Many other ( probably nearly all ) snakes at maturity are already more than half their final length .
Laurence M. Klauber put length at maturity at two thirds the ultimate length for some rattlesnakes , and Charles C. Carpenter's data on Michigan garter and ribbon snakes ( Thamnophis ) show that the smallest gravid females are more than half as long as the biggest adults .
Felix Kopstein states that `` when the snake reaches its maturity it has already reached about its maximal length '' , but goes on to cite the reticulate python as an exception , with maximum length approximately three times that at maturity .
It is hard to understand how he concluded that most snakes do not grow appreciably after attaining maturity ; ;
he was working with species of Java , so perhaps some tropical snakes are unusual in this respect .
Certain individual giants recorded later did fail to show a reasonable difference after maturity , but it is impossible to know whether this is due to captive conditions .
Additional records of slow growth have been omitted .
It is possible to make a few generalizations about the six giants themselves .
There seems to be a rough correlation between the initial and ultimate lengths , starting with the smallest ( boa constrictor ) and ending with the largest ( anaconda ) .
Data on the former are scanty , but there can be little doubt that the latter is sometimes born at a length greater than that of any of the others , thereby lending support to the belief that the anaconda does , indeed , attain the greatest length .
For four of the six ( the anaconda and the amethystine python cannot be included for lack of data ) there is also a correlation between size at maturity and maximum length , the boa constrictor being the smallest and the Indian python the next in size at the former stage .
Let us speculate a little on the maximum size of the anaconda .
If , in a certain part of the range , it starts life 1 foot longer than do any of the other ( relatively large ) giants , and reaches maturity at , let us guess , 18 inches longer than the others , a quadrupling of the maturity length would result in a maximum of ( nearly ) 40 feet .
When it comes to rate of early growth , the Indian python leads with a figure of about 3 feet 6 inches per year for the first two years , more or less .
The African rock python , a close second , is followed in turn by the reticulate python .
There are few data on the boa constrictor , those for the anaconda are unconvincing , and there is nothing at all on the amethystine python .
It seems likely that the Indian python comes out ahead because records of its growth have been made more carefully and frequently ; ;
it responds exceptionally well to captivity and does not reach proportions that make it hard to keep .
I cannot make sense out of the figures for post maturity growth ; ;
at best the annual increase appears to be a matter of inches rather than feet .
Until better records have been kept over longer periods of time and much more is known about the maximum dimensions , it will be wise to refrain from drawing conclusions .
It is often stated that the largest snakes require five years to attain maturity , but this apparently is an overestimation .
The best way to determine the correct figure ( in captives ) is by direct observation of pairs isolated from birth , a method that produced surprising results : maturing of a male Indian python in less than two years , his mate in less than three ; ;
data on the boa constrictor about match this .
Another approach is to estimate from the rate of growth and the smallest size at maturity .
Results from this approach amply confirm the direct observations : about three years are required , there being a possible slight difference between males and females in the time required .
Only the amethystine python and the anaconda must be excluded for lack or paucity of data .
The following information on snakes varying greatly in size ( but all with less than a 10-foot maximum ) shows , when considered with the foregoing , that there is probably no correlation between the length of a snake and the time required for it to mature .
Oliver , in his summary of the habits of the snakes of the United States , could supply data on the maturing period for only three species in addition to the rattlers , which I shall consider separately .
These three were much alike : lined snake ( Tropidoclonion ) , one year and nine months ; ;
red-bellied snake ( Storeria ) , two years ; ;
cottonmouth ( Ancistrodon ) , two years .
Klauber investigated the rattlesnakes carefully himself and also summarized what others have found .
He concluded that in the southern species , which are rapidly growing types , females mate at the age of two and a half and bear the first young when they are three .
Other herpetologists have ascertained that in the northern United States the prairie rattlesnake may not give first birth until it is four or even five years old , and that the young may be born every other year , rather than annually .
Carpenter's study showed that female common garter and ribbon snakes of Michigan mature at about the age of two .
Oversized monsters are never brought home either alive or preserved , and field measurements are obviously open to doubt because of the universal tendency to exaggerate dimensions .
Measurements of skins are of little value ; ;
every snake hide is noticeably longer than its carcass and intentional stretching presents no difficulty to the unscrupulous explorer .
In spite of all the pitfalls , there is a certain amount of agreement on some of the giants .
The anaconda proves to be the fly in the ointment , but the reason for this is not clear ; ;
the relatively wild conditions still found in tropical South America might be responsible .
There are three levels on which to treat the subject .
The first is the strictly scientific , which demands concrete proof and therefore may err on the conservative side by waiting for evidence in the flesh .
This approach rejects virtually all field measurements .
The next level attempts to weigh varied evidence and come to a balanced , sensible conclusion ; ;
field measurements by experienced explorers are not rejected , and even reports of a less scientific nature are duly evaluated .
The third level leans on a belief that a lot of smoke means some fire .
The argument against this last approach is comparable to that which rejects stories about hoop snakes , about snakes that break themselves into many pieces and join up again , or even of ghosts that chase people out of graveyards ; ;
the mere piling up of testimony does not prove , to the scientific mind , the existence of hoop snakes , joint snakes , or ghosts .
Oliver has recently used the second-level approach with the largest snakes , and has come to these conclusions : the anaconda reaches a length of at least 37 feet , the reticulate python 33 , the African rock python 25 , the amethystine python at least 22 , the Indian python 20 , and the boa constrictor 18-1/2 .
Bernard Heuvelmans also treats of the largest snakes , but on the third level , and is chiefly concerned with the anaconda .
He reasons that as anacondas 30 feet long are often found , some might be 38 , and occasional `` monstrous freaks '' over 50 .
He rejects dimensions of 70 feet and more .
His thirteenth chapter includes many exciting accounts of huge serpents with prodigious strength , but these seem to be given to complete his picture , not to be believed .
Detailed information on record lengths of the giants is given in the section that follows .
Growth of the six giants
Discussions of the giants one by one will include , as far as possible , data on these aspects of growth : size at which life is started and at which sexual maturity is reached ; ;
time required to reach maturity ; ;
rate of growth both before and after this crucial stage ; ;
and maximum length , with confirmation or amplification of Oliver's figures .
Definite information on the growth of senile individuals is lacking .
At birth , this species varies considerably in size .
A brood of twenty-eight born at Brookfield Zoo , near Chicago , ranged in length from 22 to 33-1/2 inches and averaged 29 inches .
Lawrence E. Griffin gives measurements of nineteen young anacondas , presumably members of a brood , from `` South America '' ; ;
the extreme measurements of these fall between the lower limit of the Brookfield brood and its average .
Raymond L. Ditmars had two broods that averaged 27 inches .
R. R. Mole and F. W. Urich give approximately 20 inches as the average length of a brood of thirty from the region of the Orinoco estuaries .
William Beebe reports 26 inches and 2.4 ounces ( this snake must have been emaciated ) for the length and the weight of a young anaconda from British Guiana .
In contrast , Ditmars recorded the average length of seventy-two young of a 19-foot female as 38 inches , and four young were born in London at a length of 35 or 36 inches and a weight of from 14 to 16 ounces .
Beebe had a 3-foot anaconda that weighed only 9.8 ounces .
A difference between subspecies might explain the great range in size .
I have little information on the anaconda's rate of growth .
Hans Schweizer had one that increased from 19-1/2 inches to 5 feet 3 inches in five years , and J. J. Quelch records a growth of from less than 4 feet to nearly 10 in about six years .
It is very unlikely that either of these anacondas was growing at a normal rate .
In 1948 , Afranio Do Amaral , the noted Brazilian herpetologist , wrote a technical paper on the giant snakes .
He concluded that the anaconda's maximum length is 12 or 13 ( perhaps 14 ) meters , which would approximate from 39 to 42 feet ( 14 meters is slightly less than 46 feet ) .
Thus , his estimate lies between Oliver's suggestion of at least 37 feet and the 50-foot `` monstrous freaks '' intimated by Heuvelmans .
The most convincing recent measurement of an anaconda was made in eastern Colombia by Roberto Lamon , a petroleum geologist of the Richmond Oil Company , and reported in 1944 by Emmett R. Dunn .
However , as a field measurement , it is open to question .
Oliver's 37-1/2 feet is partly based on this report and can be accepted as probable .
However , many herpetologists remain skeptical and would prefer a tentative maximum of about 30 feet .
It is possible that especially large anacondas will prove to belong to subspecies limited to a small area .
In snakes difference in size is a common characteristic of subspecies .
Boa constrictor :
A Colombian female's brood of sixteen boa constrictors born in the Staten Island Zoo averaged 20 inches .
This birth length seems to be typical .
When some thirteen records of newly and recently born individuals are collated , little or no correlation between length and distribution can be detected .
The range is from 14 to 25 inches ; ;
the former figure is based on a somewhat unusual birth of four by a Central American female ( see chapter on Laying , Brooding , Hatching , and Birth ) , the latter on a `` normal '' newly born individual .
However , as so many of the records are not certainly based on newborn snakes , these data must be taken tentatively ; ;
final conclusions will have to await the measurements of broods from definite localities .
Alphonse R. Hoge's measurements of several very young specimens from Brazil suggest that at birth the female is slightly larger than the male .
I have surprisingly little information on the size and age at maturity .
Carl Kauffeld has written to me of sexual activity in February 1943 of young born in March 1940 .
One female , collected on an island off the coast of Nicaragua , was gravid and measured 4 feet 8 inches from snout to vent ( her tail should be between 6 and 7 inches long ) .
The female from Central America which gave birth to four was only 3 feet 11 inches long .
What data there are on growth indicate considerable variation in rate ; ;
unfortunately , no one has kept complete records of one individual , whereas many have been made for a very short period of time .
The results are too varied to allow generalization .