Detection of water level in inverted bottles.
Slip a colored float into each inverted bottle to spot low water at a glance.
01Research in Context
What this study did
Carman (1976) built a tiny visual aid for lab cages.
The team placed a colored plastic float inside inverted water bottles.
Caretakers could see water level drop without opening the cage.
What they found
The float gives an instant yes-or-no check.
No electronics, no handling, no extra noise for the animal.
How this fits with other research
DAVIS (1961) built an electric drinkometer years earlier.
That rig logged every lick; the float only shows volume.
Braam et al. (2008) later used a $25 infrared pellet checker.
Both gadgets give fast visual confirmation, but one watches food, the other water.
Together they form a toolkit of cheap, retrofit lab hacks.
Why it matters
If you run rodent studies, you can drop a matching bead in each bottle today.
One glance during rounds tells you which cages need a refill.
No circuits, no coding, no cost—and the animals stay calm.
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02At a glance
03Original abstract
Animal maintenance facilities that do not provide water from a continuous tap source often use inverted bottles to supply individual animal cages. Although the inverted bottle system is economical and efficient, de- tection of a low water level requires more than casual inspection. This problem is compounded if colored bottles are used, particularly the amber tint of widemouth beer bottles. By placing an appropriately colored float in the bottle, the water level can be determined from a distance by cursory inspection.
Journal of the experimental analysis of behavior, 1976 · doi:10.1901/jeab.1976.25-278