Expectant Fathers

Lesson 7: Pregnancy and Nature

Did Jane Really Find Tarzan to be Enchanting?

I doubt that animals think about whether or not they should mate, but it does appear that they use one of only two broad mating strategies. One strategy is pair bonding, in which male and female come together and form a mutual tie. In pair bonding, animals go two-by-two, as they did boarding Noah’s Ark, to ride out the flood and face the future together. Usually they appear to like each other, but it isn’t a requirement. For example, Gibbons, small arboreal apes, sometimes remain together like cranky old human couples, because neither partner has any other choice. The male chases away other males, and the female chases away other females. Consequently, the two are stuck with each other, for better or for worse and until death due them part. They are like many people, for whom habit counts more than love in holding a relationship together.

The other mating strategy is that of a tournament, in which males compete with other males and the winner takes all. Using this approach one male gets many females and the loser gets none. Driving this distinction is a few centimeters of testosterone. In pair bonding, a male needs enough testosterone to win one female. After that, the pair is bonded together by other hormones and factors. In the tournament strategy, the dominant male depends more on testosterone alone. He needs enough to fight males and pursue females on a larger scale. With so much fighting and pursuing to do, his quality time with any particular female is limited to the courtship ritual and mating. And even this has to be brief.

Since mating is the natural beginning of pregnancy, and pregnancy is the beginning of parenting, let’s begin our exploration of fatherhood by looking at how other species approach courtship. Plus, this is an enjoyable place to start because it’s a love story, or some variation of a love story. The emphasis really belongs on “variation” for our fellow creatures but this is what makes them interesting. Just when you think you have it figured out, nature throws a curve ball and makes you wonder: What is natural for courting and mating?

As you might expect, courtship, copulation, and birthing activities for other creatures are programmed in a very different way than for humans. For us nothing could be more natural than the notion that some behavior is masculine and some is distinctly feminine - for example, our belief that males are naturally and inevitable aggressive and dominant and females are passive and coy. And our acceptance of the idea human gender roles in mating, pregnancy and lifelong monogamy is the most natural pattern in life.

These beliefs have endured because Aristotle, one of the first authorities on comparative biology, convincingly argued for it. He claimed that in nature, “the male stands for effective and active and the female for the passive.” Aristotle was obviously not aware of the habits of the giant water bug and the Mormon cricket.

Giant water bugs are disconcerting creatures to anyone who subscribes to Aristotle’s view of sexual nature. They are also disconcerting to anyone put off by large insects. Some giant water bugs are larger than we like insects to be, for example those found in South American ponds are the length of your hand! As if that weren’t enough reason to avoid them, they possess fearsomely long, strong raptorial forelegs and a powerful poisonous beak. These are the bugs that astounded writer Annie Dillard when she saw one suck a frog dry like a collapsing balloon one sunny afternoon shortly after her lunch. But their eating habits are less fascinating than their sex roles. By Aristotle’s account, they have it all backward.

It is the female water bug that does the courting, while the male is very careful in his hookups. The male’s caution in these trysts comes from the female’s desire to coat him with as many as 150 eggs. The eggs are delivered as neat rows of barrel-shaped canisters glued tightly across his back including covering his wings. Now this entails considerable sacrifice on his part. The male must carry this heavy load for three weeks as the eggs triple in size.

Giant water bugs are sit-and-wait predators lurking submerged and still in the water weeds and debris of ponds and streams, waiting for some hapless polliwog or newt to swim within succulent reach. This sabotage habit is also protective for the water bug since underwater, they look like old brown, decaying leaves, a camouflage that protects them from water birds and hunting mammals. They breathe air, but can only linger at the surface for a brief moment before they would be detected and become a quick meal.

The embryonic water bugs, however, require much more oxygen then the adults. So the eggs the female lays on the back of the male must be kept at the water’s surface and must be regularly groomed through the male agitating the water around them. The weight of the eggs, which essentially is his pregnancy, reduces his freedom to float freely at the surface so he clings to some stick or stone. And since his wing covers are plastered shut, unlike the female, he is rendered flightless by his situation. This is of special concern to breeding males because stuck on the water’s surface means he is more likely to be eaten and less likely to catch food. And to depress him further, he can’t fly off to a habitat like his female counterpart.

The female water bug maximizes her reproductive success by eating as much as she can to obtain the nutrients for egg production and by placing these eggs on as many males as possible. However, since one mating can provide all the sperm she will ever need to fertilize her eggs, she saves much time by simply laying all of her eggs on whatever willing male she finds handy.

Knowing all of this, the male doesn’t see this situation as a good deal at all. He has no desire to be a device of female convenience. If a male is to undertake the sacrifice - the investment in egg brooking and pregnancy - he insists on securing his paternity. After all, his reproductive success will be maximized only by brooding the eggs he has fathered.

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