How Long Can Rats Hold Their Breath?
Most brown rats (Norway and roof rats) can stay underwater for roughly 90 seconds to about 3 minutes before they must surface. Laboratory studies that forcibly submerged untrained rats found survival limits of ≈2 minutes pmc.ncbi.nlm.nih.gov while pest-control field guides and observations in sewers consistently quote an operational window of 2–3 minutes pallash.com . Those figures are enough time for a rat to swim the U-bend of a household toilet or negotiate a flooded stretch of pipe, explaining why plumbers and pest managers so often meet “surprise swimmers.”
Where the Numbers Come From
- Classic physiology experiments
Early work by Irving (1939) measured the maximum forced dive of lab rats at ~120 s, far shorter than true aquatic mammals but far longer than most terrestrial rodents pmc.ncbi.nlm.nih.gov. - Modern cardio-respiratory data
In untrained adult Sprague-Dawley rats, involuntary submersion for 90–100 s produced extreme hypoxia and acidosis but was still survivable, with heart rate plummeting from ~460 to ~106 beats min-¹ pmc.ncbi.nlm.nih.gov. - Field and pest-control observations
Field technicians regularly report sewer rats remaining submerged “about three minutes,” a figure echoed in industry guides and consumer fact sheets pestreaction.com a-z-animals.com.
The Physiology Behind the Feat
- Mammalian diving reflex. As soon as water hits the face, trigeminal-nerve input triggers bradycardia and peripheral vasoconstriction, shunting oxygenated blood to heart and brain while conserving lung stores en.wikipedia.org.
- Selective oxygen delivery. Studies show rats can cut cardiac output to less-vital tissues by ~50 % during dives, sparing precious O₂ for the CNS pallash.com.
- Rapid heart-rate suppression. Within two seconds of submersion, HR can fall 75 % and remain suppressed until resurfacing, dramatically reducing oxygen demand pmc.ncbi.nlm.nih.gov.
- Tolerant metabolism. Rats can tolerate arterial CO₂ spikes and blood-pH drops that would incapacitate many mammals, buying extra seconds underwater pmc.ncbi.nlm.nih.gov.
Why Duration Varies
Factor | Effect on breath-hold | Notes |
Training / habituation | ↑ Duration | Voluntarily diving or sewer-dwelling rats outperform naïve lab animals. |
Body size & age | ↑ Size → longer | Larger lung volume and blood O₂ stores. |
Water temperature | ↓ Cold water | Faster heat loss and metabolic stress. |
Stress & restraint | ↓ Duration | Forced dives end sooner than voluntary ones. |
Extraordinary Outliers
- Naked mole-rat (Heterocephalus glaber). Not a true Rattus, but worth mentioning: it can survive 18 minutes with zero oxygen by switching to fructose-based anaerobic glycolysis science.org theatlantic.com. That is a survival without breathing, not a breath-hold; common rats lack this pathway.
- Muskrat (Ondatra zibethicus). A semi-aquatic rodent that routinely reaches 12 minutes underwater—six times a rat’s limit ncbi.nlm.nih.gov —illustrating how specialized divers differ.
Myths Versus Measured Reality
Claim | Verdict | Evidence |
Rats hold their breath 5 minutes | Unlikely | No peer-reviewed study exceeds 2–3 min; 5 min appears anecdotal. |
They can tread water for three days | Plausible | Endurance swimming (head above water) is a separate feat; anecdotal but consistent in field reports rejectrats.com. |
Flushing will drown a rat | Usually false | A toilet’s U-bend trap is < 30 cm and navigable in < 10 s—well inside the 3-min window. |
Practical Take-Homes for Pest Management
- Plumbing matters. Because a rat can remain submerged longer than it takes to traverse most water-filled barriers, physical exclusion devices (e.g., one-way sewer valves or the Sewer Assassin bait station) are more reliable than simply filling traps with water.
- Rapid inspections count. Fresh droppings or smear marks near floor drains often mean the animal used plumbing as an entry route—verify with smoke tests or camera scopes before sealing.
- Sanitation still rules. Limited food and water inside a building discourage adventurous dives in the first place.
Key Takeaways
Typical limit: 90 s – 3 min for Norway and roof rats.
Physiology: Diving reflex, bradycardia, and selective blood flow conserve oxygen.
Variability: Training, size, temperature, and stress all matter.
Extreme rodents: Naked mole-rat (18 min without O₂) and muskrat (12 min dives) show what specialized adaptations can achieve.
Implications: A three-minute breath-hold is more than enough for a rat to negotiate toilets, flooded traps, or short sewer segments—so plan your exclusion strategy accordingly.
