Published by

Friends of the National Zoo

National Zoological Park

Washington, D.C. 20009

Phones:

Executive Director and membership:

232-7700

Educational and Editorial offices:

232-7703

Guided tours: 232-7703

Train tours: 232-7704

Window Shop: 232-7705

FONZ Board of Directors 1972-1973

Peter C. Andrews, President

Arthur Arundel, Vice President

Emanuel Boasberg, Treasurer

Joan L. Jewett, Secretary

~Fheodore Babbitt

Amy Block

Montgomery S. Bradley

John S. Brown

Timothy V.A. Dillon

Ronald Field

Donna K. Grosvenor

Stephen Hosmer

Robert Mason

Isabel J. McDonnell

Shirley J. McNair

Lavell Merritt

Ruth N. Nelson

John B. Oliver

Mary Poole

Nancy Porter

Gerald G. Wagner

Rosa M. Walker

Richardson White, Jr.

Executive Director

Warren J. lliff

Editor: Austin Hughes

Photograph on p. 10 by Pat Vosburgh;

all other photographs by Ray Faass.

THE ZOOGOER is published bi-monthly

and copyrighted © by Friends of the National

Zoo, c/o National Zoological Park, Washington,

D.C. 20009. second-class mailing permit

approved at Washington, D.C. Rate

in the United States $3 a year.

Golden Marmoset Twins

Zoo News — Mammals

Zoo News — Birds

_ Zoo Map

Zoo News — Reptiles and Amphibians

Rattlesnakes

Zoo Staff

Dr. Theodore H. Reed, Director

Mr. Edward Kohn, Deputy Director

Mr. John Perry, Assistant Director

Mr. Jaren Horsley, General Curator

Mr. Harold Egoscue, Curator

(Small Mammals and Primates)

Mr. William Xanten, Curator

(Large Carnivores and Large Mammals)

Mr. Guy Greenwell, Curator

(Birds)

Mr. Larry Collins, Assistant Curator

(Small Mammals and Primates)

Mr. Miles Roberts, Assistant Curator

(Large Mammals)

Mr. Michael Davenport, Assistant Curator

_ (Reptiles)

Miss Judy Block, Technician

(Animal Records)

Mr. Michael Johnson, Technician

(Reptiles)

Mr. Lee Schmeltz, Technician

(Reptiles)

Mr. Horsley has requested that any calls

concerning the collection be directed to his office

(381-7283 or 381-7284) and the appropriate staff

member will respond. Calls for general information

should be directed to Mr. Saul Schiffman, Division -

of Interpretation, at 381-7228 or 381-7256.

Friends

the

National

The Friends of the National Zoo is a non-profit

organization of individuals and families who

frequently visit the National Zoo and who are

interested in supporting its growth and develop-

ment, particularly in the areas of education,

conservation, and scientific research.

As members of the Friends, you and your family

will be given benefits that will make your zoo-

going more enjoyable and educational.

For more information and a membership appli-

cation, please call 232-7700.

On June 11th and 16th twins were born to two

pairs of adult golden marmosets at the Zoo’s

Small Mammal Building (number 75 on map).

This is a rare and endangered species, and the

National Zoo is involved in a concerted effort

to breed it in captivity. There are estimated

to be only about 500 golden marmosets still

living in the wild in the species’ native Brazil;

of only about 100 in the world’s zoos, 17 are.

now located at the National Zoological Park.

As far as is known, the golden marmoset

(Leontideus rosalia) has always had a re-

stricted habitat. In historic times it has been

found only in a narrow strip of mountainous

rain forest approximately 300 miles long and

60 miles wide contained within the states of

Rio de Janeiro and Espirito Santo, Brazil.

Today its range has been reduced considerably,

and it is only known to occupy an area of

about 300 square miles around the lower

reaches of the Sao Joao River in Rio de Janeiro

State, although other isolated pockets may

JEXISE,

There have been a number of reasons for the

decline of these uniquely beautiful primates.

The size of their habitat has been steadily

decreased by the destruction of forests for

agriculture and by the spread of urbanization

that has characterized the history of eastern

Brazil. A further decimating factor has been

the captive animal trade. Since its discovery

by Europeans its long golden fur made this

species a popular pet, although, due to their

highly specialized dietary and climatic require-

ments, few of the captives survived long. More

recently zoos in Europe and North America

played a large role in exporting the animals;

and in all too many cases their knowledge

proved inadequate to provide proper care. The

result was that few of the captive golden mar-

mosets bred, and the demand for more exhibit

animals continued to raid the wild population.

‘As recently as 1966, there was evidence that

200 to 300 golden marmosets were being

exported annually to zoos.

In that year, fortunately, measures were begun

to halt exportation, when the American Asso-

ciation of Zoological Parks and Aquariums

blacklisted the species. In 1967 a Brazilian law

was passed regulating export, and inclusion

of the golden marmoset under the United

States Rare and Endangered Species Act put

an end to importation to this country. The

few golden marmosets remaining in captivity

in this country were concentrated in a small

number of zoos, including the National Zoo,

where intensive efforts to breed them were

begun.

The golden marmoset belongs to a small family

of exclusively New World primates known as

the Callithricidae — the name means ‘“‘beautiful

hair’’ — or, in English, the marmosets and

tamarins. Other representatives of this family

at the Small Mammal House are the cottontop

marmoset (Saguinus oedipus), the moustached

tamarin (Saguinus mystax), and Geoffroy’s

marmoset (Saguinus geoffroyi). (The latter

two species also currently have young.) The

Callithricidae evidently represent an offshoot

of the stock that eventually led to the true

New World monkeys (family Cebidae). In some

respects they are more primitive than the

Cebidae; for instance they have never

developed the prehensile tail seen in several

members of that family. But the members of

the marmoset family have developed some

quite distinctive specializations of their own

that cannot be considered a primitive

condition.

Marmosets, for instance, have lost the opposa-

bility of the thumb that was surely possessed

by their ancestors. One reason for this is prob-

ably that they have come to rely far less on

hand-over-hand climbing than their ancestors

did. Rather, their distinctive mode of prog-

ress through the trees is by means of short

agile leaps in which the strong legs supply

the major element of propulsion, though all

four limbs are involved. This springing loco-

motion is particularly suited to the typical

marmoset habitat — the highest levels of the

tropical forest canopy. There the branches

are small, and the marmoset can grasp one

between leaps by means of its feet, the big toes

of which are fully opposable, while steadying

itself by holding on to that branch or another

with its hands. In addition, when walking quad-

rupedally along a branch, it can hold on with

its feet, while cupping its hands around the

branch in front. Nevertheless, when necessary

the marmoset is able to support itself hanging

by its hands for a short time, holding the

fingers together to form a hook.

The marmoset’s hands are admirably adapted

for capturing and holding insects and other

small prey, which are caught one-handed and

held between the flexed fingers and the palm.

In social grooming — which plays something

of the same important role in maintaining the

fur and cementing social bonds that it does in

other primates — the marmoset parts the fur

with its hands and removes alien particles from

the body of the animal it is grooming by

means of its lips, rather than picking them out

with its hands as is usual among primates with

opposable thumbs. In grooming its own fur,

the marmoset uses its feet as well as its hands.

In addition to their main diet of insects and

such other small invertebrates as spiders,

golden marmosets in the wild eat some small

vertebrates, fruit, and other vegetable matter.

At the National Zoo golden marmosets are

given a specially prepared marmoset diet sup-

plemented with vitamin D-3 along with fruits,

green vegetables, meal worms, crickets, and

young mice. The vitamin D-3 supplement is

particularly important for captive marmosets

that do not have the access to direct sunlight

that they would have in their natural tree top

habitat.

As visitors will notice in the case of the Zoo’s

recently born pair of twins, the family Calli-

thricidae are unusual among primates in their

reproductive biology. The fact that twinning

is by far the most common form of marmoset

birth in itself sets them apart from monkeys

and apes, among which, as among humans,

twin births are an exception; in the marmosets,

however, they are the rule, with single and

triple births occurring only rarely. The care of

the young is still more unusual. In all of the

marmoset species studied so far, after the first

several days of life the young are carried by

the father, clinging to the long fur of his back,

flanks, or shoulders. In most primates the

young cling only to the mother. The marmoset

father transfers the young to the mother for

nursing, which continues until they are about

three months old. Each nursing lasts about

fifteen minutes, after which the young are

returned to the father.

Immediately after giving birth, the mother

golden marmoset is usually quite hostile

towards the male and other members of the

group. She will not allow them near the infants

and may growl or attack them if they attempt

to approach. In captivity this may be parti-

cularly noticeable if she is feeding, when she

may drive off other group members from the

feed tray. However, after a period that may

vary from only one to eleven or twelve days,

but is usually about eleven or twelve days,

the female allows the father to approach her

and take charge of the young. It has been sug-

gested that the deciding factor may be the

mother’s strength; if she has been especially

weakened by giving birth, it will be much

sooner that she is willing to relinquish charge

of the young.

In weaning the young, the parents provide

small amounts of food, which the infants

remove from their hands or mouth. Though

they leave the father for short periods of time

long before weaning, it is not until they are

four months old that they are fully weaned

and fully independent of him. Thereafter

they return and cling to his fur only when in

danger or in search of warmth. Initially the

weaned juveniles are tolerated by the parents.

In fact the basic golden marmoset social unit

in the wild is believed to consist of an adult

breeding pair, their juvenile or young adult

offspring of one or two years previous, and

their current infants. Both of the Zoo’s recent

sets of twins were born in such groups, con-

taining juveniles born the previous year.

In the wild each group of this sort maintains

a territory, which is apparently demarcated

by scent. The golden marmoset has scent

glands on its chest which it rubs against

branches to mark them. The secretions of

other glands in the circumgenital area, mixed

with a few drops of urine, are also used. When

the young mature they are gradually driven

from the group, young males mainly by the

adult male and young females by the adult

female. Young males will seek to establish

territories of their own.

The National Zoo has had considerable success

in breeding this species. However, the Zoo

has not yet produced any offspring the

parents of which were both themselves bred

in Captivity; producing such offspring will be

necessary if captive breeding is going to play

a role in the survival of this species. Hopefully

it will be accomplished in a new off-exhibit

breeding facility, which will house the Zoo’s

golden marmosets, except for a small number

that will remain in the Small Mammal House.

*There the marmosets will be under intensive

study, and it is hoped that what will be

learned about their behavior and physiology

will further the international effort to save

the golden marmoset from extinction.

A SOINEMS

Mammals

White-Cheeked Gibbon Born

A white-cheeked gibbon (Hy/obates concolor)

was born July 9th in one of the large outdoor

“corn-crib”’ cages in the Monkey House, area

(number 22b on map). A birth of this species

in Captivity is a very rare event, and the

infant’s development promised to be interesting

to observe for a number of other reasons. At

birth the young gibbon’s rather sparse fur had

the pale yellowish tint of its mother’s;

but the bare skin of its ears, face, and belly

was pinkish rather than black like her skin.

The Zoo’s white-cheeked gibbon infant, nursing as

it clings to its mother.

From the first day of life it was able to hold

on to the fur of its mother’s lower abdomen,

holding on with both its hands and feet.

The gibbons, family Hylobatidae, are a

distinctive group of primates found only in

Southeast Asia and the Malay Archipelago.

It was once believed that they were closely

related to the great apes — the gorilla, orangu-

tan, and chimpanzee — and they were placed in

the same family with these other tailless pri-

mates. Recently, however, most zoologists

have tended to emphasize the marked di ffer-

ences between the gibbons and the great apes

and to see the gibbons as an only rather dis-

tantly related group that has become highly

and uniquely specialized for an arboreal

existence in which the primary means of

locomotion is swinging by the hands.

In its progress from branch to branch and

from tree to tree, the gibbon holds its hands

around the branches like hooks. The body is

swung on the long arms in such a way as to

build up momentum for leaps from one branch

to another. This form of locomotion, which ts

known as brachiation, requires that the body

axis be kept vertical, and the gibbon has

evolved a more upright body posture than any

other primate except man. Adult gibbons, in

fact, when they do walk on the ground or

along a wide horizontal branch, always do so

bipedally, with the long arms raised high

above the head. It was once thought that

human ancestors developed an upright posture

along a similar evolutionary path and then

“‘descended from the trees’’; but more recent

theories have suggested that our earliest ances-

tors never progressed as brachiators anywhere

near as far as the gibbons have and evolved

ground-dwelling habits before developing a

fully upright stance.

The young gibbon’s ability to cling unaided to

the mother is clearly a necessary adaptation

to its arboreal way of life, since the mother’s

hands are seldom free to provide support for

her infant. And when it does begin at the age

of about four months to leave its mother for

short periods, brachiation is reported to be the

first mode of locomotion it adopts. However,

it does not at first swing to gain momentum

for leaping as adults do, but proceeds by

cautiously reaching for and taking hold of

each branch. When it does move on the

ground it does so at first by means of short

four-footed jumps and only a good deal later

does it learn to walk bipedally. By the time it

is seven to eight months old, the young

gibbon has learned most of the locomotory

patterns of the adult, although it is still reluc-

tant to take long leaps — which in the adult

may reach more than 30 feet.

Hylobates concolor, the white-cheeked, Indo-

chinese, or crested gibbon occurs in three color

phases. In that represented at the National

Zoo, the adult male is black with white cheek

“whiskers,” as is the father of the recent

young, currently separated from the female

and located at the Monkey House (number

21 on map). Young of both sexes have the

yellowish-white coloration of the Zoo’s recent

infant, which clings so tightly to its mother

that its sex has not yet been determined. And,

again regardless of sex, the fur of the young

is reported to become black at the age of about

six months. Later, evidently on reaching sexual

maturity at the age of five or six years, two-

fifths of the females regain their yellowish-

white color. Males do not become sexually

mature until later, perhaps at the age of seven

or eight years; and it appears that it is not until

then that they develop the patches of white

cheek fur for which the species is named.

Females that do not have the yellowish-white

coloration resemble the males, as does a

younger female currently sharing the cage of

the Zoo’s mother and young.

Jaguar Cubs

On July 26th, a young female jaguar at the

Lion House (number 23 on map) gave birth

to her first litter, which consisted of two cubs.

She had arrived at the National Zoo in Septem-

ber, 1971, at the age of about nine months. Her

mate was even younger than she was, having

arrived in February, 1972, at the age of only

five or six months. Thus at their successful

mating this past April he was considerably

younger than the three years mentioned by

some authors as the age at which sexual matu-

rity is attained in this species.

The cubs, blind at birth, appeared much

woolier than their parents, and their coats

were more densely spotted than an adult

jaguar’s. At first they spent their time alter-

nately nursing and sleeping, and the Lion House

was kept closed to the public to prevent dis-

turbance to them or to their mother. The cubs

would not eat their first solid food until about

50 days old; by then they should weigh around

ten pounds and be frequently active and play-

ful. Full weaning will come at the age of

about four months, by which time the cubs

can be expected to weigh over 30 pounds.

Successful captive breedings of jaguars (Pan-

thera onca) are not as common as successful

breedings of their relatives the lion (Panthera

leo) and the tiger (Panthera tigris). \n fact, less

is known of the general biology and natural

history of the jaguar than of those of either

of these other great cats — the only two mem-

bers of the cat family that attain larger sizes

than it. While the jaguar is found in habitats

as varied as the pampas of Argentina and thorn

thickets along rivers in Mexico or — occasion-

ally — southern Texas, Arizona, and New

Mexico, it is most characteristically an inhab-

itant of dense tropical forests where opportu-

nities for observation are few. It seems to

prefer to live close to water; and some author-

ities have asserted that it preys mainly on

aquatic or semi-aquatic animals, such as fish,

alligators, and the large rodents known as

capybaras. Other authors mention peccaries

as a favorite food; and as the jaguar is an adept

climber, it is believed by some to take to the

trees in pursuit of sloths and monkeys.

Lesser Panda Cubs

On June 29th, the Zoo’s adult pair of lesser

pandas (Ai/urus fulgens) gave birth to their

second litter of two. As in the previous birth,

the mother built a nest of leaves, twigs, and

straw in the bottom of the hollow tree in the

lesser pandas’ enclosure (number 16 on map).

A nest box and the log cabin in the enclosure

provided additional possible shelters for the

cubs, blind and helpless at birth. Almost ex-

actly a year previously this female had given

birth toa pair of cubs, now fully grown and

on exhibit in a separate enclosure (number

18a on map). The fact that other captive

births of lesser pandas — in Darjeeling, India,

in London, and in San Diego — have also

occurred in June suggests that there is a

remarkably well defined birth season in this

little-known species.

The newborn cubs — one of which might

occasionally be glimpsed being carried from

one nest place to another in its mother’s

mouth — differed considerably in appearance

from the strikingly marked adults. Their fur

was a pale tannish white all over; and the tail,

which is nearly as long as the rest of the body

in the adult, made up only about a quarter

of each cub’s total length. The areas beneath

the eyes where the “‘tear-marks”’ of russet fur

are located in the adult were unfurred, and the

bare pink skin was visible.

The cubs’ appearance began to change rapidly,

however. When they were about two weeks

old and had both eyes open, the undersides

and legs — black in the adult — had begun to

darken noticeably. Gradually these areas

would change color, the fur of the back would

become reddish, and rings would appear on the

tail. After about two-and-a-half months,

though a good deal smaller and less steady in

their movements, they could be expected to

resemble their parents fully in appearance.

About a month later they will probably begin

to emerge from their nesting places — first

only in their mother’s company, then later on

their own — and by winter they: should be

regularly visible.

The lesser panda is native to Yunnan and

Szechuan provinces in China, northern Burma,

Sikkim, and Nepal. Like the giant panda

(Ailuropoda melanoleuca), which is its closest

living relative and is placed along with it ina

separate family, it is one of the least carni-

vorous of the members of the order of

mammals known as the Carnivora or carni-

vores. The Pandas are evidently an Asian off-

shoot of the stock that led to the now exclu-

sively New World procyonids — the family

that includes the raccoon, coatimundi, and

kinkajou. The procyonids are themselves all

omnivorous, but the pandas have evolved still

further from a predatory existence and in the

direction of an exclusively vegetarian diet.

For instance, the lesser panda’s staples in the

wild are reported to be bamboo, fruit, nuts,

and roots, though it may rob an occasional

egg or kill a small bird or mammal.

Wildebeest Calves

Three female wildebeest or white-bearded gnus

(Connochaetes taurinus albojubatus) gave birth

to single calves on June 21st, June 24th, and

July 26th. The young were light brown in

color, in contrast to the gray coloration of

their mothers, but‘they had black foreheads

like the adults. The black mane that grows

along the neck of the adult was also present,

but the long white ‘‘beard”’ for which this

subspecies is named had scarcely begun to

develop.

The wildebeest calves were able to stand and

follow their mothers within minutes of birth

and could be seen walking or running with

them around the enclosure (number 9e on

map). \n a great many antelope by contrast

— as in anumber of other hoofed animals,

such as deer ~— the young remain in one hiding

place for the first week or two of life; the

mother visits the hiding place to nurse her off-

spring but remains away from it at other times.

This behavior has the advantage of protecting

the infant from predators and keeping the

mother from being encumbered with a defense-

less infant. In the wildebeest, however, there

seem to be even greater advantages for a

relative precocity on the part of the calf, and

the calf’s ability to follow its mother can be

seen as an adaptation to a life on the open

grasslands of East Africa.

In the wild the great majority of wildebeest

births take place in January and February —

the height of the rainy season in East Africa.

Then the wildebeest are sexually segregated,

the males forming loosely organized bull herds

and the females living in more stable calving

One of the Zoo’s three recent wildebeest calves with

its mother (number 9e on map).

herds. Since the wildebeest inhabit open plains

where they are plainly visible at a distance, the

calving herds are highly vulnerable to predation

the major predator being the spotted hyena

(Crocuta crocuta). The ability to move with

the herd in order to escape a predator is thus

highly advantageous for the survival of the

young. The fact that there is a relatively short

birth season also affords protection against

predators, since there is only a short period’

when there are calves at the most vulnerable

age.

Birds

Bald Eagle Hatched

On May 25th or 26th, a single bald eagle egg

was hatched in a large stick nest located high

in the rear right-hand corner of the eagles’

spacious flight cage (number 7a on map). The

National Zoo was only the third zoo ever to

hatch our national bird in captivity. For the

first couple of weeks of the eaglet’s life the

hatching was not announced to the press and

public for fear of any disturbance to the

young bird and its parents. But the nestling

thrived, and by August it was as large as an

adult and fully fledged in its first black juvenal

plumage.

The white feathers on the head and neck

from which this species derives its common

name will not appear until much later —

when the bird is four or five years old. At

this writing the eaglet has not yet.flown from

the nest, but it is believed that it will do so

The Zoo’s bald eagle hatchling with one of its

parents; the picture was taken when the eaglet was

still in its downy plumage, at the age of about one

month.

very soon. In the wild bald eagle parents have

been observed coaxing their offspring to fly

by bringing food and placing it within sight

of the nest but at some distance away, and the

Zoo’s pair may behave similarly, perhaps

encouraging the young bird to fly to one of

the perching places in the other corners of

the cage.

During the nestling period, on the other hand,

bald eagle parents take very diligent care of

their offspring, which are almost invariably

two in number and only very rarely one or

three. Usually the male brings food to the nest,

and the female in turn feeds the hatclhiling,

tearing off pieces of food for it with her bill.

The Zoo’s female, somewhat larger than the

male, could regularly be seen feeding her

downy gray young the rats and fish that are

placed in the bald eagles’ cage. The newly

hatched eaglet was almost completely helpless, New Parrot Cages

unable to raise its head up and only barely able

to see through partly closed eyes, but as it

grew it gradually learned to tear up its own

Three new cages have been constructed behind

the Bird House (number 6s-u on map), mainly

te for housing relatively large members of the

> parrot family, particularly macaws.

The bald eagle or American eagle (Ha/iaetus In the easternmost cage are a breeding pair of

leucocephalus) isarare and endangered species. red-and-green macaws (Ara ch/oroptera);

Though it is so common in our national iconog- in the middle cage are a pair of scarlet macaws

raphy that few Americans go a day without (Ara macao); and in the third cage are a male

seeing its image — present on much of our cur- great green macaw (Ara ambigua), a female

rency as well as on the Presidential seal — in yellow-and-blue macaw, and a male sulfur-

1962 it was calculated that there were only crested cockatoo (Kakatoe galerita).

3807 bald eagles and only 515 active nests in

the continental United States. Moreover, with

a nesting success rate at that time of only 44

percent, their numbers have probably con-

tinued to decline. Once common throughout

most of North America, reaching north to

western Canada and Alaska and extending south

to Baja California, the bald eagle is now found

in substantial numbers only in the Alaskan

portion of its range, where the human popu-

lation is small and has as yet had little adverse

effect on the environment. In Maryland and

Virginia, for instance, a 1971 survey found

only 61 active nesting pairs and only 25 young

The macaws of the genus Ara are typical of

the tropical forests of South and Central

America. They feed on fruits and on nuts,

which they are able to open by means of their

large, powerful bills. In all members of the

parrot family the bill has evolved a distinctive

form that makes it useful for cracking seeds

and nutshells. The underside of the upper man-

dible usually possesses hard filing ridges, and

the lower mandible can slide backwards and

forwards to break through a hard shell. But in

the macaws this specialized bill has reached its

most spectacular development as a nutcracker.

hatched, for a success rate of only about 36 Another use of the bill found in virtually every

percent — obviously too low if the population _ parrot species can readily be seen in the Zoo’s

in this area is to continue to sustain itself. macaws. This is its function as a ‘‘third foot”’

in climbing — the macaw’s preferred method

of locomotion in feeding trees in its native

habitat. In addition, every member of the par-

rot family is also well adapted for holding on

to branches by means of its feet; the feet are

excellent grasping organs, with two toes

directed forward and two directed backward.

The central reason for the decline of the bald

eagle in recent years has been the use of DDT

in agriculture. Deposits of this pesticide build

up in fish — the bald eagle’s main food through

most of its range — and their effect on the eagle

is to reduce drastically its fertility and the sur-

vival rate of its young. Another factor has been

the spread of human settlement and the con- — Most parrots nest in cavities of some sort, and in

sequent destruction of wilderness areas. In the captivity a nest box will in many cases bu

ane a aie oe ties pd Sin accepted as a substitute. (Though many

we : ei me ‘a Aly cect liu 1a eee breeders have had success with a wide variety

usually SO 8 2 of parrot species, it must be admitted that, in

erably a pine. The destruction of forests has comparison to the great numbers of members

doubtless eliminated a great number of suitable of this family in captivity, the percentage of

pees Sites. captive breedings is still quite low.) As in

Thus conservation efforts have often been other cavity-nesting birds, the young of parrots

aimed at the preservation of known nesting are able, because of the protected situation

sites, which may be used annually for many in which they are hatched, to undergo a

years. In Florida, for instance, which of all relatively long period of development before

states after Alaska has the largest population leaving the nest. Thus the macaw’s offspring,

of bald eagles, the Audubon Society has estab- hatched blind and completely featherless, are

lished a ‘‘cooperative sanctuary plan” whereby _ still featherless at the age of a week and are

the owners of land on which traditional bald meanwhile being fed by food regurgitated by

eagle nesting sites are located agree to treat the parent. The wing quills do not begin to

their property as bald eagle preserves. Some erupt until the nestling is four weeks old, and

2,300,000 acres have been set aside as sanctu- _jt is not fully feathered until it is ten weeks

aries in this fashion. In addition, there is a old. Even so it remains in the nest another

program in the same state to plant pitch-pines —_ three weeks. This nestling period is quite pro-

in the hope of creating suitable nesting sites for longed compared with that of many song-

future bald eagles. birds, the young of which may be ready to fly

A 3 OMAP

. Connecticut Avenue pedestrian entrance

. Connecticut Avenue vehicular entrance

. Deer and antelope areas (a-j)

. Great Flight Cage

SCOMNODOAWN =

Bird House

. Pheasant and crane line (a-u)

. Raptor cages (a-d)

. Delicate-hoofed stock building (a-c)

Hardy-hoofed stock complex (a-i)

Panda House (a-c)

. Elephant House

. Water birds (a-e)

. Hawks and owls (a-c)

. Black Rhinoceros Yard

. Small Mammal Building

. Lesser Pandas

. Prairie dogs

. Bears and monkeys (a-m)

. Reptile House

. Tortoise yard

. Monkey House

. Hardy Animals (a-o)

. Lion House

. Komodo Dragon

. Bears (a-})

. Water animals (a-e)

. Sea Lion pool

. Wolves, foxes, and wild dogs (a-|)

. Monkey cages (a-b)

. Waterfowl ponds (a-d)

. Police Station—Restrooms—First Aid

. Restaurant

. Picnic Area

. Window Shop

. Souvenir Kiosk

. Rock Creek Parkway entrance

. Friends of the National Zoo Offices

. FONZ Education, Editorial, and Tour

Guide Offices

Telephone

Restrooms

Trackless Train Stops

Parking

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Walking Tour Route

(From the Trackless Train

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(} IM4P 11. Elephant House 27. Sea Lion pool | am 8 Telephone

12. Water birds (a-e) 28. Wolves, foxes, and wild dogs (a-l)

13. Hawks and owls (a-c) - | 29. Monkey cages (a-b) b 2 Restrooms

~ 14, Black Rhinoceros Yard | 30. Waterfowl ponds (a-d)

1. Connecticut Avenue pedestrian entrance 19. Small Mammal Building | 31. Police Station—Restrooms—F irst Aid x Trackless Train Stops

2. Connecticut Avenue vehicular entrance be — _ | — oe |

8 ( -| . Frairie dogs . Picnic Area :

; siealy Sle pases — —— 18. Bears and monkeys (a-m) 34. Window Shop vite peed

5. Bird House —. 19. Reptile House 35. Souvenir Kiosk .

6. Pheasant and crane line (a-u) 20. Tortoise yard 36. Rock Creek Parkway entrance |

7. Raptor cages (a-d) | 21. Monkey House 37. Friends of the National Zoo Offices ~~» Walking Tour Route

8. Delicate-hoofed stock building (a-c) 22. Hardy Animals (a-o) 38. FONZ Education, Editorial, and Tour (From the Trackless Train

9. Hardy-hoofed stock complex (a-i) 23. Lion House | Guide Offices Stations) |

10. Panda House (a-c) | 24. Komodo Dragon — [

25. Bears (a-j)

26. Water animals (a-e) , |

Db ao

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Ae 13

from the nest at the age of two weeks — not

to mention the young of precocial species

such as those of members of the pheasant

family, which follow their parents from the

nest on the day of hatching.

Other birds being kept at this writing in these

new cages include the handsome pied crow

(Corvus alba), a very common species in

tropical and southern temperate Africa, in the

A blue-and-yellow macaw (left) and a great green

macaw (number 6u on map).

middle cage, and white-winged trumpeters

(Psophia leucoptera) in the easternmost cage.

White-winged trumpeters belong to an interest-

ing family, the trumpeters or Psophidae, tropi-

cal American relatives of the cranes and rails.

They are mainly terrestrial, omnivorous birds;

they are named for their distinctive call —

which, however, is said to be a deep, melodic

rumble with very little resemblance to a

trumpet blast.

Pygmy Monitors

Some of the most interesting of recent acquisi-

tions at the Reptile House (number 19 on map)

are three pygmy monitors or mulga monitors

(Varanus gilleni). This species belongs to the

monitor family, which includes the largest

living lizard known, the Komodo dragon

(Varanus Romodoensis), and several other

good-sized species, such as the Australian lace

‘

A pygmy monitor or mulga monitor (Varanus gilleni),

one of the smallest members of the family that

includes such giants as the Komodo dragon.

monitor (Varanus varius), also on exhibit at

the Reptile House, which grows to four or

five feet. But the mulga monitor is one of the

smallest species in the family, reaching a maxi-

mum length of about a foot.

The name mulga monitor by which these

lizards are known in their native Australia

derives from the fact that they live in trees

known as mulgas (Acacia aneura), presumably

feeding on insects and perhaps small skinks.

The possession of a prehensile tail is one ob-

vious adaptation for this way of life. Mulgas

are characteristic trees of Australia’s arid

interior to which these monitors are native.

As a group the monitors are of interest for a

number of reasons. One is that they are be-

lieved to be close to the ancestral line from

which the snakes evolved. All of the monitors

are predators, and it is believed that the ances-

tors of snakes were related small predacious

forms that lost their limbs as an adaptation to

a burrowing existence. One readily seen simi-

larity between snakes and monitors is the

latter group’s possession of a long forked

tongue which is frequently protruded to |

obtain olfactory information from the environ-

ment and transmit it to a pair of sensory pits

in the mouth known as Jacobson’s organ.

Another similarity is that, like those of most

snakes, a monitor’s teeth are curved back-

wards — presumably an adaptation to prevent

the escape of living prey while it is being

swallowed.

Blue-Tongued Skinks

Other new lizards at the Reptile House are

blue-tongued skinks (Tiligua species). Members

of this genus are found in Malaysia, Indonesia,

and Australia and include some of the largest

of the world’s approximately 600 species of

skinks, many of which are very small burrowing

forms. The largest of the Ti/iqua species,

Tiliqua gigas, sometimes known as the giant

skink, may reach two feet in length. Its only

serious rival for the claim to being the largest

skink is the prehensile-tailed skink (Corucia

zebrata), which may be seen at the Reptile

House. Nonetheless, the blue-tongued skinks

possess the readily apparent characteristics of

all skinks — for instance the extraordinarily

smooth scales, in the skin beneath which there

are buried bony ossicles.

Blue-tongued skinks.

Rattlesnakes inhabit the New World exclusively,

and they have always played a prominent role

in the folklore of the Americas. This has been

particularly the case in the southwestern United

States and northern Mexico, where their

greatest numbers and greatest variety of species

occur; from the Aztecs and the Hopi, in whose

religious beliefs these reptiles figured heavily,

to the pioneers of the last century, inhabitants

of this region have long been fascinated by

them. Their possession of warning rattles as

well as a potent venom has made them appear

both malign and at the same time unaccount-

ably benevolent. Many of their habits — the

tendency of some species to hibernate in

groups; the impressive combat rituals of the

males; the unusual method of locomotion of

one species, the sidewinder — have repeatedly

excited human wonder and curiousity. The

impulse to attempt to explain the unfamiliar

is as old, or almost as old, as the impulse to

fear and worship; and by myth and conjecture

men have long sought to account for the unique

characteristics of rattlesnakes. Only compara-

tively recently have scientists begun to study

them seriously and objectively; and what they

have found has often proved to be more

interesting — and more amazing — than any

fiction.

There are approximately 26 species of rattle-

snakes, belonging to two related genera,

Crotalus and Sistrurus. The former group con-

tains the best-known American species —

including the sidewinder (Crotalus cerastes),

the eastern and western diamondback rattlers

Timber rattlesnake, illustrating the tongue-flicking

used to pick up olfactory information from the

environment.

(Crotalus adamanteus and Crotalus atrox) and

the timber rattlesnake (Crotalus horridus) that

inhabits the eastern United States, including

the Washington, D.C. area. The five S/strurus

species — known as pygmy rattlers or massa-

saugas — are much smaller snakes.

Both genera of rattlesnake are included by

herpetologists in a larger group known as the

pit-vipers or crotaline snakes. Taxonomically,

this group is usually designated as the sub-

family Crotalinae of the family Viperidae or

vipers. The pit-vipers are distinguished from

the other vipers, the mole vipers and the “true”

vipers, all of which are Old World snakes, and

from all other snakes, by the possession of

facial pits located between the eye and the

nostril on each side of the head. The pit-vipers

are found in both the New World and the Old

World and, like all of the Viperidae, are

venomous. The Old World pit-vipers are found

in Indo-Australian Archipelago and in Asia,

with one species ranging into European Russia.

The New World species include not only the

rattlesnakes but two other well-known North

American venomous snakes, the cottonmouth

(Agkistrodon piscivorous) and the copperhead

(Agkistrodon contortrix).

The existence of the crotaline facial pits has

been recognized since at least the Eighteenth

Century; but, although there was a great deal

of speculation, their function remained a

mystery until our own time. Often they were

said to be the locus of some uncanny ‘‘sixth

sense” which humans lacked; and careful

experimentation has shown that that is in

effect what they are.

Close-up of the head of an eastern diamondback

(Crotalus adamanteus), clearly showing the heat-

sensitive facial pit.

The pits are now known to be sensory organs

highly sensitive to radiant heat (or, more tech-

nically, infra-red radiation). We are of course

able to detect the presence of heat radiating

from a nearby object by means of the warming

effect it-has on our skin surfaces, but the pit-

viper is%erisitive to much subtler temperature

differences in its surroundings and can pin-

point a source of radiant heat with far greater

accuracy. In fact the pits are used to detect

the presence in the snake’s vicinity of its

usually warm-blooded prey and to guide the

direction of its strike.

The opening of each pit is clearly visible and

faces forward. The pit widens out inside and

is divided into two chambers by a thin mem-

brane — only one thousandth of an inch thick

— that is richly supplied with sensitive nerve

endings. A duct connects the inner chamber

with the outside. Experiments have shown

that there is a response in the nerves of the

membrane when an object as little as one-and-

four-fifths degrees Fahrenheit hotter or colder

than the surrounding atmosphere is intro-

duced to the pit-viper’s vicinity as far away

as almost a foot from its head. This means

that the snake is able to detect the radiant

heat given off by a single mouse about eleven

inches away. Moreover, by the angles at which

the heat waves strike the membranes, the

snake is able to ascertain the location of the

source without the use of any other sense.

The possession of a rattle is of course the

obvious characteristic that distinguishes the

Crotalus and Sistrurus snakes from the rest of

the pit-vipers. It consists of a series of loosely

interlocking segments composed of a kind of

keratin — the group of allied protein sub-

stances that compose not only reptilian scales

but also the feathers and leg-scutes of birds

and the hair, claws, and horn of mammals. A

newly hatched rattler has no rattle but only

a tiny growth of rattle-like substance known

as a “‘pre-button”’ at the end of its tail. When

it first sheds its skin, at the age of a week to

ten days, it loses the ‘‘pre-button,’’ which is

replaced in its second skin by the ‘‘button.”

The button forms the first segment of the

rattle and is retained with each subsequent

shedding of the skin until it is finally broken

or worn off. At the second shedding a new

segment is bared, which is larger than the button

and pushes it out to the end of the rattle.

This new segment in turn is retained after

the next shedding, and thus at each shedding

of the skin a new segment is added to the

rattle.

As is well known, the rattle serves as a means

of warning away any other animal that is

about to attack or inadvertently injure the

snake. Many snakes that lack rattles vibrate

their tails as a warning measure; in dead

leaves or other debris, this can make a sound

similar to that the rattlesnake makes with its

rattle. Some authorities have speculated that

the earliest rattlesnakes evolved in the open

prairie of what is now the western and

southwestern United States where such ground

debris would have been largely lacking. And

yet there were large herds of hoofed mammals,

including relatives of the present-day bison

and pronghorn, which very frequently would

threaten to trample the reptiles under foot.

According to this theory, the possession of

venom — which evolved with the immobili-

zation of prey as its primary purpose and

only secondarily proved of value in defense —

would not alone have been sufficient to

preserve the snake from harm, since even if

the venom killed one of the ungulates, the

snake might still be trampled on by it or other

members of the herd. In that case a warning

device would be of considerable survival value.

If a rattlesnake is threatened when it is near a

safe refuge, it may rattle while crawling away

towards safety. If the danger continues, the

snake will assume a characteristic defensive

posture. In this position, the front part of the

body is raised up off the ground and thrown

into a roughly S-shaped curve with the tail

flattened against the ground and the rattle

raised and shaking. The tail provides anchor-

age so that the head and neck will be free to

_ Strike if necessary. Meanwhile the rattlesnake

inhales and exhales with aloud hiss, and its

tongue is extended from the mouth to its full

length and pointed alternately upwards and

downwards with its forked tips widely spread.

Here one function of the extension of the

tongue may be to enhance the snake’s formi-

dable appearance; indeed human folk beliefs

provide some indication that it can do so, at

least in the case of man. Often it has been sup-

posed that a venomous snake’s tongue is itself

venomous; and legends of fire-breathing on the

part of mythical reptiles may have derived in

part from tongue protrusion on the part of a

snake in defensive display. But the tongue may

well be playing another role as well; for like

the tongues of many other snakes and lizards,

the rattlesnake’s tongue has an important func-

tion in the snake’s sensory exploration of its

environment.

This can readily be seen in the frequent tongue-

flicking behavior of non-aroused rattlesnakes

or other snakes and lizards. When the tongue

is extended, particles in the air are caught

in the saliva on it. When it is retracted, these

are conveyed to a pair of pits inside the mouth

known as Jacobson’s organ; one of the two

forks of the tongue is tucked into each pit. Pre-

sent in vestigial form in most terrestrial verte-

brates but well-developed in lizards and snakes,

this is an olfactory organ that like the more

ordinary channels of smell responds to the

chemical character of the particles conveyed

to it. The rattlesnake uses Jacobson’s organ in

situations similar to those in which mammals

use sniffing. When the snake becomes aware

of the approach of a potential predator or a

likely victim — usually by means of the more

ordinary channels of smell — its first reaction

is to attempt to ascertain the source of the

scent by flicking its tongue.

In hunting the rattler usually lies in wait beside

a trail where some small mammal is likely to

pass. When the approach of suitable prey has

been detected by the nasal channels of scent,

Jacobson’s organ next comes into play; finally

_ at close range sight and the heat-sensitivity of

the facial pits direct the attack. The rattle-

snake’s sight is fairly good at close quarters;

although its eyes are believed to provide only

a general impression of light intensities in

their surroundings, they have been found to

be particularly sensitive to movement within

a foot or two. Moreover, rattlesnakes are most

active and do by far the greater part of their

hunting at night, and their eyes have been

shown to be more sensitive when only a little

light is available than they are in broad day-

light.

Directly after the rattler has attacked its prey,

Jacobson’s organs play what is perhaps their

most crucial role. The hollow fangs inject

venom by means of a muscular contraction

around the poison gland at the moment the

snake strikes. Then, like other-venomous

snakes, the rattler quickly draws its head

back to avoid any possible retaliation on the

part of the stricken prey. It may take only a

few seconds or at most several minutes for the

venom to take effect, but in that time a

stricken mammal will usually run on. The

snake must rely on Jacobson’s organ to track

it to the spot where it has fallen. Upon finding

its prey, the rattler briefly investigates the

body with its tongue, then seizes it by the

nose and begins to swallow it. Since the venom

Close-up of a rattle, showing the interlocking segments,

contains digestive enzymes, the process of

digestion has already begun.

The venom-injecting apparatus of the Viperidae

is the most efficient that has ever evolved in

reptiles. One reason is that the paired fangs

are hollow, thus making them, in effect,

“hypodermic needles.” In venomous snakes

of other families this is not the case; in the

cobras, for instance, the fangs are equipped

only with grooves. Moreover, the viper’s com-

paratively larger fang and the bone to which

it is attached are movable. When the jaws are

closed a complicated system of bone articu-

lations causes the fangs to fold back inside the

mouth; when the mouth is opened the same

mechanism is used to erect the fangs.

Although the majority of rattlesnake species

inhabit arid and semi-arid regions in Mexico

and the southwestern United States, others

are found in every type of habitat from

prairie to tropical forest and at altitudes from

sea level to 10,000 feet. The species on exhibit

at the National Zoo’s Reptile House (number

19 on map) illustrate some of the variety of

habitats occupied by members of the genus

Crotalus within the United States. There are

two races or subspecies of Crotalus horridus,

for instance, that show marked differences

in habitat preference. The timber rattlesnake

(Crotalus horridus horridus), on exhibit in

cage C-1, appears throughout the Northeast

and Midwest in forested areas, particularly on

rocky hillsides. The canebrake rattlesnake

(Crotalus horridus atricaudatus), on exhibit

in cage E-14, which is found on the coastal

plain south of southern Virginia, along the

Gulf Coast, and up the Mississippi Valley as

far as southern Indiana and Illinois, is charac-

teristic of swamp and bottom lands, including

the canefields from which it derives its

common name. The other rattlesnake in the

building, the northern Pacific rattlesnake

(Crotalus viridis oreganus), \ocated in cage

C-3, is found from southern California through

Washington. In California, it is typical of sage-

brush and chaparral along the foothills of the

Sierras, while in more northerly regions it is

found in a great variety of habitats, from

rocky cliffs to mountain meadows. Inter-

estingly, another race of this same species,

Crotalus viridis viridis, is the typical rattler of

the Western prairies.

As with other reptiles, the particular micro-

habitat each rattlesnake chooses within its

habitat depends not only on the availability’

of food but also on the all-important factor

of temperature. Unlike birds and mammals,

reptiles do not produce enough heat from

their metabolic activity alone to raise their

body temperatures to the point where they

are Capable of performing the activities they

need to perform in order to survive and repro-

duce. Thus they must absorb heat from the

environment. Each reptile seeks to absorb

enough heat — whether direct solar heat or

heat that has been absorbed from the sun by

the substrate — to maintain its body tempera-

ture within a relatively small compass within

which the animal’s bodily functions are at or

near their optimum. For rattlesnakes, this

optimum temperature has been estimated at

between 80 and 90 degrees Fahrenheit.

Thus a timber rattlesnake may bask in the sun

to achieve a comfortable temperature and then

return to the shade before becoming over-

heated. It may even be found lying directly

on the dividing line between a patch of direct

sunlight and a patch of shade, thus achieving

a balance between the two environmental

temperatures. Desert rattlesnakes tend to be

more strictly nocturnal than species inhabiting

more humid areas and areas with more cover;

daytime temperatures in the desert may be too

severe for the reptile to expose himself to

them directly. Sidewinders may rest in the day

at the mouth of a burrow, partly exposed to

the sunlight. This species has also been found

in the daytime buried in the sand, its back

heated by the sun and its lower side cooled

by the considerably lower temperature an

inch or two beneath the surface. Even species

inhabiting cooler, more northerly climates

tend to be mainly nocturnal in midsummer.

But in every species, temperature is not the

only factor involved in the preference for

nocturnal activity; and the quest for optimum

temperature may be sacrificed for other

advantages. Not only is the rattler’s eyesight

better at night but the pit is more useful when

the contrast between the temperature of warm-

blooded prey and that of the surroundings Is

greater. In addition, the small mammals that

constitute the bulk of the rattlesnake’s diet

are mainly nocturnal.

gsanaananesss

Temperature plays its role in the annual life

cycle of the rattlesnake as well. Like other

reptiles in the same areas, species inhabiting

the temperate zone must spend all or part of

the winter in hibernation in order to escape

death by freezing. The timber rattlesnake,

the northern Pacific rattlesnake, and other

species are famous for their habit of wintering

together in large groups, numbering up to a

hundred in some cases. The dens they use are

traditional, used year after year. How the

rattlesnakes are able to locate the dens in the

fall is not known, but surely its numbers indi-

cate that such a denning group represents a

rattlesnake population that has been dispersed

over a considerable area. Possibly there is some

sort of homing instinct — a drive postulated

in the case of many vertebrates but little

understood in any. Learning, too, is a possible

explanation. In either case, the sense of smell

may be crucial. All snakes possess anal scent

glands; and the secretions of these glands left

by snakes in which either the homing urge is

stronger or the learning more precise may help

direct others to the den. In any event it has

been shown in the case of at least one sub-

species — the Great Basin rattlesnake (Crota/us

viridis lutosus) — that individual snakes do

return to the same den year after year.

Timber rattlers in New Jersey, it has been

_ reported, are accustomed to enter the dens in

mid-September and emerge in mid-April; but

in other cases the dates have been found to

vary rather more widely from year to year. In

one California county, northern Pacific rattle-

snakes were found to emerge from the dens

en masse at any time from mid-March to almost

mid-April. A rise in temperature above 70 de-

grees Fahrenheit was apparently the stimulus

for a general emergence. However, before

finally retiring to the dens in fall and before

definitively leaving in spring, the rattlesnakes

may gather close to the entrance of the den

at the warmest part of warm days.

Rattlesnakes in the more southerly regions of

the United States appear to give birth annually

and to mate soon after emerging from the dens

in spring. In colder regions, females seem most

commonly to give birth every other year and,

though some may mate in spring, a great many

mate in late summer or fall. Fall matings seem

to be the norm in the timber rattlesnake and

occur in perhaps a majority of cases in the

northern Pacific rattlesnake. Nonetheless, in

almost all North American species and sub-

Species it appears that the young are born in

fall — early enough to ensure that they will

have time to accumulate the stored food

energy they will need.to last them through

their first winter of hibernation.

This variation in the period between mating

and giving birth is made possible by the female

rattlesnake’s ability to store live sperm for

quite long periods before ovulation takes place.

In the case of a spring mating, ovulation — the

passage of the eggs from the ovaries where

they are formed to the uteri where they are to

be fertilized — evidently takes place in spring

as well. In fall mating, the sperm is stored in

a special pouch; and, though the eggs develop

to a large size in the ovaries, comparable to the

size they will have achieved at ovulation, ovula-

tion and fertilization do not occur until after

the female emerges from hibernation in the

spring.

Rattlesnakes bear live young. Technically

speaking, they are ovoviviparous; in other

words, the eggs — which have a soft covering

rather than the hard or leathery shell typical

of reptilian eggs — are retained in the mother’s

body until the young are ready to hatch. The

young rattler may break out of the egg at or

just before the time when it actually emerges

from the mother’s body, or it may not emerge

until some minutes after parturition has taken

place. The young are coiled inside the egg

membrane and break it by thrusting upward

several times with the snout. As in other rep-

tiles, there is a temporary ‘‘egg-tooth”’ on the

front of the upper jaw, but due to the softness

of the membrane it is much reduced in com-

parison to those of reptiles with hard-shelled

eggs. Within a day after hatching, the umbilical

cord that connected the young snake with the

yolk sac when it was in the egg dries up and

breaks off.

One of the most striking and well-known

aspects of rattlesnake natural history — the

male combat ‘‘dance”’ — evidently plays a role

in the reproductive cycle of these reptiles, but

its exact function is still a matter of speculation

and debate. In rural or wilderness areas of this

continent, human observers have often been

startled to find two rattlers with the lower

halves of their bodies entwined while their

heads, raised high above the ground, lunged

repeatedly at each other. At first, folklore

assumed that the two snakes must be male and

female and that this behavior must be courtship.

Later it was found that the two were invariably

males and that in courtship neither snake

would raise its head above the ground.

The function of these combats has not been

easy to determine. Originally it was supposed

that there must be a female present over which

the two males were fighting, but it has been

repeatedly asserted that this is far from always

the case. In captivity it was found that the

introduction of a female would sometimes

stimulate two male rattlesnakes to engage in

the combat ritual but that on other occasions

they would perform the “dance” with no

female present. In the wild it is more difficult

to prove that a female is not or has not been

present where two males are fighting, since a

definite decision requires a very thorough

search of the surrounding terrain, which is

often covered with thick underbrush in which

a single snake would be very difficult to find.

However, it was found by the examination of

the testes of two males collected during

combat that both were in breeding condition,

producing viable sperm; and perhaps the com-

bat ritual is engaged in by any two males in

breeding condition who encounter one another.

In the wild records tend to indicate that the

season in which combats occur coincides

roughly with the mating season, whether that

be in the spring or in the fall.

Though perhaps the most spectacular, the

combat dance is only one of a number of

unexplained aspects of rattlesnake natural

history. The motivation involved in denning

and the subtle interrelationships between

climate and the annual reproductive cycle are

other areas deserving further study — study

that may well serve to illuminate parallel

mysteries as to the causes of animal activity

throughout the vertebrates. For these and

other investigations to be carried out, how-

ever, it will be necessary for the constantly

spreading human population of North America

not to react to these reptiles with blind fear

and a desire to exterminate but to allow them

their place on this continent as well. Surely

they deserve it — as an invaluable control on

rodent numbers, as interesting objects of study

in their own right, and as major contributors

to our cultural heritage.