Facial shape differences between rats selected for tame and aggressive behaviors

Area of Science:

• Evolutionary biology
• Developmental biology
• Animal behavior

Background:

• The domestication syndrome encompasses traits like tameness and altered craniofacial dimensions.
• Altered neural crest cell (NCC) development is hypothesized to underlie these domestication traits.
• Dmitri Belyaev's experiments with silver foxes and rats provide models for studying domestication.

Purpose of the Study:

• To investigate craniofacial changes in Belyaev's behaviorally selected rats.
• To test if tameness in rats leads to domestication-like facial morphology.
• To determine if NCC-derived facial regions differ between tame and aggressive rats.

Main Methods:

• Computed-tomography (CT) scans of rat skulls were utilized.
• Landmark-based geometric morphometrics were applied to analyze facial skeletons.
• Facial shape was quantified and compared between behaviorally selected rat groups.

Main Results:

• Significant facial shape differences were found between tame and aggressive rats, independent of size.
• These craniofacial changes in tame rats resemble those in domesticated animals versus wild counterparts.
• Reduced sexual dimorphism in facial morphology was not observed in the tame rats.

Conclusions:

• Tameness in rats is associated with specific craniofacial alterations, supporting the NCC development hypothesis.
• However, not all aspects of the domestication syndrome, such as reduced sexual dimorphism, are consistently present.
• This suggests that phenotypic trends within the domestication syndrome may vary across different experimental models.