Why Kangaroo Rats Don’t Get Dehydrated in the Desert

Behold, the hindermost of the nations shall be a wilderness, a dry land, and a desert. (Jeremiah 50:12b)

DESERT SCRUBLAND near EL PASO, TX photo credit: Pinterest

Kangaroo rats thrive in America’s hot, dry deserts —  so why don’t they suffer from being dehydrated?  How do they get enough water to survive, since they don’t need to drink water like almost all other mammals?

In short, God has designed and constructed kangaroo rats so that they get their water from their food, especially drought-resistant seeds that abound in the desert.  As they digest such xeric foods, the rats produce (within themselves) all the water that they need, metabolically (i.e., from the normal digestion process), and they retain most of that water by releasing very little of it in their urine (as noted below).

In sum, kangaroo rats are made to get their water form their food and to conserve it better than other animals do.   (In this respect the kangaroo rat is much like a camel.)

The kangaroo rat is a rodent, but it is unlike any other rodent on Earth: it is able to survive in the desert with virtually no drinking water. The camel is the only other mammal that can match this feat…. This humble creature lives in the desert regions of North America … [with] a large head and eyes, short forelimbs and long hind limbs, and a body that ranges in length from 10 to 16 cm (4 to 6.5 in). They can jump up to 1.8 m (6 ft) in a single leap. Like [kangaroos], the kangaroo rat balances on its hind legs and hops. But that’s where the similarity ends. Kangaroo rats live in burrows by day, foraging by night for seeds, leaves and other vegetation, and carrying food in their cheek pouches to store in their underground homes. They also occasionally eat insects. But how is it possible to live with virtually no drinking water? What makes the kangaroo rat different from other mammals, which would die within days in the desert without water? The answer lies mainly in the rat’s kidneys [maximally concentrating urine, minimizing water loss]. Research has shown that the kangaroo rat produces the most concentrated urine of all mammals, and only passes a few drops per day. Humans drink a lot of water, and also gain moisture through food. As such, our urine is quite dilute. Kangaroo rats, on the other hand, take in very little water and so produce urine that is even more concentrated than that of the camel (which also concentrates its urine to survive without water). This means that the kangaroo rat loses little water in its urine. Scientists have marvelled at how the kangaroo rat’s kidney works. The study of this organ—in particular the Loop of Henle, which enables the concentration process to take place—has led to a better understanding of how human kidneys work. The kangaroo rat’s Loop of Henle is much longer than that of other rodents.  [Quoting Paula Weston, Creation Ex Nihilo, 26(3):18-20 (June 2004).

KANGAROO RAT, Sonoran Desert (Pinterest photo credit)

God cleverly designed this water-conserving rat’s kidney system to fit and to “fill” desert habitats!

The kangaroo rat … probably never takes a drink in its entire life time. In captivity, it lives nicely on just barley seeds. Carbon dioxide, water, and energy-release are the results of the [oxidative] combustion of fuel [such as gasoline]. As oxygen combines with carbohydrates, carbon dioxide is formed from the burning of the carbon atom[-based hydrocarbon or carbohydrate molecules], and water is formed from leftover hydrogen atoms. In like manner, the metabolism which powers living animals produces carbon dioxide, water, and energy-release. This metabolic water, if conserved, is sufficient to meet the needs of many small rodents. These rodents retreat to burrows during high temperature, thus keeping evaporation [of water] to a minimum. They have very efficient kidneys, which produce a urine relatively low in water concentration, and they produce very dry feces. Their ability to exist on metabolic water (probably along with licking up some dew [when available]) means that they have no need for drinking water. Some foods—seeds, in particular—are especially good at allowing the formation of metabolic water and … they are abundant in the desert. Parts of the North American desert have been found to contain from 5,000,000 upwards to 100,000,000 seeds per acre. One kangaroo rat was found to have over 900 seeds tucked away in his cheek pouches. Caching [i.e., storing] seeds appears to be a compulsive habit of many arid-country rodents. In deserts characterized by continually shifting sand and dunes, some insect species live their entire lives under the sand, existing solely on organic matter, including seeds which have blown in and been covered. [Quoting John Meyer & Kenneth Cumming, “Biology of Grand Canyon”, in GRAND CANYON: MONUMENT TO CATASTROPHE (Santee, CA: ICR, 1994), page 163.]

KANGAROO RAT photo credit: Mammalogy.org

But, the kangaroo rat can’t retain water until he gets it — so it’s vital that the little rat gets enough nutritious seeds for metabolically producing water, via digestion.  Notice how critical desert-surviving seeds are, to the kangaroo rat’s diet.

There are a number of mechanisms used by plants to help them adapt to [i.e., ecologically fill niches in] the dry conditions of the desert. Some flowers succeed by sheer opportunism, only germinating , flowering, and seeding every ten years or so when the conditions [for progressing through their life cycles] are right. Went [i.e., botanist Frits Warmolt W. Went] writes: ‘Probably their most remarkable feature is that they are perfectly normal plants, with no special adaptations [sic] to withstand drought. Yet they are not found outside the desert areas. The reason lies in the peculiar cautiousness of their seeds. In dry years the seeds lie dormant. This itself is not at all amazing; what is remarkable is that they refuse to germinate even after a rain unless the rainfall [such as rains during rare desert flashfloods] is at least half an inch, and preferably an inch or two.’ In fact, [because] living organisms are designed by a Perfect Engineer, they should reflect not only the best possible solution to various problems presented by the environment, but also utilize the most efficient solutions—those expending the least amount of energy and materials while producing the exact degree of performance required by the organism, and, at the same time, with little or [in a pre-Fall world] no waste.  [John Meyer & K. Cumming, “Biology of Grand Canyon”, in GRAND CANYON: MONUMENT TO CATASTROPHE (Santee: ICR, 1994; Steve Austin, general editor), page 159.]

Next time you see a kangaroo rat in the desert — or think of one — be amazed at God’s providential design and construction of the little rodent!  God has made sure that the little hopper gets (and keeps) enough water to survive, even in the hot and dry deserts, such as the Chihuahuan Desert lands of far West Texas, or even in southern California’s Death Valley wilderness.

O God, Thou art my God; early will I seek thee: my soul thirsteth for Thee, my flesh longeth for Thee in a dry and thirsty land, where no water is.  (Psalm 63:1)