Patterns of Raccoon Craniodental Morphology under Urbanization.

Area of Science:

• Ecology
• Evolutionary Biology
• Zoology

Background:

• Urbanization presents novel environmental pressures impacting wildlife persistence.
• Previous studies often fail to isolate urban influences from other variation sources.
• Hypotheses suggest cognitive demands, human-wildlife interactions, and diet drive urban morphological changes.

Purpose of the Study:

• To investigate craniodental morphological changes in raccoons (Procyon lotor) across urban and rural gradients.
• To test hypotheses implicating cognitive demands (CBH), self-domestication (SDH), and diet (DCH) in urban adaptation.
• To identify which craniodental structures are most responsive to urbanization.

Main Methods:

• Analysis of 98 raccoon specimens across the continental USA.
• Geometric morphometrics using linear measurements and 3D meshes.
• Stable isotope analysis to estimate diet composition.

Main Results:

• Urbanization significantly altered the occlusal area of first molars and mandibular fourth premolar, and cranial vault shape.
• Rostral shape exhibited limited variation across urban and ecological gradients.
• The self-domestication hypothesis (SDH) received the strongest support, though sex, age, size, and geography also played roles.

Conclusions:

• Craniodental morphology in raccoons is influenced by urbanization, particularly supporting the self-domestication hypothesis.
• Some craniodental structures appear evolutionarily fixed, contributing to the raccoon's generalist strategy.
• Urban adaptation involves multiple interacting factors beyond just the urban environment.