An Automated Two-Bottle Choice Test for Rats

An open source testing apparatus that uses photodetectors and depth sensors to measure and record rat drinking microstructure.

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Two-bottle choice tests are widely used in animal experiments to determine preference between two liquids. The following design is a 3D printed, Arduino controlled two-bottle choice test that automatically reads and records drinking behaviour in rats to allow for detailed analysis of their drinking microstructure. While commercial products exist that use lickometers to measure the microstructure of drinking behaviour, this design uniquely incorporates hydrostatic depth sensors to allow for real-time volumetric measurements in addition to traditional beam break lick sensing. The goal of this design is to provide a user friendly, affordable apparatus that can study unique, complex behaviours without requiring the purchase of specialized scientific equipment or software. The following design cost under $180 CAD to build, although this cost goes down significantly when building several units due to many components being reused each time i.e. the Arduino.

Researchers looking to study drinking behavior in rats are faced with the challenge of finding an accurate measure of fluid ingestion. Generally, one will manually measure the volume after a given period at the cost of losing important temporal drinking data. This can be partially solved by using a lickometer – a device that measures the physical act of licking. Unfortunately, commercial lickometers are prohibitively expensive, and require additional proprietary hardware and software to operate. Additionally, licks do not accurately correspond to a consistent volume. This hardware provides the same functionality to that of commercially available lickometers with the unique addition of real-time volumetric sensing to correspond to measured licking bouts, thus solving any issues of lickometer inaccuracy. These measures are combined into a specialized 3D printed housing that is specific to the two-bottle choice test of which no similar product is commercially available. A similar open source two-bottle choice test by Meaghan Creed is described here:

Traditionally, two-bottle choice tests are conducted without any sensors. Each bottle is weighed before and after an animal has been able to drink from them for a given time. Unfortunately, this protocol gives no information on the animal’s drinking microstructure. That is, all information regarding when and how the animal is drinking is lost. This is important information to have when studying drinking behaviors that may change throughout the day. Many researchers have made use of lickometers to measure a rat's drinking microstructure that count the number and duration of drinking events by incorporating a photo-interrupter at the base of the bottle. While this gives the researcher a general idea of the drinking behaviour, it does not perfectly correspond to volume and, as we have found in our own experiments, is subject to being blocked by other parts of the animal such as the tail and legs. By adding a hydrostatic depth sensor, researchers can measure the volumetric changes in each bottle throughout the experiment allowing each bout of drinking to correspond to a specific change in volume.

This hardware could be used to improve the quality of data in the following example experiments:

  • Using sucrose solution to measure anhedonia in rat models of depression.
  • Using ethanol solutions to determine sensitivity to addiction in rat models of addiction.
  • Measuring taste preference using a variety of solutions. 


Program that reads sensors and records data into an excel file.

ino - 26.72 kB - 12/08/2018 at 02:57



Calibrate depth sensors to the volume of the bottle.

ino - 2.42 kB - 12/08/2018 at 02:40



3D print: Bottle cap

Standard Tesselated Geometry - 23.91 kB - 12/08/2018 at 02:39



3D print: Housing

Standard Tesselated Geometry - 47.93 kB - 12/07/2018 at 23:57


View all 16 components

  • 1
    3D print the bottle housing

    The housing should be printed on its back, that is, on the side opposite to the bottle slots. No structural supports are needed for this print. The printer filament used for this design was PLA, however, any filament should work equally well. If the 3D printer being used is too small to print the housing in one piece, the housing can be sliced, printed in several pieces, and epoxied together. The choice of triangular wire channels was made so that no structural supports would be required for the print. 

  • 2
    ​​3D print two of the bottle caps

    These are designed to keep the hydrostatic depth sensors straight as they are highly error prone when bent. 

  • 3
    Cut syringe tops

    Remove syringe plungers and cut the top of the syringe off to be flush with the top of the housing.

View all 12 instructions

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