Nasal-Oral Water Administration for Rehydration of Juvenile Mohave Desert Tortoises

Some terrestrial chelonians, including Mohave desert tortoises Gopherus agassizii, reabsorb water from urine stored in their bladders, and thus they may experience an elevated risk of dehydration if they urinate in response to interactions with humans. Field biologists can use several methods to attempt to replace voided urine with hydrating fluids, but each has drawbacks or unknown efficacy. Here we evaluate the efficacy of offering juvenile Mohave desert tortoises water via needle-free syringe for ingestion through the nasal and oral passages. Only tortoises offered >= 12 mL of water, which equated to >= 40 mL of water/kg body weight, gained weight during the hydration attempt. We recommend that field biologists offer at least 40 mL of water/kg body weight when using the nasal-oral hydration method with a minimum of 15 mL offered regardless of body weight. The nasal-oral technique and minimum volume recommendations may be useful for other terrestrial chelonians, and we recommend attempting rehydration via this simple technique when alternate methods are not available to alleviate the potentially harmful effects of handling-induced loss of urine.