How do you think realistically they were gathered on the Ark?
Do you think God supernaturally helped Noah feed them and provide sanitary conditions also?

Here is a like from wikipedia to help you if you need it:
http://en.wikipedia.org/wiki/Noah's_Ark

An enormous problem some people have posed is the problem of gathering specimens of each kind of air-breathing land animal and bringing them aboard the Ark. However, the Genesis account indicates that God gathered the animals and brought them to Noah inside the ark two by two. Some have suggested this may have involved the origin of animal migratory instincts or, at least, an intensification of it. We also know that most animals possess the ability to sense danger and to move to a place of safety.
Once aboard, many have suggested that Noah's problems really began, with only 8 people to feed and water, to provide fresh air and sanitation for the huge menagerie of animals for a total of 150+ days. However, a number of scientists have suggested that the animals may have gone into a type of dormancy. It has been said that in nearly all groups of animals there is at least an indication of a latent ability to hibernate or aestivate. Perhaps these abilities were supernaturally intensified during this period. With their bodily functions reduced to a minimum, the burden of their care would have been greatly lightened.

Do you think God naturally placed these animals into a hibernation for 150+ days?

831 species is an erroneous claim, as is the 150 days.

Neither of them are in the Bible. (The flood was actually a little more than a year.)

831 species? The number is more like 10 million.

They were on the ark for 11 months according to Chapter 8 of Genesis.
The flood only had to be a local flood to wipe out all humans because they were still living in a small area. Whole world can mean "as far as the eye can see" or "the known world".
If only local animals were on board, 8 people could feed and care for them for 11 months. Otherwise, there would be millions of animals and their food - not enough room. A local flood would take of the problem of how animals got to Australia - the Ark landed close to where it began.

Look, we're trying to deal rationally with a story about unexplained magic man in the sky doing magic. With magic, anything is possible. Even adding an explained volume of water of unknown origins to earth (covering the highest mountains the story says) which would crush the earth's core like a tin can and send us off careening into the sun or into some other disastrous orbit, never mind where this unexplained water then got off to. It's all magic.

For those idiots who think it was "millions" of species, i just did a search the other day and we have a list of known mammals of only 4,320 or thereabouts. Of which; these and a few of the bird species needed this refuge, none of the fish and none of the amphibians and few of the reptiles would have needed to be in the ark. Expecialy since the floating mats of vegitation would be massive. Catastrophy theory used in geology today to predict and find deposits of coal and oil, likely caused by the flood, have revealed that these mats would have been as large as states. IN fact some SINGLE coal deposits clearly placed by such hydrological actions, are found to extend under several states at a time in the eastern U.S.A. . While such mats would NOT be useable for most larger mammels, dinosaurs or humans or large creatures, being merely traps due to the constant shifting of the trees and brush due to motion caused by the storms and waves and possibly sources of disease because of the dead bodies trapped in them, and due to larger reptilian predators and no proper sources of food, they would be usable by small reptiles, such as crocadiles and lizards and even birds and bugs etc. Possibly some small mammals as well. This may be why the flood was continued for over a year, to quaruntee that any humans who may have found such mats would have perished. There was to be NO ONE left alive but Noah and his Family.
But for those sorry excuses for intellect, stupid is as stupid says.
First of all the boat was large enough to hold the animals and their food as well. The lists in scriptures of the animals taken in show a preference for thoise animals essential to mans survival and health and such animals as were part of a a ecosystem . that it included every animals simply is not a requirement from the text as i showed you previously that some did not need an ark to survive. Noah spent several hundred years building the boat and stocking it when ready. There were 8 people not just one: and they had nothing else to do. And trust me, many of the animals would have been able to feed themselves if food was provided in a area accessable to them. Eight people is more than sufficient. For example, one average bale of hay will feed a goat for over a week, a cow for two days and elephant would need 5+ bales a day. It takes about 10 minutes... If such stores were properly placed prior to the animals arrival such as in lofts over head, its an easy matter to put sufficient food available for all the critters to eat. Some animals were low maintenance and some took more work. And we must NOT overlook God's ability to guide those people in preparation and proper care of the animals since he planned the entire thing any way. Hibernation is a possibility but not necessary to explain the logistics of this. Caloric intake would be minimal since there was little mobility neccesary that minimizes the amount of food needed. Most people now days simply don't have any grasp of what it takes to care for farm (or other) animals . Watering could have been done through a simple system of wooden troughs from a source supplied by a simple bucket system. With as much water as was present its likely that the water outside the boat was pure enough to drink as well. So all they did was open some hatch and allow them to drink ...its conceive able that they had a simple valve that they opened below the water line and this let in a small amount of water for drinking purposes. People back then were not stupid, like many people today think. They simply did not have all the high technology we have developed. But they did have iron and bronze and could have made such things, specially since God was involved. After all, the Mosaic laws, such as the social, dietary and sanitation and health laws, and in the building of the Tabernacle in the wilderness. revealed a profound knowledge of bacteriology and disease and social controls and psychology and metalurgy and other "sciences", some 3,000 years in advance of what we have only just learned in the last 300 years. And this was not that far removed from Noah's day.
IT does not require that God put them into hibernation for him to have prepared Noah, his family and the ark to sustain them for as long as necessary.

don't bother. the fundies have the obvious answer: goddidit.

We do not know all the mechanics of that, but we can see some things from the Bible record.

For instance, the account shows they were brought into the Ark in "kinds". Just as Noah's family had all the genetic material to give us all the races we see today, so too with the animals. Every breed of cat would not be necessary. Only the representatives of those kinds. At Genesis 7:2-3, it shows them putting clean animals by "sevens" and unclean animals by "twos".

It was by God's direction that this happened, so his guidance probably was used.

What we know for sure is that the animals did not have any fear of humans. We know this from Gen. 9:2 where it tells after animals were released from the Ark, then they began to have a fear of humans. It was also in verse 3 that humans were first given the permission to eat meat.