What's A Mother To Do

The importance of mothers

08-01-1981 // Bill Vogt

We humans tend to think a mother's care is virtually essential to an infant's survival. Consequently, it may surprise us to learn that, among wild animals, most mothers shun their young. It is true: 99 percent of the world's million or so animal species that have been identified simply lay their eggs or bear their babies and then move on. However, for the one percent that do tend their young, parenting is no picnic. For example, an opossum may have more than a dozen hungry mouths to feed. A hen mallard and her brood live in constant danger from roving predators. And among certain spiders, the mother may wind up being eaten by her own offspring. Still, despite popular ideas about maternal love, the actions of even the most self-sacrificing wildlife mother are suspect: the elephant that guards her dead calf, the red-winged blackbird that feigns injury to distract a predator. Such scenarios are really the result of instincts generally programmed through evolution to preserve the species.

Training for Survival

Like humans, animal parents are important teachers. This is especially true of birds and mammals, which have more highly developed brains than do lower forms of life. A Canada goose gosling "learns" its migration route by traveling with its parents. A bobcat kit requires prior training before it can even catch a mouse. And a wolf cub doesn't automatically "know" how to hunt with the pack. How do they learn? Through play, certainly, but also by watching and imitating their parents. Among herd animals such as goats and pronghorns, it's often a matter of simply keeping up, copying the parents' movements.

Creatures that take a long time to mature are generally the ones requiring the most amount of learning to supplement the instincts with which they were born. Obviously, the longer a young animal stays with its mother, the more opportunities it has to gain from her and from the male parent--if he stays around and helps with the rearing. For example, a moose calf stays with its mother until she gives birth the following year. A dolphin may remain as part of a family group all its life. And a grizzly bear cub goes through hibernation with its mother.

Sometimes the relationship seems harsh. A coyote may wean her cubs by administering painful nips. A blue-winged teal teaches her brood to swim by pushing them into the water and then threatening to paddle off and leave the stragglers behind. Often, though, the hardest lesson of all comes when an animal mother's work is done. She may forcefully drive her offspring off or simply abandon them, leaving them bewildered and confronted by an unfamiliar world.

Getting Around

The more helpless the baby, the harder it is for the mother to move it freely from here to there. Consequently, many animals have adopted some ingenious ways of transporting their young. These range from pushing and pulling to unusual ways of carrying. Some species, including certain frogs and toads, "wear" their clinging egg masses until the larvae hatch. Crayfish carry theirs beneath their curved tails by means of a short appendage called swimmerets.

One of the simplest methods of toting babies is to simply allow the entire brood to climb aboard the mother. A surprising variety of species uses this piggyback tactic: wolf spiders, scorpions and opossums to name a few. When a young one loses its grip and falls off, the mother often stops until it climbs back on.

Meat-eating animals generally carry their offsprings by mouth, as when a fox transports her kits to another den. This process is facilitated by a loose fold of skin on the back of the young one's neck that serves as a sort of "handle"--the proverbial scruff of the neck. Mice are not quite as careful; the mother grabs her babies by a limb.

Some methods of getting around are hard to categorize, as when a duck uses her bill to roll an egg back into the nest, or a whale uses her fin to support a calf that's having trouble swimming.

Many creatures whose young are precocious--able to walk almost at birth--rely on scent, sight and sound to keep track of their offspring. One of the strangest methods is called caravanning. Most noted for this trait is the European shrew: the mother walks along and her young string out behind her, each one's nose against the rump of the one ahead.

Keeping Watch

Of course, no creature is more vulnerable than a baby. Disease, predators and sudden changes in temperature all take their toll. But, conversely, few creatures have more going for them than an immature animal that has a mother to protect it. Examples are legion: a female cuttlefish attaches her eggs to the roof of an underwater cave and then stands guard. A true bug stands watch until its eggs are hatched. A web-spinning spider weaves its own legs into a cocoon and, thus ensnared, stands ready to defend her brood. The "motives," of course, are instinctive, but the results are often noble, by human standards.

One of the simplest forms of parental protection is an exchange of body heat, as when a grizzly bear curls up with its young during hibernation. Female birds have some unusual ways of accomplishing the same thing: many species have a "brood patch" of bare skin that is held against their chicks.

Scientists who have studied such things recently have come up with a fascinating theory: the smaller the brood size and the bigger the animal, the more parental care it receives. But, no theory on earth could stop some people from insisting it's "love" rather than instinct that causes a swan to attack a speeding train to protect her cygnets, or a robin to confront a stalking cat.

Strengthening the Bond

Any mother-young relationship is based on a bond that is constantly reinforced by nuzzling, sniffing, licking, grooming or calling. As a result, the parent senses when the baby is hungry, cold or frightened.

A series of calls is a common device. In fact, a duck begins quacking softly before her chicks have emerged from their eggs. Konrad Lorenz, a world-famous animal behaviorist, took advantage of this fact by making quacking noises to emerging duckling and goslings. After the young hatched, they immediately accepted Lorenz as their mother and, as he crawled around on all fours, they unhesitatingly followed him about. Endangered whooping cranes, still in their eggs, were placed by scientists in sandhill crane nests as part of an effort to restore the species. The adoption program is working, but there's one flaw: when a sandhill crane gives a warning call, its young normally head into tall grass. Whooping cranes do exactly the opposite, making for deeper water. Needless to say, this tends to confuse the whoopers' foster parents.

Similar bonds exist among domestic livestock. An ewe that has had a chance to sniff her own newborn won't accept a strange lamb unless it has first been rubbed in her afterbirth. Cows are the same way. In one test, a cow readily accepted the straw-filled skin of her dead calf. Much later, the cow discovered the fraud and promptly ate the stuffing without a qualm.

Feeding Hungry Mouths

Mothers feed their young in many ways, but the process generally is built around a conditioned response, as when a mother robin brings food to her nest; she reacts to the bright yellow interiors of her chicks' open mouths. If, for some reason, the nestlings do not open wide and flash their "hunger color," the parent may gulp the food herself and fly off for another load.

Mammals, of course, nurse their young. Some species have developed special feeding habits which enable them to produce enough milk to go around. Others ease the burden of nursing by supplementing their offsprings' milk diets with solid foods.

Insects may have the most unusual feeding methods. Among colonial species of bees and ants, the queen leaves the job to workers. The burying beetle feeds her young in an underground nest of carrion. Like chicks, the larvae raise their heads to they can be fed.

A few animal mothers are downright sneaky and let a parent of another species do their feeding for them. Cowbirds are famous for doing this, and are considered "parasitic." They leave their eggs in another bird's nest, and the unsuspecting surrogate mother tends the hatchlings as though they were her own.

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