A repost from this blog from May 2007.
In mid-June horseshoe crabs start to roll up on to the beaches in the mid-Atlantic states. They continue to come on shore through July and a few can still be found in August.
The spawn of the horseshoe crab is the essential food of the Red Knot, which migrates from the Arctic to the tip of South American and back again every year -- one of the longest winged migrations in the world. And yet, without the horseshoe crab and its predilection for group sex -- sometimes a dozen males can be found shuffled up on top of a single female -- the Red Knot would not exist at all.
Group sex makes a lot of the animal world happen, from coral and salmon to penguins and ungulates such as deer, elk and buffalo.
What's going on here?
Well, it's not that the animals are just being kinky -- it's more essential than that. Mass spawnings, nestings, and calfing are one way that nature ensures that a lot of babies are born at once. A hundred cracked eggshells, a billion wriggling salmon roe, and two dozen elk calfs in a herd are all part of the same essential design -- to overwhelm predation with fecundity.
Group sex has another purpose within the animal kingdom as well -- a way of ensuring the characteristics of dominant males are passed forward. In many animal species, it is only the dominant male that mates with a "harem" of tag-along females.
For many creatures, this is the watch-spring of evolution -- the essential driver that results in gaudier peacocks and larger lions capable of predictably taking down more zebra and buffalo.
The thing that can give a species a competitive advantage, however, can also lead to its undoing. A classic example can be found in the life history of the Passenger Pigeon.
The Passenger Pigeon once existed in numbers that boggle the mind -- 5 to 6 billion birds with individual flocks commonly numbering in the millions, and some super aggregations stretching as long as 300 miles and estimated to have been populated by a billion birds.
A billion birds in a single flock! Yet today, not a single Passenger Pigeon exits. What happened?
The usual suspects are blamed: Deforestation, commercial market hunting abetted by the fact that Passenger Pigeons settled in enormous roosts where they could be netted, clubbed, poisoned, and shot by the scores of thousands. Even Newcastle's Disease may figure into the mix -- an avian disease that made its way to this hemisphere from Europe in the late 19th Century.
This answer is incomplete, however. A lot of birds were over-hunted in the 19th Century, and a lot of birds were negatively impacted by deforestation.
How was the Passenger Pigeon different from the others? How could it be that not a single Passenger Pigeon survives to this day?
The answer lies in a trait of the Passenger Pigeon that it shares (at a reduced level) with many other types of birds: a proclivity for group sex.
While pigeons and most other birds are capable of mating even if there are just a few birds present, many bird species do much better in social settings. Pigeon Cotes and Purple Martins houses, for example, reflect the fact that is is hard to get these birds to stay and breed if they cannot flock and nest together. In fact, some pigeon breeds are so hard to mate in pairs that breeders sometimes take to installing mirrors to fool the pigeons into thinking there are more of them in the roost than there really are. The same trick has recently been used on Mures in the wild.
This proclivity for gregariousness, which is present in most pigeon species, reached new heights with the Passenger Pigeon. The social structure of this bird was so highly tuned to the concept of group that the birds simply could not initiate courtship and reproduction unless many, many other birds were present. When large flocks were shattered, disrupted, and decimated by market hunters and deforestation, individual flock numbers fell below a critical threshold, and a population death spiral resulted. In the end, even though there were captive Passenger Pigeons in a few zoos and conservatories, they could not be made to mate and the species went extinct.
Today, of course, we know more about animals and we are willing to invest millions of dollars and decades of research into turning things around. And, of course, we are not averse to a little artifice.
In China, for example, the Chinese Tiger is being brought back from the brink of extinction with the help of Viagra -- a necessary thing since the only Chinese tigers still extent were, until very recently, a few ancient zoo animals that could no longer reliably "perform" any sexual function.
The good news is that Viagra worked, and today a few young Chinese tigers are in South Africa learning how to hunt on their own. Expect to see them trotted out just in time for the 2008 Olympics.
Pandas too have had their interventions, though in their case it was porn. It seems captive pandas showed little interest in sex. When two animals finally did get interested in each other, they often fumbled the job and coitus was never actually achieved.
Some bright perverted light at the Chengdu Giant Panda Breeding Center had an idea, however: Showing them panda porn. Believe it or not, it worked. Now, when pandas reach sexual maturity, zookeepers show them panda sex videos as part of their initiation into the rites of being an adult panda.
The results speak for themselves -- a bumper crop of baby pandas.
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