Why "monogamy" isn't good enough

Area of Science:

• Primate behavior and evolution
• Social behavior in mammals

Background:

• Monogamy is rare in mammals but more common in primates, yet its definition and expression are debated.
• Existing definitions of monogamy often conflate it with pair-living and pair-bonding, hindering understanding.
• Strepsirrhine primates offer valuable models due to their diverse social structures, including combinations of these traits.

Purpose of the Study:

• To propose clear, discrete definitions for monogamy, pair-living, and pair-bonding.
• To review the variation of these three traits within strepsirrhine primates.
• To clarify which existing hypotheses explain these traits and test the Resource Defense Hypothesis (RDH) in the red-bellied lemur.

Main Methods:

• Literature review of primate social behavior, focusing on strepsirrhines.
• Analysis of existing hypotheses for the evolution of social monogamy.
• Case study applying the Resource Defense Hypothesis to pair-living and pair-bonding in Eulemur rubriventer.

Main Results:

• The Resource Defense Hypothesis (RDH) is supported for pair-living in red-bellied lemurs, characterized by stable family groups and joint territory defense.
• Data also support the RDH for pair-bonding in red-bellied lemurs, evidenced by year-round cohesive bonds and coordinated territorial defense.
• Intergroup and interspecific aggression in red-bellied lemurs correlates with food availability.

Conclusions:

• Clear definitions are crucial for understanding primate social systems, particularly monogamy, pair-living, and pair-bonding.
• The Resource Defense Hypothesis provides a robust framework for explaining pair-living and pair-bonding in species like the red-bellied lemur.
• Further research is needed to rigorously test the RDH and explore alternative hypotheses for primate social evolution.