Herpetologica 65, 363–372 (2009)

Studies have reported deleterious effects of radio transmitters attached by researchers to various animals in the wild. Charles Knapp of the San Diego Zoo in California and Juan Abarca of the National University in Heredia, Costa Rica, reveal that the arbitrary weight limit used for transmitters on lizards — of 5–10% of body mass — may be too high.

Credit: C. KNAPP

They attached transmitters of between 2.5% and 15% of body mass to green iguana hatchlings (Iguana iguana; pictured) in Costa Rica. Although these did not impede the animals' running speed, transmitters weighing 10% and 15% of the iguanas' body mass did lower climbing speeds. The animals with the 10%-of-mass transmitters also gained less weight over a month. The authors suggest limiting monitoring equipment for these creatures to 7.5% of body mass.