Why doesn't electricity kill rats? - briefly
Rats’ high body resistance and small mass limit the current from low‑voltage sources to levels below the threshold that disrupts cardiac activity. Only sufficiently high voltage or prolonged exposure can be lethal.
Why doesn't electricity kill rats? - in detail
Rats survive exposure to electric current that would be lethal to humans because their physiological and anatomical characteristics differ markedly from those of larger mammals. The key factors are body size, electrical resistance, current pathways, and the thresholds at which cardiac and nervous systems fail.
- Small mass reduces the amount of current that can pass through vital organs. Current (I) equals voltage (V) divided by resistance (R); for a given voltage, a higher resistance limits I. Rat skin and fur contain more insulating keratin, increasing overall resistance compared with human skin.
- Cardiac fibrillation in mammals occurs when a certain current density reaches the heart. The tiny heart of a rat requires a lower absolute current, but the required current density is proportionally higher because of the reduced cross‑sectional area of cardiac tissue. Many laboratory electric traps apply voltages that generate currents below this density, so the heart continues to beat.
- Nervous system damage depends on the voltage gradient across nerve membranes. Rats possess a higher threshold for depolarization due to differences in ion channel composition, allowing them to tolerate brief voltage spikes that would incapacitate larger species.
- The path of current often travels along the outer surface of the body rather than through the interior. In a typical rodent trap, the electrodes contact the paws or tail, creating a peripheral circuit that bypasses the thoracic cavity. Consequently, the heart and brain receive insufficient current to cause fatal arrhythmia or neural shutdown.
Experimental data support these mechanisms. Studies measuring the lethal dose (LD50) for rodents show that voltages in the range of 120 V AC, common in household appliances, produce only transient muscle contractions in rats, while similar exposure is fatal to humans. Increasing the voltage to several hundred volts or reducing the resistance (e.g., by wetting the animal) raises the current enough to cause cardiac arrest.
In practice, effective rodent control devices rely on higher voltage, lower resistance circuits, or mechanisms that force current through the torso. Without such design considerations, ordinary electric fields fail to deliver the lethal dose required to kill rats.