Analysis of the behavioral sequence emitted by rattlesnakes during feeding episodes II. Duration of strike-induced chemosensory searching in rattlesnakes ( Crotalus viridis, C. enyo)

Abstract

Eight rattlesnakes (four Crotalus viridis and four C. enyo ) were each observed in four experimental conditions: (1) snakes saw, smelled, and detected thermal cues arising from live mice for 3 sec but were not given an opportunity to deliver a predatory strike (the mice were then removed); (2) same as Condition 1, but a strike was permitted at the end of 3 sec (the mice were then removed); (3) same as Condition 2, but the envenomated, dead mice were left in the snakes' cages so that ingestion occurred; and (4) same as Condition 3, except that a second mouse was introduced (as in Condition 2) after the first was consumed. The dependent variable was the rate of tongue flicking (RTF) which was recorded for 315 min, beginning 5 min prior to each condition. A high RTF followed each predatory strike, but not the no-strike mouse presentation of Condition 1. In Condition 2, snakes continued searching for the envenomated mice for 150 min poststrike. Ingestion terminated the high RTF in Condition 3, but a second strike reinitiated high RTF in Condition 4. In the latter condition, snakes continued chemosensory searching for 105 min after the second strike. In Conditions 2 and 4, snakes remained attentive even after they quit chemosensory searching because a 3-sec, no-strike presentation of a live mouse (presented at least 120 min after RTF had returned to baseline) resulted in a reinitiation of tongue flicking. This did not happen after Conditions 1 and 3. Implications of these data for mechanisms mediating strike-induced chemosensory searching are discussed.