Creatures of the Night: Kangaroo Rat

Of all the mammals in the desert, the kangaroo rat is perhaps the best adapted to arid conditions: it never needs to drink, nor eat fresh vegetation; it can metabolize water directly from dry seeds.

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The diet is almost exclusively seeds, and it prefers seeds high in carbohydrates rather than seeds high in fat or protein. That’s because metabolizing fatty seeds produces heat, and metabolizing protein-rich seeds requires more water to get rid of nitrogen-rich waste products.

The K-rat stores seeds in its burrow where they absorb any humidity, thereby giving the rat some extra moisture. The K-rat has no sweat glands through which to lose water.

The kangaroo rat minimizes moisture loss during respiration with its specialized nasal passages which function as counter-flow heat exchangers. These passages warm the air during inhalation, then cool the air and extract moisture during exhalation.

The kangaroo rat can conserve water by producing urine about 5 times more concentrated than human urine. The rat also produces very dry feces pellets with about one-fifth the water content of a white lab-rat’s pellets.

The kangaroo rat is 4- to 5 inches long with a tail up to 10 inches long. It prefers to hop on its hind legs. It can jump 10 feet and change direction immediately upon landing, something that helps it avoid nocturnal predators.

Although the rat has tiny external ears, the middle ear chamber is highly developed and may be bigger than the braincase itself. This allows the rat to hear low intensity and low frequency sounds such as an owl flying or a rattlesnake ready to strike. This, together with its ability to jump 10 feet, helps it avoid predators.

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2 comments

  1. Remarkable creatures indeed. Late at night, these little guys put on quite a show by campfire light. I’ve always enjoyed their antics. Thanx for the article WH.

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