Читать книгу The Behavior of Animals - Группа авторов - Страница 50

Common toads evaluate the absolute size of prey binocularly and/or monocularly (Ewert & Gebauer 1973; cit. Ewert 1984). Among configurationally “neutral” square black prey dummies (Figure 2.8As), they prefer an object—at different distances—of about s = 10 mm edge length, generally:

s = 0.37 w for 5 ≤ w ≤ 26 [mm]; mouth-width w

including, e.g., the anuran species Bufo, Rana, Hyla, Bombina, Alytes. The size constancy phenomenon performs with stereoscopic vision after metamorphosis (Ewert & Burghagen 1969; cit. Ewert 1984). Monocularly, it requires an estimation of object’s distance calculated in connection with toad’s movement relative to the object: e.g., by triangulation (brief head shifting) and/or accommodation (lens shifting) (Collett 1977). Depth information, for example, reaches T5-type neurons.

Evidence: In pharmacologically immobilized awake toads, T5-type neurons measure objects in degrees of visual angle (Figure 2.8B,s). However, in free-moving toads, T5-type neurons are sensitive to object’s absolute size (Spreckelsen et al. 1995). So, in accordance with that, the features(p,c)-relating-algorithm is traceable in scales of absolute or visual angular size (Figure 2.8 cf. A,B).