Dehydration / Desiccation

Dehydration, also referred to as desiccation in severe cases, represents one of the most common and preventable health emergencies affecting captive invertebrates. This condition occurs when an invertebrate loses more water from its body than it can replace, leading to a dangerous deficit in bodily fluids that are essential for virtually every physiological process. Unlike vertebrates that have sophisticated internal mechanisms for water retention, most invertebrates rely heavily on environmental humidity and direct water access to maintain proper hydration levels, making them exceptionally vulnerable to inadequate moisture conditions in captivity.

Dehydration affects an extraordinarily wide range of invertebrate species kept in the exotic pet trade, though the severity and speed of onset vary considerably based on the natural habitat requirements of each species. Tropical tarantulas, hermit crabs, millipedes, isopods, land snails, and many other terrestrial invertebrates require specific humidity ranges to survive, and even short-term exposure to dry conditions can trigger rapid water loss through their permeable exoskeletons or shells. Aquatic and semi-aquatic species such as freshwater shrimp, crabs, and crayfish face immediate life-threatening consequences if removed from water or exposed to inadequate moisture during transport or tank maintenance.

The impact of dehydration on invertebrate health cannot be overstated, as water is fundamental to circulation of hemolymph, respiration, digestion, molting, and cellular function throughout the body. Dehydrated invertebrates experience cascading organ system failures as their bodies struggle to maintain basic functions without adequate fluid volume. Molting, which requires significant hydration to complete successfully, becomes impossible or dangerous for dehydrated individuals, often resulting in stuck sheds that prove fatal. Additionally, dehydration severely compromises the immune system, leaving affected invertebrates vulnerable to secondary infections that may prove fatal even if rehydration efforts succeed.

The treatability of dehydration depends entirely on how quickly the condition is identified and addressed. Mild to moderate dehydration caught early typically responds well to environmental correction and supportive care, with most invertebrates recovering fully within days to weeks. However, severe desiccation causes irreversible cellular damage that no amount of rehydration can repair, making this condition frequently fatal once it progresses beyond a certain threshold. Prevention through proper husbandry remains far more effective than treatment, emphasizing the critical importance of understanding and meeting the humidity requirements specific to each invertebrate species in your care.

The primary cause of dehydration in captive invertebrates is inadequate environmental humidity, which occurs when enclosure conditions fail to match the moisture requirements of the species being kept. Many invertebrate keepers, particularly those new to the hobby, underestimate just how humid certain species require their environment to be, leading to chronic low-level dehydration that eventually manifests as acute health crises. Species originating from tropical rainforests, humid forests, or moist microhabitats require humidity levels that may seem excessive to keepers accustomed to standard room conditions, yet these elevated moisture levels are absolutely essential for survival.

Environmental factors contributing to dehydration extend beyond simple humidity measurements to include temperature, ventilation, substrate type, and enclosure design. Excessive heat accelerates water evaporation both from the enclosure itself and directly from the invertebrate's body, particularly problematic when heating elements are improperly positioned or thermostats malfunction. Cross-ventilation, while necessary for preventing stagnant air and mold growth, can rapidly strip moisture from enclosures if not properly balanced with humidity maintenance. Inappropriate substrates that fail to hold moisture, such as dry sand or wood chips, cannot support the humidity requirements of moisture-dependent species and contribute to environmental desiccation.

Husbandry-related causes represent the most common pathway to invertebrate dehydration and encompass a wide range of keeper errors and oversights. Failure to provide adequate water sources, whether water dishes, misting, or moist substrate areas, leaves invertebrates without means to replenish lost fluids. Infrequent misting schedules, particularly during dry seasons or when indoor heating reduces ambient humidity, allow enclosure conditions to drop below safe levels. Neglecting to monitor humidity with appropriate instruments means keepers may be entirely unaware that their animals are slowly desiccating until clinical signs become obvious.

Certain risk factors predispose individual invertebrates to dehydration even when husbandry appears adequate for most specimens. Animals preparing for or recovering from molts have significantly increased water requirements, as the molting process itself demands substantial fluid reserves. Juvenile invertebrates, with their smaller body mass and proportionally larger surface area, lose water more rapidly than adults and require more attentive humidity management. Wild-caught specimens may arrive already dehydrated from capture and transport stress, requiring immediate rehydration efforts before standard husbandry routines can maintain them adequately.

The mechanism of water loss in invertebrates differs from vertebrates and helps explain their vulnerability to environmental conditions. Most terrestrial invertebrates lose water primarily through their exoskeleton, respiratory surfaces, and excretory processes, with the rate of loss directly influenced by ambient humidity levels. The cuticular wax layer that helps waterproof arthropod exoskeletons provides only partial protection and becomes less effective at very low humidity or elevated temperatures. Invertebrates lack the sophisticated kidney function and hormonal water-balance mechanisms that allow vertebrates to conserve water internally, making them almost entirely dependent on environmental moisture availability for survival.

Early warning signs of dehydration in invertebrates manifest primarily as subtle behavioral changes that attentive keepers can recognize before physical symptoms become apparent. Affected invertebrates often demonstrate increased time spent near water sources, repeatedly visiting water dishes or congregating in the moistest areas of their enclosure. Reduced activity levels and reluctance to leave humid retreats, even during normal active periods, indicate the animal is prioritizing water conservation over other behaviors. Some species, particularly tarantulas, may be observed drinking more frequently or for longer durations than usual, suggesting they recognize their fluid deficit and are attempting to compensate.

Physical symptoms of dehydration vary somewhat between invertebrate groups but share common features related to fluid loss and tissue shrinkage. In tarantulas and other spiders, the abdomen becomes visibly shrunken, wrinkled, or shriveled, losing its normally plump, rounded appearance. Hermit crabs may partially retract into their shells and become reluctant to emerge, with their abdomens appearing dry and less supple when visible. Millipedes and centipedes develop a flattened, less turgid body profile, with segments appearing more distinct as internal fluid volume decreases. Isopods curl more tightly than normal and their exoskeletons may appear dull or lighter in color.

Behavioral changes associated with progressing dehydration extend beyond water-seeking to include lethargy, decreased feeding response, and abnormal posturing. Dehydrated invertebrates typically refuse food even when presented with preferred prey items, as their digestive systems cannot function properly without adequate fluids. Movement becomes sluggish and uncoordinated, with affected animals showing reluctance to perform normal activities such as climbing, burrowing, or exploring. Some species may adopt unusual positions, remaining motionless in exposed areas rather than utilizing normal hiding spots, suggesting confusion or weakness related to their deteriorating condition.

Molting-related symptoms deserve particular attention, as dehydration frequently causes or exacerbates molting difficulties that prove fatal. Invertebrates attempting to molt while dehydrated may become stuck in their old exoskeleton, unable to complete the fluid-dependent process of expanding and hardening their new cuticle. Pre-molt animals that would normally fast may show extended periods without eating while simultaneously appearing shrunken, indicating dehydration rather than normal molting behavior. Failed molts resulting from dehydration leave invertebrates trapped in partially shed exoskeletons, often with limbs or body segments still encased in old cuticle that constricts circulation and causes tissue death.

Symptom progression in dehydrated invertebrates follows a predictable pattern from mild fluid deficit to severe desiccation and death. Initial stages involve behavioral compensation and mild physical changes that may go unnoticed by inexperienced keepers. Intermediate dehydration produces obvious physical symptoms including significant body shrinkage, color changes, and marked lethargy. Advanced dehydration causes severe tissue damage, organ dysfunction, and loss of mobility as the animal's body begins to shut down non-essential functions in a desperate attempt to preserve core systems.

Critical and emergency symptoms indicating severe, potentially irreversible dehydration require immediate intervention to give the animal any chance of survival. Complete immobility and unresponsiveness, even when gently stimulated, suggests the invertebrate has entered a critical state. Extreme shrinkage where body segments appear almost hollow indicates severe fluid loss that may have already caused fatal damage. In tarantulas, a death curl posture with legs tucked beneath the body, combined with a severely shriveled abdomen, often indicates the animal is near death or already deceased. Exoskeleton damage such as cracking, splitting, or separation at segment joints results from severe desiccation and typically indicates a terminal condition that cannot be reversed.

Visual examination forms the cornerstone of diagnosing dehydration in invertebrates, as laboratory testing options remain extremely limited for these animals. Keepers should carefully observe the overall body condition, paying particular attention to the abdomen in spiders, the body segments in myriapods, and the general turgidity of soft-bodied species. Comparison with photographs of the same individual when healthy, or with images of well-hydrated specimens of the same species, helps establish whether the current body condition represents abnormal fluid loss. Physical handling, when safe and appropriate for the species, may reveal decreased body weight and a less substantial feel compared to properly hydrated individuals.

Behavioral observation over time provides valuable diagnostic information that complements visual assessment. Monitoring how often the invertebrate visits water sources, whether it shows normal activity patterns, and its response to food offerings all contribute to evaluating hydration status. Tracking these behaviors through brief daily observations and written notes helps identify gradual changes that might not be apparent from a single examination. Abnormal behaviors such as persistent water-seeking, excessive time in humid retreats, or failure to engage in species-typical activities should raise suspicion of hydration problems.

Environmental parameter assessment is essential for confirming dehydration as the cause of observed symptoms and identifying the underlying husbandry problems that must be corrected. Accurate humidity measurements using digital hygrometers, taken at multiple locations within the enclosure including hide areas, should be compared against species-specific requirements. Temperature readings help identify heat-related moisture loss, while examination of water sources confirms availability and accessibility. Substrate moisture levels should be assessed by touch, as surface humidity readings may not reflect conditions in burrows or beneath decorations where invertebrates spend significant time.

Differential diagnosis requires consideration of other conditions that may produce similar symptoms to dehydration. Pre-molt fasting and reduced activity in arthropods can mimic dehydration symptoms, though properly hydrated pre-molt animals should maintain normal body turgor. Illness from bacterial, fungal, or parasitic infections may cause lethargy and reduced feeding similar to dehydration. Toxicity from pesticides, cleaning products, or inappropriate substrates can produce weakness and behavioral changes. Old age and natural senescence cause gradual decline that may include reduced body condition. Careful evaluation of husbandry history, environmental parameters, and symptom timeline helps distinguish dehydration from these alternative diagnoses.

Environmental correction forms the essential first line of treatment for dehydrated invertebrates and must be implemented immediately upon recognizing the condition. Humidity levels should be raised to the upper end of the species-appropriate range through increased misting, addition of larger water dishes, and reduction of ventilation if excessive airflow has been contributing to moisture loss. For critically dehydrated animals, creating an intensive care setup with elevated humidity approaching saturation levels provides the best chance for recovery, though this temporary environment should be gradually adjusted back to normal parameters as the animal improves. Temperature should be verified as appropriate and reduced if elevated, as lower temperatures decrease metabolic water loss and give the animal's body more time to recover.

Supportive care measures complement environmental corrections and actively help the invertebrate replenish lost fluids. Providing multiple easily accessible water sources ensures the animal can drink whenever needed without expending precious energy searching for hydration. For some species, particularly hermit crabs and isopods, offering water-soaked foods such as fruits and vegetables provides hydration through feeding. Misting directly on or near the affected invertebrate, allowing it to drink droplets from its body or enclosure surfaces, delivers moisture to animals too weak to travel to water dishes. Dampening the substrate beneath hiding spots creates moist microclimates where dehydrated invertebrates can passively absorb moisture through their exoskeleton.

Medical treatment options for dehydrated invertebrates remain extremely limited compared to vertebrate medicine, reflecting the broader challenges of invertebrate veterinary care. There are no injectable fluids or pharmaceutical interventions specifically designed for invertebrate rehydration comparable to those used for mammals and birds. Oral hydration using dilute electrolyte solutions has been attempted by some keepers, though effectiveness is largely anecdotal and the practice carries risks of aspiration. The most effective medical intervention remains aggressive supportive care through environmental manipulation rather than direct medical treatment, emphasizing the importance of prevention over cure for this condition.

Quarantine protocols during treatment serve both practical and health purposes for dehydrated invertebrates. Isolating affected animals in a dedicated treatment enclosure allows for precise control of environmental parameters without affecting other inhabitants. Smaller quarantine enclosures reduce the energy expenditure required for the dehydrated invertebrate to access water and maintain itself in the humid environment. Separation from conspecifics eliminates stress from competition or aggression during the vulnerable recovery period. Additionally, quarantine provides opportunity to observe the animal closely without disturbance from tank mates that might mask symptoms or interfere with assessment.

Treatment monitoring requires careful observation to assess whether interventions are producing improvement or if the animal continues to decline despite efforts. Daily evaluation of body condition, particularly abdominal turgor in spiders or body segment fullness in myriapods, tracks rehydration progress. Behavioral improvements including increased activity, interest in food, and normal movement patterns indicate successful recovery. Failure to show improvement within 48 to 72 hours of intensive care, or continued deterioration despite intervention, suggests the dehydration may have caused irreversible damage or that an underlying condition is preventing recovery.

Recognizing when treatment is not viable represents a difficult but necessary aspect of invertebrate medicine. Severely desiccated invertebrates with extreme tissue shrinkage, exoskeleton damage, complete immobility, or those already exhibiting death postures typically cannot be saved regardless of intervention intensity. Continuing aggressive treatment of animals with no realistic chance of recovery may only prolong suffering. In such cases, the most humane option may be euthanasia, though methods appropriate for invertebrates differ from those used for vertebrates and should be researched in advance. Prevention must remain the focus going forward, with lessons learned from failed treatment cases applied to improve husbandry for remaining and future animals.

Recovery timeline for dehydrated invertebrates varies considerably based on severity of the condition, species involved, and promptness of treatment initiation. Mild dehydration caught early typically resolves within three to seven days of environmental correction and supportive care, with affected animals returning to normal behavior and body condition relatively quickly. Moderate dehydration may require two to four weeks for full recovery, with gradual improvement in physical appearance and behavior over that period. Severe dehydration survivors, if any recover at all, may take months to fully regain normal body condition and may never return to their pre-illness baseline, sometimes suffering permanent effects from tissue damage sustained during the crisis.

Post-treatment care focuses on maintaining optimal conditions while gradually transitioning from intensive care parameters back to normal husbandry. Humidity should remain at the upper end of appropriate ranges for the species during the recovery period, slowly adjusted downward only after the animal demonstrates sustained improvement. High-quality, easily digestible food should be offered once the invertebrate shows interest in eating, supporting tissue repair and body condition restoration. Handling and disturbance should be minimized during recovery to reduce stress that could impair healing. Monitoring should continue more intensively than normal until the keeper is confident the animal has fully recovered and can maintain hydration under standard conditions.

Prognosis factors influencing recovery success include the degree of dehydration at the time treatment began, overall health status prior to the crisis, species resilience, and life stage of the affected animal. Invertebrates that were otherwise healthy before becoming dehydrated generally recover more successfully than those already compromised by age, disease, or chronic stress. Some species demonstrate remarkable resilience to dehydration, while others perish rapidly from even moderate fluid loss. Juvenile invertebrates may recover quickly due to higher metabolic rates and cellular regeneration capacity, but they also succumb faster if treatment is delayed due to their smaller fluid reserves.

Long-term considerations following recovery from dehydration include potential lasting effects and heightened vigilance for recurrence. Some invertebrates that survive severe dehydration may exhibit permanent changes in behavior, feeding patterns, or molting success. Animals that experienced dehydration during pre-molt periods may suffer molting difficulties when they eventually shed, as damage from the crisis affects the developing new exoskeleton beneath. Keepers should evaluate and address whatever husbandry shortcomings allowed dehydration to occur, implementing improvements to prevent future episodes. Investment in better monitoring equipment, backup systems for humidity maintenance, and education about species-specific requirements helps ensure the recovered animal does not face similar crises in the future.

Proper husbandry forms the foundation of dehydration prevention and requires thorough research into species-specific requirements before acquiring any invertebrate. Each species has evolved to thrive within specific humidity ranges, and keepers must commit to providing these conditions consistently throughout the animal's life. Understanding whether a species requires dry, moderate, or humid conditions, and whether humidity should be uniform or gradient within the enclosure, prevents the fundamental husbandry errors that cause most dehydration cases. Consulting care sheets from reputable sources, joining species-specific keeping communities, and learning from experienced keepers all contribute to developing the knowledge necessary for successful prevention.

Environmental control requires appropriate equipment and consistent maintenance routines to prevent dangerous humidity fluctuations. Digital hygrometers with accurate readings should be placed within enclosures to monitor conditions where the animal actually lives, not just ambient room humidity. Automatic misting systems or regular manual misting schedules maintain humidity levels even during busy periods when keepers might otherwise forget. Enclosure design that balances ventilation with moisture retention, using appropriate cover levels, substrate depth, and water feature placement, creates stable conditions that resist environmental changes. Backup plans for equipment failures, such as extra spray bottles and manual monitoring routines, prevent crises when technology fails.

Quarantine protocols for new specimens should include assessment and correction of hydration status before introducing animals to permanent enclosures. Many invertebrates arrive from dealers already stressed and dehydrated from shipping and holding conditions that prioritized convenience over animal welfare. Initial quarantine in optimal humidity conditions allows new arrivals to recover from transit stress and restore any fluid deficits before facing the challenges of establishing in a new enclosure. This practice also prevents introduction of potentially dehydration-weakened animals to established collections where their compromised condition might make them vulnerable to pathogens.

Stress reduction across all aspects of husbandry contributes to preventing dehydration by maintaining invertebrate health and normal behavior patterns. Stressed invertebrates may hide excessively in suboptimal microhabitats, refuse to drink or eat normally, or experience physiological changes that increase water loss. Providing adequate hiding spots, appropriate photoperiods, proper social grouping or isolation depending on species, and minimal disturbance from handling or maintenance all reduce stress. Temperature stability, protection from vibration and noise, and absence of chemical irritants from cleaning products or fragrances further minimize stress that could compromise an invertebrate's ability to maintain hydration.

Preventive monitoring establishes routines for regularly assessing both environmental parameters and animal condition before problems develop into emergencies. Daily brief observations confirm water sources are full and accessible, humidity readings are within range, and visible invertebrates appear normally hydrated. Weekly more thorough inspections assess substrate moisture, equipment function, and body condition of animals that can be safely viewed. Monthly comprehensive evaluations review long-term trends, equipment calibration, and overall husbandry success. Documentation of these monitoring activities creates records that help identify gradual changes and demonstrate commitment to animal welfare.

Enclosure maintenance for species vulnerable to dehydration requires consistent attention to moisture-related factors that directly impact invertebrate health. Substrate should be evaluated regularly for appropriate moisture content, with dry areas receiving targeted misting while overly saturated zones are allowed to dry to prevent bacterial and fungal growth. Water dishes require daily checking to confirm they remain full, clean, and accessible, with prompt replacement of fouled water or dishes that have been knocked over or buried. Cage furniture including plants, cork bark, and decorations should be arranged to create humidity gradients that offer invertebrates choices for self-regulating their moisture exposure. Ventilation openings should be assessed for appropriate airflow that prevents stagnation without creating excessive drying currents.

Environmental parameter management extends beyond simple humidity maintenance to encompass the complex interactions between moisture, temperature, and enclosure conditions. Temperature directly affects evaporation rates, with warmer conditions requiring more aggressive humidity supplementation to maintain stable moisture levels. Seasonal changes in indoor heating and air conditioning dramatically alter ambient humidity, necessitating adjustments to misting frequency and enclosure ventilation throughout the year. Room placement of enclosures should avoid locations near heating vents, air conditioning outlets, and windows where temperature and humidity fluctuations are most pronounced. Understanding the relationship between all environmental factors allows keepers to maintain stable conditions despite changing external influences.

Feeding and nutrition contribute to hydration status through both water content of foods and overall metabolic health of the invertebrate. Prey items for carnivorous invertebrates should be gut-loaded with moisture-rich foods and offered while still alive and hydrated, maximizing fluid delivery with each feeding. Herbivorous and detritivorous species benefit from fresh fruits, vegetables, and leaf litter with high water content included regularly in their diet. Ensuring adequate calcium availability supports exoskeleton health that affects water retention and molting success. Malnourished invertebrates may struggle to maintain proper hydration even in optimal environmental conditions, making balanced nutrition an essential component of dehydration prevention.

Handling considerations specifically relevant to dehydration focus on minimizing stress and direct moisture loss during any keeper interaction with invertebrates. Most invertebrates should be handled minimally or not at all, with observation and enclosure maintenance conducted in ways that avoid direct contact. When handling is necessary, such as during health assessments or enclosure transfers, duration should be minimized and the animal should be returned to humid conditions promptly. Handling in dry, air-conditioned rooms accelerates evaporative water loss from exposed invertebrates. Species particularly sensitive to desiccation, such as isopods and millipedes, should never be handled except in genuine emergencies requiring relocation.

Long-term health monitoring establishes systems for tracking invertebrate condition over months and years, enabling early detection of gradual changes that might indicate developing hydration issues. Photography taken regularly under consistent conditions provides objective records for comparing body condition over time. Weight monitoring, where practical for the species and keeper's equipment, offers quantitative data on fluid status and overall health. Behavioral logs noting activity levels, feeding responses, and position preferences create patterns that make deviations immediately apparent. Integrating these monitoring practices into routine husbandry creates comprehensive health surveillance that catches problems before they become crises, supporting the longest possible healthy lifespan for invertebrates in captivity.

High-risk species for dehydration include those originating from consistently humid environments that have evolved minimal water conservation adaptations. Tropical tarantulas, particularly those from rainforest habitats such as many Avicularia and Poecilotheria species, require elevated humidity and suffer rapidly from inadequate moisture. Hermit crabs, both terrestrial and marine varieties, need constant access to appropriate water and humidity to keep their modified gills functional and their abdomens moist. Millipedes from tropical regions, including popular species in the Archispirostreptus and Orthoporus genera, cannot tolerate dry conditions that their temperate relatives might survive. Land snails and slugs have almost no waterproofing capability and desiccate within hours in inappropriately dry environments.

Comparison between sensitive and hardy species reveals significant variation in dehydration vulnerability even among closely related invertebrates. Desert-adapted scorpions such as many Hadrurus and Smeringurus species tolerate low humidity that would quickly kill tropical forest scorpions in the Pandinus or Heterometrus genera. Arid-land tarantulas including Aphonopelma and some Brachypelma species survive conditions that would be fatal to moisture-dependent Asian species. Isopods demonstrate particularly wide variation, with some species requiring near-saturation humidity while others thrive in relatively dry conditions. Understanding these differences is essential for proper species selection and husbandry matching.

Life stage considerations affect dehydration vulnerability regardless of species, with certain developmental periods demanding extra attention to moisture maintenance. Juveniles and spiderlings have proportionally higher surface area relative to body mass, accelerating water loss compared to adults of the same species. Pre-molt invertebrates building up fluid reserves for the molting process have heightened hydration requirements that must be met for successful ecdysis. Post-molt animals with soft, newly formed exoskeletons lose water more rapidly until their cuticle fully hardens and develops protective wax layers. Gravid females and those caring for eggs or young may have altered water requirements due to reproductive demands. Recognizing these vulnerable periods and providing enhanced humidity support during high-risk times prevents molt failures and other dehydration-related casualties.

Commonly co-occurring conditions with dehydration include molting problems that arise when inadequate fluid reserves prevent successful ecdysis. Stuck sheds where portions of old exoskeleton remain attached to the new one frequently result from dehydration during the molt process. Incomplete molts that leave invertebrates trapped within partially shed cuticle often prove fatal and are directly attributable to insufficient hydration. Nutritional deficiencies frequently accompany dehydration, as affected animals stop eating and become unable to maintain normal metabolic function. Secondary infections may establish in tissues weakened by dehydration, particularly when immune function is compromised by systemic fluid loss.

Conditions presenting similar symptoms to dehydration require careful differentiation to ensure appropriate treatment. Pre-molt fasting and reduced activity can appear similar to dehydration lethargy, though body condition should remain normal in healthy pre-molt animals. Old age senescence produces gradual decline in body condition and activity that may resemble chronic dehydration. Parasitic infections, particularly internal parasites, can cause weight loss and lethargy similar to fluid loss. Bacterial and fungal infections may produce weakness and behavioral changes that overlap with dehydration symptoms. Toxicity from environmental contaminants including pesticides, heavy metals, or inappropriate substrates causes systemic illness sometimes confused with simple dehydration.

Complications arising from dehydration extend beyond the immediate crisis to affect long-term health even in surviving animals. Organ damage sustained during severe dehydration may permanently impair kidney equivalent structures, digestive function, or reproductive capability. Tissue damage to developing molt beneath the exoskeleton may result in deformed molts, shortened limbs, or exoskeleton defects that persist for multiple molt cycles. Immune system compromise from dehydration stress may leave recovered animals more susceptible to infections for extended periods. Behavioral changes including increased hiding, reduced feeding response, or abnormal activity patterns sometimes persist after physical recovery. Understanding these potential complications emphasizes the importance of prevention over treatment and the need for vigilant monitoring of animals that have experienced significant dehydration events.