Abstract
In May 2003, the United States Fish and Wildlife Service, Brookhaven National Laboratory (BNL), and the Wildlife Conservation Society (WCS) initiated a radiotelemetry study of eastern hognose snakes (Heterodon platirhinos) at BNL on Long Island (LI), New York. Although once common on LI, and still common elsewhere,4 the LI population has plummeted and the snakes remaining at BNL may represent one of the last healthy populations in the region1,3,6. The purpose of the study was to improve management and conservation efforts by developing a better understanding of the species life history, ecology, and behavior with a focus on habitat use, home-range size, and movement patterns relative to feeding, nesting, and hibernation activity. Additionally, subsequent to its regional decline, biologists plan to estimate the current population size, develop a long-term management plan for habitat preservation and enhancement, and encourage further study of this unique species at BNL.
Five hognose snakes were collected at BNL for surgical radiotransmitter placement between May and June 2003, and nine between April and June 2004 (two of these nine had also been implanted in 2003). Snakes were housed at BNL prior to surgical radiotransmitter placement at either BNL or WCS.
Radiotransmitters (AVM Instrument Company, Ltd., Colfax, CA, USA or Holohil Systems Ltd., Carp, ON, Canada) were sterilized with either ethylene oxide (Anprolene, Andersen Sterilizers, Inc., Haw River, NC, USA) or benzalkonium chloride (Benz-all, Xttrium Laboratories, Chicago, IL, USA). Snakes weighed 80–450 g, and the radiotransmitters weighed 4.5–5.5 g, with a ratio of transmitter to snake weight in the range of 1– 5%.
Surgical anesthesia was achieved by local administration of 3–5 ml/kg of a diluted solution of lidocaine (Lidocaine HCl 2%, RX Veterinary Products, Grapevine, TX, USA) without epinephrine (final lidocaine concentration 0.5%) that was injected SC at the incision site, IM within the muscle layers below the incision site, and extending SC proximally along the antennae tract. Local anesthesia has been successfully conducted in other snake species for surgical radiotransmitter placement as it was in these cases.2,5
Surgical procedures were conducted with the snake in left lateral recumbency after a routine presurgical scrub with chlorhexidine (Nolvasan Solution, Fort Dodge Animal Health, Fort Dodge, IA, USA). A transparent surgical drape was placed over the snake and a 1.5–2 cm skin incision made on the right lateral body wall dorsal to the juncture of ventral scutes and lateral scales at approximately 60–70% of the snout vent length. The coelomic cavity was entered by blunt dissection between the ribs and the ventral coelomic muscles. Radiotransmitters were inserted into the coelomic cavity and passed distally beyond the surgical site. A 5-French polypropylene catheter (Polypropylene catheter, Sherwood Medical, St. Louis, MO, USA), cut to length of the antennae, was then passed SC from the surgical site proximally along the lateral body. The antenna was inserted into the catheter and passed proximally. A stab incision (≤0.5 cm) was made over the proximal aspect of the catheter and it was removed leaving the antennae SC. Minimal hemorrhage occurred and was controlled with pressure. The coelomic muscle layer incision was closed with one or two simple cruciate 3-0 PDS (PDS, Ethicon Inc., Somerville, NJ, USA) sutures. The stab incision and skin incision were closed with one or two subcuticular 3-0 polydioxanone (PDS) mattress sutures in an appositional or everting pattern. Tissue adhesive (Nexabend liquid topical tissue adhesive, Closure Medical Corp., Raleigh, NC, USA) was applied over both skin incisions and a single SC dose of 5–10 mg/kg enrofloxacin (Baytril 2.27%, Bayer HealthCare LLC., Shawnee Mission, KS, USA) was administered.
Snakes were housed at BNL for a several day postoperative (POp) recovery period and were then released at their respective capture sites. Observations demonstrated what was believed to be normal behavior in the snakes. All moved considerable distances after release and within several days began displaying behaviors that were typical throughout the field seasons. This consisted of a pattern of late spring stasis during which they all shed, resumption of movement in early summer, reduction of movement and aestivation from mid-summer to early-fall, and resumption of movement in late fall before hibernating. One snake that was tracked for 2 yr returned to hibernate in the exact same location both years, after moving several kilometers during the active season. During the course of study of these 12 snakes, three were confirmed dead (POp day 37–319 due to presumed predation in two cases and vehicular trauma in one). Transmitters were found unassociated with snake remains in three cases (POp day 36–130 either a result of transmitter loss from the snake or predation). Three snakes in 2003 were lost to follow-up (POp day 23–124 due to presumed radiotransmitter failure). Initial information gained from the study will help biologists better manage this at-risk species at BNL.
Acknowledgments
This study was approved by the Wildlife Conservation Society’s Institutional Animal Care and Use Committee (#03-1). We thank the veterinary technicians at the Bronx Zoo’s Wildlife Health Center for their expert assistance and numerous volunteers for field assistance in locating and radiotracking the snakes.
Literature Cited
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