Updated: Jan 14, 2021
I have raised rabbits in colonies for years with few problems. My current colony is actually my second, and I have tried a number of different set ups. I have only ever had two deaths in my colonies and both were does that had issues with eating things they shouldn't. Considering the numerous deaths I have known personally and anecdotally in cage-raised rabbits, I think I have been extraordinarily lucky.
So you can imagine my distress the first time I walked out, after a new fallen snow, and saw this:
The one scary part to colony raising is that the rabbit's diet will always be a little less controlled than living in a cage. The wind will blow leaves and greens into their pen, seeds will make a valiant attempt to grow and the rabbits will polish them all off before you can say "gastrointestinal distress."
This has mostly been a concern with rabbits newly introduced to the colony. They often have not had much in the way of greens and their digestive systems will not be adapted to this new found bounty. Rabbits are capable of eating greens and fresh vegetables are good for them. So I often try to make sure they are adapted to greens before moving them to the colony. With out this, what you usually get - without some careful weeding - is several days of soft stools. However, as you can see here, the pellets are solid, and the rabbit himself seemed lively, alert and was eating and drinking well.
Since prey animals are noted for pretending to be healthy right up until they drop dead, this didn't necessarily mean anything, but it was a good sign. Still, there was the chance that something poisonous has blown in to the pen, or that he had suffered an injury. His mate was in the adjacent pen, was fed the same diet (including my Mother Nature) and showed no signs of red or bloody urine, so injury or a urinary issue seemed the most likely concern.
Thus began my frantic internet search for options that did not involve expensive bladder surgery. I breathed a sign of relief when I realized his activity level made a UTI unlikely. It likewise ruled out most other injuries, so I began to hunt for possible poisoning suspects. And I found the culprit...
Yup, pine needles. Which turned out to be no culprit at all. In some rabbits, pine needles will combine with the rabbit's own body chemicals to produce a urine that is, and stays, bright red. Against a white snowy bank, it looks like a murder has taken place when in actuality, everything is fine. In fact, pine needs are a great source of nutrients for rabbits in the winter! Mine will eat not only the needles, but the tender twigs they grown on.
This is not a common occurrence in rabbits - even colony raised ones. In all the years I have raised rabbits, or known people who raised rabbits, I had never experienced this before. I currently have nine rabbits, and only one of them seems to have the trait. It apparently just exists to scare the dickens out of us and keep us on alert.
So how do you know if somethings is wrong with your rabbits urinary system?
Much of it is the rabbit's behavior, not their urine color. Rabbits with a UTI are likely to be blocked up and be unable to pee, so look for rabbits who are straining, standing on tip toes or otherwise seem to be having difficulty urinating. Rabbits will stop eating and drinking when they cannot pass anything through their system. If you have boxes or other shelters for them, sick rabbits will be likely to hide, so try to see all your rabbits every day.
If in doubt, take your rabbit to a vet. If that is not possible, isolate them from the other rabbits in the colony to prevent the spread of disease until you are sure they are recovered. If this takes more than a day or two, introduce them back in carefully in case the other rabbits no longer see them as "one of the group."
And above all, no need to panic if you are in your rabbit's enclosure and you find yourself seeing red.