Journal of Tropical Ecology
http://journals.cambridge.org/TRO
Additional services for Journal of Tropical Ecology:
Email alerts: Click here
Subscriptions: Click here
Commercial reprints: Click here
Terms of use : Click here
Frugivorous bats drink nutrient- and clay-enriched water in the Amazon
rain forest: support for a dual function of mineral-lick visits
Simon J. Ghanem, Hans Ruppert, Thomas H. Kunz and Christian C. Voigt
Journal of Tropical Ecology / Volume 29 / Issue 01 / January 2013, pp 1 - 10
DOI: 10.1017/S0266467412000740, Published online: 21 January 2013
Link to this article: http://journals.cambridge.org/abstract_S0266467412000740
How to cite this article:
Simon J. Ghanem, Hans Ruppert, Thomas H. Kunz and Christian C. Voigt (2013). Frugivorous bats drink nutrient- and clay-
enriched water in the Amazon rain forest: support for a dual function of mineral-lick visits. Journal of Tropical Ecology, 29, pp
1-10 doi:10.1017/S0266467412000740
Request Permissions : Click here
Downloaded from http://journals.cambridge.org/TRO, IP address: 134.76.162.165 on 04 Feb 2015
Journal of Tropical Ecology (2013) 29:1–10. © Cambridge University Press 2013
doi:10.1017/S0266467412000740
Frugivorous bats drink nutrient- and clay-enriched water in the Amazon
rain forest: support for a dual function of mineral-lick visits
Simon J. Ghanem∗,§,1, Hans Ruppert†, Thomas H. Kunz‡ and Christian C. Voigt∗,§
∗ Leibniz Institute for Zoo and Wildlife Research, Evolutionary Ecology Research Group, Alfred-Kowalke-Str. 17, 10315 Berlin, Germany
†Geosciences Center, Department of Sedimentology and Environmental Geosciences, University of Go¨ttingen, Goldschmidtstr. 3, 37077 Go¨ttingen, Germany
‡Center for Ecology and Conservation Biology, Department of Biology, Boston University, 5 Cummington Str., 02115 Boston, USA
§ Freie Universita¨t Berlin, Verhaltensbiologie, Takustr. 6, Berlin, Germany
(Received 4 May 2012; revised 17 December 2012; accepted 18 December 2012; first published online 21 January 2013)
Abstract: In Central Amazonia, large mammals create water-filled puddles when consuming soil. These mineral licks
are visited by pregnant and lactating frugivorous bats; possibly for two reasons. Frugivorous bats could supplement
their mineral-depleted fruit diet by drinking salty water, or they could buffer dietary plant secondary compounds by
consuming soil. We analysed bat fruits from Ecuador and showed that they are depleted in elemental concentrations
(Na, K, P) compared with similar fruits collected from Costa Rica, where no mineral licks occur (n = 32). Analyses
of water from Ecuador revealed that water samples from six mineral licks contained more physiologically relevant
elements (Na, K, Mg, Ca) than four samples from river and stream water control sites (Mann–Whitney U-test). In
support of the nutrient supplement hypothesis, we observed bats drinkingmineral-enriched water at these licks (video
observation). Furthermore, blood collected from68bats differed in compositionwith respect to physiologically relevant
minerals (Na, K, Mg, Fe) from that of frugivorous bats captured at control sites. To test whether frugivorous bats also
consumed clay for detoxification, we checked for soil tracer elements in 31 faecal samples. Soil tracers are insoluble
in water and, thus, are not included in a strict fruit diet. Bats from mineral licks showed higher aluminium soil tracer
concentrations in their faeces than bat species that never visit licks, suggesting that frugivorous bats take up clay
material at mineral licks. Our results provide evidence that frugivorous bats ingest soluble mineral nutrients and
insoluble soil by consuming soil-enriched water at mineral licks, thus supporting the hypothesis that frugivorous bats
of western Amazonia may derive a dual benefit from drinking water frommineral licks.
Key Words: detoxification, geophagy, nutrient supplementation, secondary metabolites, soil tracer
INTRODUCTION
Over recent decades, consumption of soil, called
geophagy, has been described for various frugivorous
and omnivorous animals. Among vertebrates, examples
for this widespread behaviour can be found in birds
(Brightsmith &Mun˜oz-Najar 2004, Diamond et al. 1999,
Gilardi et al.1999)andmanymammals (Blake et al.2010,
Kreulen 1985, Montenegro 2004). Several explanations
for geophagy have been suggested (reviewed in Diamond
1999, Klaus & Schmid 1998) and usually at least
some medicinal benefit has been associated with the
consumption of soil (Krishnamani & Mahaney 2000).
However, the most common explanation for geophagy
has been associated with nutrient supplementation or
1 Corresponding author. Email: sghanem@gmx.de
detoxification of plant secondary compounds (Abrahams
& Parsons 1996, Holdø et al. 2002, Mahaney &
Krishnamani 2003, Voigt et al. 2008). The nutrient-
supplementation hypothesis assumes that animals ingest
clay material for its nutrient content (Brightsmith &
Mun˜oz-Najar 2004, Emmons & Stark 1979, Kreulen
1985). Thedetoxificationhypothesis argues that ingested
claymayhelp inbuffering toxic, carcinogenic, teratogenic
ornutrient-bindingeffectsofplant secondarycompounds,
such as tannins or alkaloids (Brightsmith et al. 2008,
Diamond 1999, Gilardi et al. 1999).
In western Amazonia, frugivorous and omnivorous
bats visit muddy depressions in forested areas for geo-
phagy (Bravo et al. 2008, 2010; Tuttle 1974, Voigt et al.
2007). In particular, pregnant and lactating frugivorous
bats of Phyllostomidae subfamily Stenodermatinae have
been observed visiting these mineral licks in high
numbers. During reproduction, frugivorous bats may
2 SIMON J. GHANEM ET AL.
suffer from severe nutrient stress, becausemany fruits are
low in physiologically relevant minerals. One example is
sodium (Na) that is responsible for a wide set of body
functions, such as nerve impulses or the homeostatic
balance (National Research Council 2005). This nutrient
stress may be pronounced for fruit-eating bats living in
nutrient-depleted ecosystems, such as the Amazonian
lowlands (Terborgh 1992). Therefore, geophagy serving
as mineral supplementation for frugivorous bats has
been suggested by several authors (Bravo et al. 2008,
2010; Voigt et al. 2007). However, bats in times of high
nutritional demand may also benefit from geophagy by
buffering toxic plant secondary compounds in their fruit
diet (Voigt et al. 2008).Thus far, it is unclearwhether free-
ranging bats consume water or clay material at mineral
licks. If bats only drinkwater, theymost likely supplement
their nutrient-depleted fruit diet with essential nutrients
dissolved in the water. Alternatively, if bats ingest
additionally clay, it is more likely that they detoxify plant
secondarycompounds in theirdiet. In this study,we tested
the hypotheses that frugivorous bats visit mineral licks to
drink water and to ingest clay.
To evaluate whether frugivorous bats drink water or
ingest clay or soil-enriched water at mineral licks, we
conducted video observations and analysed chemical
elements in bat blood and faeces. We predicted that
frugivorous bats captured at mineral licks should have
an altered blood composition in relation to frugivorous
bats captured in the nearby forest. Further, we predicted
that soil tracer elements in bat faeces would indicate soil
consumption, if frugivorous bats consume soil or soil-
enriched water at mineral licks.
Aswe examined the elemental composition of available
water sites in the area,we predicted thatwater sampled at
mineral licks should showhighervaluesofphysiologically
relevant elements than water sampled at nearby sites.
Additionally, we compared the nutrient concentration in
fruits from Costa Rica and Ecuador, predicting that fruits
from rain forests in the Ecuadorian Amazon which grow
on ancient nutrient-poor soils would be more depleted
in essential nutrients than those of the more recent Costa
Rican rain forests growingonnutrient-rich volcanic soils.
METHODS
Study sites
We conducted our study between October and December
2008 at the Tiputini Biodiversity Station (TBS, 0◦38′S,
76◦8′W), located in a lowland Amazonian primary rain
forest,OrellanaProvince,Ecuador.Forvideoobservations
and sampling of bats, we chose nine mineral licks and
15 control sites in the forest. Control sites were randomly
selected at open locations such as trails or gap openings at
the TBS. Additionallywe collected and analysed elements
in fruits that are known to be consumed by bats.
For comparative purposes,we collected fruit samples in
2009 at La Selva (LS) Biological Station near Puerto Viejo
deSarapiqui inCostaRica (10◦26′N,85◦59′W).LS served
as a control site in our study, because nomineral licks are
known to exist in Central America, even though local bat
assemblages include many frugivorous bats, sometimes
eventhesamegeneraor speciesasatTBS(Rex et al.2008).
Video observations at mineral licks
We observed bats at the mineral licks in Ecuador by
using a digital video camera (Sony Digital Handycam
DCR-H C39E PAL, Sony Europe) with the night-shot
function active. For illumination, we used an ECOLINE
IR-Illuminator (Security-Center, Germany). At each of
the nine licks, we recorded the behaviour of visiting bats
from shortly after sunset (c. 18h00) until 20h00–24h00,
depending on battery capacity and weather conditions.
We performed video observations directly via a handheld
cameraor as automated observationswith a tripod. Focus
points of observation were chosen according to one of
three criteria: (1) sites were visited by other animals,
such as scraping or drinking spots of spider monkey
(Ateles belzebuth, E´. Geoffroy) or tapir (Tapirus terrestris,
Linnaeus); (2) sites with a good overview of the entire
mineral lick; and (3) sites with high bat activity based on
our netting experience.
Collection of fruit samples
We collected potential bat fruits, from a total set of 32
ripe fruits (Table 1), in the vicinity of the two biological
stations LS (n = 15) and TBS (n = 17). All fruits were
cut into pieces and dried at 50 ◦C for about 72 h. All
dried samples were kept at ambient temperature in closed
ZipLockTM –bags until analysis.
Collection of bat blood and faeces
In31nights,wecapturedbatsbetween18h00and21h00
atninemineral licks and15control sites byusingground-
level mist nets (length 6–12 m; 70 dernier/2 ply, 36-mm
mesh, five shelves; R. Vohwinkel, Velbert, Germany). We
identified bats based on their morphology using two field
keys (Timm& LaVal 1998, Tirira 2007). We held all bats
individually in cloth bags for approximately 1 h to collect
faeces. We recorded the following data using a standard
protocol: species,bodymass(accuracy0.5g;Pesolaspring
balance, Baar, Swiss), sex, age (juvenile, subadult, adult),
and reproductive status (reproductively active, inactive,
lactating, post-lactating) as outlined in Handley et al.
(1991) and Kunz et al. (2009). We measured the length
of forearm using a vernier caliper (accuracy 0.1 mm; SPI
Tropical fruit-eating bats and mineral licks 3
Table 1. Fruits consumed by bats and collected at the study
sites in CostaRica (CR; n=15) and Ecuador (E; n=17). The
number of different individuals that have not been identified
to the species level but that contributed as separate species
to the analyses is given in parentheses after the genus name.
Species Origin
Cecropia sp. CR
Cecropia insignis Liebmann CR
Cecropia obtusifolia Bertoloni CR
Dipteryx sp. CR
Ficus americanaAublet CR
Ficus insipidaWilldenow CR
Ficus sp. CR
Lycianthes multiflora Bitter CR
Passiflora sp. CR
Piper spp. (3) CR
Sacoglottis sp. CR
Solanum sp. CR
Virola sp. CR
Cecropia spp. (4) E
Dialium guianense Sandwith E
Ficus spp. (4) E
Lecythidaceae sp. E
Lauraceae E
Melastomataceae E
Piper spp. (4) E
Virola sp. E
2000 caliper, West Chester, Pennsylvania, USA). Thirty-
one faecal samples were stored singly in Eppendorf tubes
filled with 70% ethanol until further analysis (Table 2).
We used ethanol blank samples to account for possible
impurities or contamination. From each of 68 bats, we
took 50–120 μl of blood, depending on body mass of the
species by piercing the antebrachial vein (Kunz & Nagy
1988) using sterile 23–30-gauge needles (Microlance,
BectonDickisonS.A., Spain).All blood samplesweredried
at 50 ◦C for approximately 48 h and kept at ambient
temperature in closed Eppendorf tubes until analyses.
We released all bats at the site of capture after species
identification and processing as noted above.
Collection of water samples
At TBSwe collected 50-ml samples of water from puddles
at each of six mineral licks and four control sites, such as
rivers, streams and ponds that are potentially accessible
for the bats.We sampledunfilteredwater from the surface
of thepuddles inorder toevaluate theactualwaterbatsare
confrontedwithatpotentialdrinkingsites.Thiswaterwas
stored in a polytetrafluoroethylene (PTFE) vessel mixed
with1mlof 65wt.%ultrapurenitric acid for preservation
and was kept at ambient temperature until analysis.
Measurement of elemental composition
For elemental analyses in blood, fruit and faeces samples,
wedissolved the samplesusinga total digestionapparatus
Table 2. Alphabetical list of insectivorous (I) and fruit-eating bats (F)
from which faecal and blood samples were collected around Tiputini
Biodiversity Station in Ecuador.
Species Diet
Sample size
Faeces Blood
Artibeus lituratus (Olfers, 1818) F 1 3
Artibeus obscurus (Schinz, 1821) F – 13
Artibeus planirostris (Spix, 1823) F 1 4
Carollia castaneaH. Allen, 1890 F – 1
Carollia perspicillata (Linnaeus, 1758) F – 9
Chiroderma salvini Dobson, 1878 F – 1
Chiroderma trinitatum Goodwin, 1958 F 3 –
Chiroderma villosum Peters, 1860 F – 2
Lophostoma silvicolum d’Orbigny, 1836 I 2 –
Mesophylla macconnelli Thomas, 1901 F 8 2
Mimon crenulatum (E´. Geoffroy, 1810) I 5 –
Phyllostomus elongatus (E´. Geoffroy, 1810) I 2 –
Platyrrhinus lineatus (E´. Geoffroy, 1810) F – 6
Platyrrhinus sp. F – 6
Rhinophylla fischerae Carter, 1966 F – 1
Rhinophylla pumilio Peters, 1865 F – 6
Sturnira lilium (E´. Geoffroy, 1810) F 1 4
Sturnira magna de la Torre, 1966 F 4 1
Trachops cirrhosus (Spix, 1823) I 1 –
Uroderma bilobatum Peters, 1866 F 1 1
Uroderma magnirostrum Davis, 1968 F 1 1
Vampyressa sp. F – 2
Vampyressa thyone Thomas, 1909 F 2 5
(Picotrace, Bovenden, Germany; Ruppert 1987). A series
of 32 solid samples was simultaneously digested in
PTFE vessels using a mixture of ultrapure fluoric acid
(40%), perchloric acid (70%) and nitric acid (65%) at
elevated pressure and temperature (170 ◦C, all acids
cleaned by sub-boiling distillation). During evaporation,
acid fumes were removed directly from the samples using
clean airflow. Residues of evaporation were dissolved in
nitric acid and hydrochloric acid and water at 150 ◦C.
After cooling, the clear solutions were transferred into
a 10-ml volumetric flask. The homogenized solutions
were stored in polyethylene bottles. During the digestion
procedure, we assumed minimal risk of contamination,
because ultraclean, sub-boiling distilled acids were used,
and because the system was closed during the pressure
phase and was sheltered during evaporation. Elemental
analyses of the digested samples as well as of the
water samples were conducted using inductively coupled
plasma emission spectrometry (ICP-OES; Optima 3300
DV, Perkin Elmer) and by inductively coupled plasma
mass spectrometry (ICP-MS Elan DRC II; Perkin Elmer
SCIEX).TheelementsNa,potassium(K),magnesium(Mg)
and iron (Fe) in faeces and blood samples were selected
because they are physiologically relevant nutrients in
mammals. Concentrations of Na, K, Mg, Fe, calcium (Ca)
and phosphorus (P) from fruit and water samples were
also analysed. To evaluate whether bats consume clay
at mineral licks, we used the elements aluminium (Al),
titanium (Ti), yttrium (Y), cerium (Ce), lanthanum (La)
4 SIMON J. GHANEM ET AL.
Figure 1. Frames of a video recording within a mineral lick, showing a bat approaching (from left to right) a puddle (in white margins in frame (1)).
Frames (2) – (4) show the snout of the bat moving towards the water surface; see online supplementary material for full video.
and neodymium (Nd) in bat faeces as markers to detect
soil consumption (Calabrese & Stanek 1995, Calabrese
et al. 1997). These elements are insoluble in water and
thus are only sparsely contained in plant products, such
as fruits. Bats with a strict fruit diet should not come into
contact with these elements when only feeding on fruits
that grow on trees or tall shrubs.
Statistics
We applied a Mann–Whitney U-test to reveal significant
differences in the elemental composition between fruit
samples from La Selva (Costa Rica) and TBS (Ecuador),
as well as for differences in the elemental composition of
water samples frommineral licks and control sites.
We transformed blood-sample data using the log(x+1)
function to reduce the effects of numerically dominant
categories. Differences in blood composition were tested
with samples of two frugivorous-bat groups for both
sexes, collected atmineral licks and fromopen-forest sites,
using the statistical software Primer v6 (Primer-236 E
2000 Ltd., Plymouth, UK).We computed the Bray–Curtis
similarities for a MDS (multi-dimensional scaling) plot
to document evidence of groupings. This plot illustrates
the relationship between the two frugivorous groups, by
representing the samples as points in two-dimensional
space, where the relative dissimilarities of the samples
are shown by the relative distances between points. We
verified differences in elemental composition of blood by
using a two-way crossed analysis of similarity (ANOSIM)
permutation test (Clarke &Warwick 1994).
We applied a Mann–Whitney U-test to reveal signifi-
cant differences in the soil tracer concentrations between
faecal samples of frugivorous bats captured at mineral
licks and of co-existing insectivorous bats that have
never been recorded to visit mineral licks (Table 2).
We used faeces of insectivorous bats that never visit
mineral licks as a control group, as we cannot rule out
that frugivorous bats captured away from mineral licks
might have visited the licks before. This was necessary
because the retention time of clay or soil material in
the digestive system of an animal is potentially long,
as Gilardi et al. (1999) reported for mineral-lick-visiting
parrots.We calculated the upper 95%confidence interval
of the median (95% CI) of the insectivorous group to
establish thresholdvalues that indicatedsoil consumption
by frugivorous species. Since the faecal dataset is not
normally distributed we used a non-parametric method
to calculate the 95% CI of the median according to
Olive (http://www.math.siu.edu/olive/ppmedci.pdf). All
individuals with values above the upper 95% CI were
considered to have consumed soil. Valueswithin the 95%
CI suggest that animals had not consumed significant
amounts of soil recently. We set the level of significance
at 5% and used two-tailed tests.
RESULTS
Video observations at mineral licks
During 13 nights (total of 48 h of recording), we never
observed bats feeding directly on clay at scraping spots
of other lick-visiting animals. It was difficult to obtain
good overview recordings using the automated video
observation, due to the size and illumination of the
mineral licks. However, by focusing on smaller areas at
the same mineral licks using the handheld camera, we
detected and observed many bats drinking water from
small depressions (Figure 1).
Tropical fruit-eating bats and mineral licks 5
Table 3.Median mineral nutrient concentrations (mg g−1 of dry matter) of fruits collected from Costa Rica (n = 18; CR) and Ecuador (n = 20; E);
(Mann–WhitneyU-test, P:U = 64; P = 0.016; K:U = 72; P = 0.037; Na:U = 56; P = 0.007; ∗ P < 0.05). The mineral concentration of Piper sp.
infructescences was used to calculate the dailymineral shortfall of Carollia bats when consuming exclusively Piper infructescences.We estimated a
daily fruit consumption of ∼24g for C. brevicauda and assumed that 70% of consumed element amounts were taken up by the bat (70% taken up).
Additionally, we calculated the difference in element content () between diets of Piper spp. fruits in Costa Rica and Ecuador as well as the average
element concentration (μg g−1) of lickwater (ML; n=6mineral licks) and controlwater sites (CW; n=4 control sites) in Ecuador (Mann–Whitney
U-test, n = 10, Na:U = 64; P < 0.001; Mg:U = 32; P < 0.001; K:U = 96; P = 0.007; Ca:U = 32; P < 0.001; ∗ P < 0.05).
All fruits Conc. in water
(mg g−1) median (range) Only Piper 70% taken up (μg g−1)
CR E CR E CR E  ML CW
Na 0.1 (0.01–0.84) 0.03∗ (0.0–0.15) 0.22 0.06 1.46 0.4 1.05 28.5∗ (0.21–118) 2.3 (1.1–4.2)
Mg 2.49 (0.92–10.2) 2.48 (0.93–5.42) 2.81 2.16 18.4 14.2 4.26 8.6∗ (1.8–19.5) 1.8 (0.6–4.4)
Fe 0.05 (0.01–0.35) 0.06 (0.01–0.25) 0.05 0.05 0.30 0.35 −0.05 4.9 (0.79–11.1) 3.2 (0.46–7.1)
K 16.1 (4.73–35.5) 10.5∗ (5.38–16.6) 22.1 10.0 144 65.8 79.1 5.0∗(2.76–7.5) 2.5 (0.5–7.9)
Ca 6.92 (0.69–14.5) 6.93 (0.7–16.1) 10.2 9.03 66.8 59.2 7.6 55.3∗ (4.69–126) 6.7 (2.1–19.5)
P 2.15 (0.63–5.05) 1.58∗ (0.95–2.64) 2.77 2.2 18.2 14.5 3.7 0.12 (0.04–0.26) 0.14 (0.04–0.3)
Elemental composition of fruits
Fruits from Ecuador showed significantly lower
concentrations of P, K and Na than fruits from Costa Rica
(Mann–Whitney U-test, n = 32; phosphorus: U = 64;
P = 0.016; potassium: U = 72; P = 0.037; sodium: U =
56; P = 0.007; Table 3).
Elemental blood composition
The two-way crossed ANOSIM permutation test revealed
a significant global R value of 0.188 (n = 68; P = 0.025)
for the two locations, suggesting significant differences in
elemental composition of blood between the two groups.
Of the 9999 permutations in our model, only 245 were
equal to or greater than the global R, which indicates a
high within-group similarity. The tests for the differences
between sexes did not reveal a significant difference
(GlobalR=0.032;P=0.246).Of the9999permutations,
2463 were equal to or greater than the global R. The
Bray–Curtis dissimilaritymatrixamongall pairs of objects
was used to construct a MDS plot for the two locations
(Figure2),whichsuggestsgroupingsaccordingtocapture
site (two-dimensional stress level = 0.19).
Elemental composition of water
Water collected from puddles at mineral licks showed
significantly higher concentrations of Na, Mg, K and Ca
when compared with the concentrations of the control
sites (Mann–Whitney U-test, n = 10, sodium: U = 64;
P<0.001; magnesium: U = 32; P <0.001; potassium:
U=96; P=0.007; calcium:U=32; P<0.001; Table 3).
The concentrations of Fe and P did not differ significantly
(Mann–Whitney U-test, n = 10, iron: U = 132; P = 0.1;
phosphorus: U = 93; P = 0.404; Table 3).
Figure 2. Two-dimensional MDS plots of soil tracer elements in blood of
bats captured atmineral licks (filled triangles, n= 48) and nearby forest
sites (open triangles, n=20). The similaritymatrixwas computed using
the Bray–Curtis Similarity Index (2D stress 0.19). The more similar the
elemental compositions of bats, the closer the symbols appear on the
plot.
Soil markers in faeces
The calculated threshold (upper 95% CI of the median of
insectivorous group) for soil consumption revealed that
19–48% of the frugivorous species exhibited soil-tracer
concentrations in faeces that were higher than those of
insectivorous species (Figure 3). Faeces of frugivorous
species that visit mineral licks were significantly more
enriched in the soil tracer aluminium than the droppings
of insectivorousbats thatdonotvisitmineral licks (Mann–
WhitneyU-test; n = 31,U = 40; P = 0.032).
DISCUSSION
We tested the hypothesis that frugivorous bats ingest
water for nutrient supplementation or soil material
6 SIMON J. GHANEM ET AL.
Figure 3. Soil tracer concentrations (μg g−1 of dry matter) of the soil tracer elements Al = aluminium (a), Ce = cerium (b), La = lanthanum (c),
Nd=neodymium (d), Ti= titanium (e), andY= yttrium (f), in droppings of frugivorous bats (every tick on the x-axis is a sample, n=21) captured at
mineral licks in eastern Ecuador. Theupper95%confidence interval of themedian (95%CI) of soil tracer concentrations in the faeces of insectivorous
bats (n = 10) served as a baseline soil tracer concentration for bats not consuming soil. We considered frugivorous bats as soil consumers, when
tracer concentrations in their faecal material were above the upper 95% CI of soil tracer concentrations in the faeces of insectivorous bats (see given
percentages).
for detoxification at mineral licks of the Amazon rain
forest. Similar to previous studies, we captured mostly
reproductively active female frugivorous species visiting
mineral licks (Bravo et al. 2008, 2010; Tuttle 1974,
Voigt et al. 2007, 2008). Although, we were not
able to document large numbers of drinking bats with
our automated camera setup, our video observations
with hand-held cameras demonstrate unambiguously
that bats drank water at mineral licks in the lowland
Ecuadorian Amazon. We suggest that this water uptake
is most likely unrelated to the daily water requirements,
because frugivorous species usually consume large
amounts of water when ingesting fruits (Morrison
1980, Ruby et al. 2000). The high water content of
fruits is presumably sufficient for lactating bats when
facing elevated water demands during milk production.
Instead, frugivorous bats are probably attracted to the
water-filled depressions at mineral licks, because the
water is more enriched in nutrients such as sodium
than water from local creeks, ponds or rivers. In
support of the nutrient supplementation hypothesis, we
found that the composition of physiologically relevant
Tropical fruit-eating bats and mineral licks 7
elements (Na, Mg, K and Fe) differed between blood
collected from frugivorous bats at mineral licks and
blood collected from bats at open-forest sites. Still, one
has to be careful interpreting the results of the blood
elemental comparison. Because bats are highly mobile,
our study design allows that individuals captured far
away from mineral licks may have visited mineral
licks as well. Further, the calculated ANOSIM might
be sensitive to the varying sample sizes of species. Not
controlling for this variation might compromise our
data by pseudoreplication and bias the results towards
those species with large sample size, for example Artibeus
obscurus. However, none of the species with large sample
sizes showed extreme values and therefore, we consider
our analysis as robust against such biases. Nevertheless,
we have been able to document significant differences
in the elemental blood composition between bats from
the two locations. Based on these differences, we infer
that traces of the nutrient-enriched water consumed
by bats at mineral licks can be found in their blood
samples, even though elemental composition of blood is
probably regulated within narrow ranges. This finding
is interesting given that extreme deviations of elemental
concentrations fromthe rangeof physiological acceptable
values may be detrimental or even fatal to mammals.
Thus, our finding may provide further support for the
hypothesis that bats take up nutrients at mineral licks
by drinking water from small puddles. A key question
related to this is whether fruits from plants growing in
the Amazonian ecosystem provide sufficient quantities of
essentialmineralnutrients tomeet thedaily requirements
of frugivorous bats during reproduction. Bravo et al.
(2010) reported that figs in Peru include less sodium
than fruits of other tropical regions. Other studies in
Peru showed that parrots with diets extremely low in
sodium often supplement their diets by eating soils with
high concentrations of sodium, most likely to meet their
daily nutrient demands (Brightsmith & Mun˜oz-Najar
2004, Gilardi et al. 1999). In the present study, we
showed that nutrient concentrations of fruits collected
from Ecuadorian rain forests had less sodium, potassium
and phosphorus than fruits fromCosta Rican rain forests.
Although we may introduce a bias with dry-weight
comparisons or a limited sample size, our findings are in
accordance with the data of the Peruvian studies that
suggest that the western Amazon region is generally
depleted in mineral nutrients. This can be attributed
to the unique geographical features of the western
lowlandAmazon.This region is essentiallybeyondcoastal
climate and thus marine input of sodium, because of
its isolation from the Pacific Ocean by the Andes to
the west, and the Atlantic Ocean to the east (Kaspari
et al. 2008). Moreover, the soils of the Amazonian rain
forest are ancient and have degraded and leached over
millions of years (Terborgh 1992). A recent study by
Dudley et al. (2012) proposed a cross-taxonomic need
for sodium especially in the Western Amazon region,
where mineral licks are used to minimize the nutritional
deficit. Thus, low concentrations of nutrients in plants
and their associated fruits may be caused by the nutrient
depletion of Amazonian soils (Jordan & Herrera 1981,
Stark 1970). Mineral licks and mineral supplementation
may become superfluous in areas with overall higher
levels of mineral nutrients in their soils, such as in
Costa Rica.
Basedonnutrient data fromthe infructescences ofPiper
collected in Ecuador and Costa Rica, and the measured
rates of water flux in Carollia brevicauda, a frugivorous
bat species and Piper specialist (Voigt et al. 2006), we
estimated the nutritional deficit in this species when
consuming only Ecuadorian fruits. For the daily water
flux of 30 ml d−1 for C. brevicauda (Voigt et al. 2006), we
assumed that about20%of thiswater fluxoriginates from
theoxidationof fat asmetabolicwater. Thus,C. brevicauda
must consume approximately 24 ml d−1 of water from
fruits to maintain its daily water balance. Given that
fruits are comprised of about 70% water, we estimated
that this fruit-eating species handles approximately 31 g
of fruits each day. As a conservative approach, we
assumed that a bat takes up about 70% of the nutrients
of the consumed fruits. Thus, C. brevicauda in Ecuador
would be expected to consume about 1 mg sodium, 8 mg
calcium and 4 mg magnesium less than a respective
Costa Rican individual on a daily basis. For sodium the
daily minimum requirements of small mammals in their
most demanding life periods have been reported to be
600 ppm on a dry matter basis (Dempsey 2004). The
estimated sodium values for Ecuadorian C. brevicauda
when consuming exclusively Piper infructescences lay
below these minimum requirements. However, our
nutrient analysis of water from mineral licks suggests
that a daily consumption of 1–2 ml of mineral-
lick water may be sufficient to compensate for this
deficit depending on the bioavailability of the dissolved
nutrients.
A notable problem in most studies that have measured
the composition of tropical fruits is that they focused
on total availability of nutrients in fruits rather than
on the bioavailability of mineral elements. Fruits that
contain large amounts of secondary compounds such as
phytateoroxalatecan limit thebioavailabilityofnutrients
(Kamchan et al.2004).Onesuchexamplecanbeobserved
in figs, a food item largely preferred by the genusArtibeus.
While figs are known to be rich in total calcium (Wendeln
et al. 2000), they often contain high levels of oxalate
that not only bind the calcium in the fruit (Kamchan
et al. 2004), but may also reduce the amount of calcium
available to the animal when it is consumed. Thus, many
fig-eating bats may actually lack essential nutrients in
their diet.
8 SIMON J. GHANEM ET AL.
In addition to a higher demand for nutrients,
reproductively active bats also have higher energy
demands (Korine et al. 2004, Racey & Speakman 1987,
Voigt 2003). Thus, an increase in fruit consumption in
response to these demands should lead to an increase
in secondary metabolites absorbed. Many of these
compounds negatively affect their consumers, because
they can be carcinogenic, teratogenic, toxic, or they may
simply bind to elements as do phytate or oxalate (Heiser
1969, Kamchan et al. 2004).
The elemental analysis of bat droppings in our study
revealed higher concentrations of soil tracers in faeces
collected from frugivorous species compared with our
calculated threshold for soil consumption (95% CI of
the median). As this threshold is based on insectivorous
bats that were never observed at mineral licks, higher
concentrations of soil tracers provide clear evidence for
geophagy in frugivorous bats of the lowland Amazonian
rain forest.
The soil tracer aluminium is a major structural
componentof clayminerals suchaskaolinitesor smectites
(Mahaney & Krishnamani 2003). A higher enrichment
of this element in faeces strongly suggests that fruit-
eating bats consume clay minerals or other soil fractions
while they are visiting water puddles at mineral licks.
In a wide range of studies on birds and mammals, the
consumption of claymineralswas linked to detoxification
of plant secondary compounds. Brightsmith et al. (2008)
andGilardi et al. (1999) showed that clayminerals suchas
kaolinite buffer remarkable amounts of the toxin quinine,
which is similar in structure to other compounds that
occur in the diets of frugivorous parrots. Given these
observations, it seems quite likely that bats could also
benefit from the buffering and thus detoxifying effects of
consumed clay minerals.
Our findings provide direct evidence that frugivorous
bats obtain both essential mineral nutrients and soil
material at mineral licks by drinking water from
these sites. Two reasons may be causal for the
drinking behaviour of female frugivorous bats during
reproduction, apart from a demand for water: (1) female
frugivorous bats may require more essential elements
duringreproductionthantheirdietof fruitcansupply,and
(2) possible exposure to higher levels of plant secondary
metabolites may require the use of clay minerals as a
detoxifying buffer. Although our correlative study design
may allow other explanations, we suggest that in a
mineral-depleted area, such as Western Amazonia, the
drinking behaviour of frugivorous bats at mineral licks
serves a dual function, namely nutrient supplementation
and detoxification of plant secondary compounds in their
diet. Our findings may help as a basis for future captive
studies to quantify mineral and toxic levels of diets and to
disclose their physiological consequences for bats in the
wild such as mineral deficiency or intoxication.
SUPPLEMENTARY MATERIAL
For supplementary material for this article, please visit
http://dx.doi.org/10.1017/S0266467412000740.
ACKNOWLEDGEMENTS
We wish to thank the administrative staff at the Tiputini
Biodiversity Field Station and the La Selva Biological
Station, as well as the governmental authorities of
Ecuador and Costa Rica for granting permission to work.
Wealso thankLena John, JaimeGuerra for fieldassistance
andUrsula Grunewald and IrinaOttenbacherwho kindly
did the sample preparation and the digestion for the
geochemical analysis. All protocols were approved by the
AnimalCareandUseCommittee fromtheLeibniz Institute
for ZooandWildlifeResearchand fromBostonUniversity.
This study was supported by a grant from the German
National Council to CCV (Vo 890/15), and from Boston
University’sCenter forEcologyandConservationBiology.
LITERATURE CITED
ABRAHAMS, P.W. & PARSONS, J. A. 1996. Geophagy in the tropics: a
literature review. The Geographical Journal 162:63–72.
BLAKE, J. G., GUERRA, J., MOSQUERA, D., TORRES, R., LOISELLE,
B. A. & ROMO, D. 2010. Use of mineral licks by white-bellied
spider monkeys (Ateles belzebuth) and red howler monkeys (Alouatta
seniculus) in eastern Ecuador. International Journal of Primatology
31:471–483.
BRAVO, A., HARMS, K. E., STEVENS, R. D. & EMMONS, L. H. 2008.
Collpas: activity hotspots for frugivorous bats (Phyllostomidae) in
the Peruvian Amazon. Biotropica 40:203–210.
BRAVO, A., HARMS, K. E. & EMMONS, L. H. 2010. Puddles created by
geophagous mammals are potential mineral sources for frugivorous
bats (Stenodermatinae) in the Peruvian Amazon. Journal of Tropical
Ecology 26:173–184.
BRIGHTSMITH, D. J. & MUN˜OZ-NAJAR, R. A. 2004. Avian geophagy
and soil characteristics in southeastern Peru. Biotropica 36:534–
543.
BRIGHTSMITH, D. J., TAYLOR, J. & PHILLIPS, T. D. 2008. The roles
of soil characteristics and toxin adsorption in avian geophagy.
Biotropica 40:766–774.
CALABRESE, E. J. & STANEK, E. J. 1995. A dog’s tale – soil ingestion by
a canine. Ecotoxicology and Environmental Safety 32:93–95.
CALABRESE, E. J., STANEK, E. J., PEKOW, P. & BARNES, R. M. 1997.
Soil ingestion estimates for children residing on a superfund site.
Ecotoxicology and Environmental Safety 36:258–268.
CLARKE, K. R. & WARWICK, R. M. 1994. Change in marine
communities: an approach to statistical analysis and interpretation.
Natural Environment Research Council, London. 144 pp.
DEMPSEY, J. L. 2004. Fruit bats: nutrition and dietary husbandry.
Nutrition Advisory Group Handbook 14:1–17.
Tropical fruit-eating bats and mineral licks 9
DIAMOND, J. M. 1999. Evolutionary biology: dirty eating for healthy
living.Nature 400:120–121.
DIAMOND, J., BISHOP, K. D. & GILARDI, J. D. 1999. Geophagy in New
Guinea birds. Ibis 141:181–193.
DUDLEY, R., KASPARI,M. &YANOVIAK, S. P. 2012. Lust for salt in the
Western Amazon. Biotropica 44:6–9.
EMMONS, L. H. & STARK, N. M. 1979. Elemental composition
of a natural mineral lick in Amazonia. Biotropica 11:311–
313.
GILARDI, J. D., DUFFEY, S. S., MUNN, C. A. & TELL, L. A. 1999.
Biochemical functions of geophagy in parrots: detoxification of
dietary toxins and cytoprotective effects. Journal of Chemical Ecology
25:897–922.
HANDLEY, C. O., WILSON, D. E. & GARDNER, A. L. 1991. Demography
and natural history of the common fruit bat, Artibeus jamaicensis,
on Barro Colorado Island, Panama. Smithsonian Institution Press,
Baltimore.
HEISER, C. B. 1969. The wonderberry. Pp. 62–105 in Nightshades: the
paradoxical plants. W. H. Freeman & Co., San Francisco.
HOLDØ, R.M., DUDLEY, J. P., MCDOWELL, L. R. & TOMASI, T. E. 2002.
Geophagy in theAfrican elephant in relation to availability of dietary
sodium. Journal of Mammalogy 83:652–664.
JORDAN, C. F. &HERRERA,R. 1981. Tropical rain forests: are nutrients
really critical? American Naturalist 117:167–180.
KAMCHAN, A., PUWASTIEN, P., SIRICHAKWAL, P. P. &
KONGKACHUICHAI, R. 2004. In vitro calcium bioavailability of
vegetables, legumes and seeds. Journal of Food Composition and
Analysis 17:311–320.
KASPARI, M., YANOVIAK, S. P. & DUDLEY, R. 2008. On the
biogeography of salt limitation: a study of ant communities.
Proceedings of the National Academy of Sciences USA 105:17848–
17851.
KLAUS, G. & SCHMID, D. B. 1998. Geophagy at natural licks and
mammal ecology: a review.Mammalia 62:481–497.
KORINE, C., SPEAKMAN, J. & ARAD, Z. 2004. Reproductive energetics
of captiveand free-rangingEgyptian fruit bats (Rousettus aegyptiacus).
Ecology 85:220–230.
KREULEN, D. 1985. Lick use by large herbivores: a review of
benefits and banes of soil consumption. Mammal Review 15:107–
123.
KRISHNAMANI, R. & MAHANEY, W. C. 2000. Geophagy among
primates: adaptive significance and ecological consequences.Animal
Behaviour 59:899–915.
KUNZ, T. H. & NAGY, K. A. 1988. Methods of energy budget analysis.
Pp. 277–302 in Kunz, T. H. (ed.) Ecological and behavioral methods
for the study of bats. Smithsonian Institution Press, Washington,
DC.
KUNZ, T. H., ADAMS, R. A. & HOOD, W. R. 2009. Methods for
assessing postnatal growth and development of bats. Pp. 273–324
in Kunz, T. H. & Parson, S. (eds.) Ecological and behavioral methods for
the study of bats. (Second edition). Johns Hopkins University Press,
Baltimore.
MAHANEY, W. C. & KRISHNAMANI, R. 2003. Understanding
geophagy in animals: standard procedures for sampling soils. Journal
of Chemical Ecology 29:1503–1523.
MONTENEGRO, O. L. 2004.Natural licks as keystone resources for wildlife
and people in Amazonia. Ph.D. dissertation, University of Florida,
Gainesville.
MORRISON, D. W. 1980. Efficiency of food utilization by fruit bats.
Oecologia 45:270–273.
NATIONAL RESEARCH COUNCIL. 2005. Mineral tolerance of animals.
National Academies Press, Washington, DC. 510 pp.
RACEY, P. A. & SPEAKMAN, J. R. 1987. The energy costs of pregnancy
and lactation in heterothermic bats. Symposium of the Zoological
Society of London 57:107–125.
REX, K., KELM, D. H.,WIESNER, K., MATT, F., KUNZ, T. H. & VOIGT, C.
C. 2008. Structure of three Neotropical bat assemblages. Biological
Journal of the Linnean Society 94:617–629.
RUBY, J.,NATHAN,P.T.,BALASINGH, J.&KUNZ,T.H.2000.Chemical
composition of leaves and fruits eaten by the short-nosed fruit
bat, Cynopterus sphinx (Megachiroptera). Journal of Chemical Ecology
26:2825–2841.
RUPPERT, H. 1987. Bestimmung von Schwermetallen im Boden sowie die
ihr Verhalten beeinflussenden Bodeneigenschaften. Beilage zum GLA-
Fachbericht 2, Munich. 11 pp.
STARK,N. 1970. The nutrient content of plant and soils fromBrazil and
Surinam. Biotropica 2:51–60.
TERBORGH, J. 1992. Diversity and the tropical rain forest. Scientific
American Library, New York. 242 pp.
TIMM, R. M. & LAVAL, R. K. 1998. A field key to the bats of Costa
Rica. Occasional Publication Series, Center of Latin American Studies,
University of Kansas 22:1–30.
TIRIRA, S. D. 2007. Guı´a de Campo de los Mamı´feros del Ecuador. Quito.
576 pp.
TUTTLE, M. D. 1974. Unusual drinking behavior of some stenodermine
bats.Mammalia 38:141–144.
VOIGT, C. C. 2003. Reproductive energetics of the nectar-feeding
bat Glossophaga soricina (Phyllostomidae). Journal of Comparative
Physiology B 173:79–85.
VOIGT, C. C., KELM, D. H. & VISSER, G. H. 2006. Field metabolic rates
of phytophagous bats: do pollination strategies of plants make a
life of nectar-feeders spin faster? Journal of Comparative Physiology
B 176:213–222.
VOIGT, C. C., DECHMANN, D. K. N., BENDER, J., RINEHART,
B. J., MICHENER, R. H. & KUNZ, T. H. 2007. Mineral licks attract
neotropical seed-dispersing bats. Research Letters of Ecology 2007:
Article ID 34212.
VOIGT, C. C., CAPPS, K. A., DECHMANN, D. K. N., MICHENER, R.
H. & KUNZ, T. H. 2008. Nutrition or detoxification: why bats
visit mineral licks of the Amazonian rainforest. PLoS ONE 3:
e2011.
WENDELN, M. C., RUNKLE, J. R. & KALKO, E. K. V. 2000. Nutritional
values of 14 fig species and bat feeding preferences in Panama.
Biotropica 32:489–501.
10 SIMON J. GHANEM ET AL.
Resumen: En la Amazonia Central, los mamı´feros grandes construyen charcos de agua durante el consumo del suelo.
Estos saladeros son frecuentemente visitados por murcie´lagos frugı´voros por dos posibles razones: suplementar su
dieta baja en minerales por medio de beber agua con alto contenido de sales o amortiguar compuestos secundarios
provenientes de plantas. Hemos analizado frutos consumidos pormurcie´lagos en Ecuador y observamos una reduccio´n
en el contenido deminerales (Na, K, P) en comparacio´n con frutos similares colectados en Costa Rica, donde no existen
saladeros (n = 32). Los ana´lisis de agua de seis saladeros en Ecuador revelaron un mayor contenido de minerales con
relevancia fisiolo´gica (Na, K, Mg, Ca) a cuatromuestras de puntos de control de rı´os y afluentes. Con el uso de ca´maras
infrarrojas grabamosmurcie´lagos tomando agua en saladeros. Determinamos si los murcie´lagos ingierenminerales al
tomar agua rica en nutrientes en los saladeros comparando el contenido de minerales con relevancia fisiolo´gica (Na,
K, Mg, Fe) en la sangre de 68murcie´lagos que visitan los saladeros conmurcie´lagos capturados en sitios de control. La
sangredemurcie´lagos frugı´voroscapturadosen lossaladerosdifiereensucomposicio´ndemineralesde lademurcie´lagos
capturados en otros sitios. Tambie´n examinamos si los murcie´lagos consumı´an arcilla buscando trazas de suelo en
31 muestras de heces. Dichas trazas son insolubles en agua y, por lo tanto, no incluidas en una dieta frugı´vora.
Los murcie´lagos frugı´voros que visitan los saladeros mostraron una mayor concentracio´n de trazas de suelo en las
heces que murcie´lagos insectı´voros que nunca los visitan. Nuestros resultados proveen evidencia que los murcie´lagos
frugı´voros ingieren nutrientes minerales solubles y arcilla insoluble al consumir agua enriquecida con arcilla en los
saladeros. Esto apoya la hipo´tesis que losmurcie´lagos frugı´voros de laAmazonia occidental obtienenundoble beneficio
al visitar dichos saladeros.