Table Of Content^4C
Papers
Scientific
Museum
Natural History
The University of Kansas
10 April 2002 Number 24:1-6
A Comparison of Growth and Rattle Strings in
Three Species of Rattlesnakes
MCZ
By
\RY
Henry S. Fitch
Fitch Natural History Reservation, The University ofKansas
2060 East 1600 Road, Lawrence, Kansas 66044-9540, USA
UNIVERSITY
CONTENTS
ABSTRACT
1
INTRODUCTION
2
Acknowledgments 2
INTRODUCTION
2
MATERIALSAND METHODS
2
RESULTS 2
LITERATURE CITED 6
ABSTRACT Rattlestringsarecompared in a largeseries ofCrotalusatrox from fiveOklahoma round-
ups with those ofC. viridis from the SharonSprings, Kansas, roundup, and with a smallerseries ofC.
horridus from the Fitch Natural History Reservation and environs in northeastern Kansas. The 1590
rattlesnakes examined included 153 C. horridus, 426 C. viridis and 1011 C. atrox. Those from the round-
ups were mostly adults. Adolescents of all three species have tapered rattle strings with the natal
"button" atthetip. Adultswithmorethaneightrattlesegmentsrarelyretainthebutton,butmayhave
tapered rattle strings if they still have segments acquired when they were smaller, or they may have
parallel-sided stringsofuniformsized rattlesifall ofthesegmentsacquired during growth havebeen
lost. Inadult C. horridus justoverhalfofthe rattlesaresame-sizesegments, in C. viridis theratio isjust
over one-third, and in C. atrox not quite one-fourth. Reverse taper, with an occasional undersized
segment seemingly caused by undernourishment, was observed in all three species.
Key words: Crotalus atrox, C. horridus, C. viridis, rattle segments, reverse taper
©NaturalHistoryMuseum,TheUniversityofKansas ISSNNo. 1094-0782
Museum of ' ^.ooiogfy
Harvard University
Papers
Scientific
Museum
Natural History
The University Kansas
of
10 April 2002 Number 24:1-6
A Comparison of Growth and Rattle Strings in
Three Species of Rattlesnakes
By f
RY
Henry S. Fitch
Fitch Natural History Reservation, The University ofKansas
2060 East 1600 Road, Lawrence. Kansas 66044-9540, USA
ERSITY
CONTENTS
ABSTRACT
1
INTRODUCTION
2
Acknowledgments 2
INTRODUCTION
2
MATERIALSAND METHODS
2
RESULTS 2
LITERATURE CITED 6
ABSTRACT Rattle strings arecompared in a largeseries ofCrotalusatrox from fiveOklahoma round-
ups with those ofC. viridis from the Sharon Springs, Kansas, roundup, and with a smallerseries ofC.
Iiorridus from the Fitch Natural History Reservation and environs in northeastern Kansas. The 1590
rattlesnakes examined included 153 C. Iiorridus, 426 C. viridis and 1011 C. atrox. Those from the round-
ups were mostly adults. Adolescents of all three species have tapered rattle strings with the natal
"button" atthetip. Adultswithmorethaneightrattlesegmentsrarelyretain thebutton,butmayhave
tapered rattle strings if they still have segments acquired when they were smaller, or they may have
parallel-sided stringsofuniform sized rattles ifall ofthesegmentsacquired during growthhavebeen
lost. Inadult C. Iiorridus justoverhalfofthe rattlesaresame-sizesegments, in C. viridis theratioisjust
over one-third, and in C. atrox not quite one-fourth. Reverse taper, with an occasional undersized
segment seemingly caused by undernourishment, was observed in all three species.
Key words: Crotalus atrox, C. Iiorridus, C. viridis, rattle segments, reverse taper.
©NaturalHistory Museum,The UniversityofKansas ISSN No. 1094-0782
Musei * /.oology
Harvard University
Si ii \iiiic Papi rs, Nati km History Mi si i m. The Um\i rsity of Kansxs
IMRODLt IIO\
[Tie rattlesnake rattle was evolved in these highly During routine checking of specimens at rattlesnake
venomous animals as a sematic organ to warn awa) roundups in Kansas and Oklahoma I noticed that many
potentially harmful animal associates, and perhaps adult snakes possessed untapered rattle strings with
particular!) those thatmightunintentionally kill orinjure segments of uniform size, and in fewer individuals the
a snake by trampling. The megafauna of North America more distal segments occasionally were slightlv larger
included many large herbivores which might haveposed than those nearer the tail that had been shed earlier. In
a threat until the end of the Pleistocene more than 10,000 a rattlesnake the usual taper in more distal rattles
years ago. The evolution of the rattle involved a reflects increased body size as the individual grew.
shortening of the tail, development of a complex Presumably undersized rattle segments are produced
musculature for its rapid vibration, and change in its because ofundernourishment and represent periods of
shape, with transverse constrictions to hold the edge of stress in the lifetime of the snake. However,
the slough in place (Klauber, 1956). When the tail tip is experimental evidence is largely lacking. The purpose
shed, its tined slough continues to cling to the tail and of the present study was to compare the rattle strings
eventually, after several or many sloughs, the loosely in threespecies, Crotalusatrox, C. horridus and C. viridis.
interlocking rattle segments, rapidly vibrated, have the
ACKNOWI IK.Ml \ls
potential to produce the characteristic buzzing sound of I
warning. thank the Oklahoma Department of Wildlife
1
Klauber (1956) described the tapered rattle strings of Conservation Nongame Program, and the Kansas
juvenile and adolescent rattlesnakes and the untapered, Department of Wildlife and Parks for sponsoring my
parallel-sided strings that are found in many adults. In trips to the roundups in their respective states.
some snakes there is a reverse taper, that is a segment Individuals who deserve special thanks forhelping me
farther out on the string from the snake's body is larger at the roundups, even to the extent ofhandling the live
than itsnearestproximalsegment. Itisgenerallyassumed snakestocontrol themwhiletheywerebeingexamined
that the undersized segments are produced because the by me include: Robert Clark, Deborah Cowman (Mrs.
snake is undernourished. Klauber (1956:274) had access Donald A. Clark), Virginia Fitch, HankGuarisco, David
to the many live snakes in the San Diego Zoo, and noted Reber, Randy ReisererandTravisTaggart My daughter,
"...in captive specimens, segments acquired subsequent Alice Fitch Echelle, helped me with the manuscript in
tocaptivity, particularlyifthesnakehasfailed toeat,may many ways.
besmaller than those that had previously been acquired
in the wild..."
MATERIALSAND METHODS
attended seven rattlesnake roundups in Oklahoma; Study Area (NESA) and nearby areas in northeastern
I
those at O'Keene and Apache were attended in 1988 and Kansas, one snake at a time. Rattle segments of timber
1989, but those at Mangum, Waurika, and Waynoka were rattlers were not individually measured until 1984.
attended only in 1988. The snakes at these roundups were Nearly half the sample of Crotalus horridus was
almost exclusively Crotalusatrox (Fitch and Pisani, 1993). I obtainedinSeptemberandOctober,partlybecauseneonate
attended the roundup at Sharon Springs, Kansas in 1942, snakes were relatively abundant at that time of year, but
1944, and 1995; all snakes were C. viridis. When time alsobecausefield work wasconcentrated along the rocky,
allowed,each rattlesegment was measured separately,but wooded hilltop edges that are favored timber rattlesnake
when largenumbersofsnakes wereavailable torchecking, habitat: 35 (43.3%) of the September-Octobersample were
only the length of the rattle string and the number of first-year young. In contrast, only 2.2".. of the C. atrox
segments were recorded. I he sample of C. horridus was sample and 2.(>",. of the C. viridis sample were first-year
based on snakes captured on or near the Fitch Natural young(Fitch, 1999, 2000). Snout-vent length isabbreviated
History Reservation (FNHR), the Nelson Environmental SVL.
Rl MJLTS
—
Traits of rattle strings. Although adult snakes may appearing to be just the same size. Segments of the same
continue to grow slowly, the increment from one rattle to size and segments with reverse taper occur frequently in
the next is so small as to make no noticeable difference in all threespecies, butare most common in Crotalushorridus
thesizeofthesegments. Large and old rattlesnakes often (Tables 1-3; Fig. 1). Reverse taper rarely occurs in more
have Strings ol several or main rattles with segments than one segment. Klauber (1956:279) stated "an
Rattlesnakes
Table 1. Rattlenumberand bodysi/ein threespeciesof rattlesnakes. Snout-vent length (SVL) includes mean ± 1 standard deviation, followed by
rangein parentheses.
Int.ut
Si ii \ tn k P\i't rs, N \n km History Museum, The University of Kansas
Table. 2- Extentol reverse
Rattlesnakes
20
18
I
I
16
I
O
E 14
O
E
O
8
W
12
12 3
15
o 27 9
9
LU T 1 18 11 7
43
CO 1 12 18
30
O£ 10 45 12 49
X 52 8 61
h- 16 3
D
I 4 i 36 16
3 11
J I
2
_L
20
26
9
I
17
26
20
13
26
_1_
Scientific Papers, Nam rai Himory Mi shim. Thi Umyfrsity of K.ws\s
with Klauber that estimates are subject to error, but 4.2"" of the sample, which consisted essentially of adults
the terminal segments do reflect the size of the snake at and adolescents, because first- and second-year young
the tune they were formed and the taper of the string could not he collected legally at the roundups. The same
reflects the trend oi grow th. Ifonly two or three segments constraints apply to samples of C. viridis from Sharon
plus the button are missing, the estimate will be correct Springs,butin these samples thesnakeswereyoungeron
more often than not. Although individual estimates are average than in C. atrox. There were only four snakes (2
subject to error, they work well enough to divide a males,2females,0.09%ofsample) thatwereexceptionally
populationintoputativeagegroups,asKlauberdid.Males large and had rattle strings consisting ofseveral or many
are consistently larger than females that have the same segments with no discernible taper. In the sample of C.
number of rattle segments. Forany rattle number there is horridus nearly one-third were first-year young; second-
a widerangeoi varianceinlengthofsnakewiththeshortest year young and adolescents also were well represented.
only 7(1 toSt) percent ofthelongest,andwiththevariance However,therewereeight largeand old adults(5.3%) that
in males somewhat greater than it is in females. lacked noticeable taper. Itseems that C. horridus is longer-
In thesampleof1011 Crotalusatrox, thelargestand lived than C. viridis on average, and tends to resemble C.
oldest snakes that had untapered rattle strings were onl\ atrox in this respect.
LITERATURE CITED
\shton, K.G.2001. Bodysizevariationamongmainland populationsof Fitch, H. S. 2000. Population structure and biomass of some common
thewesternrattlesnake{CrotalusviridisI.Evolution,55(l2):2523-2533. snakes in Central North America. Scientific Papers, University of
Fitch, H. S. 1949. Study of snake populations in central California. Kansas Natural History Museum 17:1-7,
American Midland Naturalist41:513-579. Fitch, H. S. and G. R. Pisani. 1993. Lite History traits of the western
Fitch, H.S. 1985.Observationson rattlesizeand demographyofprairie diamondback rattlesnake {Crotalus atrox) studied from roundup
rattlesnakes {Crotalus viridis) and timber rattlesnakes (Crotalus samples in Oklahoma. Occasional Papers, Universit) of Kansas
horridus) in Kansas. Occasional Tapers, University of Kansas Natural History Museum 156:1-24.
MuseumofNatural History 118:1-11. Klauber, L. M. 1956. Rattlesnakes. Tharhabits, Life Histories and Influence
Fitch, H. S. 1998. The Sharon Springs roundup and prairie rattlesnake onMankind. Berkeley: University ofCalifornia Press
demography. Transactions Kansas Academy of Science 1013(3- Rahn, H. 1942.The reproductivecycleofthe prairie rattlesnake Copeia
4):101 113 1942:233-240.
MS
Fitch, 1999.A KansasSnakeCommunity:CompositionandChangesovei
>0 Years. Malabar, Florida: Krieger PublishingCompany.
3 2044 072 228 778
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