Several populations of western painted turtles (Chrysemys picta belli) were sampled during 1970 to determine the possible relationship between turtle growth rate and type of pond substrate. The populations sampled were selected because they existed in lentic habitats that had either highly organic, mud substrates or relatively inorganic, sand substrates. Age determinations based on plastral annuli showed turtles from highly organic substrates to grow more rapidly than those from substrates with less apparent organic matter. Females attained greater size than males in both habitat extremes

Christiansen, James L.

Quinn, Anthony J.

English

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The Relationship Between Pond Bottom Type and Growth Rate of Western Painted Turtles Chrysemys picta belli in Iowa, a Preliminary Report

University of Northern Iowa

Proceedings of the Iowa Academy of Science Volume 78 Number 3-4 Article 11 1972 The Relationship Between Pond Bottom Type and Growth Rate of Western Painted Turtles Chrysemys picta belli in Iowa, a Preliminary Report Anthony J. Quinn Drake University James L. Christiansen Drake University Copyright ©1972 Iowa Academy of Science, Inc. Follow this and additional works at: https://scholarworks.uni.edu/pias Recommended Citation Quinn, Anthony J. and Christiansen, James L. (1972) "The Relationship Between Pond Bottom Type and Growth Rate of Western Painted Turtles Chrysemys picta belli in Iowa, a Preliminary Report," Proceedings of the Iowa Academy of Science, 78(3-4), 67-69. Available at: https://scholarworks.uni.edu/pias/vol78/iss3/11 This Research is brought to you for free and open access by the Iowa Academy of Science at UNI ScholarWorks. It has been accepted for inclusion in Proceedings of the Iowa Academy of Science by an authorized editor of UNI ScholarWorks. For more information, please contact scholarworks@uni.edu. TURTLE GROWTH 67 The Relationship Between Pond Bottom Type and Growth Rate of Western Painted Turtles Chrysemys picta belli in Iowa, a Preliminary Report1 ANTHONY J. QUINN and JAMES. L. CHRISTIANSEN2 ANTHONY J. QUINN & JAMES L. CHRISTIANSEN. The Relationship Between Pond Bottom Type and Growth Rate of Western Painted Turtles Chrysemys picta belli in Iowa, a Preliminary Report. Proc. Iowa Acad. Sci. 78 ( 3-4): 67-69, 1972. SYNOPSIS. Several populations of western painted turtles ( Chry-semys picta belli) were sampled during 1970 to determine the possible relationship between turtle growth rate and type of pond substrate. The populations sampled were selected because During 1970 the authors undertook a study of the rela-tionship between lentic substrates and growth rates of west-ern painted turtles ( Chrysemys picta belli) in Iowa. Previous studies of turtle growth demonstrate that growth rates vary from one geographic locality to another and from one indi-vidual to another in the same geographic locality (See Cagle, 1946 and Gibbons, 1967). Oagle ( 1946) suggested that av-emge size of Pseudemys scripta varied from one population to another in Illinois because of population age and varying ecological factors such as water temperature and availa:bility of food. He observed that juvenile growth was very great and that it was probably limited by ecological factors. Gib-bons (1967) suggested that growth rate of painted turtles in Michigan, probably C. picta marginata, was limited by the quality rather than the quantity of food consumed, primar-ily by the amount of animal protein in the diet. Lagler ( 1943) and Knight and Gibbons ( 1968) found that plants and insects made up most of the diet of painted turtles in Michigan. They and others, also found large amounts of un-identified detritus in the stomachs of turtles but no correla-tion between either the amount of decayed detritus in the stomachs or in the habitat and turtle growth rates was found. The present study is designed to test the hypothesis that tur-tles from ponds with highly organic substrates possibly pro-viding among other things a more nutritive detritus, may grow more rapidly than those from ponds with relatively little bottom organic matter. METHODS Bodies of water were chosen for sampling on the basis of amount of organic matter apparent in the bottom substrates. The substrates were either light colored sand with rela:tively little organic matter or dark colored mud mixed with consid-eraible decaying organic matter. The sand habitats were abandoned gravel pibs or strip mines. Bottom samples could easily be distinguished by settling rate. When mixed with an equal volume of water in a tall half-quart jar the solid ma-terial from sand habitats settled in ten minutes or less, leav-1 Contribution No. 40 from the Department of Biology, Drake University. 2 Department of Biology, Drake University, Des Moines, Iowa 50311. they existed in lentic habitats that had either highly organic, mud substrates or relatively inorganic, sand substrates. Age determina-tions based on plastral annuli showed turtles from highly organic substrates to grow more rapidly than those from substrates with less apparent organic matter. Females attained greater size .than males in both habitat extremes. INDEX DESCRIPTORS: Chrysemys picta belli, growth rate, bottom type. ing a slightly turbid decantate. Mud samples took more than one hour to settle when mixed in this way. Hach Kit tests were made fat nitrates, nitrites, and phosphates as indicators of decaying organic matter. Secchi disk readings were taken to measure turbidity. Localities with sand subsh·ates from which turtles were taken were: 1. Three sand~bottomed ponds, south end Lake Aquabi, 6.5 mi. south Indianola, Warren Co., Iowa (7 speci-mens). 2. Four ponds, Banner Mines, }~ mi. east U.S. 65, 5}f mi. north Indianola, Warren Co., Iowa ( 11 specimens). 3. Three ponds, Monaghan Farm, }f mi. north Iowa Hwy. 2, ~4 mi. east Missouri River, Fremont Co., Iowa· ( 31 specimens) . Bodies of water with highly organic substrates were· mud-bottomed ponds, swamps, or ditches. Bubbles of hydrogen sulphide were usually released when the substrates were disturbed, indicating a high degree of decay. Localities with organic subs,trates from which turtles were collected were as follows: 1. Two portds, 4 mi. southwest Cummings exit from I. 35, Madison Co., Iowa ( 5 specimens). 2. Ditch, Riverton Game Area, 2}f mi. west Riverton, Fre-mont Co., Iowa (14 specimens). 3. Ditch entering Missouri River, sampled }f mi. south Iowa Hwy. 2, 1/8-1/4 Ini. east Missouri River, Fremont Co., Iowa ( 3 specimens). No ponds with intermediate conditions were used in the study. Only lentic habitats were used although a small sam-ple was taken from a stagnant estuary not far from its junc-tion with the Missouri River. All localities sampled were from southern Iowa. Turtles were collected in hoopnet traps modified from the form described by Legler ( 19'60) . Canned sardines were used as bait. All specimens were preserved with the shell and most skeletal elements stored dry. Skins were fixed in 10% formalin and stored in alcohol. Internal organs were stored in 10% formalin for studies of stomach. contents, para-sites, and reproduction. Where possible, oviducal eggs were removed and hatched and the hatching records were re-tained. Complete locality data and dates of collection and sacrifice were attached to the specimens. All specimens are 1Quinn and Christiansen: The Relationship Between Pond Bottom Type and Growth Rate of WestPublished by UNI ScholarWorks, 197168 PRoc. IowA AcAD. Sc1. 78 ( 1971-197.2) available for examination in the Drake Research Collection. All carapace and plastral lengths were determined to the nearest mm. Age was determined by counts of annuli of the right abdominal scute as described by Sexton ( 1959) . Mean plastral length was determined for hatchlings from three clutches of eggs removed from females collected during the study. These data were used in calculation of growth rate by the following formula: Plastra!l length - mean hatchling plastral length growth rate = age RESULTS The following results are based on examination of 71 tur-tles from the two environmental extremes described in the previous section; 31 were males and 40 were females. 'J'lhe relationship between age and plastral length for tur" tles from the two ha!bitats is shown in Figure I. Turtles from bodies of water with highly organic (mud) substrate grow considera1bly more rapidly than those from ponds with rela-tively inorganic (sand) substrate. No turtles beyond age six from S'andy habitats had grown as rapidly as those of the same age from mud habitats. It should be noted that speci-mens more than ten years old could not be aged accurately, and therefore are excluded from Figure I. 180~ 160r-E 140r-..S ..c ..,_ 120r-CJ) c Q) 0 "--..,_ 100~ (/) 0 Q._ 0 80~ • • • 0 • 0 • 0 0 o • • • 0 • ••• • • • • 0 0 0 0 0 0 0 • • 0 • • 0 • • o • • • o •• •• o• • • o\ •• • •• • • • 190~ 180 r--E s 170.-_c -+-0'! c Q) 0 ~ +--([) 0 160~ Q_ 150~ 140,_ -~(II) -~(27) _5~(10) -Fig. 2. Comparison of the five largest females (f) and the five largest males· ( m) from highly organic (mud) and relatively inorganic (sand) substrates. Numbers in parentheses show sample sizes from which the sets of five were selected. Vertical lines represent ranges, rectangles show 95% confidence limits, and hori-zontal lines in center of rectangles show means . five largest males from mud habitats were larger than those from sand ha1bftats, some overlap occurred. It is our opinion that this overlap resulted from sampling error because of the small sample size ( 10 individuals) from which the five larg-est males from mud habitats were selected. Figure 2 sup-ports the observation of Gibbons ( 1967) that females attain 60 .__,.J __ *"'" '-=-' -!:--'--,!:-'--!'.,_--=l,,,..--'*:-'- ,;:,----,'='"'--t larger sizes than males and show that this is true for both I 2 3 4 5 6 7 8 9 10 habitat extremes considered in the present study. A faster age (years of growth) rate of growth has been observed for females than for males '--------------'------------~' of several other turtle species (Cagle, 1946, for Pseudemys Fig. 1. Growth rates of western painted turtles ( Chrysemys picta belli) from southern Iowa. Open circles represent specimens from lentic habitats with highly organic substrates; closed circles repre-sent specimens from relatively inorganic substrates. Many of the largest and oldest specimens are represented in Figure 2 .. This figure shows that the five largest females from mud substrates were aII larger than the five largest fe-males collected from sand 1substrates. Although three of the scripta, e.g.). The fact that both males and females are in-cluded in Figure I is partly responsible for the ovel'lap in growth rates seen for years four and five. G~bbons ( 1967) showed that juvenile C. picta in southern Michigan grew more rapidly than adults. Our findings show this to be true in Iowa, and also indicate that growth rate slows as turtles age after they have attained maturity. Differ-ences in growth rate for Iowa painted turtles of different ages are shown in Table I. Age-correlated differences in growth rates are affected by the habitat extremes investi-2Proceedings of the Iowa Academy of Science, Vol. 78 [1971], No. 3, Art. 11https://scholarworks.uni.edu/pias/vol78/iss3/11TURTLE GROWTH 69 gated. The data emphasize the impovtance of both age com-position and haibitat when comparing the size of turtles in dHiferent populations. TAtBLE I-GROWTH RATE OF PAINTED TURTLES (mm PER YEAR) FROM THE Two HABITAT EXTREMES CONSIDERED IN THE STUDY. Rates were determined from turtles sacrificed in each age category; hence categories are not mutually exclusive. Substrate Sand Mud Age Categories (Years of Growth) 0.1-3.0 (n) 3.1-5.0 (n) 5.1-7.0(n) 7.1-10.5 (n) Mean 26.4 ( 6) Range 22-2-29.3 Mean 32.7 ( 3) Range 23.4-43.l 18.4 (11) 11.5-22.7 27.3 (4) 21.2-38.5 17.1 (13) 13.3 (12) 15.5-19.l 11.0-16.2 21.0 ( 8) 18.5-24.8 16.7 (6) 14.7-19.3 No consistent differences in the concenh·ation of several products of protein decomposition were observed. Concen-trations of inorganic nitrates, nitrites, and phosphates varied only slightly and were not correlated with any other mea-surements; Secchi disk readings did vary consistently, how-ever, and showed higher turbidity in water from mud habi-tats than from sand. Readings for water over mud substrates were 7-22 cm while. those for water over sand substrates varied from 27 to 32 cm. DISCUSSION The fastest growth rates were found in populations from water with highly organic, mud, substrates and the slowest from ponds with relatively inorganic, sand substrates. Gib-bons ( 1967) attributed growth rate differences in Michigan populations of painted turtles to diet, primarily the amount of animal matter consumed. He did not provide ecological reasons for these dietary differences. He suggested that dense vegetation might make it difficult for large turtles to locate animal food, thereby making consumption of less nu-tritive, plant food necessary, but major differences in the density o'f aquatic vegetation were not described among the areas where he found vastly different growth rates. In the present study, aquatic vegetation varied from one pond to another but the variation was not consistent with the ob-served differences in growth rate. We are inclined to tent,a-tively accept the hypothesis that the amount of animal mat-ter in the diet is a major factor in detemlining growth rate, pending further analysis of stomach contents. Our observations of turtles searching for food both in the 1a:borntory and in the field indicate that they spend much of their time eating benthic detritis. This material may be iden-tified as to its plant or animal origin when it is removed from turtles' stomachs, but it should not be assumed that it was living at the time it was eaten. Bacterial decomposition of plant detritis may increase its nutritional value to tuvtles in the same way that bacterial action releases nutrients from plant material in ruminates. This hypothesis could be tested in the laboratory by feeding captive turtles varying amounts of fresh and decayed plant material, the latter allowed to decay under water. That extensive decomposition of organic matter was tak-ing place in the mud substrates we sampled was indicated by the bubbles of hydrogen sulphide released when the sub-strates were disturbed. Lack of correlation between avallahle nitrogen and amount of apparent decaying organic matter might best be explained by assuming that the nitrogen was still bound to organic compounds rather than circulating as inorganic nitrates and nHrites. That the effect of a highly organic pond bottom on turtle growth might well function through increased production of certain aquatic insects with low dissolved oxygen requirements is unders,tood. We wish only to point out that turtles feeding under these circum-stances may also obtain a more nutritive detritus which may at least in part be responsible for a more rapid rate of growth. ACKNOWLEDGMENTS We are grateful to Dr. Edward 0. Moll for verifying the ages of some of our specimens and to Dr. Paul Meglitsch for reading the manuscript. The work of Mr. Quinn was sup-ported by a grant from the Iowa Academy of Science and other support was provided by Drake Research Council Grant No. 249-656 to Dr. Ohristiansen. LITERATURE CITED CAGLE, FRED R. 1946. The growth of the slider turtle, Pseudemys scripta elegans. Amer. Midl. Nat. 36:685-729. GIBBONS, J. WHITFIELD. 1967. Variation in growth rates in three populations of the painted turtle Chrysemys picta. Herpetologica 23( 4) :296-303. KNIGHT, ALLEN W. & J. WHITFIELD GIBBONS. 1968. Food of the painted turtle, Chrysemys picta, in a polluted river. Amer. Midl. Nat. 80(2):559-562. LAGLER, KARL F. 1943. Food habits and economic relations of the turtles of Michigan with special reference to game management. Amer. Midl. Natur. 29:257-312. LEGLER, JOHN M. 1960. A simple and inexpensive device for trapping aquatic turtles .. Utah Acad. Proc., 37:63-66. SEXTON, OwEN J. 1965. The annual cycle of growth and shedding in the midland painted turtle, Chrysemys picta marginata. Copeia 1965:314-318. 3Quinn and Christiansen: The Relationship Between Pond Bottom Type and Growth Rate of WestPublished by UNI ScholarWorks, 1971

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The Relationship Between Pond Bottom Type and Growth Rate of Western Painted Turtles Chrysemys picta belli in Iowa, a Preliminary Report

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