Water is not something most of us give much thought. When we are thirsty, we turn on the tap or reach for a water bottle. But what do animals do when they are thirsty? Do animals need water to survive, and what happens if animals cannot find a safe water source?
All life on Earth needs water to survive. Without water, their bodies would cease to function, unable to swallow food or process nutrients. Carnivores get a lot from their prey, while herbivores take their water from plants. Insects will use the morning condensation to survive. Desert animals use a combination of all of these to survive the harsh conditions.
This article looks at why animals need water to survive and some of their adaptations when water is scarce.
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Animals Need Water To Survive
Regardless of its physical state, water forms the basis of all life on Earth. Water can be found as a gas, liquid, or solid depending on the environment. Approximately 70% of the surface of the Earth is covered in water. Some organisms can be formed of almost 90% water, with the human body carrying roughly 60% water.
Our brains are formed of 83% water, as are the kidneys. The heart and muscles around the body are approximately 75% water, and blood is a staggering 94% water. On average, men carry around 5% more water in their bodies than women.
Water is a simple, naturally occurring solution made from one oxygen atom and two hydrogen atoms. Oxygen atoms have a negative molecular charge, while hydrogen atoms are positive. This is what causes water droplets to be attracted to one another.
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Water is vital for many bodily processes such as secretion and absorption of hormones and enzymes throughout the body and the production of bodily fluids such as urine, saliva, and even our tears.
Without water, all animals would begin suffering from eye conditions due to their eyes drying out. Water is essential for regulating body temperature, especially for endothermic (warm-blooded) animals. During digestion, water is required for efficient metabolic reactions to ensure the proper breakdown of food and absorption of nutrients.
A lack of water in the bowel can cause constipation, so a regular water source is vital to maintaining a healthy digestive tract.
Water helps to keep joints lubricated, so animals with a water deficit will begin to experience joint stiffness and other related conditions.
Blood is 94% water and is responsible for transporting oxygen and other substances around the body. A lack of water can slow these processes, reduce oxygen delivery to cells and cause a dramatic change in blood pressure.
Without water, animals would not be able to produce saliva, which would create issues with swallowing. An animal could eventually starve to death due to their inability to swallow if they do not have access to water.
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Can Animals Survive Without Water?
In short, no, but this is a much more complex situation than a simple question. Animals living in arid environments like deserts do not have access to water like those in marshlands or along riverbanks. Animals in dry habitats have adapted ways to store water for use during drought.
Avoid Heat
The easiest technique to adapt in the desert is to search for shade. The body will use less water if an animal can keep its body temperature low. Most desert animals are crepuscular, meaning they are active in the hours after sunset and before sunrise. Temperatures at these times are much cooler than they are during the day.
Gila monsters and rattlesnakes are crepuscular, which explains why sightings of these animals do not happen very often. For reptiles, avoiding heat is vital as they use their environment’s temperature to regulate their body temperature. Even on a mild day in the desert, staying in the sun can quickly cause death due to heat exposure.
Smaller animals will dig burrows to avoid daytime temperatures. It is much cooler below ground, and many small mammals, most reptiles, and all desert amphibians use this technique.
Some desert animals will aestivate during the hottest hours of the day. Aestivation is similar to hibernation. An animal will enter a deep sleep where their heart and metabolic rates fall and their core body temperature. Their reduced metabolic rate means they use less energy. Once the temperature cools, the animal will come round and be active.
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Water Retention
Desert toads will burrow into damp soil during the day, keeping their skin moist. Animals like vultures get most, if not all, of their water from their diet. Prey animals carry a lot of water in their blood and organs, sustaining a predator’s water requirement for some time.
Most reptiles and bird species excrete uric acid, removing waste from the body without losing too much water. Mammals, on the other hand, do not produce this. Instead, they produce urea, which contains a high volume of water. This is why it is so important for desert mammals to conserve water.
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Life In The Water
Some animals live in water and cannot survive on land. North American manatees, for example, have evolved entirely to live in water. They do not have hind legs. Instead, they have a large, flat tail that provides propulsion through the water. Although they must breathe air, they can remain submerged for almost 20 minutes at a time while they forage on aquatic plants and nurse their young.
Manatee calves are born in the water and can swim unaided just one hour after birth. They are helped to the surface by their mother to take their first breath, but their nostrils close in a reflex action to keep the water out.
Manatees have thick skin, but because the skin tissue has evolved to remain submerged, manatees can suffer from skin blistering and burns during hot weather if they are out of water for too long. They also require a source of fresh drinking water to maintain their normal bodily functions.
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Finding Water In The Desert
How do animals find water in a hot, dry environment? Most deserts do not have rivers or lakes, and those that do are only available during the short rainy seasons. So, how does an animal find water when there is none on the surface?
Many animals acquire water from their diet. The American badger has a varied diet of small mammals, lizards, birds, and eggs. All of these are vital sources of water as well as nutrition. They dig dens along desert river beds where the soil is soft, and the badger will stay underground during the hottest parts of the day.
Carnivores have access to plenty of water sources from their prey, but what about herbivores? Surprisingly, most desert plant life has high water content. They use their long root systems to absorb water far below the surface. Fruits, seeds, and leaves from vegetation can provide ample water for the many herbivorous mammals, reptiles, and amphibians found in North America’s deserts.
Some desert animals, such as the bobcat, have adapted to living near urban towns with plenty of water sources. Bobcats can often be seen drinking from garden ponds, man-made lakes on golf courses, and even puddles formed on pathways or rural sidewalks.
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The desert bighorn sheep have adapted to living on the steep rocky mountainsides of North America’s deserts. At higher altitudes, the air holds more moisture, and more vegetation can be found. Bighorns are very agile creatures, which is how they can navigate the steep hillsides. The plants they eat provide most of their water requirements, but they can be seen drinking from puddle formations when rain occasionally does fall.
Desert insects find water collection much easier than larger animals. They tend to do most of their water sourcing at dawn and dusk. As water condenses in the air, the water droplets land on the ground or plant leaves. Insects and some other invertebrates, such as earthworms, will collect these water droplets. As the temperature rises, the water droplets will eventually evaporate, so desert insects tend to be more active around dawn and dusk.
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References
A Level Biology. (2016, December 9). The Biological Importance of Water. Retrieved from A-Level Biology: https://alevelbiology.co.uk/notes/the-biological-importance-of-water/
ACS Distance Education. (2021). Don’t Let Your Pets Be Thirsty! Retrieved from ACS Distance Education: https://www.acs.edu.au/Info/Pets/Pet-Care/water-needs.aspx
Gurera, D., & Bhushan, B. (2020). Passive water harvesting by desert plants and animals: lessons from nature. Philosophical Transactions Of The Royal Society A.
Hess, P. (2017, March 16). How some animals survive on almost no water. Retrieved from Popular Science: https://www.popsci.com/how-some-animals-survive-on-almost-no-water/
Schmidt-Nielson, K. (1965). Desert Animals: Physiological Problems of Heat and Water. Oxford: Oxford Clarendon Press.