A detailed description of the Kurrii can be found in Beast of Gor, pages 364 - 370. It deals with their social structure, their breeding and their civilization. The entire quote can be found here for those wishing to learn more about the Kurrii.

�No,� said the Forkbeard. �In the dark they have excel�lent vision. If it had been you it sought, it would have been you it killed.�
�Why did it enter the hall ?� I asked.
�Kurrii,� said Ivar Forkbeard, �are fond of human flesh.�
Humans, like other animals, I knew, are regarded by those of the Kurii as a form of food.

Marauders of Gor, pg 53

�Even now,� said the Kur, the skin drawing back from its fangs, �there are those among you who wish our death, who urge our destruction.�

Marauders of Gor, pg 84

�We were not always simple farmers,� said the Kur. It opened its mouth, that horrid orifice, lined with its double rows of white, heavy, curved fangs. �No,� it said, �once we were hunters, and our bodies still bear, as reminders, the stains of our cruel past.� It dropped its head. �We are by these,� it said, and then it lifted its right paw, suddenly exposing the claws, �and these, reminded that we must be resolute in our attempts to overcome a sometimes recalci�trant nature.� Then it regarded the assembly. �But you must not hold our past against us. What is important is the pres�ent. What is important is not what we were, but what we are, what we are striving to become. We now wish only to be simple farmers, tilling the soil and leading lives of rustic tranquility.�

Marauders of Gor, pg. 85

I did not tell Ivar that those he knew as Kurii, or the beasts, were actually specimens of an alien race, that they, or those in their ships, were locked in war with Priest-Kings for the domination of two worlds, Gor and the Earth.In these battles, unknown to most men, even of Gor, from time to time, ships of the Kurii had been shattered and fallen to the surface. It was the practice of Priest-Kings to destroy the wrecks of such ships but, usually, at least, they did not attempt to hunt and exterminate survivors. If the marooned Kurii abided by the weapon and technology laws of Priest-Kings, they, like men, another life form, were permitted to survive. The Kurii I knew were beasts of fierce, terrible instincts, who regarded humans, and other beasts, as food. Blood, as to the shark, was an agitant to their systems. They were extremely powerful, and highly intelligent, though their intellectual capacities, like those of humans, were far below those of Priest-Kings. Fond of killing, and technologically advanced, they were, in their way, worthy adversaries of Priest-Kings. Most lived in ships, the steel wolves of space, their instincts bridled, to some extent, by Ship Loyalty, Ship Law. It was thought that their own world had been destroyed. This seemed plausible, when one considered their ferocity and greed, and what might be its implementation in virtue of an advanced technology. Their own world destroyed, the Kurii now wished another.
The Kurii, of course, with which the men of Torvaldsland might have had dealings, might have been removed by as much as generations from the Kurii of the ships. It was regarded as one of the great dangers of the war, however, that the Kurii of the ships might make contact with, and utilize, the Kurii of Gor in their schemes.
Men and the Kurii, where they met, which was usually only in the north, regarded one another as mortal enemies. The Kurii not unoften fed on men, and men, of course, in consequence, attempted to hunt and slay, when they could, the beasts. Usually, however, because of the power and ferocity of the beasts, men would hunt them only to the borders of their own districts, particularly if only the loss of a bosk or thrall was involved. It was usually regarded as quite sufficient, even by the men of Torvaldsland, to drive one of the beasts out of their own district. They were especially pleased when they had managed to harry one into the district of an enemy.

Marauders of Gor, pg 92-93

I noted that his ax, which he always carried, was bloodied. The blood of Kurii, like that of men, is red, and of simllar chemical composition. It is another similarity adduced by Priest-Kings when they wish to argue the equivalence of the warring species. The major difference between the blood content of the Kur and of men is that the plasma of the Kur contains a greater percentage of salt, this acting in water primarily as a protein solvent. The Kur can eat and digest quantities of meat which would kill a man.

Marauders of Gor, pg 99

1 saw the Kur who had pursued the bond-maid now again gomg toward that holding area near the door. On her back, then on her side, then on her stomach, rolling and squirming eyes wild, her fingers hooked inside the collar, trying to keep it from choking her, was dragged the bond-maid. Then her leash was surrendered into the keeping of the Kur who held the others, and then the first Kur, leaving his prize in the care of the other, turned about, to hunt yet another delicacy from the herd within the hall.

Marauders of Gor, pg 100

It was not more than ten feet from me. It lifted its face from the half-eaten body of a man. Its eyes, large, round, blazed in the light of the torch. I heard the screaming of the bond-maids, the movements of their chains. Their ankles were held by their fetters. "Weapons!" cried the Forkbeard. "Kur! Kur!" I heard men cry. The beast stood there, blinking, bent over the body. It was unwilling to surrender it. Its fur was sable, mottled with white. Its ears, large, pointed and wide, were laid back flat against its head. It was perhaps seven feet tall and weighed four or five hundred pounds. Its snout was wide, leathery. There were two nostrils, slit like. Its tongue was dark. It had two rows of fangs, four of which were particularly prominent, those in the first row of fangs, above and below, in the position of canines; of these, the upper two were particularly long, and curved. Its arms were longer and larger than its legs; it held the body it was devouring in clawed, paw like hands, yet six-digited, extra jointed, almost like tentacles.
It hissed, and howled and, eyes blazing, fangs bared, threatened us.

Marauders of Gor, pgss 108-109

The thing, its head lifted, surveyed the assembly of free men. The pupils of its eyes, in the sunlight, were extremely small and black. They were like points in the yellowish green cornea. I knew that, in darkness, they could swell, like dark moons, to fill almost the entire optic orifice, some three or four inches in width. Evolution, on some distant, perhaps vanished world, had adapted this life form for both diurnal and nocturnal hunting. Doubtless, like the cat, it hunted when hungry, and its efficient visual capacities, like those of the cats, meant that there was no time of the day or night when it might not be feared. Its head was approximately the width of the chest of a large man. It had a flat snout, with wide nostrils. Its ears were large, and pointed. They lifted from the side of its head, listening, and then lay back against the furred sides oft he head. Kurii, I had been told, usually, in meeting men, laid the ears back against the sides of their heads, to increase their resemblance to humans. The ears are often laid back, also, incidentally, in hostility or anger, and, always, in its attacks. It is apparently physiologically impossible for a Kur to attack without its shoulders hunching, its claws emerging, and its ears lying back against the head. The nostrils of the beast drank in what information it wished, as they, like its eyes, surveyed the throng. The trailing capacities of the Kurii are not as superb as those of the sleen, but they were reputed to be the equal of those of larls. The hearing, similarly, is acute. Again it is equated with that of the larl, and not the sharply-sensed sleen. There was little doubt that the day vision of the Kurii was equivalent to that of men, if not superior, and the night vision, of course, was infinitely superior; their sense of smell, too, of course, was incomparably superior to that of men, and their sense of hearing as well. Moreover, they, like men, were rational. Like men, they were a single-brained organism, limited by a spinal column. Their intelligence, by Priest-Kings, though the brain was much larger, was rated as equivalent to that of men, and showed similar random distributions throughout gene pools. What made them such dreaded foes was not so much their intelligence or, on the steel worlds, their technological capacities, as their aggressiveness, their persistence their emotional commitments, their need to populate and expand, their innate savagery. The beast was approximately nine feet in height; I conjectured its weight in the neighborhood of eight or nine hundred pounds. Interestingly, Priest-Kings, who are not visually oriented organisms, find little difference between Kurii and men. To me this seems preposterous, for ones so wise as Priest-Kings, but, in spite of its obvious falsity, Priest-Kings regard the Kurii and men as rather similar, almost equivalent species. One difference they do remark between the human and the Kur, and that is that the human, commonly, has an inhibition against killing. This inhibition the Kur lacks.

Marauders of Gor, pgs 169-170

The Kur has two rows of fangs. Its mouth is large enough to take into it the head of a full-grown man. Its canines, in the front row of fangs, top and bottom, are long. When it closes its mouth the upper two canines project over the lower lip and jaw. Its tongue is long and dark, the interior of its mouth reddish.

Marauders of Gor, pg 170

I, in this time, now came to understand that Torvaldsland stood, in effect, as a wall between the Kurii and the more southern regions of Gor. The Kur, moreover, tends to be an inveterate land animal. They neither swim well nor enjoy the water. They are uneasy on ships. Moreover, they knew little of the craftsmanship of building a seaworthy ship. That now, suddenly, large numbers of Kurii were conjoined, and intent upon a march southward could not be a coincidence in the wars of such beasts with Priest-Kings. I supposed it quite probable this was, in effect, a probe, and yet one within the laws of the Priest-Kings. It was Gorean Kurii that were clearly, substantially, involved. They carried primitive weapons. They did not even use a translator. In the laws of Priest-Kings it was up to such species, those of Kurii and men, to resolve their differences in their own way. I had little doubt but what the Kurii, perhaps organized by Kurii from the steel worlds, were to begin a march in Torvaldsland, which might extend, in a generation to the southern pole of Gor. The Kurii were now ready to reveal themselves. At last they were ready to march. If they were successful, I had little doubt that the invasion from space, in its full power, would follow. In their mercy or disinterest, Priest-Kings had spared many Kurii who had been shipwrecked, or shot down, or marooned on Gor. These beasts, over the centuries grown numerous and strong, might now be directed by the Kurii of the steel worlds. Doubtless they had been in contact with them. I expected the speaker himself was of the steel ships painfully taught Gorean. The Kurii native to Gor, or which had been permitted to survive and settle on Gor, would surely not be likely to have this facility. They and men seldom met, save to kill one another.

Marauders of Gor, pg 175

The soft flesh of the human female, I knew, was regarded as a delicacy among the Kurii.

Marauders of Gor, pg 177

In the doorway, silhouetted against flames behind them we saw great, black, shaggy figures. Then one leapt within the hall. In one hand it carried a gigantic ax, whose handle was perhaps eight feet long, whose blade, from tip to tip, might have been better than two feet in length; on its other arm it carried a great, round, iron shield, double strapped; it lifted it, and the ax; its arms were incredibly long, perhaps some seven feet in length; about its left arm was a spiral band of gold; it was the Kur which had addressed the assembly.
It threw back its head and opened its jaws, eyes blazing, and uttered the blood roar of the aroused Kur; then it bent over, regarding us, shoulders hunched, its claws leaping from its soft, furred sheaths; it then laid its ears back flat against the sides of its great head.
No one could move.
Then, other Kurii behind it, crowding about it, past it, it shrieked, lips drawn back, with a hideous sound, which, somehow, from its lips and mien, and mostly from its eyes, I took to be a sign of pleasure, of anticipation; I would learn later that this sound is instinctively uttered by Kurii when they are preparing to take blood. This cry, like a stimulus, acted upon the others as well; almost instantly, with the velocity that the stranger signal can course through a pack of urts, this shriek was picked up by those with it; then, the hall filled with their horrid howling, eyes blazing, led by the Kur with the golden band, frenzied by the blood shriek, they leaped forward, great axes flailing.

Marauders of Gor, pgs 203-204

It moved a switch on the box. It uttered sounds, low, guttural, inquisitive. It did not use human phonemes and so it is difficult, if not impossible, to convey the quality of the sound. If you have heard the noises made by great cats, such as the Bengal tiger or the black maned lion, and can conceive such noises articulated with subtlety and precision of a civilized speech, that will provide you with an approximation of what I heard. ~ "Our brain cases are larger then yours," it said. "Our anatomy could not well support a larger cranial development. In our history, as in your, larger brain cases have been selected for." "In what way?" I asked. "In the killings." It said. "Is the Kur a social animal?" I asked. "It is a social animal," it said," But it is not as social as the human." "that is perhaps a drawback to it as a species," I said. "It has its advantages," it said. " the Kur can live alone. It can go its own way. It does not need its herd." "Surly in ancient times, Kurri came together," I said. "Yes" it said. "in the matings, and the killings," It looked at me , chewing." But that was long ago," it said." We have had civilization for one hundred thousand years, as you would understand these things. In the dawn of our prehistory small bands emerged from the burrows and the caves and forests. It was a beginning." ~ "What do you put above all?" I asked. "Glory," it said. It looked at me. "can you understand that?" it asked. ~ "How is it that an animal without strong social instincts can be concerned with Glory ?" I asked. "It emerges, we speculate, from the killings." "the killings?" I asked. "Even before the first groups," he said, "we would gather for the matings and killings. Great circles, rings of our people, would form in valleys to watch." "You fought for mates?" I asked. "We fought for the joy of killing," it said, " Mating, however, was a prerogative of the victor." It took a rib bone from the lart and began to thrust it, scraping, between his fangs, freeing and removing bits of wedged meat. "Humans, as I understand it, perform all the functions pertinent to the continuance of the species." "Yes," I said, "that is true." "We have three, or, if you prefer, four sexes," it said. "There is the dominant, which would, I suppose, correspond most closely to the human male. It is the instinct of the dominant to enter the killings and mate. there is then the form of the Kur which closely resembles the dominant but does not join in the killings or mate. You may , or may not, regard this as two sexes. There is then the egg carrier who is impregnated. This form of Kur is smaller then the dominant or the non dominant, speaking thusly of the non reproducing form of Kur." "the egg carrier is the female." I said. "If you like" said the beast. "But shortly after the impregnation, within a moon, the egg carrier deposits the fertilized seed in the third form of Kur, which is mouthed, but sluggish and immobile. those fasten themselves to hard surfaces, rather like dark, globular anemones. the egg develops inside the body of the blood nurser and, some months later, it tears its way free." "It has no mother." I said. "Not in the human sense." It said. "It will however, usually follow, unless it itself is a blood nurser, which is drawn out, the first Kur it sees, providing it is either and egg carrier or a non dominant." ~ "the young receive blood in the nurser," he said. "When it is born it does not need milk, but water and common protein." "It is born fanged?" I asked. "Of course," it said. "And it is capable of stalking and killing small animals shortly after it leaves the blood nurser." ~ "But there are native Kurrii on Gor," I said, " or at any rate Kurrii who have reproduced themselves on this world." "Certain ships, some of them originally intended for colonization, carried representatives of our various sexes, with the exception of non dominants," it said "We have also, where we have known of Kurrii groups, sometimes managed to bring in egg carriers and blood nursers." ~ "Is there an order to your sexes?" I asked. "Of course there is a biological order," He said, "Structure is a function of nature. How could it be otherwise? There is first the Dominant, and then the egg carrier, and then the non dominant, and then , if one considers such things Kur, the blood nursers." "the female, or egg carrier, is dominant over the non dominant?" I asked. "Of course," he said." They are despicable." "Suppose a dominant is victorious in the killings?" I said, "What then occurs?" "Many things could occur," He said, " but he then, generally, with a club, would indicate what egg carriers he desires. He then ties them together and drives them to his cave. In the cave he impregnates them and makes them serve him." "Do they attempt to run away?" I asked. "No," he said, " He would hunt them down and kill them. But after he has impregnated them they tend to remain, even when untied, for he is then their dominant."

Explorers of Gor, pgs 369-370

Incidentally, there are many brands on gor. Two that almost never occur on Gor, by the way, are those of the moons and the collar, and of the chain and the claw. The first of these commonly occurs in certain of the Gorean enclaves on Earth, which serves as headquarters for agents of the priest kings, the second tends to occur in the lairs of the Kurri agents on earth; ~the chain and claw brand, signifies, of course, slavery and subjection within the compass of the Kur yoke.

Explorers of Gor, pg 12