Reduced Performance of Prey Targeting in Pit Vipers with Contralaterally Occluded Infrared and Visual Senses

Abstract

Both visual and infrared (IR) senses are utilized in prey targeting by pit vipers. Visual and IR inputs project to the contralateral optic tectum where they activate both multimodal and bimodal neurons. A series of ocular and pit organ occlusion experiments using the short-tailed pit viper (Gloydius brevicaudus) were conducted to investigate the role of visual and IR information during prey targeting. Compared with unoccluded controls, snakes with either both eyes or pit organs occluded performed more poorly in hunting prey although such subjects still captured prey on 75% of trials. Subjects with one eye and one pit occluded on the same side of the face performed as well as those with bilateral occlusion although these subjects showed a significant targeting angle bias toward the unoccluded side. Performance was significantly poorer when only a single eye or pit was available. Interestingly, when one eye and one pit organ were occluded on opposite sides of the face, performance was poorest, the snakes striking prey on no more than half the trials. These results indicate that, visual and infrared information are both effective in prey targeting in this species, although interference between the two modalities occurs if visual and IR information is restricted to opposite sides of the brain.

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“…The sensory field of the IR‐device substantially overlaps that of the eye. The sensory field overlap is also reflected by the neural spatiotopic maps for both systems (Hartline et al, ) as well as in the targeting areas (Chen et al, ).…”

“…Pit vipers possess four sensors (e.g., two eyes and two pits) for detecting electromagnetic radiation, each seemingly of equal weight for decision making. A previous study showed that compared to controls, about 75% of prey attacks were successful when one eye and one pit were occluded on the same side of the face, or when either both eyes or both pit organs were occluded (Chen et al, ). These results suggest that the eye and pit on the same side of the head work in concert for targeting prey.…”

“…Chen et al () found that snakes with either the pit organs or eyes occluded on both sides of the face exhibit about 75% success in prey capture. Similarly, occlusion of both eyes or both pits constrict strike angles during prey capture to the same extent, within 30° to the left and right sides of the midline (Chen et al, ).…”

“…Chen et al () found that snakes with either the pit organs or eyes occluded on both sides of the face exhibit about 75% success in prey capture. Similarly, occlusion of both eyes or both pits constrict strike angles during prey capture to the same extent, within 30° to the left and right sides of the midline (Chen et al, ). In addition, congenitally blind pit vipers using IR‐imaging have been shown to aim and strike at prey as accurately as normal siblings under a variety of conditions (Kardong, ; Kardong and Mackessy, ).…”

“…Nevertheless visual and IR-information are projected in register spatially and temporally to the midbrain and the available evidence indicates that the snakes can use either modality for hunting prey. Chen et al (2012) found that snakes with either the pit organs or eyes occluded on both sides of the face exhibit about 75% success in prey capture. Similarly, occlusion of both eyes or both pits constrict strike angles during prey capture to the same extent, within 308 to the left and right sides of the midline .…”