Abstract

As part of a preliminary study in the long term movements of wild American alligators, 16 alligators from the Conservation area of the Everglades were captured, brought to the University of Florida, College of Veterinary Medicine, weighed, measured, and radio transmitters were surgically implanted. All alligators were anesthetized with diazepam followed with succinylcholine. A line block with lidocaine was made at the surgical site. The surgical procedure is described. All alligators were returned to the site from which they were taken the day following surgery.

Introduction

Tracking the long term movements of wild American alligators (Alligator Mississippians) in the Florida everglades is a project currently being undertaken by the Department of Wildlife Ecology and Conservation at the University of Florida. In order to facilitate tracking of the alligator, it was decided to permanently install radio transmitters into the alligators for the purpose of this study. Three sizes of radio transmitters, cylindrical in shape with an antenna trailing from one end were built for surgical implant. The transmitters used either a "C" cell battery for the two smaller units and a "D" cell for the larger one. All transmitters and antennas were coated with a biologically inert material so that tissue reaction would be minimized.

Materials and Methods

A special surgical table was constructed of wood and painted white. The table had one board along the side and running parallel that was fixed and one opposite to it that had adjustment holes so that the width the animal could be placed into was variable. This was done because of size variation in the alligators, to hold the animals in position, and also so it could be moved to a remote site for field work. All surgical implantations were made using this table for the purpose of the study.

American alligators captured from the conservation area of the everglades were delivered to the University of Florida, College of Veterinary Medicine over a two day period. Nine alligators were delivered the first day and surgery was performed on five of them. Eight alligators were delivered the following day and surgery was performed on all remaining alligators except one that measured 143 cm in length and was deemed to be of insufficient size for transmitter implantation. The length of the alligators varied from 282 cm to 189 cm. Individual weights varied from 79 kg to 18 kg. Nine of the alligators were male and eight of them were female. Surgery was not performed on the smallest female. All of the alligators delivered were restrained with duct tape holding the jaw closed, and also had their eyes covered with tape so they could be more easily handled. The fore and hind limbs were taped together with the limbs drawn caudally so as to further restrict the animals movement and provide safety in animal handling. The animals were weighed, measured, and washed down with water and a dilute solution of Rocal before being anesthetized.

Anesthesia was performed with a combination of diazepam and succinylcholine. Diazepam was administered IM in the hindlimb. Fifteen minutes later succinylcholine was administered in the opposite hindlimb.² A surgical plane of anesthesia was judged present when there was lack of voluntary movement and a slowed respiration rate. The animals would generally tilt their heads when this level was achieved. Normally this would occur within fifteen minutes after injection with succinylcholine. The animal was then transported and lifted to the surgery table and placed in left lateral recumbency. A series of three surgical scrubs alternating with Chlorhexidine and 70% isopropyl alcohol were performed on the lateral surface of the animal approximately three inches cranial to the right hindlimb. The surgical area was not draped and instruments were cold sterilized so that field conditions could be more closely approximated. Sterile gloves were worn for each procedure. A line block using 2% lidocaine was performed in a dorsal-ventral direction so the animal would not be in discomfort for the incision. Approximately 5mL of lidocaine was infiltrated into the site where the incision would be made.

An incision was made using a #10 scalpel blade, in a ventral-dorsal direction, for a length of 7.5cm to 8.75cm over the area where the fine block had been made. The outer musculature of the abdomen was incised and transected with a pair of surgical scissors. The internal oblique muscle layer was left intact. Using Metzenbaum scissors, blunt dissection of the fascial layers was performed between the two muscle layers running cranially and ventrally to the incision site. Fascia was separated just enough to allow insertion of the transmitter selected for the animal. After the fascia had been separated, the radio transmitter was inserted into the defect created between the two muscle layers. The transmitter had been cleaned with alcohol and coated with paraffin and beeswax for smooth insertion into the proposed site. Another pocket was then created for the antenna. The Metzenbaum scissors were again used to bluntly dissect between the two muscle layers ventral to the right hindlimb for a distance of two to three inches. The pro half of the antenna was placed in the pocket created with the distal half facing cranially. Using the scissors as a trocar, a small defect was made between the muscle layers on the right lateral to dorsal surface of the running cranially. The distal half of the antenna was inserted into this defect. The antenna was then secured to the underlying muscle tissue using 0 vicryl placed in various locations accessible from the surgical site. A simple continuous pattern was used. This method of radio transmitter implantation bad been done successfully, in the gharial.¹

The entire area of the incision site was infiltrated with approximately 80 to 120 mg. of gentamicin prior to closure to reduce the possibility of infection. (Although aseptic technique was initially attempted during these procedures, some minimal contamination of the surgery site occurred and will undoubtedly occur under actual field conditions). Cold sterilization using Rocal was initiated after the first surgery for the instruments utilized Surgery was considered to be clean, but not sterile.

Closure of the surgical site was accomplished by approximating the opposing surfaces and initially using stay sutures with number 1 Maxon. The defect was then completely closed with number 1 Ticron in an inverted simple continuous pattern using buried knots. This non-absorbable suture was chosen because of its high tensile strength and its low tissue reaction rate. This was important since the alligators would be released the next day and any follow-up of the incision site would not be possible. Sutures were placed in close approximation to minimize dehiscence. Since the initial incision had been between the scoots on all surgeries, excellent apposition of tissue was obtained. Ethibond was used on the exterior of the skin to completely seal the tissue. Blood loss throughout the entire procedure was negligible.

Recovery of the animal was routine and complications were not noted. All animals were returned to the place of capture the day following surgery. None of the animals were fed or otherwise charged with protein because of the short duration of capture and holding, and the minimal blood loss and trauma involved.

Results and Discussion

The surgical procedure described appeared to be completely successful and can be performed with minimal personnel present. The procedure time normally took 23 minutes after the animal was anesthetized. A number of implantation procedures could probably be performed under field conditions using the procedures described for the purposes of long term tracking with radio transmitters. The transmitters implanted are designed to have a battery life of between four and five years and will not be removed. Follow-up observations of the animals will be done as they are seen during tracking for the next several years. This may also facilitate inspection of the surgical site for any potential long term complications, if any, that may arise.

Two of the alligators, both female, were found dead soon after release. One of the animals had bite marks consistent with attack by another alligator. It was not noted in the report whether the surgical site had been compromised or dehiscence had occurred. The cause of the mortality of these two alligators is not known. AU of the alligators had been captured during the month of November and were subjected to cold temperatures and long transport times. The added stress of anesthesia and surgery may have been a factor in their deaths. Although these alligators were of sufficient size for transmitter implantation, all of them were underweight and malnourished. It was also later determined that all were infected with a Haemogregarina spp. parasite in the blood. Although this parasite is normally a commensal organism, it is possible that they may have further debilitated the animals. A combination of effects is most probably present in these alligators. Malnutrition, parasitism, and concomitant subclinical disease may all be playing a role in the debilitation of these animals, and could have contributed to the deaths of the two female alligators in the experiment.

Radio tracking of the surviving alligators continues at this time. It was found on experimental trials with the transmitters that a straight antennae gave a transmission that averaged over 1 kilometer farther than one with an arched antennae. Utilization of a trocar to create a canal for antennae placement down the animal's tail between the skin and musculature will be attempted in all further implantations to maximize the range of reception.

References

1.  Shrestha, Sundar, D.V.M., (Personal communication). Implantation of Gharials with radio transmitters. November, 1996.

2.  Speigel, R.A., T.J. Lane, R.E. Larsen, and P.T. Cardeilhac. 1984. Diazepam and Succinylcholine for restraint of the American Alligator. Journal of the American Veterinary Medical Association 185:1335-1336.