High Predation on Green Snakes, Opheodrys aestivus

Abstract

In the course of monitoring movements and behavior of gravid green snakes (Opheodrys aestivus) by radiotelemetry, I observed predation by kingsnakes (Lampropeltis getulus) and racers (Coluber constrictor). The high frequency of the observed predation warrants this report. Miniature radio transmitters (220 MHz, Model SOPI1038-LD; Wildlife Materials, Inc.) were implanted into nine large (>500 mm snout-vent length, SVL), gravid 0. aestivus. The snakes were released on 19 June 1988 at the sites of captures made during the previous week in the shoreline vegetation of a small lake 2 km W of Denmark, White County, Arkansas. Snakes were relocated several times each day until oviposition, and at least once each day thereafter. After relocating Opheodrys nos. 255 and 584 several times on 24 June, weak signals were received in the afternoon from each snake indicating extensive movements atypical for the sedentary 0. aestivus. Both signals were emanating from L. getulus (670 mm SVL male; 860 mm SVL female) from which Opheodrys nos. 255 and 584 with implanted transmitters were subsequently palped. On 6 August, signals from Opheodrys no. 5 were received from underground, atypical for the arboreal 0. aestivus. Underground signals continued to be received from no. 5 at various locations within an approximate 30 m2 area over the next 14 days. On 20 August, I dug into a system of rodent burrows at the signal source and eventually found a 720 mm SVL female L. getulus. The Lampropeltis was taken to the laboratory where on 23 August it passed the transmitter originally implanted in Opheodrys no. 5. ' S EY, R. T., AND K. A. BAI . 1987. Asse ment petitive interactions between two iguanid species. Oikos 48(2):206-210. At dusk on 9 July, Opheodrys no. 37 was ovipositing in a hollow tree. The next morning three Opheodrys eggs were found scattered on the ground at the base of the tree and a signal could not be detected. After extensive searching, a signal was detected, eventually leading to a 960 mm SVL female Coluber constrictor. Dissection revealed that the Coluber had first ingested an Opheodrys egg and then ingested Opheodrys no. 37. The posterior gut of the Coluber was full of grasshoppers. Additional observations implicate Coluber as a predator of 0. aestivus during this study. On 24 June, signals from Opheodrys no. 605 were lost. The last contact with the snake had been made the previous day at a ocation within 3 m of an active Coluber. A subsequent search for the Opheodrys was unsuccessful. On two other occasions (22 and 23 July), two different Coluber were observed actively foraging arboreally in the narrow band of alder at the shoreline, the preferred habitat of 0. aestivus (Plummer, 1981). Studies of telemetered Coluber support strong arboreal tendencies (Fitch and Shirer, 1971). At dusk on 7 July, Opheodrys no. 110 retreated into a rotted stump as she moved back toward her activity range after ovipositing in a hollow tree. The next morning, her transmitter was found on the ground next to a large oak tree, but she could not be located. The sutures at the site of implantation were intact on 7 July suggesting that the transmitter was lost as a result of predation, perhaps by a bird or mammal. On several occasions, I and my assistants have observed predation by bluejays (Cyanocitta cristata) on 0. aestivus in an outdoor enclosure (Plummer, unpubl. obs.). Typically, bluejays carried snakes to a tree, pecked them to death, and eviscerated them as they ate. Parts not eaten, including most of the carcass, were allowed t fall to the ground (see also Sledge, 1969; Hammerson, 1988). Mammalian predation would also free the transmitter, but no tooth marks were found on the transmitter.