Water scooping: tool use by a wild bonobo (Pan paniscus) at LuiKotale, a case report

Tool use diversity is often considered to differentiate our two closest living relatives: the chimpanzee (Pan troglodytes) and the bonobo (P. paniscus). Chimpanzees appear to have the largest repertoire of tools amongst nonhuman primates, and in this species, many forms of tool use enhance food and water acquisition. In captivity, bonobos seem as adept as chimpanzees in tool use complexity, including in the foraging context. However, in the wild, bonobos have only been observed engaging in habitual tool use in the contexts of comfort, play, self-directed behaviour and communication, whilst no tool-assisted food acquisition has been reported. Whereas captive bonobos use tools for drinking, so far, the only report from the wild populations comes down to four observations of moss sponges used at Lomako. Here, we present the first report of tool use in the form of water scooping by a wild bonobo at LuiKotale. An adult female was observed and videotaped whilst using an emptied Cola chlamydantha pod to scoop and drink water from a stream. We discuss the conditions for such observations and the importance of looking out for rare behaviours and attempt to put the observation into the context of the opportunity versus necessity hypotheses. By adding novel information on tool use, our report contributes to the ongoing efforts to differentiate population-specific traits in the behavioural ecology of the bonobo.

Drinking on the wing: water collection in polarotactic horseflies

Many insects detect water bodies by observing the linearly polarised light which is reflected from the water surface. Polarotactic horseflies exhibit acrobatic manoeuvres above the water and are able to plunge on its surface, collect a droplet and fly away. This behaviour is extremely fast and has not yet been analysed. We recorded the flight patterns and kinematics of drinking horseflies using a pair of high-speed cameras. The animals of both sexes are attracted to water puddles where they make short, millisecond pitstops to collect a droplet of water that is then presumably drank "on the wing". Before the collection, the flies perform several low-altitude flybys above the puddle. After a few passes, the fly suddenly reverses its body orientation, decelerates, briefly touches the water surface and immediately flies away, usually with a droplet carried between its front legs. During the approach flight, the horseflies fly low but do not show any angular preference. Thus, they view the reflections from the sky, sun, or vegetation with a wide band of ventral ommatidia. Polarotaxis in drinking horseflies is a very robust visually guided behaviour, which operates at a broad range of intensities and various spectral compositions of reflected light.

Water intake and risk of type 2 diabetes: A systematic review and meta-analysis of observational studies

BACKGROUND AND AIMS

The association of water intake with type 2 diabetes mellitus (T2DM) is still unclear. Therefore, the aim of this systematic review and meta-analysis was to synthesize the knowledge about the relationship between water intake and the risk of T2DM.

METHODS

We conducted a systematic search in PubMed and Scopus up to June 2018 for observational studies. Risk ratios (RR)s and 95% confidence intervals (95% CI)s were calculated and fixed effects models were used.

RESULTS

Overall, 6 studies were included in the meta-analyses. There was an inverse relationship between water intake and risk of T2DM (RR: 0.94; 95% CI: 0.91-0.97, P < 0.001) with low heterogeneity (I2 = 24%, P = 0.24).

CONCLUSION

Our findings indicated that the intake of water was correlated with reduced risk of type 2 diabetes in women and men. These results support the current recommendations of water intake as an inseparable part of a diet with the lowest risk of diabetes mellitus.

"I know it's just pouring it from the tap, but it's not easy": Motivational processes that underlie water drinking

Water drinking behaviour is under-researched despite the prevalence and adverse health consequences of underhydration. We conducted a qualitative exploration into the motivational processes underlying water drinking, informed by a grounded cognition perspective on desire and motivated behaviour. We interviewed and analysed data from 60 participants stratified by age, gender, and education level using thematic analysis, to generate three key themes. "Water as situated habits," suggests that participants form and maintain situated water drinking habits, so that within certain situations they regularly drink water. However, participants who situated their water intake only in one key situation (e.g., work routine), had low and inconsistent intake when they left this situation. Some situations happened so infrequently during the day (e.g., before bed) that participants' daily water intake was low. Many participants reported drinking water in reaction to thirst cues, but these were easily suppressed or ignored, so that water drinking was inconsistent. Participants who saw drinking water as part of their self-identity had consistent and high water intake across a variety of situations. "Knowledge and attitudes," suggests that few participants had knowledge or attitudes that promoted water intake (e.g., perceived water as positive or understood the importance of hydration). "Strategies underlying attempts to increase intake" suggests that many participants lacked insight into strategies to increase water intake, although they spontaneously discussed attempts to drink more. This lead to ineffective attempts at behaviour change. Participants' mentions of dehydration and their responses to a urine colour chart suggested that many participants were possibly underhydrated. Our findings suggest that interventions and practitioners attempting to increase water intake need to increase knowledge about the importance of hydration, and encourage individuals to develop effective situated water drinking habits.

Seasonal changes in background levels of deuterium and oxygen-18 prove water drinking by harp seals, which affects the use of the doubly labelled water method

The aim of this study was to monitor seasonal changes in stable isotopes of pool freshwater and harp seal (Phoca groenlandica) body water, and to study whether these potential seasonal changes might bias results obtained using the doubly labelled water (DLW) method when measuring energy expenditure in animals with access to freshwater. Seasonal changes in the background levels of deuterium and oxygen-18 in the body water of four captive harp seals and in the freshwater pool in which they were kept were measured over a time period of 1 year. The seals were offered daily amounts of capelin and kept under a seasonal photoperiod of 69°N. Large seasonal variations of deuterium and oxygen-18 in the pool water were measured, and the isotope abundance in the body water showed similar seasonal changes to the pool water. This shows that the seals were continuously equilibrating with the surrounding water as a result of significant daily water drinking. Variations in background levels of deuterium and oxygen-18 in freshwater sources may be due to seasonal changes in physical processes such as precipitation and evaporation that cause fractionation of isotopes. Rapid and abrupt changes in the background levels of deuterium and oxygen-18 may complicate calculation of energy expenditure by use of the DLW method. It is therefore strongly recommended that analysis of seasonal changes in background levels of isotopes is performed before the DLW method is applied on (free-ranging) animals, and to use a control group in order to correct for changes in background levels.