Male jumping spiders (Phidippus clarus) size one another up before engaging in a fight—whether the aggression is based on rights to mating or territory—and in many cases, the pre-fight displays are sufficient to deter physical contact. The males do not nest but instead wander between female nests looking for opportunities to mate. The females, on the other hand, are not nomads—they build nests from silk and leaves in which they wait while they draw closer to sexual maturity.
Currently, upper respiratory tract disease (URTD) and habitat loss are contributors to a decline in gopher and desert tortoise populations. And since these reptiles are keystone species—that is, the habitats they create are home to more than 300 other species—their population decline significantly affects the ecosystem. According to a recent study in Ecology, sexually-mature male tortoises were at the greatest risk of carrying and spreading URTD due in large part to their social behavior.
Since Darwin, scientists have been theorizing as to why there is variation in brain size between species and individuals. Does a larger brain, in say humans, indicate advanced cognitive abilities and complex language processing? Or is a smaller brain, such as the Olive-backed thrush’s, adapted to weigh less to accommodate lengthy flights?
In psychology, the field of phrenology has generally been dissolved, and with it, the idea that variations in brain size could indicate differences in intelligence, creativity or personality between humans. In the field of biology, however, scientists are discovering that brain variation across species might actually be linked to ecological competence. In this case, ecological competence describes the efficiency of a species to engage in ecological processes—such as flexible foraging abilities or advanced spatial memory for migration.