Flirting, Back Rubs, Meat Gifts: How Animals Do Valentine's Day
Think Valentine's Day is stressful? Just look at the animal kingdom.
Let's face it: Valentine's Day is stressful. Maybe you've been making eyes at a guy or gal, and it seems like time is right for some grand gesture. Or maybe you did the hard part, found someone great, and you don't want to disappoint. We can look at books, or art, or history for inspiration. At Lloyd Dobler in Say Anything, at Nebuchadnezzer II, who built the Hanging Gardens of Babylon to "ease the homesickness of his wife Amytis." But love and life are primal things, and for some inspiration, some proof that you're not doing it wrong--or that you are--there is no better place to look than in the animal kingdoms around us.
It all begins with sexual selection. Darwin broke the science of selection into two main categories: intersexual and intrasexual. In the former (also called "mate choice" or, depending on the species, "female choice") males compete for the attention of females, the ultimate arbiters. In the latter, members of one sex (generally males) compete directly for access to the other sex — this is where you get epic battles like those between elephant seals:
Male elephant seals do all their fighting over territory, before the females are even around. By the time the females get to the rookery, the beach is already divided. Intrasexual selection can also help to explain the development of antlers, and, surprisingly, the long neck of the otherwise elegant giraffe, which can be used for some very vicious street fighting:
But don't go out there ready to bust heads just yet. Even if you are the dominant hopeful on your block, you've got to be attractive too. Even Darwin recognized that in most cases, mate selections still came down to (female) preference:
“Nevertheless, when we see many males pursuing the same female, we can hardly believe that the pairing is left to blind chance—that the female exerts no choice, and is not influenced by the gorgeous colours or other ornaments with which the male alone is decorated.”
Not only that, but often the tools of battle (think antlers, tusks, and whatever elephant seals have on their faces) serve double duty as mechanisms for defense. Which is to say: if you're good at beating up your competition, you're probably also good at protecting your mate.
To me, this says that all those tournaments are really just foreplay. Everything comes down to attraction in the end.
Attracting That Special Someone: Display and Gift-Giving
Intersexual competition can break down, broadly, as either display-based or gift-based. On the one hand, you can look real fly and attract a good mate that way. On the other, you can prove yourself as a provider. Both methods seem to work.
On the display side, birds of paradise are pretty well up there when it comes to presenting themselves as impressive physical specimens.
It’s still not known generally whether the flashiness attracts the ladies because they see the male as healthy (given his fancy feathers), or because they want their sons to be good-looking (give her offspring flashy feathers) or because her predecessors were into the flashiness, predisposing her to be drawn to flashy males ( i.e. she’s hardwired to find them attractive).
The first option, that a male's appearance is indicative of his health, can also help explain the handicap principle, which argues that males can prove they're healthy and strong by (paradoxically) evolving hindrances to their survival. The peacock is a classic example: Those huge feathers certainly aren't helping a peacock escape predators, but the fact that it can survive (and grow) such incredible plumage shows females that they aren't some sickly weakling.
The second option was articulated by British biologist and statistician Ronald Fisher as the sexy son hypothesis, which proposes that females are inclined to help out their offspring as much as possible in the future mating department. The root of the argument is that a highly-attractive male can likely reproduce with a lot of females; therefore a female that produces sexy sons will see a lot more of her genes pushed into the next generation.
A male peacock mating with a female. (Dave Blackey/All Canada Photos/Corbis)
Moving back to the peacocks, how did the bird get such huge feathers in the first place? That's partly explained by another of Fisher's ideas, a concept known as Fisherian runaway. This would fall under the third option: At some point, females found a proto-peacocks tiny blue feathers attractive, which means only those birds with those feathers would create more of themselves. This positive feedback loop essentially encourages the growth of bigger and bluer feathers; the ladies like them, and the biggest ones stand out. Over time, you end up with a peacock.
But if you don't have the feather's to flash, there's still hope for you yet. Male manakins don't look like much, so they attract mates with spectacular dance moves -- or something close to it. Hopefuls form groups, or leks, which are basically just a bunch of dudes showing off, trying to impress the ladies. There they strut and buzz, trying to communicate just how amazing their genes are. (What they're not offering is any kind of partnership or support.)
Bowerbirds are a little different. They don't look too special, either, but here the males present themselves as ideal homemakers, without all that adolescent competition.
There are trade-offs there obviously: Male bowerbirds are only attractive when they're home, so, they can't chat up likely candidates at the local bird bath. But then, they don’t have to worry about their bodies being conspicuous to predators, nor do they need the energy to molt-in crazy feathers.
But if you don't have the chops or the ornamentation to attract a mate, you've got one more shot: Buy a fancy dinner.
An orb-weaving spider, Nephila pilipes, uses a massage to lure a female into multiple matings. (Photo by Zach Holmes)
Gift giving is prevalent across kingdom and phylum. Male spiders will show up with neatly wrapped prey, though this can be a dangerous proposition. For example, the nursery web spider (Pisaura mirabilis) generally offers nuptial gifts of captured prey, wrapped up nicely in silk. Males make the offer, and then get down to business when females accept the gift and start eating.
For the lady spiders, it's best to be careful here: A number of studies have shown that the same P. mirablis is prone to offering worthless gifts, if real food isn't easily at hand. According to Danish biologist Maria Albo:
"The evolution of male deceit involves a complex equation of costs and benefits. It costs the males to find and wrap a gift, but these costs can be reduced if the male does not have to first catch his gift, or gives one that has already been eaten. The benefit of the gift is longer mating, which leads to more sperm being transferred, and potentially a higher number of offspring. However, the females are wise to deception and terminate mating early for worthless gifts."The key to female acceptance seems to be scent. So if it looks good, and smells good (maybe taste it too, just to be sure), the gift pays off. Then again, according to one study, most encounters end when "the female terminated the copulation and ran away with the gift."
It's not always food. The male of one species of orb-weaving spider, Nephila pilipes, uses a "back rub" to lure a female into multiple matings. He’s not just in it for the love though–he uses the opportunity to plug up her sex organs with part of his body to make sure she can only use his sperm to produce offspring. He is, of course, also trying to avoid being eaten.
Birds, too, often give gifts to effect a positive outcomes. With great gray shrikes, it's the size that counts: large larders can influence females both inside and outside of pairs. This is to say, males who offered food both to their mates and extra-pair females generally had a lot more going on.
Sometimes--and this might not be so useful right now--you have to be in it for the long haul.
Photo via Max Planck Institute
Cristina Gomes and Christophe Boesch spent 22 months studying a group of of wild chimpanzees in the Taï National Park, Côte d'Ivoire, and in that study, they found that, "although males were more likely to share meat with estrous [fertile] than anestrous females given their proportional representation in hunting parties, the relationship between mating success and sharing meat remained significant after excluding from the analysis sharing episodes with estrous females. These results strongly suggest that wild chimpanzees exchange meat for sex, and do so on a long-term basis."
This is to say: giving a female meat did not lead to immediate, passionate primate sex. But it drastically increased the chances that said passionate sex would happen down the line.
A final lesson from the animal kingdom: All that mushy stuff about animals mating for life has been mostly falling apart in modern science. Basically, even among species that tend to form strong, long term pair bonds, those partnerships last until they don't. Of the roughly 5,000 species of mammals, only three to five percent are known to form lifelong pair bonds.
Albatross mates. Photo by Flickr user James Preston
Science has been generally down on the whole monogamy thing for the last twenty years or more. ''Nobody can take monogamy for granted anymore, in any species they look at," Dr. Susan M. Smith, a biologist at Mt. Holyoke College, told the Times in an extensive piece about the sea change published in 1990. Smith suggested that a new order was in store. "[W]e're all trying to rewrite the rules we once thought applied.''
Now, people talk about many species as being "socially monogamous," which is to say: while some pairs certainly go the distance, a good deal of extra-pair dalliance is very much acceptable. Within the albatross community, for instance, pairs form for the long term, and mate swapping is a high cost behavior. So, females tend to keep their mates--maybe flirting only a little on the side.
But don't think about that now. Instead: it's time for some last minute strategizing. Are you a dancer or a fighter? A gift giver or a peacock? With so many tools at your disposal, not to mention thumbs, what's it going to be?