Humping Crayfish

"A great name for a band." -- Dave Barry

No, seriously, there's a report
http://news.yahoo.com/s/nm/20061121/sc_nm/science_crayfish_dc_2


WASHINGTON (Reuters) - Like dogs mounting one another or rolling onto their backs, crayfish act out elaborate rituals of dominance and submission, U.S. researchers reported on Monday.

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They said it was the first time an invertebrate species had been seen to display such "humping" behavior, common in higher animals.

It appears to work, defusing tensions that might otherwise lead to a fight, Fadi Issa and Donald Edwards of Georgia State University, report in this week's issue of the journal Current Biology.

"We found that crayfish display such a complex ritual, when two males engaged in pseudocopulatory behavior to signify their dominance relationship," they wrote.

"This was followed by a reduction in aggression and an increased likelihood of the subordinate's survival."

Lower-ranking crayfish that did not go along with another male's overtures were "killed, dismembered and partially eaten," the researchers wrote.
...
The behavior was most common when two strange males first met, and appeared to defuse tensions after a few days.

"These effects are similar to those of copulation between male and female crayfish, and such copulation can also begin with an aggressive encounter and has been seen as an extension of male dominance behavior. Moreover, if the female refuses the male's attempts to mate, she can be killed."

Chimps go for older women

http://news.yahoo.com/s/nm/20061120/sc_nm/science_chimpanzees_dc_1

Another report from Current Biology. Male chimps chase older females more. Evolutionary psychology debunked? Maybe not:


Older female chimpanzees are more dominant socially and have access to better food. Muller said. "The females that have access to the most food are the most fecund -- the most likely to conceive in any cycle," he said.

Older females may also be better mothers, the researchers guessed.

"The males do end up mating with all the females for the most part," Muller noted. But he said the study challenges common conceptions.

But female chimpanzees do not experience the rapid decline in fertility that is seen in human females after their 20s.

Humans may prefer younger females because of marriage and other "long-term pair-bonds," something that is nonexistent in the promiscuous world of chimps. Human men seeking progeny may need to start with younger prospective mothers, Muller said.