Northern Prairie Wildlife Research Center
Dale M. Madison, Department of Biological Sciences, State University of New York, Binghamton, NY 13902-6000 USA
The year-round radio-tracking of Ambystoma maculatum, A. tigrinum, Cryptobranchus alleganiensis, and Rana clamitans has lead to improved package design, surgical procedures, field release and recovery methods, and positioning techniques. We have found that external packages are generally unacceptable for tracking amphibians. Amphibian skin is too physiologically active, delicate, and moist for the attachment of external units by waist bands, harnesses, collars, glues or sutures. Packages fixed to the amphibian integument has caused tethering and even injury and death in the animal's struggle to free itself. External packages can also prevent amphibians from entering or turning around in important refuges, such as small mammal tunnels, runways, vegetative tangles, and rock crevices. External packages, stomach inserts, and surgical (coelomic) implants were used on aquatic hell benders to test the various methods in a natural setting. The implants worked best, followed by the inserts, which were eliminated after 10 days. The external packages, despite their hydrodynamic and "snuggles" design, were unsatisfactory.
Radio-transmitter implants were used successfully in all the above species, but precautions with design, implant surgery, and field deployment must be taken. Implant packages should be small enough to allow amphibians to turn around in tight spaces. In salamanders, the greatest implant dimension must be substantially less than the diameter of the crevice or tunnel used. Implants should be coated or potted with substances to keep the implants from being rejected by the animal's immune system. Otherwise, the implants may become encysted or be sloughed by the animal through the body wall. Paraffin is counter-indicated as an implant coating for amphibians.
Surgical implant procedures on poikilotherms must anticipate protracted healing during cold weather early and late in the year. Specifically, suture spacing should be reduced to about 1 mm to add strength and promote physiological closure of the incision. Layered sutures are necessary in larger amphibians. Skin adhesives such as cyanoacrylate should be avoided, because they stay fixed to the sutures but become detached from the skin, leading to the sutures being pulled out prematurely as the adhesive slab snags on habitat features.
Contrary to expectation, those animals released within two days of capture and implant surgery generally recover more quickly and behave more like resident animals than those animals held longer. Many factors may contribute to poorer performance after longer recovery, including declamation and loss of social and ecological cuing. Thus, to the extent possible, animals should be released in the same pulse of ecological and social events from which they were removed. Finally, animals should also be released at the point of capture at the beginning of their activity cycle so that they can seek natural refuges when it is safest to do so.
Local triangulation is recommended for obtaining position fixes to prevent over-tracking, which can alter the response patterns and increase the likelihood of direct injury. Local triangulation also diminishes alterations of the micro environment, such as the creation of structural channels for temperature and moisture flux and even predator approach.
Potential users of telemetry are advised to seek experienced assistance, especially involving animals as delicate and specialized as amphibians. Doing so would eliminate repeating the same mistakes in the past and possibly enable one to better anticipate generic types of difficulties in new species applications.