# Study of honey bee (Apis mellifera) water preferences: do bees really like dirty water?

Pierre Le Bivic, Cedric Alaux, Jules Domalain, Cyril Vidau, Yves Le Conte, Luc P Belzunces, Maryline Pioz

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Pierre Le Bivic, Cedric Alaux, Jules Domalain, Cyril Vidau, Yves Le Conte, et al. Study of honey bee (Apis mellifera) water preferences: do bees really like dirty water?. Apidologie, 2025, 56 (6), pp.99. 10.1007/s13592-025-01219-3. hal-05457569

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# Study of honey bee (Apis mellifera) water preferences: do bees really like dirty water?

Pierre LE BIVIC<fnref n="1" />,<fnref n="4" /> Ⓓ, Cedric ALAUX<fnref n="1" />,<fnref n="4" /> Ⓓ, Jules DOMALAIN<fnref n="1" />,<fnref n="4" />, Cyril VIDAU<fnref n="2" />,<fnref n="4" /> Ⓓ,
Yves LE CONTE<fnref n="1" />,<fnref n="4" /> Ⓓ, Luc P. BELZUNCES<fnref n="1" />,<fnref n="3" />,<fnref n="4" /> Ⓓ, and Maryline PIOZ<fnref n="1" />,<fnref n="4" /> Ⓓ

Received 12 February 2025 – Revised 4 August 2025 – Accepted 20 August 2025

**Abstract** – Honey bees collect water primarily for thermoregulation and larval food production. For these purposes, honey bees can collect water from a wide range of sources, raising concerns among beekeepers about the risks this may pose to colony health if these waters are polluted or contaminated. However, honey bee preferences for different water sources are poorly understood, except that bees prefer to collect mineral-rich water to achieve colony nutritional homeostasis. Therefore, we investigated honey bee water preferences and how ambient temperatures, which influence thermoregulation, affect these preferences. To this end, we tested, under semi-field conditions and multiple-choice conditions, waters sampled from different environmental sources (rainwater, swimming pool water, pond water and farm puddle water) likely to be collected by bees, and slurry waters (mixture of livestock feces and urine), a reported but controversial source of water and nutrients, diluted at different rates. Unexpectedly, our results showed that honey bees expressed a strong preference for distilled water and the least mineralized waters (i.e., rainwater and 0.1% dilution of slurry water). Visits to the waterers decreased with increasing mineralization of environmental waters or with increasing concentration of slurry waters. Finally, we found that, as expected, the number of bees foraging at the waterers increased with temperature, but the bees' water preferences remained unchanged. Our study provides a better understanding of honey bee water collection as a function of temperature and sheds light on the influence of water quality on bee's water preferences.

**Feeding preferences / Foraging behavior / Salts / Slurry / Temperature**

## 1. INTRODUCTION

Honey bees (Apis mellifera L.) collect water mainly to produce food for larvae (Lindauer 1955; Seeley 1995) and to maintain colony thermal homeostasis (Lensky 1964; Kühnholz and Seeley 1997; Ostwald et al. 2016; Bordier et al. 2017). Water collected by honey bees comes

from a wide range of sources, including puddles, streams, irrigation, swimming pools, or even the sea (Lau and Nieh 2016). This diversity of water collected by honey bees raises questions about the exposure of colonies to biological (MacInnis et al. 2021) and chemical agents (Johnson and Pettis 2014; Samson-Robert et al. 2014) that may be present in the environmental water sources. However, it is unclear how honey bees detect a water source and what factors determine their choice when different water sources are available in their environment, making it challenging to

<footnote n="1">¹ INRAE, UR406 Abeilles Et Environnement, Avignon, France</footnote>

<footnote n="2">² ITSAP-Institut de L'Abeille, Avignon, France</footnote>

<footnote n="3">³ Laboratoire de Toxicologie Environnementale, INRAE, UR 406 Abeilles Et Environnement, Avignon, France</footnote>

<footnote n="4">⁴ UMT PrADE, Protection Des Abeilles Dans L'environnement, Avignon, France</footnote>

<footnote>Corresponding author: P. Le Bivic, pierrelebivic@gmail.com</footnote>

<footnote>Manuscript editor: Juliana Rangel.</footnote>
effectively advise beekeepers on how to ensure an efficient colony water supply.

We assume that honey bees use multi-sensory cues to find water sources, just as they do to find floral resources (Leonard and Masek 2014). First, studies have shown that some insects can detect water visually using light polarized by reflection from water or moist substrates (Schwind 1991, Shashar et al. 2005). These may be either insects that have a ventral or dorsal eye region that is sensitive to polarized light, such as aquatic insects and honey bees, respectively (Horváth 1995; Rossel 1989). Since honey bees are attracted to visibly occupied flowers (observational learning) (Avarguès-Weber et al. 2015), seeing other honey bees foraging at a water source could be another visual cue that helps honey bees locate water. Water foragers can also expose their Nasonov glands to release pheromones that help recruits find water sources (Free and Williams 1970). In addition, honey bees have hygroreceptors in most antennal segments (Yokohari et al. 1982) that are sensitive to changes in air humidity, presumably to help them maintain their water balance (Tichy and Kallina 2014). Therefore, we can assume that hygroreceptors are involved in the detection of water sources by honey bees.

Water odor cues could also be used by honey bees to locate or select water sources. To our knowledge, only one study has investigated the effect of olfactory cues on honey bee water choice (Butler 1940). Butler collected rainwater from a gutter clogged with leaves, cow dung water, and urine, and compared the attractiveness of these solutions to bees with their distillates and residual salts dissolved in distilled water, both obtained by evaporation. He found that the distillates were highly preferred to distilled water and residual salts, but that this preference was significantly reduced after the distillates were filtered with animal charcoal for 36 h. The honey bee's choice of water sources is also influenced by the colony's specific nutritional needs (Bonioan et al. 2017, 2018; Khan et al. 2021). In fact, some terrestrial insects (e.g., Hymenoptera, Lepidoptera, Orthoptera, Diptera) are known to feed on moist soil, mud, or vertebrate fluids (blood,

secretions, feces), presumably to collect nutrients such as mineral salts, nitrogen, or amino acids, that are scarce or absent in their diet, a behavior known as “puddling” (Molleman 2010). Among bees, some stingless (e.g., *Lisotrigona sp.*) and solitary bees (e.g., *Centris sp.*) in tropical areas have been observed collecting sweat and tears from mammals (including humans), reptiles, and birds (Bänziger et al. 2009; Bänziger and Bänziger 2010; Dangles and Casas 2012; de la Rosa 2014; Sazima et al. 2020). In Spain, bumble bees (*Bombus terrestris* L.) have been observed foraging on human urine and fluids from a wild goat carcass (Herrera 1990) and, in India, Asian honey bees (*Apis dorsata* F.) have been observed foraging on brackish water containing animal waste (Abrol et al. 2012). Honey bees have also been reported to collect diluted livestock effluent (Butler 1940), presumably to supplement their diet with mineral salts.

Since the water preferences of honey bees remain poorly known, we investigated in a first experiment which of a selection of environmental water sources would be most visited by the bees. To this end, we tested, under multiple-choice conditions, environmentally sampled waters (hereafter referred to as “environmental waters”) likely to be visited by honey bees (rainwater, swimming pool, pond and farm puddle waters). Then, in a second experiment, we analyzed the attractiveness of waters collected from farm slurry pits (mixture of livestock feces and urine), since livestock effluent has been reported to be collected by honey bees (Butler 1940) for water or nutrients. Such water was referred to as “slurry waters” to distinguish the two experiments (experiment 1: preferences for sampled environmental waters in a multiple-choice test, experiment 2: preferences for slurry water diluted at different rates in a multiple-choice test).

We investigated bee water preferences from different perspectives: the number of bee visits to each experimental water (foraging effort), the probability that a bee foraged at an experimental water (visiting probability), and the daily visitation rate. Based on the literature, we expected distilled water to be less attractive to
bees, because bees seek minerals in water that are lacking in their diet to achieve nutritional homeostasis of the colony. However, because high mineral content may be repulsive to bees (de Sousa et al. 2022), we postulate that experimental waters with low to moderate mineral content should be the most attractive to bees. In addition, honey bees may also use water for thermoregulation to protect the colony from heat stress. However, to our knowledge, the effect of ambient temperature on honey bee water preferences has never been investigated. We therefore investigated whether ambient temperature affects honey bee water preferences. We expected that honey bee water preferences may be less restrictive for thermoregulatory purposes than for feeding purposes, especially under intensely warm conditions.

## 2. MATERIALS AND METHODS

### 2.1. Experimental set up

The study was carried out at the INRAE research center in Avignon (France) from May 2021 to July 2021. A semi-field design was chosen in order to control water collection by the colonies and to avoid any external supply via nectar or other water sources. Each choice experiment lasted 4 consecutive days, during which two colonies (6 to 8 brood frames in a 10-frame Dadant-sized hive) were placed under a tunnel (15 × 7 m) covered with an insect-proof net (polyethylene high-density, 920 × 920 µm openings, Diatex France). Both colonies were placed at one end of the tunnel one day before starting the experiments to allow them to familiarize with the waterers. The experiments were conducted on sunny and, if possible, on windless days (average wind speed < 20 km/h). Throughout the experiment, colonies were fed ad libitum with organic pollen (chestnut, Castanea sativa Mill., dominance) and sugar paste (Apimel, Apitec). Chestnut pollen was chosen because of its availability in the experimental area and its good nutritional quality (Di Pasquale et al. 2013). A “training table” (120 × 60 cm) was used

to investigate honey bee water preferences, and was placed approximately 10 m from the colonies. The “training table” consisted of two parts: one to allow honey bees to collect experimental water (free waterers) and the other to measure evaporation (control waterers covered by a cage with an insect-proof net as described above). On each part of the “training table” the waterers were placed in a 4 × 4 pattern, with two replicates for each experimental water. An illustration of this device can be found in Bonoan et al. (2017). The Free waterers were placed on a removable plate that was rotated at a 90° clockwise every two hours to prevent the honey bees from learning their location. The waterers consisted of a 50 ml Falcon tube turned upside down on a Petri dish (85 mm) with the cap pierced to allow the solutions to drain (such as siphon drinkers). The Falcon tubes were painted white to prevent honey bees from seeing the experimental waters. White was chosen because bees cannot distinguish it (Kevan et al. 1996). Each morning, the waterers were filled with approximately 40 mL of experimental water (then refilled as needed throughout the day) and randomly placed on the “training table” using a random list generator (https://www.random.org). The waterers were extensively washed with water, then with 70% (v/v) ethanol, and finally rinsed with distilled water at the end of each day to remove any traces of odors or pheromones.

### 2.2. Experimental water collection

We investigated honey bee preferences for sampled environmental waters and slurry water diluted at different rates in multiple-choice conditions, using distilled water as a control.

#### 2.2.1. Environmental waters

Environmental waters included rainwater, swimming pool water, pond water and puddle water sampled from manure spreading areas in cattle, sheep, and horse farms (giving 6 environmental waters and 1 control water). Note that 2
waterers were left empty to maintain the 4×4 square design. This selection is based on the fact that some of these water sources are known to be visited by honey bees (e.g., rainwater or swimming pool water), or because we have observed honey bees visiting them (e.g., pond water), or finally because they are likely to be visited by honeybees (e.g., farm puddle waters). These waters were all sampled at once, each from a single source, after a rain event on April 11, 2021 (except for the swimming pool water sampled on April 20, 2021). After sampling, they were stored in borosilicate glass bottles at +2 °C until the choice experiments. The multiple-choice test of environmental waters was conducted first between May 18 and May 21, 2021, and then between June 29 and July 02, 2021, by using the same two colonies.

### 2.2.2. Slurry waters

Choice experiments with slurry waters were performed with new colonies. Slurry water was collected from slurry pits on two cattle farms on May 11, 2021, and then stored until the experiments in borosilicate glass bottles at +10 °C. The storage temperature differed from that of the environmental waters because more slurry than environmental water was collected and the two could not be stored in the same place. Although Butler (1940) reported that honey bees collect diluted livestock effluents, no additional information was available. Therefore, we tested a wide range of dilutions, especially very diluted solutions (i.e., between 1 and 5% slurry), to accurately determine the concentrations that might attract bees. To this end, we tested 12 dilution levels ranging from 0.1% to 100% slurry water. Because there were 16 waterers, including control and replicates, the range of slurry water solutions was split and investigated separately: the very dilute solutions (0.1, 0.25, 0.5, 0.75, 1, 2.5 and 5% (v/v)) on one hand, and the wider range of dilutions (0.1, 1, 10, 25, 50, 75 and 100% (v/v)) on the other hand. Dilutions were made with distilled water the day before the experiments and stored at +2 °C. The multiple-choice

test was conducted separately for each slurry water collected from two farms, each of which was tested twice as described above (see Table S1 for the experimental dates). Two colonies were used for the tests on the slurry water collected from the first farm, and two new ones were used for the slurry water from the second farm. The last week of the experiment, involving the second slurry water, was conducted under real conditions (i.e., outside the tunnel), after the bees had been trained to come to the waterers. This was done to investigate if the bees' preferences would change in a free-flying environment.

## 2.3. Data collection

Data collection started one day after moving colonies to the tunnels provided with experimental waters. Each day, measurements were made between 09:00 h and 17:00 h. Counts of bees were made every 15 min (refers as counting session) by checking each waterer (5 s per waterer). All honey bees collecting water, i.e. with submerged proboscis and pulsating abdomen, were counted. For each counting session, three consecutive counts were made to account for observed differences in the number of foragers arriving at the waterers. Temperature was recorded before each counting session using a digital thermometer (accuracy 1 °C) placed inside the tunnel and out of sunlight. Finally, the daily quantity of experimental water collected by honey bees was measured by weighing the waterers before and after each filling and subtracting the evaporation (OHAUS NVT6201 portable scale, 0.1 g accuracy). It should be noted, however, that weighing was not possible during the last week of the experiment (i.e. outside the tunnel) due to wind.

## 2.4. Chemical analyses of environmental waters

The chemical analyses were performed by the Terana Drôme Laboratory (26000 Valence, France) under the requirements of the ISO/IEC
17025 standard (i.e. quality management). The chemical parameters sought in these waters included concentrations in nitrogen (Kjeldahl nitrogen, nitrates and nitrites) and ionic compounds (phosphorus, chloride, calcium, potassium, magnesium, and sodium). The methods used by the laboratory and their limits of quantification (LOQ) are listed for each chemical parameter in the Supplementary Material (Table S2). However, chemical analysis of the slurry waters could not be performed with these methods because their color and turbidity interfered with the results. The percent mass (% w/w) of environmental waters was calculated by dividing the mass of the solute by the mass of the solvent and multiplying the result by 100. The density of environmental waters was assumed to be of 1 g/L.

## 2.5. Statistical analysis

Statistical analysis were performed using R software v4.3.1 (R Core Team 2020). The data from the choice tests for environmental waters (N=3696) and diluted slurry waters (N=8448) were analyzed separately. However, the data from the two slurry water experiments (two farm origins) were analyzed together because they showed a similar response pattern (see the Results section).

We investigated honey bee water preferences and the effect of temperature by modeling, first, the foraging effort, second, visiting probability, and third, daily visitation rates with generalized linear mixed effects models (GLMMs) fitted to a Poisson distribution with a log link, a Bernoulli distribution with a logit link, and a binomial distribution with a logit link, respectively. The GLMMs were fitted using the package glmmTMB v1.1.8 (Brooks et al. 2017). For each experiment, all three response variables were derived from the same raw data counts. For foraging effort, we used the maximum number of bees among the three consecutive counts as the dependent variable for each waterer. For the visiting probability, data were transformed into binary data (presence/absence) to obtain the

dependent variable of the Bernoulli models. For the daily visitation rates (N=56 and N=128 for environmental waters and diluted slurry waters, respectively), the dependent variable was the proportion of counts in which foragers were seen relative to the total number of counts made each day (at a rate of one count every 15 min between 09:00 h and 17:00 h). We selected these three response variables to investigate bee water preferences from different perspectives: foraging effort, likelihood of visiting, and frequency of visits.

In all GLMMs, fixed effects included experimental waters, temperature (the daily maximum temperature for the model with daily visitation rates, otherwise the temperature recorded during the counts), and a two-way interaction between experimental waters and temperature. For the modelling of foraging effort and visiting probability, we also accounted for time of day (mins) by including in the fixed effects time elapsed from the first count (expressed in minutes from 0, corresponding to the first measurement, to 480, the last). Natural cubic splines were used to account for a non-linear effect of time, and the degree of complexity (i.e., the number of knots) of the spline function was selected by the Akaike's Information Criterion (AIC) (Harrell 2015). Natural cubic splines were computed using the package splines v4.3.1 (R Core Team 2020). For the models of foraging effort and visiting probability, we specified random intercepts for dates and the waterers within a date, and a random slope to allow the effect of time to vary between waterers. In contrast, in the models of daily visitation rates, we specified random intercepts for dates only. Prior to model fitting, temperature was centered and scaled to unit SD. We did not include an offset term in the foraging effort models, as each count occurred within the same short time interval of 5 s (Hilbe 2014). We also checked for overdispersion and zero inflation. We used Conway-Maxwell-Poisson (CMP) distributions to account for underdispersion (Lynch et al. 2014) in the foraging effort models, as their dispersion ratios were 0.90 and 0.66 for the environmental waters and slurry data, respectively. Finally, for all GLMMs, we
estimated the proportion of variance explained by either the fixed part (marginal R² or R²_m) or by both the fixed and random parts of the models (conditional R² or R²_c). Model predictions were extracted using the package ggeffects v1.2.3 (Lüdecke 2018). Zero inflation and overdispersion were checked, and coefficients of determination were computed using the package performance v0.10.4 (Lüdecke et al. 2021). The slopes (and their 95% CI) for each level of experimental waters were estimated using the package emmeans v1.8.7 (Lenth 2023).

Principal Component Analysis (PCA) was used to perform the chemical typology of the environmental waters. The PCA was performed with the package FactoMineR v2.8 (Lê et al. 2008). Nitrites were excluded from the PCA because they were detected at a low concentration (0.1 mg/L) only in the sheep farm puddle water (see the Results Section). The variables included in the PCA were centered and scaled to unit SD. For all statistical tests used in our data analysis, the statistical significance level was set at α=0.05.

## 3. RESULTS

We tested honey bee preferences for either environmental waters (Fig. S1) or diluted slurry waters (Fig. S2) under multiple-choice conditions, and then investigated whether changes in ambient temperature affected them, by focusing on foraging effort, daily visitation rates, and visiting probability.

For the diluted slurry waters experiment, we sampled from two farms and investigated whether bee preferences differed between semi-field and field conditions (i.e., inside and outside the tunnel, respectively). Our results showed that bee preferences for diluted slurry waters were unaffected (Fig. S2) by slurry origin (Spearman's ρ=0.80, df=427, p-value <0.001) or experimental conditions, i.e. semi-field and field conditions (ρ=0.78, df=427, p-value <0.001). Therefore, we analyzed all data from the diluted slurry waters experiment together.

Regarding the proportion of variance explained by the selected models, their fixed part explained 65%, 93%, and 50% of the observed variance in foraging effort, daily visitation rate, and visiting probability respectively, for the environmental water experiment. For the diluted slurry waters experiment, the fixed part of the selected models explained 79%, 89%, and 68% of the observed variance in foraging effort, daily visitation rate, and visiting probability respectively (conditional R² are given in Tables S3 to S8).

### 3.1. Mineral composition of environmental waters

The concentrations of the investigated chemical compounds (Figure 1) were higher in the horse and cattle farm puddle waters than in the other environmental waters, except for nitrates which were higher in the swimming pool water. Regarding the chemical typology of the environmental waters, the first two axes of the PCA (Figure 2) accounted for 79.9% (PCA1) and 13.3% (PCA2) of the total variance. PCA1 contrasted, on the negative side, waters with low (distilled water and rainwater) and medium (pond water, swimming pool water and sheep farm puddle water) concentrations of chemical compounds (all except nitrates) and, on the positive side, waters with high mineralization (horse and cattle farm puddle waters). While PCA2 contrasted waters with high nitrate concentrations (swimming pool water) on the positive side, with waters with low or no nitrate concentrations (all other waters) on the negative side.

### 3.2. Honey bee water preferences

We found a strong positive correlation between the daily amount of water collected by the colonies and the total number of foragers counted per day (Pearson's r=0.88, 95% CI [0.47, 0.98], t=4.6, df=6, p-value = 0.004 for environmental waters, and r=0.91, 95% CI [0.72, 0.98], t=7.2, df=10, p-value < 0.001 for slurry waters).
<figure><img src="image_2.png" /><figcaption>**Figure 1.** Chemical composition of environmental waters. Environmental waters are shown on the x-axis. Values in facets denote results expressed in mg/L. Note: Ca: calcium, Cl: chloride, K: potassium, Mg: magnesium, Na: sodium, P: phosphorus.</figcaption></figure>

<figure><img src="image_3.png" /></figure>
<figure><img src="image_4.png" /><figcaption>**Figure 2.** Chemically-based typology of distilled water and environmental waters. Ordination diagrams show (a) the distribution of the environmental waters and (b) their chemical parameters along the first two axes (dimensions) of a PCA. Ca: calcium, Cl: chloride, K: potassium, Mg: magnesium, Na: sodium, P: phosphorus.</figcaption></figure>
waters, Fig. S3). All of the experimental waters were visited less than distilled water, except for rainwater (Figures 3 and 4, the coefficients of the models are shown in Tables S3 and S6). Holding all other covariates (i.e., temperature and time) at their mean values and considering distilled water as the reference level, the number of visits was of 58% for swimming pool water, 45% for pond water, 24% for sheep farm puddle water, while it was only 3% and 2% for horse and cattle farm puddle waters, respectively. Similarly, for slurry waters, the number of visits was of 78% for the 0.1% dilution of slurry water, 39% for the 0.50% dilution, 22% for the 1% dilution, 10% for the 2.5% dilution, and almost zero for dilutions equal to or greater than 25%.

The daily visitation rate is the proportion of daily counts in which at least one bee was observed foraging in an experimental water (Figures 3 and 4, the coefficients of the models are shown in Tables S4 and S7). In other words, it shows how frequently bees visit the experimental waters. When the daily maximum temperature was kept at its mean value, the daily visitation rate was greater than 85% for distilled water, rainwater, swimming pool water, and pond water. Similarly, the daily visitation rate was over 75% for the most diluted slurry waters (i.e., those containing 1% slurry or less). In addition, our results showed that some waters visited by few bees could still have moderate to high daily visitation rates. This occurred with the sheep farm puddle water, which had a daily visitation rate of about 70%, and with the 10% dilution of slurry water, which had a daily visitation rate of 20%. However, the daily visitation rate was below 20% for horse and cattle farm puddle waters and 5% or less for the most concentrated slurry waters (i.e., those with 25% or more slurry).

The visiting probability expresses the likelihood that a bee will visit an experimental water (Figures 3 and 4, the coefficients of the models are shown in Tables S5 and S8). With the temperature and time covariates held at their means as above, the visiting probability was between 80 and 100% for distilled water, rainwater, swimming pool water, and pond water, but it decreased rapidly with increasing mineralization

or slurry concentration. Thus, the visiting probability was only 55% for the 1% dilution of slurry water and 46% for the sheep farm puddle water, while it was almost zero for the horse and cattle farm puddle waters, as well as above the 10% dilution of slurry water.

### 3.3. Effect of temperature on bee water preferences

Regarding the effect of temperature on foraging effort (Figures 3, 4, S4 and S7), when time was held at its mean value, a 6 °C increase in temperature increased the number of visits to distilled water by 74% in the environmental waters experiment, and by about 90% in the diluted slurry waters experiment. Increasing ambient temperatures did not alter the bees' preference for water in either experiment. The effect of temperature on foraging effort was close in magnitude to that of distilled water for rainwater, swimming pool water, and pond water, as well as for dilutions ranging from 0.1% to 5% of slurry water. However, a 6 °C increase in temperature only increased the number of visits by 24% for sheep farm puddle water, while it decreased the number of visits by about 40% and 65% for horse and cattle farm pond water, respectively. For dilutions equal to or greater than 10% of slurry water, the temperature had no effect on foraging effort.

For the daily visitation rate (Figs. S5 and S8), we found that it increased with temperature only for the 0.75%, 2.5%, and 5% dilutions of slurry waters, while it decreased with temperature for horse and cattle farm puddle waters. For the other experimental waters, temperature did not affect the daily visitation rate. Finally, the visiting probability (Figs. S6 and S9) increased with temperature for distilled water and all environmental waters, except for horse and cattle farm puddle waters, as well as for dilutions ranging from 0.1% to 5% of slurry water.

In conclusion, we found that bee water preferences decreased monotonically with increasing mineralization or slurry concentration of waters,
<figure><img src="image_5.png" /></figure>

<figure><img src="image_6.png" /></figure>

<figure><img src="image_7.png" /></figure>

<figure><img src="image_8.png" /></figure>

**Figure 3.** Effect of ambient temperatures on honey bee preferences for distilled water and environmental waters. (a) Predicted number of foragers (with the 95% confidence intervals) for three temperature levels: the mean of the recorded temperature (28.3 °C), denoted by 0, and plus or minus one standard deviation (6 °C) thereof. *Time* is held at its mean value. Bee counts were recorded every 15 min, between 09:00 h and 17:00 h. (b) The daily visitation rate is the proportion of daily counts in which at least one bee was foraging in an environmental water (at a rate of one count every 15 min, between 09:00 h and 17:00 h). The dots show the predicted daily visitation rates and the bars show their 95% confidence intervals for three temperature levels: the mean (32.4 °C) of the daily maximum temperature (*Tmax*), denoted by 0, and plus or minus one standard deviation (5.1 °C) thereof. (c) Predicted probability of a bee foraging on distilled water and environmental waters as a function of temperature. Shaded areas represent the 95% confidence intervals.

<figure><img src="image_9.png" /></figure>
<figure><img src="image_10.png" /></figure>

**Figure 4.** Effect of ambient temperatures on honey bee preferences for distilled water and diluted slurry waters. Diluted slurry waters were prepared by diluting slurry water with distilled water and the resulting concentration was expressed as a percentage (v/v) of the slurry water. Raw slurry (without added water) is reported as 100%. (a) Predicted number of foragers (with the 95% confidence intervals) for three temperature levels: the mean of the recorded temperature (30.1 °C), denoted by 0, and plus or minus one standard deviation (6 °C) thereof. *Time* is held at its mean value. Bee counts were recorded every 15 min, between 09:00 h and 17:00 h. (b) The daily visitation rate is the proportion of daily counts in which at least one bee was foraging in a diluted slurry water (at a rate of one count every 15 min, between 09:00 h and 17:00 h). The dots show the predicted daily visitation rates and the bars show its 95% confidence intervals for three temperature levels: the mean (34.5 °C) of the daily maximum temperature (*Tmax*), denoted by 0, and plus or minus one standard deviation (3.8 °C) thereof. (c) Predicted probability of a bee foraging on distilled water and diluted slurry waters as a function of temperature. Shaded area are the 95% confidence intervals. For readability, only six solutions of diluted slurry waters are shown.

<figure><img src="image_11.png" /></figure>
and that in multiple-choice conditions the tem-
perature did not affect these preferences.

4. DISCUSSION

We aimed to test the honey bee preferences for field-sampled waters and to investigate how ambient temperature affects their choice, by focusing on foraging effort, daily visitation rate and visiting probability. To this end, we conducted two experiments, one with waters sampled from the environment and another with solutions of diluted slurry waters. Under multiple-choice conditions and in accordance with the water samples used in this study, our results showed that honey bees have a stronger preference for distilled water and the least mineralized waters (i.e., rainwater, or 0.1% (v/v) dilution of slurry water) and, to a lesser extent, for waters with intermediate mineralization (i.e., swimming pool water, pond water, sheep farm puddle water, or slurry dilutions ranging from 0.25% to 1% of slurry water). Conversely, the most mineralized waters were weakly visited (here horse and cattle farm puddle waters, or slurry dilutions at concentrations above 1% of slurry water). However, it should be noted that although the bees showed a strong preference for distilled water and weakly mineralized waters, all the experimental waters were visited at least once, likely in a foraging exploratory process. Also, despite the low number of visits (and therefore the low visiting probability) observed at the most mineralized waters, their visiting rate could be high (e.g., the visiting rate was 20% of the total daily counts for the 10% dilution of slurry water): in other words, few bees visited these waters, but they were visited several times a day. Regarding the effect of temperature on honey bee water preferences, as expected, we showed that the number of bees foraging for the experimental waters increased with ambient temperature, but bee water preferences remained unchanged.

Lau and Nieh (2016) tested the salt solution
preferences (NaCl, MgCl₂, KCl, and Na₂HPO₄)
of water foragers via the proboscis extension
reflex (PER) response in the concentration range

of 0 to 10% (w/w). They found a maximum PER
response at 1.5% w/w for NaCl and MgCl2, 0.4%
and 0.75% (w/w) for Na2HPO4, and at concen-
trations below 1.5% (w/w) for KCl, while they
observed the minimum PER response at 10%
(w/w) concentration for all but one salt (i.e.,
NaCl). In our study, environmental waters had
mineral concentrations in the range of 0—0.08%
(w/w), with the exception of Cl and K in horse
farm puddle water at 0.17% and 0.16% (w/w),
respectively (Figure 1). However, horse and cat-
tle farm puddle waters were hardly collected at
all, even though their salt concentrations were
well below those that elicited the lowest PER
response in the study by Lau and Nieh (2016).
A first explanation is that the bees preferred the
less mineralized waters because the chestnut
pollen we provided met their mineral needs.
However, this remains a hypothesis because we
could not find any information in the scientific
literature regarding the mineral composition
of chestnut pollen. Next, the seasonal condi-
tions could have affected the water preferences
of the bees. Indeed, we know that honey bees
can detect different salts by taste (i.e., contact
chemoreception) with gustatory sensillae located
on their antennae, proboscis and tarsomeres (de
Brito Sanchez 2011). Salt-sensing by honeybees
seems to be concentration-dependent (Butler
1940; de Sousa et al. 2022), with sensitivity to
salt showing inter-individual variation (Lau and
Nieh 2016) and depending on season (Bonoan
et al. 2017, 2018; Khan et al. 2021), age, and
task specialization (Bestea et al. 2021). In addi-
tion, honey bees have a feeding aversion to
diets with high concentrations of mineral salts
(Butler 1940; Cairns et al. 2021; de Sousa et al.
2022), which could be reflected by an avoidance
response to toxic levels of salts (Raubenheimer
and Simpson 2009; de Sousa et al. 2022). Hence,
the multiple-choice conditions could also have
influenced the choice of the bees towards the less
mineralized waters by offering different types of
water instead of a unique type water proposed to
bees at various salt concentrations.

Another explanation could be based on the
fact that the experimental waters used in our
study are complex mixtures of mineral salts,
organic compounds, and volatiles, among others. These can affect the scent and the taste of the water, which may ultimately alter bee water preferences. Although our results are consistent with a salt-concentration-dependent preference, this could also explain the lower number of visits observed in our study for farm puddle waters compared to other environmental waters. In addition, like slurry, the farm waters tested contain livestock effluents, and our results with slurry showed that only the most dilute slurry solutions were highly frequented by bees. As the mineral diet of honey bees is poorly understood, it would be interesting to conduct further studies to better understand the proximate and ultimate causes of salt sensitivity in water foragers. It is also important to note that our experiments were conducted in spring and summer, and we expect honey bee water preferences to change later in the year according to seasonal variation in honey bee salt preferences and colony needs (Bonoan et al. 2017; Khan et al. 2021).

Regarding the collection of diluted slurry water by honey bees, to the best of our knowledge, only two other studies besides ours and Butler's (1940) have investigated this issue. Piscitelli (1959) offered honey bees different concentrations of slurry water under multiple-choice conditions, but never observed the bees collecting them. Ricchiuti et al (2019) offered slurry water to honey bees to investigate the hypothesis of oxytetracycline transfer from water collected by bees in the slurry to honey, but saw only drone flies (*Eristalis tenax* L.) visiting the slurry water, while bees collected water from surrounding puddles. Based on our results, we cannot exclude the possibility that livestock effluents may be visited by honey bees, especially in a highly diluted form, a behavior that could increase with ambient temperature. In addition, the low number of visits observed for more concentrated slurry waters (i.e., dilutions greater than 1%) could be due to the specialization of some bees in mineral foraging. As a next step, it would therefore be interesting to investigate in situ (e.g. through seasonal insect inventories) whether honey bees, like butterflies (Anoop et al. 2023),

perform “puddling” on livestock effluents, and if so, under which conditions. Additionally, it remains unclear to what extent non-*Apis* bees depend on environmental water sources to meet their physiological needs in and/or minerals. As far as we know, aside from tear-feeding behavior observed in tropical areas (Bänziger and Bänziger 2010; Dangles and Casas 2012), only a few instances of bumblebees collecting water (Ferry and Corbet 1996) or body fluids (Herrera 1990) have been documented. In fact, the water content of nectar, as well as the metabolic water production of wild bees (in larger species), could be sufficient to maintain their water balance (Nicolson and Louw 1982; Bertsch 1984; Willmer 1988). However, more research is needed to understand how non-*Apis* bees meet their water needs, particularly in the context of a warming world.

Honey bee colonies store only a small quantity of water and collect water on a “just-in-time” basis to meet their needs (Ostwald et al. 2016). In addition, the foraging range of water collectors is spatially more limited than that of nectar collectors, because their return flight is solely provided by their body’s energy reserves (Visscher et al. 1996). This, combined with the fact that honey bees collect water from a wide range of sources (Butler 1940; Lau and Nieh 2016), leads us to assume that honey bee are primarily opportunistic water collectors. Therefore, and based on our data, we suggest that providing clean water in apiaries should allow colonies to meet their essential water needs while limiting their exposure to health-damaging contaminants that may be present in environmental water sources. Additionally, we know that sodium holds a special place among the nutrients sought by bees. For instance, adding sodium chloride (0.5% w/w) to floral nectar increases both the diversity of pollinators visiting flowers and the number of visits per flower (VanValkenburg et al. 2024), and when added to water (e.g. at 0.5% or 1.5% w/w), honey bees prefer to collect this salty water over pure water (Bonoan et al. 2017; McCune et al. 2021; Khan et al. 2021). In fact, consumers of plant products seek out alternative sources of sodium
because it is present in low concentrations in most plants, but remains essential for electrochemical equilibrium of organisms (Subbarao et al. 2003; Kaspari 2020). Therefore, and consistent with empirical beekeeping knowledge, beekeepers can use sodium chloride to attract bees and perhaps help them remain loyal to the water they provide to their colonies, in concentrations ranging from 0.5% (McCune et al. 2021) to 1.5% (w/w) (Khan et al. 2021).

## 4.1. Study Limitations

Several points must be carefully considered when interpreting our results. First, our study is based on only two colonies per experiment, and we used only one sample of each type of experimental water. However, is noteworthy that true replicates cannot be performed when studying waters collected from the environment, due to large variability in water composition. Second, we used a multiple-choice condition design with “clean” waters, such as distilled water, rain-water, and slurry waters containing less than 1% slurry. This might have caused the bees to reject the less attractive waters more readily than if they had only been exposed to one of these unattractive waters. Third, we could not clean the waterers during the counts in order to eliminate any odors and/or Nasonov pheromone that could have been left by the foragers (Free and Williams 1970). These substances might influence the bees’ water preferences. Finally, we did not track individual foragers from both colonies. Thus, multiple visits by the same bees to some experimental waters could have amplified the measured foraging effort on these waters. Therefore, before generalizing our results, it would be necessary to repeat our study with more colonies and with several samples of each type of experimental waters.

To conclude, our study provides new insights on the relationship between bees and water resources, and we hope that this will be useful to beekeepers to better manage this resource in their apiaries, especially in the context of climate change and increasing pollution of water resources linked to anthropogenic activities.

# SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at https://doi.org/10.1007/s13592-025-01219-3.

# A KNOWLEDGEMENTS

The authors thank Bernard Vaissière for his review and constructive feedback on our manuscript, Julien Vallon, Julie Fourrier and Antoine Sudan for providing the honey bee colonies, as well as Christophe Roy and Axel Decourtye for providing some of the experimental waters. We would also like to thank the three anonymous reviewers for their helpful comments, which improved the manuscript.

# AUTHOR CONTRIBUTIONS

Conceptualization: Pierre Le Bivic, Maryline Pioz; Methodology: Pierre Le Bivic, Maryline Pioz; Investigation: Jules Domalain, Pierre Le Bivic, Maryline Pioz; Data Curation: Jules Domalain, Pierre Le Bivic; Formal Analysis: Pierre Le Bivic; Visualization: Pierre Le Bivic; Writing – original draft: Pierre Le Bivic; Writing – review & editing: Cedric Alaux, Luc P. Belzunces, Yves Le Conte, Maryline Pioz; Project Administration: Maryline Pioz; Supervision: Luc P. Belzunces, Maryline Pioz, Cyril Vidau; Funding Acquisition: Luc P. Belzunces, Maryline Pioz, Cyril Vidau.

# FUNDING

This work was supported in part by grants from the European Agricultural Guarantee Fund as part of the French National Apiculture Program (FranceAgriMer agreement number 20-01 R).

# DATA AVAILABILITY

Data will be made available on reasonable request.

# DECLARATIONS

**Competing Interests** The authors have no relevant financial or non-financial interests to disclose.

**Ethics approval** Honey bees are not covered by European Union legislation on the welfare of animals used for scientific purposes (Directive 2010/63/EU), which applies in France. The data collection was purely observational and the experiments were carried out with care to ensure the welfare of the colonies by providing pollen, sugar and water ad libitum. At the end of the experiments, the colonies were returned to an environment suitable for meeting their needs.
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