Effect of Manual Restraint and Visual Security on Heart Rate in Dyeing Poison Dart Frogs (Dendrobates tinctorius azureus) and Leopard Frogs (Lithobates pipiens)
Frogs are popular exotic pets and research subjects. Manual restraint is routinely used for basic procedures in frogs, including examination and sample collection, but there is little information on its physiologic effects in amphibians. Previous literature suggested that amphibians lack emotional responses and, therefore, consciousness, based upon an inability to elicit stress tachycardia with gentle handling. To determine if manual restraint results in a stress tachycardia in frogs, 10 poison dart frogs (Dendrobates tinctorius) and 8 leopard frogs (Lithobates pipiens) were manually restrained and heart rate (HR) recorded at both the pectoral girdle and pelvic patch using a Doppler flow probe. Frogs were randomly placed in one of two (opaque versus translucent) types of plastic containers for 22 min and HR measured every 2 min through the bottom of the container using the frogs' pelvic patch area. Frogs were then removed from the container, manually restrained again, and HR recorded. Heart rate decreased significantly after the frogs were placed in the containers following manual restraint, and increased significantly for the second restraint period. There were no significant differences in measured HR between anatomic sites (pelvic vs. pectoral) or container types. Contrary to previous descriptions, these results demonstrated that, similar to other mammal and reptile species, frogs demonstrated stress tachycardia during manual restraint, and, therefore, clinicians and researchers should be mindful of induced stress when restraining amphibians.Abstract
Measurement of heart rate using a Doppler pencil probe in a restrained dyeing poison dart frog. Heart rate is measured by placing the probe over the pectoral girdle (A) and in the area of the pelvic patch or caudoventral coelom (B).
Measurement of heart rate through a translucent, plastic deli container in a nonrestrained leopard frog (Lithobates pipiens) using a Doppler pencil probe coated with transducer gel. Heart rate is measured by placing the probe adjacent to the pectoral girdle.
Measurement of heart rate (HR) through an opaque, plastic deli container in a nonrestrained dyeing poison dart frog (Dendrobates tinctorius azureus) using a Doppler pencil probe coated with transducer gel. The deli container was placed inside an apparatus constructed to permit HR measurement without the frog being able to see observer movement or created shadows. The housing permitted the observer to localize the frog within the container by use of a live video feed.
Mean (±standard error of the mean) heart rate (HR) in dyeing poison dart frogs (Dendrobates tinctorius azureus) manually restrained for HR measurement (0-min time point) then placed in plastic containers. Once in the plastic containers, nonrestrained HR measurements were performed every 2 min until frogs were removed from the containers and manually restrained a second time for HR measurement (22-min time point). To evaluate the effect of visual security on HR, frogs were placed into either a translucent (white circles) or opaque plastic container (black circles).
Median (±25th and 75th percentiles) heart rate (HR) in leopard frogs (Lithobates pipiens) manually restrained for HR measurement (0-min time point) then placed in plastic containers. Once in the plastic containers, nonrestrained HR measurements were performed every 2 min until frogs were removed from the containers and manually restrained a second time for HR measurement (22-min time point). To evaluate the effect of visual security on HR, frogs were placed into either a translucent (white circles) or opaque plastic container (black circles).
