The 3% Rule and What It Means for a Tiger
Wildlife biologists work with a standard: a tracking device should not exceed 3% of the animal's body weight. For a 180-kilogram Bengal tiger, that ceiling is 5.4 kilograms. Most modern GPS collars for large cats weigh between 400 and 700 grams, which keeps them well inside the limit. For smaller animals, the arithmetic gets brutal. A collar that is acceptable on a leopard becomes a serious burden on a jungle cat. On a bird, a lesser florican, a sarus crane, the harness carrying a transmitter must stay under 3 to 5 grams, because a bird carrying more than 3% of its body weight shows measurable changes in flight speed and foraging time within days. The 3% rule is not a comfort standard. It is the threshold below which researchers believe the device does not fundamentally alter the behaviour it is trying to measure. Above it, the data becomes unreliable for a specific reason: the animal is no longer behaving like itself.
