camponotus ager
C. atriceps
C. linnaei
C. novogranadensis
C. sericeiventris
C. simillimus
C. zoc
Camponotus sp. 1
Paratrechina guatemalensis
Ground
Arboreal
Arboreal
Arboreal
Arboreal
Arboreal
Arboreal
Arboreal
Arboreal
Ground
34
1
17
2
1
33
2
1
2
37
59
100
100
50
0
3
100
0
0
76
59
100
41
0
100
30
50
0
50
73
0.392
0.692
0.035
0.008
Equal
Equal
Protein
Carbohydrate
356 Hahn and Wheeler
APPENDIX 1. Continued.
Species
Foraging
location
Total
baits
occupied
% Total
baits
occupied
in
evening
% Total
baits
occupied
carbohy-
drate
Binomial
P-value Bait preference
Subfamily Myrmicinae
Cephalotes umbraculatus
Crematogaster brasiliensis
C. curvispinosa
C. distans
C. erecta
C. limata
C. parabiotica
C. victima
Crematogaster sp. 1
Pheidole sp. 1
Pheidole sp. 2
Pheidole sp. 3
Pheidole sp. 4
Pheidole sp. 5
Pheidole sp. 6
Pheidole sp. 7
Pheidole sp. 8
Pheidole sp. 9
Pheidole sp. 10
Pheidole sp. 11
Rogeria blanda
R. scandens
Solenopsis sp. 1
Solenopsis sp. 2
Solenopsis sp. 3
Wasmannia auropunctata
Arboreal
Arboreal
Arboreal
Arboreal
Arboreal
Arboreal
Arboreal
Ground
Arboreal
Ground
Arboreal
Ground
Ground
Arboreal
Ground
Arboreal
Arboreal
Arboreal
Ground
Ground
Ground
Ground
Ground
Ground
Arboreal
Ground
1
19
1
2
7
62
24
10
31
1
6
1
1
7
121
6
12
91
27
27
2
2
39
1
29
95
0
53
100
0
25
37
38
90
48
100
100
100
100
71
48
33
33
57
59
52
0
50
38
0
32
34
0
47
100
0
29
34
42
30
32
100
17
100
100
57
59
33
25
37
67
67
100
100
41
0
55
54
1
0.015
0.541
0.344
0.071
0.069
0.146
0.021
0.089
0.089
0.337
0.711
0.006
Equal
Protein
Equal
Equal
Equal
Equal
Equal
Protein
Equal
Equal
Equal
Equal
Carbohydrate
Subfamily Poinerinae
Ectatomma ruidum
E. tuberculatum
Odontomachus bauri
O. hastatus
Pachycondyla carinulata
P. stratinoda
P. villosa
Paraponera clavata
Ground
Arboreal
Ground
Arboreal
Ground
Unknown
Ground
Arboreal
288
67
3
1
4
3
8
22
21
39
67
100
0
0
33
86
60
36
100
100
100
100
88
91
,0.001
0.027
,0.001
Carbohydrate
Protein
Carbohydrate
Subfamily Pseudomyrmicinae
Pseudomyrmex sp. 1 Arboreal 4 0 25