Orientation Based on Ambient Directional Information by Red-Spotted Newts (Notophthalmus Viridescens)

Abstract

AbstractRed-spotted newts migrate between breeding sites in ponds and upland habitats. I tested the use and importance of slope as an orientation cue among adult male newts that I had removed from ponds. Newts reliably oriented downhill upon being released in a sloped orientation arena and in enclosures on the forest floor. By contrast, juvenile newts, which are wholly terrestrial animals, oriented randomly with respect to slope. Adult newts oriented downhill after having spent five days in pens at the test sites even though they presumably had access to information about the location of their pond during that time. Newts kept on land for 10 or 20 days prior to testing still oriented downhill in the orientation arenas but oriented randomly with respect to both slope and the homeward direction in the forest enclosures. I trained newts to exhibit shoreward orientation in aquaria, then tested their response in orientation arenas. Newts oriented toward shore in a flat arena and when the downhill direction coincided with the trained shoreward direction, but they oriented downhill rather than toward shore when the two directions conflicted. These results show that slope is an important cue to adult red-spotted newts returning to ponds and suggest that orientation based on ambient directional information is one of the mechanisms red-spotted newts employ when migrating to their breeding sites.