How do rats drink water? - briefly
Rats lap water with rapid, up‑and‑down tongue motions that create a cup‑shaped tip to draw liquid into the mouth. Whiskers detect the water surface, guiding the tongue’s precise placement.
How do rats drink water? - in detail
Rats obtain liquid by rapidly flicking their tongues against the water surface, creating a thin film that adheres to the papillae on the tongue tip. The tongue’s dorsal surface is covered with fine, backward‑pointing ridges that act like tiny capillary channels. When the tongue retracts, the film is drawn upward, and suction generated by the oral cavity pulls the water into the mouth.
The drinking cycle consists of several distinct phases:
- Contact: The tongue tip contacts the water at an angle of approximately 30° to 45°, maximizing surface area.
- Lamination: A narrow sheet of water spreads across the papillae, forming a capillary bridge.
- Retractile suction: Muscular contraction of the floor of the mouth reduces intra‑oral pressure, drawing the water column into the pharynx.
- Swallowing: The tongue returns to a neutral position, and the bolus is passed to the esophagus.
Rats can execute this sequence up to 200 times per minute, allowing intake rates of 0.5–1 ml min⁻¹ for an adult. Their small size and high metabolic demand require such rapid ingestion to maintain hydration.
Behavioral observations show that rats prefer shallow containers, which reduce the distance the tongue must travel. When water is scarce, they increase licking frequency and extend each lick’s duration, compensating for the reduced volume per lick.
Physiological studies using high‑speed video and pressure transducers have quantified the suction pressure generated during each lick at roughly –0.5 kPa. The combination of capillary action on the tongue surface and negative pressure creates an efficient mechanism that does not rely on gravity or large oral cavities.
In laboratory settings, providing smooth, narrow drinking tubes enhances water consumption because the tube geometry aligns with the natural licking motion, reducing the need for excessive tongue extension. Conversely, rough or wide openings disrupt the lamination phase and lower intake efficiency.
Overall, the rat’s drinking method integrates specialized tongue morphology, precise motor control, and adaptive behavior to secure fluid intake swiftly and reliably.