females

Mother birds increase progesterone to hatch females

In mammals, sperm from the male determines the sex of the offspring. In birds, however, it is the female's sex chromosome that determines offspring sex. Now, Cornell University researchers think they understand the mechanism that several bird species use to bias the sex ratios of their offspring toward female. By experimenting with domestic chickens, they have determined that the presence...

Male elephants woo females with precise chemistry

The exact chemical blend of a pheromone emitted by older male elephants in musth influences both a female elephant's interest in mating and how other surrounding elephants behave, a new study has found. The researchers at Oregon Health & Science University and the University of Auckland in New Zealand say the release of a specific proportion of two mirror images of the pheromone, fron...

New study explores beetle species with two forms of females

A fascinating new study from the forthcoming issue of The American Naturalist attempts to explain the mysterious persistence of two forms of females in many diving beetle populations. Their findings have important implications for theories of sexual conflict, which arises when the costs and benefits of multiple matings differ for males and females. "The male versus female arms race (invo...

Male rivalry increases when females at most fertile, say researchers

Men become more jealous of dominant males when their female partner is near ovulation, researchers at the University of Liverpool have found. Previous studies have found that women's preferences for male physical appearance vary according to their fertility status. During ovulation women tend to find masculine looking men more attractive and prefer their voices and odour. During this fer...

Brain differences could explain why males and females experience pain relief differently

A study conducted by investigators at Georgia State University and the Atlanta-based Center for Behavioral Neuroscience (CBN) reports that anatomical and functional differences in the brain may explain sex differences in the experience of pain and in the effects of certain drugs on pain. The finding, reported in the April 13 issue of the Journal of Comparative Neurology, is the first rep...

UCLA study finds same genes act differently in males and females

UCLA researchers report that thousands of genes behave differently in the same organs of males and females ?something never detected to this degree. Published in the August issue of Genome Research, the study sheds light on why the same disease often strikes males and females differently, and why the genders may respond differently to the same drug. "We previously had no good understandi...

Choosy females make colourful males

Female fish prefer brightly coloured males because they are easier to see and are in better shape concludes Dutch researcher Martine Maan following her study of fish speciation in the East African Lakes. Environmental variation subsequently leads to differences in preference and eventually to speciation. Evolutionary theory predicts that species can diverge if different females choose dif...

Zebra finch males prefer females with exaggerated maternal traits

Researchers have demonstrated that learning about the appearance of their parents may give birds a preference for mates with exaggerated parental traits, rather than traits that more exactly match those of their parents. Such learned mate preferences may help drive the evolution of exaggerated traits and strong morphological differences between sexes ?phenomena seen frequently in birds and other...

Male chimpanzees prefer mating with old females

Researchers studying chimpanzee mating preferences have found that although male chimpanzees prefer some females over others, they prefer older, not younger, females as mates. The findings uncover a stark contrast between chimpanzee behavior and that of humans, their primate cousins. The basis for this difference may lie in the fact that whereas chimpanzees participate in a relatively promiscuous...

CU study reveals why starling females cheat

The study found that superb starling females (Lamprotornis superbus) cheat on their mates for a variety of reasons. Some females mate with subordinate...