Global Assessment of Predation Rates
COMMON PREDATORS IN MAIZE FIELDS
Birds
Bird attack marks are typically “U-” or “V-” shaped, although they can also result in two quasi-parallel lines. Occasionally, the caterpillar may be chewed vigorously or even broken into pieces
Rodents
Mammal teeth impressions are typically easy to identify and mainly restricted to rodent bites in maize fields. Rodent attack marks are characterized by the upper and lower front teeth
Reptiles
Reptile attack marks are uncommon in European maize fields, but have been recorded in tropical and sub-tropical regions. These marks are presumably variable, but should always present two rows of teeth marks of approximately the same diameter
Chewing insects
Chewing insects such as carabids leave characteristics mandible marks. Based on the strenght of their bite, they can leave marked lines or small holes. Holes are of approximately triangular shape with the vertex pointing to the vertex of the correspondent opposite hole
Chewing insects
Other invertebrate predators can leave singular marks or holes, or more complex chewing marks involving more than single lines
Chewing insects
However, arthropods can leave different marks (e.g., lines rather than triangles, deep in the plasticine or on the surface) plausibly depending on their size and the strength of their bites
Slugs
Slugs typically leaves radula marks. They scrape the caterpillar surface in a seemingly random way (without leaving a consistant pattern). They are able to entirely consume plasticine caterpillars
Isopod
Isopod marks are similar to slug marks, with the difference that isopods leave much finer incisions (which could be confused with those left by small ants). They rarely consume caterpillars entirely
Artifacts
Beware that non-predatory marks can be accidentally caused by humans (e.g., nail marks, shoes) or by the vegetation (e.g., leaves, thorns) and stones due to extreme weather conditions (e.g., strong wind, heavy rain). Most often, these marks can be easily recognised, although they can occasionally be confused with attack marks by arthropods. In contrast with arthropod attack marks, accidental marks lack symmetries and unambiguous shapes