The female reproductive tract is where competition between the sperm of different males
takes place, aided and abetted by the female herself. Intense postcopulatory sexual …

Three principal types of chromosomal sex determination are found in nature: male
heterogamety (XY systems, as in mammals), female heterogamety (ZW systems, as in birds) …

Discrete variation where one sex has more than one means of achieving the same
functional end, such as mating or nesting (alternative strategies and tactics), requires an …

Environmental change poses challenges to many organisms. The resilience of a species to
such change depends on its ability to respond adaptively. Social flexibility is such an …

Alternative reproductive tactics (ARTs) coexisting within a population are found in many
organisms. Their existence has been an enduring puzzle in evolutionary biology. Why …

Abstract When selection acts on social or behavioral traits, the fitness of an individual
depends on the phenotypes of its competitors. Here, we describe methods and statistical …

Previously, it was widely believed that each species has a specific social organization, but
we know now that many species show intraspecific variation in their social organization …

It is our goal in this text to use evolutionary principles as a unifying theme for exposing
students to a number of approaches to the field of animal behavior and to demonstrate that …

Sexual selection has been portrayed as acting predominantly on males who compete with
each other over copulatory access to females; selection was considered to be driven by …

Paternity analyses using molecular markers have become standard in studies of mating
systems, parentage, and kinship. In systems where individuals exhibit alternative mating …