Owls Aren't Wise and Bats Aren't Blind (14 page)

Many people have a virtual love affair with the armadillo, especially in Texas, where it’s the official state mammal. Armadillo races are held, and so are armadillo “beauty pageants.” For the latter, proud owners groom their armored charges to ensure that they look their best. Beauty is indeed in the eye of the beholder!

Not everyone takes such a benign view of armadillos, however. Owing to their propensity for digging up grubs and earthworms, the little beasts can be the bane of homeowners who take pride in their lawns. Even worse can be their effect on a golf course, where an armadillo can gouge up a lot of valuable turf in a short time.

Many armadillo oddities have already been described, but nothing about them is stranger than their role in Hansen’s disease, more commonly known as leprosy. According to Dr. Richard Truman, Chief of Microbiology at the G. W. Long Hansen’s Disease Center, the armadillo is the
only
mammal besides humans that’s known to develop leprosy at a high level of frequency in a natural population. Chimpanzees and sooty mangabys have been known to contract the disease, but these cases have been rare. On the other hand, up to 20 percent of wild armadillos in some areas harbor the bacteria that cause leprosy.

At present, says Dr. Truman, there is no proof that humans can acquire Hansen’s disease by handling infected armadillos, nor is there any way of assessing the level of risk involved. There is an immense amount of human contact with infected armadillos, considering the number of people who adopt wild armadillos as pets, pick them up to move them out of yard or garden, hunt them for meat, or handle road-killed specimens. Despite this level of contact, only thirty to forty new cases of the disease annually are diagnosed in the United States that don’t result from infection in other parts of the world, so the level of risk obviously is not great. Nonetheless, advises Dr. Truman, people should at least take this information into account before deciding whether or not to handle armadillos.

If, however, armadillos present a possible risk of acquiring Hansen’s disease, they might ultimately be of use in finding a vaccine against this ancient scourge. One of the greatest difficulties in research on Hansen’s disease is the fact that
Mycobacterium leprae,
the cause of the disease, can’t be grown successfully except
in situ,
that is, in or on a living organism. This feat was first successfully accomplished on the foot pads of laboratory mice in 1961, and it was theorized that a slightly lower temperature outside the body might have made this possible.

Enter friend armadillo, which, among its many other unique characteristics, has an internal body temperature 2 degrees to 3 degrees Celsius lower than that of humans. Researchers found in 1968 that
Mycobacterium leprae
would, in fact, develop inside armadillos injected with it. Thanks in part to subsequent research, there are currently three studies testing a vaccine against leprosy, although it’s too early to tell whether or not it will be effective.

Armadillos have had a long evolutionary journey and have stood the test of time very well. Although they’ve been food for a variety of predators, including humans, their various defenses have been more than adequate to the task of preserving the species. Their worst enemy today is the automobile, but the armadillo’s reproductive rate seems more than adequate to compensate for this loss. In fact, this strange little creature is actually increasing its range and appears to be on its way to surviving for many millennia more.

Eastern (red spotted) newt—red eft stage

9

One and the Same: The Newt and the Red Eft

MYTHS

The newt and the red eft are two different species.

PEER INTO PONDS, POOLS, AND QUIET STREAMS IN THE EASTERN UNITED STATES AND CANADA, AND YOU MAY SEE SMALL, BROWNISH, RED-SPOTTED CREATURES THAT BEAR A PASSING RESEMBLANCE TO MINUSCULE ALLIGATORS. They bear no relationship to alligators and other reptiles, however; instead, they’re a type of salamander known as the newt—in this case, the Eastern or red-spotted newt
(Notophthalmus viridescens).

Like frogs and toads, salamanders are amphibians, meaning that they can lead a double life, one stage aquatic and the other terrestrial. The newts, however, have added a unique extra complexity in that they have not two but
three
distinct life stages, two of them aquatic and one terrestrial. Further, in a rather mystifying anomaly, some red-spotted newts skip the second, intermediate stage and spend both life stages in the water!

When is a newt not a newt? The answer to this riddle is linguistic rather than biological, and lies far in the past. In Old English (also termed Anglo-Saxon), spoken in England from about A.D. 450 to A.D. 1050, this type of salamander was originally known as an
efete.
This soon became
evet
and, in an unusual shift from
v
to
w
a little later still,
ewt.
This brings us into Middle English, which reigned from just before the Norman Conquest until about 1475.

But a funny thing happened to the ewt on the road from Middle English to Modern English. The articles
a
and
an
had sometimes been combined with the words which followed them. Then, late in the Middle English period, they began to be separated again, and considerable confusion was the result. In this process,
an ewt
(or
anewt
) became
a newt.
This uncertainty and subsequent incorrect separation worked both ways. Old English
naedre,
for example, gave way to Middle English
nadder,
which was finally transformed from
a nadder
(or
anadder
) to
an adder.
In similar fashion,
a napron
became
an apron.
Of such vagaries are names sometimes fashioned! This shift had clearly taken place before Shakespeare’s time, for “eye of newt” is one of the ingredients in the infamous witches’ brew in
Macbeth.

Newts are common and widely distributed from the Canadian Maritimes to southern Ontario and south to eastern Texas. The adult newt is not very large—three and a half to almost four inches long. Its color varies somewhat from yellowish to greenish brown on the upper side, with scattered black dots and larger, black-ringed red spots along the back. The underside is colored with yellow in varying shades, sprinkled generously with tiny black dots. The tail, which constitutes about 40 percent of the newt’s total length, is keeled— that is, there is a thin, soft ridge running the length of the tail on both the upper and lower sides.

Life for the red-spotted salamander begins during the spring in quiet water, sometimes in a pool or pond that eventually dries up in late summer, although not early enough to kill the newt’s completely aquatic larval stage. The advantage to the newt of such temporary pools is that they contain no fish, which are major predators of both larval and adult newts in permanent waters. Adult newts, though mostly aquatic, are capable of migrating across land to reach permanent pools if their more temporary breeding pools have dried up.

After mating, the female newt lays her eggs, which are attached to the stems or leaves of either aquatic or temporarily submerged vegetation. For this reason, newts greatly prefer waters that contain abundant plants, since these serve both to hold the eggs and to protect the adults from predators. There’s a wide variation in the number of eggs laid by female newts; some lay fewer than a hundred, while others may deposit nearly five hundred.

Depending somewhat on water temperature, the eggs hatch in about a month. The tiny larvae have keeled tails and feathery external gills located just behind the head. This larval stage is exclusively aquatic, totally dependent on water to provide it with oxygen and sustenance. Newts in all stages are carnivorous, and the larvae eat a wide variety of small fare. These include tiny crustaceans and snails, larvae of insects such as mosquitoes, and water fleas.

The newt larvae continue to grow and develop throughout the summer. Then, just before the onset of autumn, metamorphosis takes place. The gills gradually disappear, the tail loses its keels, and the smooth, slippery skin becomes rougher. At last the young newt is ready to enter the second stage of its life and leave the water for dry land.

Now let’s switch to an entirely different scene. Imagine going for a walk in the summer woods during or just after a rain. There you’re likely to encounter small creatures that, like the newt, look somewhat like tiny alligators; in fact, they bear considerable resemblance to a newt in size and shape, yet they lack the keels on the tail and are colored red or orange. This is the red eft, which changed from drab brown to red or orange just before it left its aquatic habitat.

Who would think, looking at this often brightly colored forest dweller, that it was the rather drab aquatic newt? Logically, one would assume it was an entirely different species, but in this instance logic would be wrong. After its gills disappear and its lungs develop, the young newt, now officially an eft, or red eft, usually waits for a rainy night in late summer or early autumn. Then, forsaking the aquatic world of its natal pond or stream, it sets forth to seek nearby forest land.

Once ensconced in its terrestrial habitat, an eft spends much of its time hiding in cool, damp places—beneath logs or sticks, under leaves, burrowed under rocks, and similar places. From such places of concealment, the eft emerges at night to feed on the smaller sorts of spiders, snails, worms, caterpillars, and other invertebrates. On dark, rainy days, however, efts emerge in daylight hours to forage and wander about. The number of them at such times is quite astonishing, considering that a walk through the same area before the rain would reveal nary an eft!

The color of the eft’s dry, slightly pebbly skin is quite variable. Many efts are a bright red that stands out like a beacon against the rather dull colors of the forest floor. Others are an orange that’s nearly as bright, but still others are of varying lesser intensities of red and orange, all the way down to a sort of dusky reddish brown. In common with the adult newt, however, they all have little black spots and the larger black-ringed red spots along both sides of the back.

At first glance, the bright color of the efts might seem to work to their disadvantage by making them more visible to predators, but efts are to some degree toxic—though not for humans to handle—and scientists speculate that their bright color may serve as a warning to predators that they should be left alone.

The time that efts spend in this intermediate, terrestrial stage is as variable as their color. At least two years, but sometimes as many as seven, elapse before they begin to assume the form of the adult newt. This transformation takes place over several months, and the efts, now sexually mature, migrate back to water. There they develop the fully adult form, including the keeled tail. This migration back to water can occur any time during the warmer months.

The eft can be regarded as a wonderful adaptation that greatly increases the chances of the newt’s survival. Because it’s terrestrial, the eft stage allows newts to breed in ponds that at least occasionally dry up by late summer or early autumn, thereby eliminating fish, one of their most important predators. Even if waters that are generally more permanent dry up in a lengthy and extreme drought, the efts will survive to return to water somewhere and perpetuate the species.

The aquatic adult newts feed on all sorts of insect larvae, especially those of mosquitoes and midges. Thus they’re valuable from a human perspective by controlling many ferocious little insects that love to sip our blood. Newts also eat a wide variety of insect nymphs, adult insects, snails, eggs of frogs and toads, and even the larvae of their own species.

In winter, adult newts hibernate either underwater or on land beneath objects such as logs. However, some remain active all winter beneath the ice. Efts also hibernate during their years on land. They burrow beneath the leaves or other litter on the forest floor, or crawl beneath logs and other objects that offer shelter for the winter.

This account doesn’t quite complete the tale of this rather strange and very interesting little creature, however. As previously mentioned, some newts skip the eft stage entirely. These individuals, known as
neotenes,
pass directly from the larval to the adult stage without ever leaving the water. In the process, they retain such larval characteristics as external gills, although these may be substantially smaller than the gills on a normal newt larva. It’s uncertain why some newts become neotenes—one more mystery in the incredibly complex world of nature.

Although newts are fortunately a very long way from being an endangered species, they can suffer locally from an increasing number of highways that interfere with the outward migration of efts and their return to water as adults. On rainy nights, large numbers of efts or newts may be killed by cars while crossing the highways. Drainage of wetlands and pollution can also pose threats to local populations. On the brighter side, construction of many farm and recreational ponds has created new habitat for newts and other amphibians, which should help to ensure the future of these interesting and enjoyable little creatures.