For an animal living in an arid region, water is a more critical resource than food. Hunger can be measured in weeks, whereas a lack of water has consequences much sooner. Scorpions' success in the desert belt comes not from skill in finding water but from their mastery at not losing the water they find.
Where does the water come from?
Scorpions' water sources can be grouped under three headings. The first is the prey itself: most of a captured arthropod's body is water, and liquid feeding allows this water to be taken in directly. The details of how they feed are covered in the article on feeding.
The second is metabolic water. Water is released inside cells as nutrients are broken down; in animals of arid environments, this contribution is far from negligible. The third is water taken directly from the environment. Scorpions have been observed taking water from damp ground at the entrance to their shelter or from condensed droplets; so the short answer to the question is yes, scorpions do drink water when they have the chance.
Whether they can absorb moisture directly from the air is more debatable. In some arthropod groups, water uptake from the air has been demonstrated under conditions of high relative humidity; the extent to which scorpions have this ability varies by species, and it would be wrong to generalize. What is certain is that droplets collecting on surfaces through condensation provide an accessible source.
The share of these three sources varies with conditions. An individual that feeds regularly gets most of its water from its prey, whereas for an individual that has not found prey for a long time, environmental moisture becomes decisive.
Structures that limit loss
The real issue is not intake but output. The scorpion's body design cuts water loss at three separate points.
- Exoskeleton: The waxy layer in the outer part of the cuticle largely prevents evaporation. When this layer is damaged, the animal's water loss increases markedly.
- Respiratory structures: The book lungs lie inside the body and have narrow openings, so the moisture lost during gas exchange remains limited.
- Excretion: Most waste is eliminated in semi-solid form as compounds that are poorly soluble in water. This keeps the water spent on removing waste to a minimum.
Working together, these three structures allow the animal to keep its water budget within an extremely narrow range. As body size decreases, the surface-area-to-volume ratio increases, and so does evaporative pressure; for this reason, the risk of desiccation is higher in young and freshly moulted individuals than in adults. This is why these groups are considered separately in the care plan.
A behavioural layer is added to this. Staying in the shelter during the hot hours of the day, shifting activity to the night and keeping close to the ground keep the animal away from the most desiccating conditions. In captivity, the counterpart of this behaviour is a suitable shelter in every container that the animal can retreat into.
How is water provided in a closed enclosure?
Recreating the balance of nature in a closed system requires adjustment in two directions. The aim is not to wet the container but to leave the animal a limited source of moisture that it can reach.
| Practice | What it provides | Risk |
|---|---|---|
| Small, shallow water dish | Directly accessible water | Drowning in a deep dish; microbial growth in contaminated water |
| Moisture held in absorbent material | Slow-release source of moisture | Mould, increase in mites |
| Moistening one corner of the container | A moisture gradient the animal can choose from | Unnatural conditions if everything is wetted |
| Feeding with fresh prey | Water intake via prey | Gaps between feeds |
The options in the table are not alternatives to one another but practices that are often used together. Which one carries the most weight depends on the species' natural habitat, the size of the enclosure and the general humidity of the room. For species from the arid belt, the rule of thumb is to keep water accessible without letting the environment dry out.
Maintenance of the water dish is often overlooked. Standing water quickly becomes contaminated; if it is not changed regularly, it stops being a water source and becomes a source of contamination. Keeping the dish shallow and placing a surface inside that makes it easier to grip is established practice.
The general humidity of the environment should not be confused with this local source of moisture. How relative humidity and temperature are managed together in the colony is explained in the article on temperature and humidity. What is described here is a small damp area that the animal can reach by its own choice.
Reading the signs
A disturbed water balance shows itself during husbandry through a few signs. Individuals that have gone without water for a long time may show sluggish movements, marked shrinkage of the body and a lack of interest in prey. The opposite error, a constantly wet substrate, can be recognized by a musty smell, condensation on the container walls and clumping of the substrate.
The moulting period has a special place here. It is the stage at which the animal is most sensitive to its water balance, and an environment that is too dry makes it harder for the old exoskeleton to come away cleanly; the stages are covered in detail in the article on moulting. During this period, care is taken to ensure the moisture source is accessible, but the animal is not disturbed.
Signs should not be interpreted hastily. Inactivity can be explained not only by dehydration but also by low temperature, an approaching moult or satiety. For this reason, decisions are not based on a single observation; temperature, humidity and feeding records are read together.
Recording observations is more valuable than any individual sign. When the dates on which the water dish was changed, humidity readings and individual observations are written in the same logbook, it becomes easier to trace the cause when a problem arises. This also gives a continuous picture when care is carried out by different people. The role of this record-keeping in colony management is explained in the article on closed-cycle breeding.
