Urts of Gor
This research is done on the series of books written by John Norman, the comments in italics are mine and my point of view.
Woman of Gor
The urt is a loathsome, horned Gorean rodent; some are quite large, the size of wolves or ponies,
but most are very small, tiny enough to be held in the palm of one hand. Nomads of Gor, page 125

Cernus and Ho-Tu rode together in another basket. The tarn basket may or may not have
guidance attachments, permitting the tarn to be controlled from the basket. If the guidance
attachments are in place, then the tarn is seldom saddled, but wears only basket harness. If the
basket is merely carried, and the tarn cannot be controlled from the basket, then the tarn wears
the tarn saddle and is controlled by a tarnsman. The basket of Cernus and my basket both had
guidance attachments, similar to those of the common tarn saddle, a main basket ring
corresponding to the main saddle ring, and six leather straps going to the throat-strap rings. The
other three baskets, however, had no control attachments and those birds wore saddles and
were guided by tarnsmen. Tarn baskets, incidentally, in which I had never (page 95) before
ridden, are of many different sizes and varieties, depending on the function for which they are
intended. Some, for example, are little more than flat cradles for carrying planking and such;
others are long and cylindrical, lined with verrskin, for transporting beverages and such; most
heavy hauling, of course, is done by tharlarion wagon; a common sort of tarn basket, of the sort
in which I found myself, is a general utility basket, flat-bottomed, square-sided, about four feet
deep, four feet wide and five feet long. At a gesture from Cernus the birds took wing, and I felt
my basket on its heavy leather runners slide across the roof for a few feet and then drop
sickeningly off the edge of the cylinder, only to be jerked up short by the ropes, hover for a
moment as the tarn fought the weight, and then begin to sail smoothly behind the bird, its
adjustments made, its mighty wings hurling the air contemptuously behind it. Assassins of Gor,
page 94

On the racing saddle there are two small straps, rather than the one large strap on the common
saddle; both straps fasten about the rider and to the saddle, in a sense each duplicating the
work of the other; the theory is that though smaller straps can break more easily the probability
of both straps breaking at the same time is extremely small; further the two straps tend to divide
strain between them, thereby considerably lessening the possibility of either breaking; some
saving in weight, of course, is obtained with the two smaller straps; further, the broad strap
would be a bit large to fasten to the small saddle; even beyond this, of course, since races take
place largely and most often over a net there is normally not as much danger in a fall as there
would be in common tarn flight; the main purpose of the straps is simply to keep  the rider in the
saddle, for the purpose of his race, not primarily to protect his life. Assassins of Gor, page 171-172

Throughout the stands, startling those multitudes, unsettling the other birds being drawn by the
horned tharlarion on the low carts, there was heard the sudden shrill, ringing challenge scream of
a tarn, unhooded, a giant tarn, black, a wild mountain cry of one of Gor's fiercest, most beautiful
predators, that might have been heard in the sharp crags of  the Mountains of Thentis, famed for
its tarn flocks, or even among the red peaks of the lofty, magnificent Voltai itself, or perhaps in
battle far above the swirling land below as tarnsmen met in duels to the death. Assassins of Gor,
page 220-221

Somewhere I heard the squealing and thrashing of two of the giant urts fighting in the water,
among the floating garbage. Raiders of Gor, page 119

I heard an arrow flash into the water near me and heard a high-pitched pain squeal from one of
the web-footed canal urts. Then there was the sound of biting and tearing and thrashing in the
water, as other urts attacked the injured one. Raiders of Gor, page 170

"At the edge of the thicket to the northeast, days ago," said the second man, "we found the
bones of brush urts!" Captive of Gor, page 243

"I don't know," I said. "I looked. I had not seen one like it before. It is some kind of brush urt, I
think. It is very ugly." Captive of Gor, page 245