by a single nighttime interruption. 3. Navigation: Experimental findings based largely on studies conducted in planetariums indicate that nocturnal migratory animals, especially birds, may rely upon celestial cues to aid in navigation over long distances. This mechanism may also be invovled in the unusual long distance migrations and site specificity of some open ocean marine animals including fish, reptiles (sea turtles) and invertebrates. 4. Nocturnal behavior: Nocturnal animals are generally keenly sensitive to low levels of illumination and abrupt increases in normal ambient levels of light may have a multitude of effects on behavioral patterns and general ecological relationships. For example, since nocturnal predators may hunt visually, any added illumination may assist them in locating and capturing prey. The fact that many small animals tend to reduce activity abroad or even remain secluded on nights of full moons suggest that such nocturnal illumination may be detrimental to their survival. The sudden change in illumination on an otherwise dark night may cause abnormal behavioral patterns. IV. ESTIMATION OF POTENTIAL EFFECTS OF REFLECTED LIGHT The above considerations raise the possibility that reflected light may have multiple effects on the biology of animals. Information required to evaluate the effects of this light include the following: 1. Intensity of light: Illumination must exceed threshold levels required to stimulate appropriate photoreceptors (note: these receptors are known to be extra-ocular in the case of photoperiodism, and hence have
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