In contrast, if prairie voles are injected with the neurohormones, they may form a lifelong attachment, even if they have not mated. As such, polygamous relationships can be polygynous, polyandrous or polygynandrous. One explanation for the sexual activity at feeding time could be that excitement over food translates into sexual arousal. He also points to the presence of the clitoris in some female mammals, and evidence for female orgasm in primates. Unlike chimpanzees, they have not been observed to hunt monkeys. If intergroup combat is indeed unusual, it may explain the lower rate of all-male associations. To demonstrate that, here are some intriguing and unusual facts about our chest-beating cousins. Sometimes, these extra-pair sexual activities lead to offspring. They can no longer assume social monogamy determines how genes are distributed in a species. Habitat loss due to increasing human populations and poaching for the bushmeat trade are two of the most dangerous threats to the survival of these great apes: Given the need to stick together against males of neighboring communities, their bonding is not surprising: The first suggestion that the sexual behavior of bonobos is different had come from observations at European zoos. Furthermore, the oxytocin levels of the couples correlate positively; when the oxytocin secretion of one increases the other one also increases. Technically, polygyny in sociobiology and zoology is defined as a system in which a male has a relationship with more than one female, but the females are predominantly bonded to a single male. Whereas chimpanzees use a rich array of strategies to obtain foods--from cracking nuts with stone tools to fishing for ants and termites with sticks--tool use in wild bonobos seems undeveloped. Nancy Thompson-Handler, then at the State University of New York at Stony Brook, saw bonobos in the Lomako Forest of the Democratic Republic of the Congo formerly Zaire engage in sex after they had entered trees loaded with ripe figs or when one among them had captured a prey animal, such as a small forest duiker.