This article is from the WSSF 2007 AFRMA Rat & Mouse Tales news-magazine.

Q I had to go out of town over a weekend, but was only away from the house for one day. I had someone come to check on the mice and our other pets that Saturday morning I wasn’t home, but they didn’t see anything out of place. However, when I got home at 5 P.M. on Sunday, the water bottle in one of my mouse’s tanks was empty. The 7-month-old male looked down, but he perked back up after I gave him water. I had imported him from out-of-state a few months prior. He went through the shipping and quarantine fine and had no problems until this incident. I had bred him with some of my other females prior to this without any problems. I had put three does in with him the Thursday before I left. The bottle was 8 oz for four mice but it gets around 80 degrees in the house at 2 P.M. even with the air conditioner on. The mice were not wet, but I usually fill the tanks up pretty high with bedding, so the likelihood of them actually getting soaking wet from a bottle leak is slim.

However, by the next Saturday I noticed severe weight loss in him again, and it happened rather fast. I talked to a fellow breeder and she had said it was possibly the does stressing him out, so I removed two of the does, thinking if I took out all three, it would make his condition worse. I also offered him several different treats and things to get him to eat because his only real symptom was rapid weight loss.

However, after all my efforts, I found him passed away in his cage Monday morning. He was still down, but okay on Sunday. Do you have any idea what this might have been? I would’ve taken him to the vet on Monday, but it was too late by then, and we don’t have an emergency vet in the area.

No other mice here are sick or have similar problems, so I don’t know what could’ve caused it other than stress.

Do you think the empty water bottle had anything to do with my mouse dying a week later? He had water all week long, and had actually perked back up and was looking good for a few days, and then just started losing weight, which is what threw me. Especially when all the cagemates were fine.

I’m positive this incident was environmental caused by stress of no water. I worried that he may have come in contact with some sort of pathogen while his immune system was compromised by the lack of water. But I can’t imagine what with no other sick animals in the colony.

Answer by Karen Robbins
ASorry to hear about your mouse. I haven’t had males react like this if I put in several females at once so I’m not sure it would be from that. The only thing I can suggest is when you have something strange like this, is to have a necropsy done and tissue and blood samples sent in for testing.

My experience with mice not having water for a couple days (babies that are super jumpy and get down on the floor and I’m unable to get them right away) are that even though they perk back up once they get water and food, they never seem “right” after that, and I always end up putting them down later. Perhaps he did pick up something or the stress weakened him too much and just wasn’t able to recover. Of course being a bigger mouse, he would need more water than the smaller mice. My suggestion when you go away for a weekend even with someone coming in to check things, add an extra bottle to the cages.

I know that mice can get some moisture out of their food if given seeds.

When you raise animals, things happen. I like to know when things happen so I can keep an eye on siblings/the line so if there is something “wrong” I can eliminate it or determine if it was just a one-time thing.

Other notes on water bottles
I’ve had people who thought their water bottles were okay because they had water in them, but didn’t notice that the ball bearings in the spout were not working properly (one being stuck at the top of the spout) and the animals would go for a day or more before the problem was noticed. They may have noticed the animals were looking poorly but didn’t attribute this to the lack of water. So, when filling bottles and putting on the cages, always listen for two balls going down the spout. Another indication is the loud clicking sound of the one ball in the spout when the animals are trying to get water (sounds as if the bottle was empty).

Also, you get to know how much water is drunk from each bottle per cage depending on how many animals are in there—if you don’t see the water going down the appropriate amount each day, then it is time to check to see if the bottle needs fixing. Most people will run their finger over the end of the spout several times when they put a fresh bottle of water on the cage to make sure it is working properly.

For the glass spout tube bottles, sometimes the air bubbles will not clear out of the spout into the bottle when the mouse drinks. The answer to this is to take a piece of broom straw almost as long as the entire length of the spout. Put this in the spout far enough in that the mouse can’t reach it when drinking and with a small amount sticking out into the tube part so the bubbles travel up this and the water is refilled into the spout.

Answer by Carmen Jane Booth, D.V.M., Ph.D.
A If the cage had been flooded, and the mice were wet, they can become compromised from hypothremia and dehydration. If the cage was normal, I would wonder if the mice were really checked on Saturday for adequate food and water? A lack of water is a very serious event in mice. They have such a high metabolic rate that this is a significant issue.

There is no way to know why this mouse died without a necropsy. Even then, if the mouse has been dead for a while, the tissues degrade pretty fast at room temperature and prohibit histology.

Mice of this age can and do die occasionally from a variety of different things. My suspicion is that the dehydration incident may have exacerbated an underlying problem and although the mouse initially recovered from the dehydration, the underlying problem ultimately caused the death. We will never know.

Suggestion for the next time, put an extra bottle on the cage and/or put a check list by the cage so that whomever checks them has to initial these points: Water bottle refilled, gave food, etc., each mouse checked and doing well.

Many people just look in the cage and if the bottle has any water they don’t refill it. Water is even more critical than food. An animal will stop eating if they are dehydrated. My kids don’t always refill the bottles when they check the rats every day and we have 3 bottles on a cage with 2 rats just to make sure they never run out.

There is some debate regarding water deprivation; however, I found two articles that relate. I will use mice but it is likely similar for rats.

Question: What are the water requirements for mice? How long can rats or mice survive without water before problems occur?

Answer: Here are the published water requirements for normal rats and mice¹:

Mice: 15 ml water per 100 grams body weight per day
Rats: 10–12 ml water per 100 grams body weight per day

Example 25 gram adult mouse = 25 grams x 15 ml/100 grams = 3.75 ml per day
Example 300 gram adult rat = 300 grams x 12 ml/100 grams = 36 ml per day

Mice have a higher metabolic rate than rats which accounts for the higher metabolic need for water. The metabolic requirement for water is increased with gestation, lactation, exercise, and some diseases such as diabetes, kidney failure, etc.

The answer to the second question is more difficult and relates in part to the metabolic demands on the animals.

I found one study where they were studying the effects of stress from water or food deprivation on transport in mice². In this study the author stated but did not show published data that most normal laboratory strains of mice are distressed after 16 hours of water deprivation. In another study3, they found that they could restrict water up to 22 hours a day for 5 days a week in mice with moderate weight loss and no compromise to the animals welfare.

However, one must also consider the high metabolic food requirements¹:

Mice require 12–18 grams per 100 grams body weight per day
Rats require 5–6 grams per 100 grams body weight per day

In the absence of food, mice can die when they lose 20% of their body weight². In obese mice, this may take longer and in smaller mice, this may occur with a lower loss of body weight.

References

1. Harkness JE, Wagner HE. The biology and medicine of rabbits and rodents. 1995 Williams and Wilkins.
2. Wallace ME. “Effects of stress due to deprivation and transport in different genotypes of house mouse.” Lab Anim. 1976 Jul;10(3):335-47
3. Tucci V, Hardy A, Nolan PM. “A comparison of physiological and behavioural parameters in C57BL/6J mice undergoing food or water restriction regimes.” Behav Brain Res. 2006 Oct 2;173(1):22-9.

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