The alligator and its allies

Classification

As in most groups of animals, there is considerable difference of opinion as to the proper classification of the Crocodilia.

One of the older textbooks (Claus and Sedgwick) divides the order Crocodilia into three sub-orders: the Teleosauria, Steneosauria, and Procœlia, the last only being represented by living forms. The Procœlia or Crocodilia proper are divided into three families,—the Crocodilidæ, the Alligatoridæ (including the caiman as well as the alligator), and the Gavialidæ.

This division into families seems to be based mainly on the shape of the head, or, at any rate, it throws those forms together that have heads of the same outline.

It is this outline of the head that Ditmars (Reptiles of the World) uses in classifying the Crocodilia, which, he says, are all included in the single family—Crocodilidæ. The following list, taken from his Reptiles of the World (pp. 68-69), will give a clear idea of the number, distribution, and maximum size of the members of the order Crocodilia. More will be said of some of the members of this list later.

Gadow in the Cambridge Natural History (p. 450) agrees with Boulanger in believing that the recent Crocodilia cannot be separated into different families, yet he describes seven families of Crocodilia, two of which, the Gavialidæ and Crocodilidæ, include the living members of the order; the former includes the gavials, of course, and the latter the crocodiles, alligators, and caimans.

Though “doctors disagree” thus in regard to the scientific classification of this small group of animals, this fact does not in the least diminish the intense interest in the individual members of the order.

Ancestry

Although the huge dragon-like dinosaurs or “terrible reptiles,” some of which were probably more than one hundred feet long, became extinct during the Mesozoic epoch, perhaps millions of years before man made his appearance upon earth, we have one group of reptiles still living in certain parts of the earth of which the Mesozoic lords of creation need not feel ashamed. While most of the living Crocodilia are mere pigmies in size, compared to the Atlantosaurus, there are a few representatives of the living group, to be discussed later, that are said to reach a length of thirty feet, which length makes pigmies, in turn, of most of the other living reptiles.

Considering the extinct as well as the living Crocodilia, Gadow says it is very difficult to separate them from the Dinosauria. In the Mesozoic Crocodilia the fore limbs were much shorter and weaker than the hind limbs, as was often the case with the dinosaurs; they were almost entirely marine, but gave indications of descent from terrestrial forms.

Various facts point, thinks Gadow, “to some Theropodous Dinosaurian stock of which the Crocodilia may well form an aquatic, further developed branch” (Cambridge Natural History, p. 432).

The direct ancestors of the Crocodilia, Gadow says, are still unknown.

Geographical Distribution

As will be seen by examination of the table (p. 2) from Ditmars, and of Figure 1, the recent Crocodilia are found in all of the great continental areas except Europe; mainly in the tropical or subtropical regions.

The alligator is found in the southwestern United States and in China.

The crocodile is the most numerous in species and is the most widely distributed of the group. It is especially characteristic of Africa and Madagascar, but is found also in Florida, Mexico, Central and South America, the West Indies, South Asia, the East Indies, and Australia.

The gavial is found in India and some of the islands of the Orient, especially Borneo and Sumatra.

The caiman occurs in southern Mexico, Central and South America.

The distribution of individual forms will be mentioned again when they are discussed in detail.

Alligator Mississippiensis

Since this animal, generally known as the American or the Florida alligator (formerly A. lucius), is the one upon which most of the facts of this book are based, it will be discussed first.

At this point it may be well to answer the question that is sure to be asked by someone early in any conversation upon the Crocodilia. The writer, and doubtless every other zoölogist, has been asked countless times, “What is the difference between an alligator and a crocodile?” As a matter of fact there is, perhaps, no absolute distinction between the two groups, but there are certain features that make it easy to distinguish, say, between the American alligator and the American crocodile.

The most striking difference is in the outline of the head; the alligator has a broad, rounded snout, while that of the crocodile is narrower and more pointed (Fig. 2). Again, in the crocodile the fourth tooth from the front projects slightly outwards and fits into a notch in the side of the upper jaw, while in the alligator (also in the caiman) the corresponding tooth on each side fits into a socket in the upper jaw and hence is hidden, except in some old animals with very long teeth, in which it may pierce the upper jaw and show from above. According to Ditmars, the crocodile has, as a rule, larger and more exposed teeth than the alligator. Finally, as will be brought out later, the crocodile is usually more quick and active, and also more vicious, than the alligator.

Very young alligators are nearly black, with distinct, yellow cross bands; as they grow older these markings become less distinct until in maturity the animals are of a uniform gray or dirty black color.

Habitat.

The American alligator is found in the rivers and swamps of the Southern States, from the southern part of North Carolina to the Rio Grande, though Florida is usually thought of as being the region in which they particularly abound. Years ago, before the rifle of the ubiquitous tourist and so-called sportsman had gotten in its deadly work, the alligators were probably very abundant in the Southern States; but they have been so ruthlessly destroyed by native hunters for their skins, and by others for mere wanton sport, that one may travel, perhaps, for days along the rivers of the South without seeing a single ’gator.

The account quoted by Clarke from Bartram’s travels of more than one hundred years ago, while probably exaggerated, gives an idea of the abundance of the alligators at that time: “The rivers at this place from shore to shore, and perhaps near a half mile above and below me, appeared to be one solid bank of fish of various kinds, pushing through the narrow pass of San Juans into the little lake on their return down the river, and the alligators were in such incredible numbers, and so close together from shore to shore, that it would have been easy to have walked across their heads, had the animals been harmless.” At the present time it is usually necessary to travel far from the usual routes of the Northern tourists to find alligators in any abundance.

At Palm Beach, Florida, lived, a few years ago, and probably still lives, a well-known hunter and guide, “Alligator Joe.” Just what nationality he may be is difficult to determine, but that he knows that trackless waste, the Everglades, at least in the region of Palm Beach, is evident. He has an “alligator farm” near the great hotels of that famous winter resort, at which he keeps, or did a few years ago, a large number of alligators of all sizes, as well as a number of crocodiles. For a consideration (by no means a modest one) he would take out a party of tourists for a day into the Everglades, guaranteeing that he would find an alligator for them to shoot. It was rumored by the natives that an accomplice was always sent ahead to free the alligator at the psychological moment, after the hunters had been paddled by a devious course to the selected spot, but whether this were true or not the writer was not able to determine. It is true, however, that he and the writer paddled in a rather graceful canoe, dug out of a single cypress log, and waded through the Everglades for several days, searching for alligator eggs, and that we found only one nest and saw only one or two alligators (Fig. 3).

Doubtless in more remote parts of the Everglades the alligators are much more numerous.

During another summer the writer, with a guide, penetrated the very center of the State, to the region southeast of Lake Kissimmee, forty miles from the nearest railroad; here the alligators, and in consequence their nests, are fairly abundant, though the native hunters are, even in this remote region, rapidly thinning their ranks.

A still greater number of alligators was found, the following summer, in the Okefinokee Swamp in southern Georgia. In the center of this great waste, ten miles or more from dry land, nearly one hundred alligators, ranging from about four to eight feet in length, were killed within a week by a small party of native hunters with whom the writer was traveling (Fig. 4).

Whether this wholesale destruction by sportsman and native hunter will eventually exterminate our giant reptile, as has been the case with the buffalo and other game animals, it is impossible to say. Unless the Everglades and the Okefinokee are largely drained it seems probable that a few alligators will always remain in the most inaccessible regions.

The collection of eggs for sale and for hatching purposes, as well as their destruction for food by bears and other animals, will also tend towards the annihilation of the species in the course of time. The economic importance of the alligator will be discussed later.

While in the old days, as has been said, the alligator was common in the larger rivers and lakes, and may even have ventured short distances into salt water, he must now frequently be satisfied to hide his great body in a “’gator hole” that is scarcely more than a puddle. These “holes” (Fig. 7) are common in central Florida and are sometimes scarcely large enough to allow the alligator to dive into them to seek the underground cave in which he hides. It is on the edge of such a hole that the nest is built, as will be described later.

Often from a small swamp or slough alligator “trails” lead off in different directions. These trails are narrow, winding gullies such as might be made by cattle in a damp pasture. If followed from the main slough the trail will usually be found to end in a “hole,” in which an alligator will probably be found (Fig. 7). In a great swamp like the Everglades or the Okefinokee such holes would naturally not be found.

On one side of the hole is usually a smooth place where the vegetation is worn away; it is here that the ’gator “pulls out” to sleep in the sun; and wary must the hunter be to approach within sight of the animal before being seen or heard by him. At the first alarm he slides quietly or plunges quickly into the muddy water, and the hunter must wait long if he expects to see the ’gator come to the surface.

The opening of the cave is always below the surface of the water, but it is possible that there may be a subterranean chamber that is not completely filled with water. How the animal is gotten from his cave will be described later. According to some writers the alligator retires to his cave to hibernate during the cooler winter months. This is possibly true in the more northerly limits of his range. It is well known that if kept in cool water the alligator will lie dormant and refuse all food for months at a time. The writer has had young alligators in captivity, under these conditions, that refused food from late in the autumn until nearly the first of April.

The proprietor of one of the largest alligator farms in the country says: “Our alligators stop eating the first week in October and do not begin to eat until the latter part of April. We have experimented with our stock to see if we could get them to eat in the winter, and found that by keeping the water in the tanks at a certain temperature they would eat, but we found out that the warm water would make their bowels move, and that they would not eat enough to keep themselves up, as in the summer, and as a result they would become very poor and thin, so we do not force them to eat any more.” The effect upon the growth of an animal of these two methods of feeding will be noted later when the age and rate of growth are discussed. The same writer says, in answer to a question about hibernation: “In their wild state they go into their dens under water and remain dormant all winter.” Whether this statement is the result of actual observation the writer is not able to say, but, judging by some other statements from the same source, it is probably from hearsay. The writer, having visited the alligator haunts only in late spring and summer, has had no opportunity of studying the habits of the animal in its natural habitat during the winter season. During the heat of summer the animal does not seek the sun as he is said to do during cooler weather, but spends more time on the bank at night and during the cooler parts of the day.

That he sometimes wanders over dry land, perhaps going from hole to hole, is evident from the tracks that are sometimes seen crossing a dusty road or path. These trails are easily recognized by the clawed footprints with a line, made by the dragging tail, between them. Although most awkward on land, he can, if necessary, move very quickly. It is, however, in the water that he shows to best advantage; he is an active, powerful swimmer, his tail being used as a propeller as in the fishes. When swimming actively the legs are held close against the body in order that they may retard the animal’s motion as little as possible. While swimming in a leisurely way the top of the head is at the surface of the water, perhaps just the nostrils and eyes projecting above the surface, so that the size of the animal can be estimated by the distance between these projecting points. One afternoon the writer and a guide, while paddling along an old canal that was dug years ago into the Okefinokee Swamp, were preceded for perhaps half a mile by a large alligator that swam just fast enough to keep out of our reach until he came to the place where he wanted to turn off into the swamp.

Although so awkward on land, the alligator is said to be able to defend himself very effectively with his tail, which he sweeps from side to side with sufficient force, in the case of a large specimen, to knock a man off his feet. Although the writer has seen captured and helped to capture alive several alligators up to eight feet in length he has never seen this vigorous use of the tail as a weapon of defense.

While the alligator, like most other wild animals, will doubtless defend itself when cornered, it will always flee from man if possible, and the writer has frequently waded and swam in ponds and lakes where alligators lived without the least fear of attack. This might not have been possible years ago when the animals were more numerous and had not been intimidated by man and his weapons.

Food.

The food of the adult alligator consists of fishes, birds, mammals, and possibly smaller individuals of its own species. The young eat small fish, frogs, insects, or worms.

If the animal be too large to swallow whole it is shaken and torn, the shaking being so vigorous that, according to Ditmars, the entrails of the prey may be thrown to a distance of twenty feet or more. Should two alligators seize the same prey at the same time they whirl about in opposite directions so violently that the prey is torn apart. This action may be illustrated by giving two small captive alligators a piece of tough meat; they hold on with bulldog tenacity, and each, folding its legs close to its body, will use its tail like a propeller until the animal whirls around with remarkable speed. The commotion that two ten-foot alligators would cause when thus struggling can easily be imagined. That a large alligator, if it tried, could easily drag under the water and drown a man or possibly a much larger animal is evident.

While the alligator has a valve-like fold of skin in its throat that enables it to open its mouth and crush its prey under water, it is said that it must raise its head above water in order to swallow its food. A young alligator on land will usually throw back its head when trying to swallow a large piece of meat, so that it may be simply this motion that brings the head of the alligator above the surface of the water.

Ditmars thus describes the fate of a dog that approached too near a very large alligator: “As a dog, weighing about fifty pounds, unwarily approached the edge of this creature’s tank, it was suddenly grasped and before completing its first yelp of terror was dragged beneath the surface. A few minutes later the twelve-foot saurian appeared at the top, holding the dead canine in its jaws. The dog was shifted about, amid the sound of breaking bones, and swallowed head first, and entire, after a few gulps.”

Size and Growth.

Although, years ago, alligators of fifteen feet length may have been common in favorable localities in the South, it is probable that few if any such monsters now exist. A twelve-foot alligator, owing to its great girth, is a huge animal and but few of this size are to be found in captivity. The largest specimen the writer has ever seen is the one in the Bronx Zoo, which is barely thirteen feet in length. At hatching the alligator is about eight inches in length.

Clarke (17) says: “The largest specimen I saw measured twelve feet in length; and none of the many hunters and natives of Florida I have met have seen any longer than thirteen feet. All the hunters agree that it is only the males that acquire the great size; no one had ever seen a female that measured over eight feet, and the majority are not over seven. The male has a heavier, more powerful head, and during the breeding season especially is more brilliantly colored.”

It is a very common belief, even among those who should be most familiar with their habits, that the growth of the alligator is remarkably slow, so that a large specimen may be described by the exhibitor as more than a century old. The same dealer in alligators quoted above says upon this subject: “You can figure about two inches a year to their growth.” He also says: “We judge that an alligator about twenty-five to thirty years old will breed.” Even scientific writers of reputation have not been free from this error in their writings. That the alligator may live to an extreme age, as seems to be true of some of the tortoises, is quite possible, and it is probable that after reaching a length of twelve or fifteen feet the growth is very slow.

In captivity, when kept in warm water and other favorable conditions, the alligator will grow, according to measurements taken at the New York Zoölogical Park, at the rate of about one foot a year, for about the first ten years. Under unfavorable conditions the growth may be exceedingly slow. Under favorable conditions in nature the rate of growth may exceed that given above.

Instead of requiring twenty-five to thirty years to reach sexual maturity, as quoted above, it is likely that the female may lay eggs at five to ten years, though such a fact is difficult to determine of animals in their native haunts.

Voice.

The alligator, unlike most other members of its class, the Ophidia, Chelonia, and Lacertilia, has a voice, which, in an adult bull, may be heard for a mile or more. This bellowing is difficult to describe; it is something between a moan and a roar, and may be to attract the opposite sex or to serve as a challenge to other large animals. It is usually ascribed to the male, but whether confined to him or not the writer is unable to say.

In younger animals the voice is, of course, less deep and in very young individuals it is a squeak or grunt, easily imitated by hunters for the purpose of luring the animals from their hiding places.

Breeding Habits.

Judging from the statements of native hunters the laying season of the alligator might be thought to be at any time from January to September. As a matter of fact the month of June is the time when most, if not all, of the eggs are laid. S. F. Clarke gives June 9th and June 17th as the limits of the laying season in Florida, but I found at least one nest in which eggs were laid as late as June 26th: no eggs were found before the first date given by Clarke. It seemed quite certain that the laying, during the season in question, had been delayed by an extreme drought that had dried up the smaller swamps and reduced the alligator holes to mere puddles. Nests were found in considerable numbers as early as June 8th, but no eggs were laid in any of them until the end of the dry period which occurred nearly two weeks later. Almost immediately after the occurrence of the rains that filled up the swamps eggs were deposited in all of the nests at about the same time. From the fact that all of these completed nests had stood for so long a time without eggs, and from the fact that all of the eggs from these nests contained embryos in a well-advanced state of development, it seemed evident that the egg-laying had been delayed by the unusually dry weather. Eggs taken directly from the oviducts of an alligator that was killed at this time also contained embryos that had already passed through the earlier stages of development. Thus it was that the earliest stages of development were not obtained during this summer.

It is said that during the mating season, which precedes by some time, of course, the laying season, the males are noisy and quarrelsome, and that they exhibit sexual characteristics of color by which they may be distinguished from the females. Never having been in the alligator country at this season, the writer has made no personal observations along these lines, but from the frequency with which alligators with mutilated or missing members are found it is evident that fierce encounters must sometimes take place, whatever the cause. During June and July, at least, and probably during most of the year, the alligators are very silent, an occasional bellow during the very early morning hours being the only audible evidence that one has that the big reptiles are in the neighborhood. Whatever may be the sexual differences during the mating season, at ordinary times the two sexes are so much alike that I have, on more than one occasion, seen experienced hunters disagree as to the supposed sex of an alligator that had just been killed.

Although I have never seen a nest actually during the process of construction, it is easy to imagine, after the examination of a large number of freshly made nests, what the process must be like.

The alligator, probably the female, as the male, after the mating season, takes no interest whatever in the propagation of his species, selects a slight elevation on or near the bank of the “hole” in which she lives. This elevation is generally, though not always, a sunny spot, and is frequently at the foot of a small tree or clump of bushes. Where the alligator is living in a large swamp she may have to go a considerable distance to find a suitable location for her nest; when her hole is scarcely more than a deep, overgrown puddle, as is often the case in the less swampy regions, she may find a good nesting place within a few feet of her cave. That the female alligator stays in the neighborhood of her nest after she has filled it with eggs seems pretty certain, but that she defends it from the attacks of other animals is extremely doubtful: certainly man is in very little danger when he robs the nest of the alligator, and, according to the statement of reliable hunters, bears are very persistent searchers for and eaters of alligator eggs. Having selected (with how much care it is impossible to say) the location for the nest, the alligator proceeds to collect, probably biting it off with her teeth, a great mass of whatever vegetation happens to be most abundant in that immediate vicinity. This mass of flags or of marsh grass is piled into a conical or rounded heap and is packed down by the builder repeatedly crawling over it.

There is a great deal of variation in the size and form of the different nests, some being two meters or more in diameter and nearly a meter in height, while others are much smaller in diameter and so low as to seem scarcely more than an accidental pile of dead vegetation. It is probable that the nests are under construction for some time, perhaps to give time for the fresh vegetation of which they are composed to ferment and soften, and also for the material to settle into a more compact mass. The compactness of the alligator’s nest was well illustrated one day when the writer used an apparently deserted nest as a vantage ground from which to take a photograph: on opening this nest it was found, after all, to contain eggs, and though some of the eggs were cracked, none of them were badly crushed. This nest although it was so low and flat that it was thought to be one that had been used during some previous season, contained forty-eight eggs, a greater number than was found in any other nest; while in other nests that were twice as large as this one were found less than half as many eggs, showing that there is no relation between the size of the nest and the number of eggs. The average number of eggs per nest, in the twelve nests that were noted, was thirty-one. One observer reported a nest that contained sixty eggs, but this, if true, was a very unusual case. Reports of still larger numbers of eggs in one nest probably refer to crocodiles, which are said to lay one hundred or more eggs in a nest. Although crocodiles may be found in certain parts of Florida, the writer has had no opportunity of observing their nesting habits.

The eggs are laid in the nest without any apparent arrangement. After the nest has been prepared, and has had time to settle properly, the alligator scrapes off the top, and lays the eggs in a hole in the damp, decaying vegetation; the top of the nest is again rounded off, and it is impossible to tell, without examination, whether the nest contains eggs or not.

As to whether the same nest is used for more than one season there is a difference of opinion among alligator hunters, and the writer has had no opportunity of making personal observations.

While it is usually stated that the eggs are incubated by the heat of the sun, it is held by some observers that the necessary heat is derived not from the sun but from the decomposition of the vegetable matter of which the nest is composed. Possibly heat may be derived from both of these sources, but it seems likely that the conditions that are especially favorable to normal incubation are moisture and an even, though not necessarily an elevated, temperature. Moisture is certainly a necessary condition, as the porous shell allows such rapid evaporation that the egg is soon killed if allowed to dry. The inside of the nest is always damp, no matter how dry the outside may become under the scorching sun, so that this condition is fully met. The eggs of the Madagascar crocodile, according to Voeltzkow,[3] offer a marked contrast to those of the alligator. Instead of being laid in damp nests of decaying vegetation, they are laid in holes that are dug in the dry sand, and are very sensitive to moisture, the early stages, especially, being soon killed by the least dampness. A crocodile’s nest containing eggs is shown in Figure 5. In this species of crocodile, probably C. porosus, the nest resembles that of the Florida alligator. The photograph was taken by Mr. Rowley on the edge of a small lake on the Island of Palawan, P. I.

The daily range of temperature in the Southern swamps is sometimes remarkably great, so that if the eggs were not protected in some way they would often pass through a range of temperature of possibly fifty degrees or more; while in the center of a great mass of damp vegetation they are probably kept at a fairly constant temperature. Unfortunately no thermometer was taken to the swamps, so that no records of the temperatures of alligator nests were obtained, but it was frequently noticed that when, at night or very early in the morning, the hand was thrust deep into the center of an alligator’s nest the vegetation felt decidedly warm, while in the middle of the day, when the surrounding air was, perhaps, fifty degrees (Fahrenheit) warmer than it was just before sunrise, the inside of the same nest felt quite cool. It is probable, then, that the conditions of temperature and moisture in the center of the nest are quite uniform. One lot of eggs that had been sent from Florida to Maryland continued to incubate in an apparently normal way when packed in a box of damp sawdust, the temperature of which was about 80 degrees Fahrenheit. Another lot of eggs continued to incubate, until several young alligators were hatched, in the ordinary incubator, at a temperature of about 95 degrees Fahrenheit.[4]

The fact that eggs taken directly from the oviducts of the cold-blooded alligator contain embryos of considerable size seems to indicate that no such elevation of temperature as is necessary with avian eggs is necessary with the eggs of the alligator.

The complete process of incubation probably extends through a period of about eight weeks, but no accurate observations along this line could be made. For some hours previous to hatching the young alligators make a curious squeaking sound inside the shell, that may be heard for a distance of several yards: this sound may be for the purpose of attracting the attention of the female alligator, who will open the top of the nest in time to allow the just hatched alligators to escape: unless thus rescued, it would seem impossible for the little animals to dig their way out from the center of the closely packed mass of decaying vegetation.

At the time of hatching the alligator is, as already noted, about eight inches in length, and it seems impossible that it should have been contained in so small an egg.

The size of alligator eggs, as might be expected, is subject to considerable variation. In measuring the eggs a pair of brass calipers was used, and the long and short diameters of more than four hundred eggs were obtained. A number of eggs of average size, when weighed in mass on the scales of a country store, gave an average of 2.8 oz. per egg.

There was more variation in the long diameter of eggs than in the short diameter.

The longest egg of all those measured was 85 mm.; the shortest was 65 mm. The widest egg (greatest short diameter) was 50 mm.; the narrowest egg (least short diameter) was 38 mm.

The average long diameter was 73.742 mm.; the average short diameter was 42.588 mm.

The greatest variation in long diameter in any one nest of eggs was 15.5 mm.; the greatest variation in short diameter in the eggs of any one nest was 11 mm.

The average variation in the long diameter of the eggs from the same nest was 11.318 mm.; the average variation in the short diameter of the eggs from the same nest was 5.136 mm.

It will be seen from the above that the average variation in the long diameter of eggs from the same nest is between one sixth and one seventh of the long diameter of the average egg; while the average variation in the short diameter of the eggs from the same nest is less than one eighth of the short diameter of the average egg.

S. F. Clarke[5] gives the limits of the long diameter as 50 mm. and 90 mm., and the maximum and minimum short diameters as 45 mm. and 28 mm. No such extremes in size were noticed among the eight hundred or more eggs that were examined.

Economic Importance.

[6] More than one hundred years ago attempts were made to utilize the skin of the alligator, but it was not until about 1855 that these attempts were successful and alligator leather became somewhat fashionable and some thousands of hides were converted into leather. The demand was short-lived, however, and was not again felt until the demand for shoe-leather during the war between the States revived the business. At the close of the war the business again failed, but about 1869 the demand became greater than ever and has continued unabated to the present time. The supply of skins from our own States proving inadequate, large numbers of skins were soon imported from Mexico and Central America. The skins from South America are so heavy that they are of little value in making leather. Of the States of the Union, Florida has been the chief producer, the most important centers for hides being Cocoa, Melbourne, Fort Pierce, Miami, and Kissimmee. Ten men at the first-named place took, in 1899-1900, 2500 skins; one man took 800 skins in one year; another man collected 42 skins in one night. At Fort Pierce twelve men took 4000 skins in 1889. In 1899, three firms at Kissimmee handled 33,600 hides. After this time the total number of hides taken and the average per man diminished greatly.