Tales of sons and lovers

WE can be reasonably certain who our mothers are. Although babies get mixed up in maternity wards, very occasionally, we can be pretty sure of maternal identity.

Paternity, however, is a different matter. There are no such certainties here and random DNA profiling shows that some of us are not the offspring of our putative fathers. The old Celtic and Jewish traditions took account of this; primary descent in these cultures was through the maternal line.

Ensuring paternity is a problem for many animals. A father devoting his energies to raising young, must be sure that he is supporting his own offspring and not somebody else’s. If he is mistaken, not only will his own genes have lost out, but those of a rival will have prospered. Nobody wants to be cuckolded.

Becoming a daddy can be a challenging business. Grey squirrels are now familiar animals in Ireland. In squirrel society, would-be fathers are put to the test. A female squirrel becomes sexually receptive for only one day. She emits an odour which attracts suitors from all over the neighbourhood. A dozen, or more, hopefuls may arrive on the scene. Each male has a two-fold task; to mate with the female and to prevent others from doing so. The gallants chase the unfortunate damsel and try to mount her.

Mating is an extremely brief affair. It has to be; once a squirrel mounts, the posse of contenders intervenes. Rivals launch themselves at the lover, trying to knock him off the female and deny him his thrill. The female grey squirrel will usually gratify several Don Juans in the course of her big day. Another female will be in heat tomorrow and so the erotic circus moves on. With such uncertain paternity, a male can’t risk supporting a female or her young. ‘Love them and leave them’ is the rule for squirrels.

Foxes, on the other hand, are devoted husbands and fathers, bringing food to the den for their vixens and cubs. A fox, however, can be reasonably sure of his paternity; his vixen is kept safe from temptation within a closely guarded territory.

Magpies have a conservative approach to fatherhood. They form long-term, sometimes life-long, marriages. The pair copulates only about three times during egg formation. But the male has little confidence in the virtue of his spouse. He adopts a chastity belt approach, barring access to her by other males and guarding her jealously until the eggs are laid. However, sauce for the magpie goose is not sauce for the magpie gander. Once his female is safely incubating, he will readily proposition unguarded neighbouring females. Indeed, magpies may copulate more frequently outside marriage than within. Females welcome such extra-marital encounters.

HAVING some of her eggs fertilised by a different father is a useful insurance policy. After all, her mate may not contribute such good genes to her offspring and having a second string to her bow is a valuable security.

Of course, illicit liaisons must be kept hidden. The spouses work together to drive away intruding Magpies. However, when the spouse’s back is turned, a Magpie behaves differently. In a Dutch experiment, a caged female was introduced to a territory. When the territory owner’s wife was present, he indignantly tried to drive the intruder out. But if the wife was not around, he courted, and attempted to mount, the introduced female.

Every body hates Magpies and this despicable behaviour will surprise no one, but it turns out that most songbirds are no more virtuous.It used to be thought that songbirds were models of marital fidelity. Then, in 1983, came some shocking revelations. Working in Cambridge, NB Davies studied the family lives of Dunnocks, using DNA profiling to determine parenthood. Dunnocks, known as Hedge Sparrows in Ireland, maintain an outward show of virtue, but closer scrutiny revealed that threesomes were common. Even in conventional Dunnock households, a wife would occasionally give her husband the slip and head off to rendezvous with another male. This makes good ecological sense. Male Dunnocks will feed the young of any female they’ve had sex with so, by having affairs, a female maximises the number of breadwinners for her offspring. For the adulterous male, such liaisons are opportunities to increase his paternity.

Unlike magpies, Dunnocks don’t bother with chastity belt antics. Instead, they copulate very frequently. This is advisable in situations where infidelity is rife. By depositing plenty of sperm, a male may swamp the competition and so secure his paternity. Robins may copulate twice an hour during the egg laying season. Nor is sperm competition confined to birds.

Rats are notorious sperm competitors and human males produce astronomical amounts of sperm, presumably to eclipse the efforts of adulterers. There is even evidence that the excitement of an illicit affair leads men to release more sperm than they would in the marriage bed. It has even been claimed that ecstasies of the naughtier kind induce ovulation in females, increasing the chances of pregnancy. Moral forces guard paternity. Immoral ones promote it.