Donkeys tolerate heat remarkably well but struggle with cold, wet, and windy conditions. This split traces directly to their evolutionary origins in the semi-arid landscapes of northeast Africa, where water scarcity and high temperatures shaped their physiology over millions of years. The mismatch between that desert heritage and the temperate or rainy climates where many donkeys now live is the single biggest factor in temperature-related welfare problems.
Desert Ancestors, Desert Bodies
Domestic donkeys descended from wild asses that evolved in the hot, dry climates of Africa, while domestic horses trace back to the more temperate grasslands of Eurasia.1Journal of Veterinary Behavior. Shelter-seeking behavior of donkeys and horses in a temperate climate That difference in ancestral environment shows up in nearly every aspect of how the two species regulate body temperature. Donkeys have longer ears with extensive blood vessel networks that radiate heat. Their bodies are leaner, with less subcutaneous fat. Their coats are thinner and shorter than a typical horse’s winter coat, which is great for shedding heat but poor insulation when temperatures drop. Understanding this evolutionary context helps explain most of what follows: donkeys are not poorly adapted animals, they are superbly adapted animals that happen to be living far from the conditions they were built for.
How Donkeys Cool Themselves
Donkeys sweat, but the mechanism is not identical to what you see in horses. Research into donkey sweat glands showed that thermal sweating is controlled by adrenergic nerves rather than the cholinergic system that drives sweating in many other mammals. When researchers blocked adrenergic nerve activity, thermal sweating stopped entirely, while blocking the cholinergic pathway with atropine had no effect.2PubMed Central. Sweat gland function of the donkey (Equus asinus) During exercise, the adrenal glands may kick in with extra adrenaline to boost sweating beyond what the local nerves produce. The takeaway is that donkeys have a functional sweating system tuned for sustained heat exposure, but it works through a different neurological pathway than you might expect based on horse physiology.
Sweating is only half the cooling picture. Donkeys also rely heavily on behavioral thermoregulation, actively seeking shade and shelter when conditions demand it. A study of donkeys in a hot climate found that shelter use climbed predictably as temperatures and light intensity rose. Wind speed also drove donkeys toward windbreaks and covered areas.3Applied Animal Behaviour Science. Shelter seeking behaviour of healthy donkeys and mules in a hot climate Rates of protection use were high enough that the researchers concluded shelters confer a real welfare benefit even in climates donkeys are nominally well suited to. If you keep donkeys in a hot region, they still need access to shade. The idea that “they’re from the desert so they’ll be fine” does not hold up once you observe how much time they spend getting out of the sun when given the option.
Water Conservation and Rapid Rehydration
One of the donkey’s most impressive heat-adapted tricks has nothing to do with sweating or shade. It is the hindgut. When dehydrated donkeys were allowed to drink freely, they consumed roughly 17 to 18 liters of water, and the volume increase in their gut closely matched that intake. About 80 percent of the water was retained in the hindgut, and for hours afterward, only slow, moderate changes in gut volume occurred. Plasma volume changes were similarly suppressed.4PubMed. Dehydration and rehydration in donkeys: the role of the hind gut as a water reservoir The hindgut essentially acts as a water reservoir, buffering the rest of the body against sudden shifts in hydration, much like the rumen does in goats and sheep.
The kidneys play an equally efficient role. During dehydration, the donkey kidney conserves both water and sodium aggressively. After drinking, donkeys returned to their baseline kidney function within about two hours, which is considerably faster than goats doing the same thing.5Israel Journal of Zoology. Kidney response to rapid rehydration in the donkey This rapid stabilization means a donkey can go from dehydrated to physiologically normal in a short window after a single drinking session. For owners, the practical implication is straightforward: donkeys in hot weather need reliable access to water, but they do not need to sip continuously the way some animals do. They can drink infrequently and in large volumes, and their bodies handle the rest.
Why Cold and Rain Are the Real Danger
If donkeys handle heat like pros, cold and wet weather is where they flounder. Research comparing the hair coat properties of donkeys, mules, and horses in a temperate climate found that donkeys appear not to be as well adapted to colder, wet conditions as horses. The study concluded that donkeys may require additional protection from the elements, such as access to a wind- and waterproof shelter, for their welfare needs to be met.6PubMed Central. Hair coat properties of donkeys, mules and horses in a temperate climate A horse’s winter coat traps air and repels moisture to a degree that a donkey’s coat simply cannot match.
Behavioral data backs this up. In a study comparing shelter-seeking in donkeys and horses, donkeys sought constructed shelter significantly more often at lower temperatures. They were also far more affected by rain, with the majority moving indoors when precipitation began. Increasing wind speed pushed donkeys toward shelter at moderate levels, while horses stayed outside. Horses, by contrast, actually moved inside more when temperatures rose above 20°C, essentially seeking shade in warm weather rather than shelter from cold.1Journal of Veterinary Behavior. Shelter-seeking behavior of donkeys and horses in a temperate climate The pattern is clear: donkeys treat cold rain and wind as threats worth avoiding, while horses are comparatively unbothered.
For anyone keeping donkeys in a climate with cold winters, wet springs, or persistent wind, this means shelter is not optional. A three-sided field shelter open on the leeward side is the bare minimum. Ideally the shelter should be waterproof overhead and large enough that all animals can use it simultaneously without crowding. Donkeys left without shelter in cold rain are not just uncomfortable; they can develop hypothermia, and prolonged cold stress opens the door to secondary health problems.
Recognizing Heat Stress When It Does Happen
Despite their heat adaptations, donkeys are not immune to overheating, especially when working hard or when humidity is high. A study of working horses and donkeys found that heat stress behavior was significantly associated with elevated rectal temperature in both species. Observable signs included increased respiratory rate and depth, flared nostrils, head nodding, and apathy.7PubMed. Validity of a behavioural measure of heat stress and a skin tent test for dehydration in working horses and donkeys Donkeys are stoic animals that tend to mask discomfort, so by the time you notice these signs, the animal may already be in significant distress.
Accurate temperature monitoring matters more than you might think. A comparison of thermometer types used on donkeys during hot-dry season conditions found that digital, mercury-in-glass, and infrared thermometers all underestimated body temperature compared to a rectal probe. The mean rectal probe reading was about 38.4°C, while the other methods gave readings roughly 1 to 1.5 degrees lower.8PubMed. Comparison of body temperature in donkeys using rectal digital, infrared, and mercury-in-glass thermometers during the hot-dry season in a tropical savannah The researchers cautioned that relying on these less invasive thermometers could lead to wrong diagnoses and compromise the control of hyperthermia. If you suspect heat stress, a proper rectal thermometer gives the most reliable reading.
Seasonal Shifts in Heart Rate and Breathing
Donkeys do not just passively endure seasonal changes; their bodies adjust metabolically. Research tracking heart and respiratory rates across cold-dry and hot-dry seasons in a tropical environment found clear differences. Adult donkeys had an average heart rate of about 42 beats per minute during the cold-dry season compared to roughly 48 during the hot-dry season. Yearlings and foals showed a similar pattern, with foals running the highest rates in both seasons. Respiratory rates followed the same trend, climbing during hot weather.9Physiological Reports. Diurnal rhythms of heart and respiratory rates in donkeys of different age groups during the cold-dry and hot-dry seasons in a tropical savannah
These shifts are normal and expected. A donkey’s cardiovascular and respiratory systems ramp up in the heat to move more blood to the skin for cooling and to increase respiratory evaporation. The fact that younger animals show higher baseline rates in both seasons reflects their higher metabolic rate and smaller body mass. For practical purposes, knowing these seasonal baselines helps you distinguish a donkey that is hot but coping normally from one that is dangerously overheated. An adult donkey with a heart rate well above 50 beats per minute at rest during hot weather deserves a closer look.
Working Donkeys and Exercise in the Heat
Millions of donkeys worldwide are working animals, pulling carts, carrying loads, and plowing fields in temperatures that would sideline most livestock. Research on exercising donkeys found that ambient temperatures between 29 and 34°C with humidity between 43 and 65 percent were the working conditions during exhaustive driving tests, where donkeys pulled loads equal to about a fifth of their body weight at a trot until they would not continue.10Applied Animal Behaviour Science. Physiologic responses during an exhaustive driving test in donkeys: effect of conditioning Heart rate, rectal temperature, respiratory rate, and blood lactate were all monitored during and after exercise.
The study looked at whether conditioning (gradual physical training) improved these responses, and the broader finding relevant to owners is that a donkey’s fitness level makes a real difference in how well it handles heat during work. An unfit donkey working in hot weather reaches dangerous physiological thresholds faster. If your donkey works during warm months, building fitness gradually before the hot season arrives is one of the most effective things you can do. Scheduling heavy work for cooler parts of the day, providing water breaks, and watching for apathy or labored breathing are all standard precautions that save lives in working donkey populations.
Mules Handle Heat Differently
Mules, the offspring of a male donkey and a female horse, inherit traits from both parents, and their heat tolerance falls somewhere between the two species. A comparative study found that mules were more heat-tolerant than local donkeys when exposed to direct sun, as judged by the rise in rectal temperature and respiratory rate. Exotic (non-native) donkey breeds fared worst of the three groups.11Annals of Arid Zone. Heat Tolerance in Donkeys and Mules The likely explanation is hybrid vigor: mules tend to have slightly more robust thermoregulatory capacity, possibly combining the donkey’s efficient sweating with the horse’s somewhat greater body mass and blood volume.
Separate research on coat properties found that mules sit between donkeys and horses in terms of weather protection, with coats that offer more insulation than a donkey’s but less than a horse’s.6PubMed Central. Hair coat properties of donkeys, mules and horses in a temperate climate If you are choosing between a donkey and a mule for work in a hot climate, the mule may tolerate direct sun slightly better. In a cold, wet climate, neither is as well protected as a horse, but the mule has a modest edge over the donkey.
Feeding, Fermentation, and Internal Heat
What you feed a donkey affects its internal heat production. Donkeys are extraordinarily efficient at extracting energy from fibrous forage, with roughly 30 percent superior fiber digestibility compared to horses. Their specialized hindgut microbiota provide an estimated 60 to 70 percent of their metabolic energy through fermentation.12PubMed Central. Effects of Feeding Strategies on Gut Microbial Communities in Donkeys: A Comprehensive Narrative Review Fermentation generates heat as a byproduct, which is beneficial in cold weather but can add to heat load in summer.
This has practical feeding implications in both directions. During cold weather, providing adequate fiber (good-quality straw or mature hay, not rich pasture) helps donkeys generate internal warmth through fermentation. During hot weather, overfeeding energy-dense concentrates or lush green pasture ramps up fermentation heat and can push an already warm donkey closer to heat stress. Donkeys evolved to thrive on sparse, dry vegetation, and their digestive system reflects that. The common mistake of feeding donkeys like horses, with high-calorie grain mixes or rich grass, creates problems year-round but especially in summer.
Hyperlipaemia and the Cold-Stress Connection
One of the most dangerous consequences of temperature stress in donkeys is not overheating but a metabolic crisis called hyperlipaemia. When donkeys stop eating, whether due to cold stress, illness, or any other cause, their bodies mobilize fat reserves into the bloodstream at an alarming rate. A survey of donkey health in Pakistan found that hyperlipaemia was the most commonly observed medical problem, affecting about 28 percent of the animals assessed.13Frontiers. Participatory appraisal for healthcare and welfare management strategies of donkeys (Equus ascinus) in Balochistan, Pakistan A donkey that becomes dull and loses its appetite is a clinical emergency because hyperlipaemia can be fatal if not treated quickly.
Cold weather is a common trigger because donkeys that are miserable, wet, and shivering often go off their feed. The same survey noted that about a third of donkeys assessed were underweight, and that donkeys routinely worked in extreme weather conditions including severe cold and humidity. The combination of cold stress, insufficient shelter, and inadequate nutrition creates a perfect storm for hyperlipaemia. Keeping donkeys eating through winter is not just about nutrition; it is about preventing a potentially lethal metabolic cascade. Provide shelter, ensure constant access to palatable forage, and monitor body condition closely when temperatures drop.
Practical Shelter Across Climates
Putting all of this together, the shelter needs of donkeys vary enormously depending on where you live. In hot, arid regions where donkeys are well within their comfort zone, shade structures and windbreaks still improve welfare measurably. Donkeys choose shade when it is available, and access to shelter during peak heat reduces the physiological cost of thermoregulation.3Applied Animal Behaviour Science. Shelter seeking behaviour of healthy donkeys and mules in a hot climate Even in these climates, water access is the non-negotiable priority.
In temperate and cold climates, the requirements are more demanding. Donkeys need enclosed, waterproof shelter they can enter freely. Rugging (blanketing) is sometimes necessary during prolonged cold, wet spells, particularly for older, thin, or clipped donkeys. Good drainage around shelters prevents standing water that saturates coats and chills feet. Bedding inside the shelter provides insulation from the cold ground. None of this is exotic or expensive, but neglecting it has real consequences: hypothermia, reduced appetite, weight loss, and the hyperlipaemia risk described above. The science consistently points to one takeaway for donkey keepers in cooler climates: your donkey’s tolerance for cold, wet, windy weather is much lower than a horse’s, and acting on that knowledge is the single most impactful thing you can do for its health.