males. There was a trend for monogamous males to have
smaller relative litter weights and species distribution areas
compared with nonmonogamous males, and these relation-
ships were absent in females. Our results not only demon-
strate differences in male and female mating strategies, but
also show that ecological, physiological, and life-history
characteristics influence breeding behaviors differently for
males and females. The independence of male and female
spacing behaviors is counter to the paradigm in mammal-
ian behavioral ecology that reproductive success of males is
limited by their ability to secure matings and that males are
mainly responding to the distribution of females in space.
The independence of male and female spacing behavior,
coupled with the relationships between male breeding be-
haviors and diet and BMR, suggests an energetic constraint
to male reproductive success in Neotomine-Peromyscine
rodents.A Phylogenetic Analysis of the Breeding Systems of Neotomine-Peromyscine Rodents 85