An evolutionary biologist at The University of Texas at Arlington is studying seasonal weight gain in male squirrel monkeys to determine its relationship to the species’ potential to sire offspring.

Northern muriquis, which live in the Atlantic forest of Brazil, are one of the most endangered species of monkey in the world. Choosing good mates and rearing thriving offspring are key to the species ...

Source: Sofya Dolotovskaya, used with permission. Many birds and mammals are socially monogamous—males and females pair up, live together, and often raise their young together. However, once methods ...