A Demographic Study of the Ringneck Snake (Diadophis Punctatus) in Kansas
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UNIVERSITY OF KANSAS ^'mmL^i^ATfoM MUSEUM OF NATURAL HISTORY No 52 MUS. APf? 1 4 1975 Harvard A Demographic Study of the Ringneck Snake (Diadophis punctatus) in Kansas By Henry S. Fitch UNIVERSITY OF KANSAS LAWRENCE 1975 April 3, 1975 UNIVERSITY OF KANSAS PUBLICATIONS MUSEUM OF NATURAL HISTORY The University of Kansas Publications, Museum of Natural History, beginning with volume 1 in 1946, was discontinued with volume 20 in 1971. Shorter research papers formerly published in the above series are now published as Occasional Papers, Museum of Natural History. The Miscellaneous Publications, Museum of Natural History, began with nimiber 1 in 1946. Longer research papers are pub- lished in that series. Monographs of the Museum of Natural History were initiated in 1970. All manuscripts are subjected to critical review by intra- and extramural speciaHsts; final acceptance is at the discretion of the publications committee. Institutional libraries interested in exchanging pubhcations may obtain the Occa- sional Papers and Miscellaneous Publications by addressing the Exchange Librarian,!i University of Kansas Library, Lawrence, Kansas 66045. Individuals may purchase separate numbers of all series. Prices may be obtained upon request addressed to Publications Secretary, Museum of Natural History, University of Kansas, Law- rence, Kansas 66045. The University of Kansas Museum of Natural History Miscellaneous Publication No. 62 April 3, 1975 A Demographic Study o£ the Ringneck Snake (Diadophis punctatus) in Kansas by Henry S. Fitch Department of Systematics and Ecology Natural History Reservation The University of Kansas The University of Kansas Lawrence 1975 University of Kansas Publications, Museum of Natural History Editor: Richard F. Jolinston Miscellaneous Publication No. 62 pp. 1-53; 19 figures Published April 3, 1975 Museum of Natural History The University of Kansas Lawrence, Kansas 66045 U.S.A. Printed by University of Kansas Printing Service Law^rence, Kansas CONTENTS ABSTRACT 4 INTRODUCTION ............ 4 Acknowledgements 5 Materials and Methods 5 Morphology 8 HABITAT 11 BEHAVIOR 12 TEMPERATURE RELATIONSHIPS 18 SEASONAL SCHEDULE 19 ASSOCIATED ANIMALS 20 FOOD HABITS 22 SPATIAL RELATIONSHIPS 24 REPRODUCTION 27 Aggregation and Mating 27 Reproductive Cycles 28 Eggs 29 Size of Clutch 29 Reproductive Effort 31 Nests 32 GROWTH 33 POPULATION DENSITY 39 COMPOSITION OF THE POPULATION 43 Age Structure 43 Sex-ratio 45 PREDATION 47 DISCUSSION 50 LITERATURE CITED 52 ABSTRACT Field records of more dian 14,000 individuals of Diadophis piinctatus were assembled over a 26-year period on several small study areas at the University of Kansas Natural History Reser\ation, mostly within a half-mile radius, with emphasis on marking and recapture. Emergence from hibernation begins in late March and continues into early April, ovulation occurs in the latter half of May, and the elongate, sausage-shaped eggs, averaging approxi- mately 3.9 per clutch, are laid in late June or early July. Hatching occurs at the end of August or in September. Females become sexually mature after their third hibernation, typically at a snout-vent (S-V) length of approximately 235 mm, but males mature a year earlier, at a min- imum length (S-V) of 166 mm. Growth continues, but at a reduced rate, after attainment of sexual maturity. Snakes already above average adult size typically gain from one to three per cent in length annually. Mortality of adults is not age-specific, and loss is approximately 25 per cent annually. A small percentage of the snakes survives to an age of 15 or more years. Young seem more secretive than adults and are less well represented in samples. Sex-ratio in samples is subject to drastic seasonal fluctuation; females range from 24 per cent in early fall to 71 per cent in midsummer, but in late March, April and early May, when the snakes are most in evidence, males are always more numerous. The snakes are active over a wide range of temperatures but tend to maintain body temperatures between 25 and 29.5 degrees C. Their surface activity is chiefly at air temperature witliin or below this range, and at higher air temperatures they retreat underground. Body temperature is maintained by con- tact with sun-warmed objects that the snakes use for shelter. Occasionally, at relatively low air temperatures, the snakes venture into the open and bask in sunshine. Earthworms, especially AHoIohophora caliginosa, provide most of the food, and it is esti- mated that each snake consumes on the average approximately three times its body weight in earthworms annually. Seven calculations of population density (based upon recapture ratios) varied from 719 to 1849 per ha and averaged 1266. Eight kinds of predators on the Reser- vation were found to eat ringneck snakes, but their toll would account for only part of popu- lation regulation. The copperhead, racer and Red-tailed Hawk were the predators in most recorded instances, but moles, mice and birds other than raptors may also be among the im- portant predators. Marked snakes were recaptured at distances of zero to 520 m from the original capture site; however, one-fourth were within 10 m, even after intervals of several years, showing a strong tendency to remain within a home area. Home ranges were often elongate, with maximum axes of approximately 140 m. Ranges tend to be progressively altered through time. INTRODUCTION The ringneck snake (Diadophis piinc- as a consumer of invertebrates and as an tatus) is a highly successful transconti- abundant food source for larger preda- nental North American species. Its local tors. In the ensuing 26 years the species populations are adapted to the swamp- has been allotted more time and effort land of subtropical southern Florida, the than any other kind of animal in the boreal forest of heavily glaciated areas many autecological studies carried out in northern Michigan and the desert on the Reservation. grassland of the southwestern United This small snake has proven to be a States. Partly because of retiring or se- difficult subject for field study, despite cretive habits, the species is considered its great abundance. Individuals ordi- rare throughout most of its extensive ge- narily cannot be observed readily under ographic range. However, in a central natural conditions. When uncovered or area including northeastern Kansas, discovered in the open, they are glimpsed where my study was made, it is abun- only momentarily, escaping underground dant and ecologically prominent. or into dense vegetation. The snakes Soon after field work began on the cannot be found for most of the year, newly-created University of Kansas Nat- including, of course, their hibernation ural History Reservation, the ringneck season. But they are also difficult to find snake attracted attention as one of the in summer, especially in hot and dry common animals meriting intensive study weather. because of its probable ecological roles The present study had its inception FITCH: A DEMOGRAPHIC STUDY OF THE RINGNECK SNAKE and in the spring of 1949 when I began tak- eleven-year period, was supple- mented 15 accumulation of ing field notes on ringneck snakes and by years' individually marking those that were earlier data. Expenditure of so much time and on a local of captured. In the 1950s the snakes were energy population observed or marked only occasionally, one species may appear prodigal; yet, the records that were the as part of a comprehensive program to recapture key study the vertebrates of the Reservation. to an understanding of ecological rela- Several students at different times under- tionships and population dynamics to- a few and when took ecological studies of Diadophis in talled only hundred, the area: John Hawken (1951-1952), these were subdivided into sexes and Robert M. Hedrick (1956-1957) and ages, some samples were inadequately Kenneth Shain (1958-1959). Hawken's small. and Hedrick's records were mostly from the Rat Ledge area, whereas Shain's Acknowledgments were from the vicinity of the Reservation Members of my family, Alice Fitch headquarters. Although each of these Echelle, Chester W. Fitch, John H. projects was of short duration, their Fitch and Virginia R. Fitch, helped me combined data contributed substantially from time to time, both with the field to my study. work and with various stages in the In the spring of 1964 large-scale cap- analysis of data. Many persons helped ture and of was un- marking Diadophis in the search and capture of the snakes; dertaken at Rat in the field near Ledge, Robert R. Fleet's contribution of many Reservation headquarters "House Field," large series was especially outstanding. and in Field" the northern "Quarry along John Hawken, the late Robert M. Hed- of the Reservation 1 . On 24 edge ( Fig. ) rick, and Kenneth Shain each contrib- a was initiated September 1965 system uted data accumulated from one or more for the of recording pattern pigmentation seasons of field work. Donald R. Clark, on the ventrals to posterior supplement Robert W. Henderson, Richard L. Lattis, the clipping of scales as a means of posi- Julian Lee, Michael V. Plummer, Eric tive individual identification. In 1966, Rundquist, and Arnold K. Smith were at Rat were abandoned operations Ledge employed as research assistants at differ- and field work was concentrated in the ent times, and all contributed substan- House Field and Quarry Field areas, while tially. In 1971, 1972, and 1973, which were close that snakes enough engaged in his own field research on the often shifted from one to the other. Reservation, Lattis captured and con- The marking program was suspended tributed many ringneck snakes marked at the end of May, 1968, but in the in 1969 or before; these long term sur- of 1969 all spring first-year young cap- vivors provided some of the most reveal- tured were and those group-marked ing records of longevity, growth, and considered were yearlings individually population structure.