Mar 10, 1994 - F. Mkxico, V. Rasgos de la vegetacibn y su clasificacion en la Cuenca del Rio Balsas. Rev. Soc. Mex. Hist. Nat. 8:95-114. MIRANDA,F., AND. X.
[Val. 51, No. 1
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1983. Forced copulation in waterfowl. Behaviour 86:250-294. MITCHELL,F. J. 1973. Studies on the ecology of the agamid lizard Amphibolorus maculosus. Trans. R. Soc. S. Aust. 97:47-76. SOKAL,R. R., AND F. J. ROHLF. 1981. Biometry, 2nd ed. W. H. Freeman, San Francisco. STAMPS,J. 1983. Sexual selection, sexual dimorphism, and territoriality. Pp. 169-204. In R. Huey, E. Pianka, and T. Schoener (Eds.), Lizard Ecology-Studies of a Model Organism. Harvard University Press, Cambridge, Massachusetts. THORNHILL, R. 1980. Rape in Panorpa scorpionflies and a general rape Anim. Behav. 28: - hypothesis. .52-59. THORNHILL. R.. AND 1. ALCOCK. 1983. The Evolution of Insect Systems. Harvard University Press, Cambridge, Massachusetts.
THORNHILL, R., AND K. P. SAUER.1991. The notal organ of the scorpionfly Panorpa vulgaris: An adaptation to coerce mating duration. Behav. Ecol. 2:156-164. WERNER, D. I. 1978. On the biology of Tropidurus delanonis, Baur, (Iguanidae). Z . Tierpsychol. 47: 337-395. WILLIAMS, G. C. 1966. Adaptation and Natural Selection: A Critique of Some Current Evolutionary Thought. Princeton University Press, Princeton, New Jersey. WITTENBERGER, J. F. 1981. Animal Social Behavior. Duxbury Press, Boston.
Accepted: 10 March 1994 Associate Editor: Richard Howard
ati in^
Herpetologica, 51(1),1995, 2 4 3 3 O 1995 by The Herpetologists' League, Inc
REPRODUCTIVE BIOLOGY OF THE LIZARD UROSAURUS BICARINATUS BICARINATUS (REPTILIA: PHRYNOSOMATIDAE) FROM RIO BALSAS BASIN, MEXICO AURELIORAM~REZ-BAUTISTA,'ZEFERINO U R I B E - P E ~ A , ' AND LOUISJ. GUILLETTE, JR.~
'Laboratorio de herpetologia, Departamento de Zoologia, lnstituto de Biologia,
UNAM, A. P. 70-153 C . U . , C.P. 04510, Mdxico 20, Distrito Federal, Mdxico
2Department of Zoology, University of Florida,
Gainesville, FL 3261 1 , USA
ABSTRACT: We studied the reproductive biology of two populations of the arboreal lizard Urosaurus b. bicarinatus from 1980-1984 in western MAxico. One population is located in the elevated portion of the Rio Balsas Basin, in the state of Morelos, and the other at a lowland site of the basin in the state of Michoacin. Data were obtained from specimens collected in the field and from museum collections. Females and males of both populations exhibit a pattern of late spring and summer reproduction. Males show maximal testicular volume and activity during the late spring and summer months in Michoacin and during the spring and summer months in Morelos. Vitellogenesis begins in April in both populations, with most females ovulating in the summer. Incubation occurs during the summer with hatching in late summer and early fall. Individuals reach sexual maturity within a year. Mean clutch size for oviductal eggs was 7.7 2.4 and 6.7 1.8 in populations from Morelos and Michoacin respectively. No correlation between snout-vent length of females and clutch size was found.
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Key words: Reptilia; Sauria; Phrynosomatidae; Urosaurus bicarinatus; Reproduction; Oviparity; Life-history; MBxico
VARIATION in reproductive patterns in numerous reptilian species has been well documented, and a great diversity of life history characteristics has been recorded (Dunham and Miles, 1985; Licht, 1984;
Vitt, 1986). Since the classic studies of Tinkle (1969) and Tinkle et al. (1970) on life history evolution of lizards, additional ideas have been formulated to explain life history patterns. These patterns have been
March 19951
HERPETOLOGICA
recently reviewed (Dunham et al., 1988; Miles and Dunham, 1992; Shine and Charnov, 1992; Stearns, 1984). These studies have found that most ph~logeneticvariance effects occur at the familial level. Life history studies attempt to explain variation on age at maturity, fecundity, and longevity within and among populations. The differences in life histories between syntopic, congeneric species can be minor, and sometimes less than the differences between geographically separated populations of one species (Ballinger, 1979; Dunham, 1982; James, 1991). However, syntopic, congeneric species can also differ strongly in their life histories (James, 1991; Tinkle and Dunham, 1986). Seasonal and annual fluctuations of several environmental variables can also induce proximate variation in life history traits (Dunham, 1982). These variables, which include food availability, precipitation, and temperature, can affect growth rate (Dunham, 1982), clutch size (Ballinger, 1977; Dunham, 1982), clutch frequency (Dunham, 1982;Jones et al., 1987), and age and size at maturity (Dunham, 1982; Tinkle, 1972). Variability in reproductive characteristics, such as the period of reproductive activity, clutch size, clutch frequency, age at maturity, and egg size in Urosaurus ornatus are usually associated with variation in resource availability, temperature, rainfall, and food (Ballinger, 1976, 1977; Dunham, 1980, 1981, 1982; Martin, 1977; Michel, 1976; Vitt et al., 1978). While there has been a recent interest in the reproduction of several temperate and tropical species of lizards (Ferguson et al., 1990; Patterson, 1991; Shine, 1983), little has been published on the reproductive biology of the arboreal lizard Urosaurus b. bicarinatus. Its distribution ranges from the mountains of Michoacin to the center of Guerrero and into Rio Balsas south to Puebla. To date, there are only anecdotal notes concerning the general biology of this species by Alvarez del Toro (1982), Castro and Aranda (1984), and Fitch (1970). In this study, we focus on the male and
25
female reproductive cycle of two populations of Urosaurus b. bicarinatus in the Rio Balsas Basin in Mbxico: one in the state of Michoacin and the other in the state of Morelos. Utilizing data collected over several years, we investigated the following questions. (1) How much variation exists between the two populations with regard to the reproductive cycle? (2) Is there a correlation between peak reproductive activity of both populations and environmental factors (temperature, photoperiod, and rainfall)? (3) Does the clutch size vary with female size? (4) What is the frequency of clutches?
Study Area We obtained the data for the population from Michoacin from individuals collected in an area called Rancho "Paso del Chivo" located on HWY 37 (km 219) that connects Apatzingan with Playa Azul, 35 km northwest of Presa El Infiernillo at an elevation of 350 m. The study area contains several hills and small valleys located near 18'35' N and 101'55' W. The site belongs to the Municipio de Arteaga in the lower Balsas-Tepacaltepec Basin. The climate is semi-arid with rains in the summer. The mean annual temperature is 28 C with an average annual rainfall of 700 mm (Garcia, 1980; Garcia and Reyna, 1969). The dominant vegetation is thorn bush and large cacti which reach > l o m in height (Miranda, 1974; Miranda and Hernindez, 1963; Uribe et al., 1981). We obtained the data for the population from Morelos from specimens collected in the south of the state: in Amacuzac, Puente de Ixtla, Zacatepec, Jojutla de Juirez, and Tepalcingo Counties (18'30' N and 99'30' W). The area is situated on the elevated portion of the Rio Balsas Basin (1000 m). Topography is characterized by numerous valleys and hills. The area has a warm, subhumid climate with a mean annual rainfall of 838 mm and a temperature of 24 C (Garcia, 1980). The dominant vegetation is subhumid tropical forest (Castro and Aranda, 1984; Rzedowski, 1978). An-
26
HERPETOLOGICA
nual mean temperature, photoperiod, and precipitation over a 10-yr period in the study areas are shown in the Fig. 1. Reproductive Analysis Specimens were collected during 19801984 and were captured by hand and rubber bands. We captured 490 lizards: 301 from Morelos (155 adult males, 94 adult females, 46 juveniles and six neonates) and 189 from Michoacin (83 adult males, 76 adult females, 22 juveniles, and eight neonates). Samples of both sexes were obtained systematically during each month of the year. Lizards were most active during the summer, with less activity during the winter months (December, January, and February). All lizards were killed and fixed in the field (10% formalin) and transported to the laboratory where the gonadal analysis was performed. The following linear measurements were taken to the nearest 1 mm on necropsied lizards: snout-vent length (SVL), tail length, width of left and right testis, diameter of oviductal eggs, and the diameter of vitellogenic and non-vitellogenic follicles. The number of nonvitellogenic and vitellogenic follicles and/ or oviductal eggs was also recorded. We used the length and width of the testes to obtain testicular volume (V) as calculated using the formula for the volume of an ellipsoid (Selby, 1965):V = 413 ra2b,where "a" is one-half the shortest diameter and "b" is one-half the longest diameter. Testicular volume was used as an indicator of the reproductive activity of males. We tabulated these indices for all individuals to obtain a monthly mean and standard error. We performed one-way ANOVA and Scheffe's F-test to determine significant differences among monthly values. We calculate a Pearson's product-moment correlation coefficient to determine if a relationship existed between clutch size and SVL of females, and between gonadal activity and environmental conditions in both sexes during all months. The smallest female containing enlarged vitellogenic follicles or oviductal eggs was used to indicate the minimum SVL at maturity. Clutch size was determined with the eggs found in the oviduct of adult females dur-
[Vol. 51, No. 1
ing the reproductive season. The second clutch was established by the presence of oviductal eggs and growing vitellogenic follicles in the ovary in the same individual lizards. Reproductive potential, as used here, is the average number of eggs produced in 1 yr by one female. We established minimum SVL at maturity for males by the presence of enlarged testis (25 mm3). Individual growth was calculated by comparing the mean SVL of all individuals of three samples taken in August, September, and October-November in Morelos, and in August, September, and November-December in Michoacin. We used a = 0.05 to assess statistical significance. Results are expressed as means zk 1 SD. RESULTS The distribution of body size (SVL) of adult males in the population from Morelos exhibited a mean length of 51 3.9 mm (41-65 mm, n = 155), which was not significantly larger than the mean SVL of the females (% = 47.2 3.1 mm, 40-53 mm, n = 94: t = 0.571, P > 0.05). In the population from Michoacin, adult males exhibited a mean SVL of 53 4.6 (41-61 mm, n = 83), which was not significantly (t = 0.847, P > 0.05) larger than the mean SVL of females (2 = 47 2.6 mm, 40-51 mm, n = 76).
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Reproductive Cycle In both populations, testes of male lizards showed a seasonal regression and recrudescence (Fig. 2). Significant increases in testicular volume of U . b. bicarinatus from Morelas occurred during March and April and decreases occurred between August and September ( F ,,,,, = 65.37, P < 0.001). Males exhibited maximal testicular volume during April, May, July, and August (n = 90.6 mm3). Similar changes in testicular volume ( F , , , = 60.00, P < 0.001) were found in the population from Michoacin during the year. Testicular recrudescence began in April with peak gonadal volume occurring from May-August. A significant decline in gonadal size occurred during August, with continued testicular regression during the fall and winter. The period of maximal testicular growth of the
March 19951
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HERPETOLOGICA
MORELOS 200
-E E
150-
Y
z 0
t
100-
g a
P
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+TEMPERATURE ?C)
PRECIPTATION (rnrn)
J
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PRECIPITATION (rnm)
J
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FIG.1.-Monthly mean temperature, precipitation, and photoperiod for the study areas: (Top) Morelos and (Bottom) MichoacPn.
populations from Morelos and Michoacin was positively correlated with increasing photoperiod (r = 0.888, P < 0.05;r = 0.834, P < 0.05, respectively) and ambient tern-
perature (r = 0.830, P < 0.05; r = 0.929, P < 0.05, respectively), but not with precipitation (r = -0.195, P > 0.05; r = 0.145, P > 0.05, respectively).
28
HERPETOLOGICA MORELOS 10
120
J
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* MALES
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MONTHS -"i MALES
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FEMALES
FIG.2.-Monthly changes in testicular and ovarian activity throughout the reproductive cycle from two populations of the lizard Urosaurus b. bicarinatus: (Top) Morelos and (Bottom) Michoacin. Data are presented as f ? 1 SD. Values having different superscripts have significantly different.
We used 155 adult males of the population from Morelos for this study, and all specimens (n = 105) collected between the end of March and mid-September showed evidence of reproductive activity. Sexually mature males ranged in size from 41.065.0 mm SVL (f = 51.0 3.9).Of 83 adult males in the population from Michoacin, all adults collected between April and midAugust (n = 54) exhibit evidence of reproductive activity; SVL averaged 53.0 4.0 mm (range 41.0-61.0). All specimens collected during the peak of the reproductive season were 41 mm SVL or more, suggesting that reproductive maturity occurs in their first reproductive season after hatching at an age of 9-10 mo in both
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IVol. 51. No. 1
populations, except two females from Morelos collected in June were 33 mm SVL. Females of the population from Morelos exhibited reproductive activity from early spring to late autumn. Females having vitellogenic ovarian follicles occurred from the end of February to mid-September, and the peak of reproductive activity occurred during June and July (Fig. 2). Average follicular diameter increased in February, decreased between February and April, increased again between May and July, and decreased in August (F,,, = 25.50, P < 0.001). In Michoacin, follicular diameter increased from March-April, reached a maximum between May and August, and decreased during September (F,, = 36.09, P < 0.001). We used 94 adult females from Morelos for this study. Three of six females caught in February, with SVL ranging from 37.047.0 mm, contained vitellogenic ovarian follicles (X = 4.0 mm3, range = 3.0-6.0). Of 34 females collected during April and May, a small portion (five) of the females had yolking ovarian follicles. During June and July, 11 of 22 adult females (SVL 40.053.0 mm) had yolking follicles (2 = 4.0 -11.0 mm3, range = 3.6-6.0 mm3) whereas nine females had oviductal eggs (X= 8.0 mm3, 1 SD = 1.3, 6.0-10.0 mm3) and two females (SVL 33 mm) were non-reproductive. Of 16 females caught in August and September, four had vitellogenic follicles (Fig. 3). We used 76 specimens to calculate the reproductive condition of adult females from Michoach. One of seven females collected during April showed evidence of vitellogenic follicles whereas during May and June, of 36 females collected, 21 exhibited vitellogenic follicles and 11 had oviductal eggs. Of 10 females caught during August, six had oviductal eggs and one had vitellogenic follicles. Of 10 females collected in September, only one had vitellogenic follicles (Fig. 3). Vitellogenesis and follicular growth of the population from Morelos were positively correlated with increasing photoperiod (r = 0.613, P < 0.05) and with precipitation (r = 0.502, P < 0.05), and were negatively correlated with decreas-
HERPETOLOGICA
March 19951
29
ing ambient temperature (r = -0.546, P < 0.05). A similar pattern occurred in the population from Michoacin [photoperiod (r = 0.732, P < 0.05),ambient temperature (r = 0.656, P < 0.05),and precipitation (r = 0.463, P < 0.05)].
MORELOS
Clutch Size and Frequency We made estimates of clutch size in the populations from Morelos and Michoacin from eggs or vitellogenic follicles counted in 32 and 41 females, respectively. The clutch size of the population from Morelos obtained from vitellogenic follicles was 3 = 7.7 2 1.8 (range 3-1 1, n = 23), and five of these females also had oviductal eggs [f = 7.8 2.4, (3-8)]. However, nine females had only oviductal eggs: i= 7.7 2.4 (range 5-1 1, n = 9). The mean clutch size of 17 females from Michoacin that had vitellogenic follicles was 7.0 1.5 (3-9), seven of these females showing vitellogenic follicles in the ovaries (= i5.8 f 1.1, 3-7) and oviductal eggs simultaneously (3 = 7.2 1.6, 2-9). However, females that had only oviductal eggs [= i6.7 1.86 (2-9), n = 171, the number of oviductal eggs was not significantly different from the mean number of vitellogenic follicles ( P > 0.05). The female size was not related to clutch size in either Morelos (r = 0.337, P > 0.05),or Michoacin (r = -0.014, P > 0.05). Some females in both populations laid at least two clutches during the reproductive season. We observed empty, enlarged oviducts and corpus lutea, which characterize oviposition, in samples collected early in May, June, and July. The majority of females from Morelos that we analysed from 9-26 June, and again from 5-27 July, had vitellogenic follicles and oviductal eggs. The first hatchlings were observed from 8-15 August and a second set of hatchlings was noted on 10 September. These data suggest that eggs probably remain in the oviduct for 16-22 days and the incubation period is approximately 4350 days in both populations. The mean reproductive potential of U . b. bicarinatus from Morelos was 15.5 eggs in two clutches during the reproductive season, whereas in the Michoacin popu-
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fell fall c l e ~
Viiell Falltcles
L 3 Eggs
FIG.3.-Seasonal distribution (percent) of female Urosaurus b. bicarinatus in each of the three reproductive states of both populations; sample sizes are above bars.
lation the mean reproductive potential was 13.0 eggs in two clutches.
Growth Mean SVL of neonates at birth from the Morelos population in August was 23 2.0 mm (20-25, n = 6). In September, the mean length of juveniles had increased to 30 2.0 mm (26-32 mm, n = 7). These data suggest that young born during the summer exhibited a growth rate 0.23 mm/ day. Juveniles in a third sample obtained during early November had a mean SVL of 33 mm 2.2 mm (31-37 mm, n = 8), indicative of a growth rate of 0.05 mm/ day. Mean SVL of newly hatched young in August in population from Michoacin was 25 2.3 mm (21-27 mm, n = 8). In September, mean length of juveniles had in-
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HERPETOLOGICA
30
creased to 31.2 .+ 1.8 mm (28-34 mm, n = 9). These data suggest that young born during the summer exhibited a growth rate 0.21 mm/day. A third sample obtained during November and December had a mean SVL of 34.5 3.0 mm (30-39 mm, n = 8), indicative of a growth rate of 0.03 mm/day. These data suggest that the growth is rapid in the summer and early fall and slower in late fall in both populations. Furthermore, these data support the hypothesis that, for individuals of U . b. bicarinatus, size at sexual maturity is reached within a year or less.
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DISCUSSION The reproductive biology of U . b. bicarinatus from the high elevation Rio Balsas site in Morelos differs only slightly from the low elevation site in Michoacin. Reproductive period for both populations is seasonal with a slight extension on reproductive activity of females and males at the site in Morelos. Reproduction, however, apparently terminates during September in both populations. In Morelos, the longer reproductive activity, and greater clutch size, reproductive potential, juveniles growth rate, and SVL of adult females may be influenced by the higher mean annual precipitation (838 mm in Morelos versus 700 mm in Michoacin). Ballinger (1977) and Dunham (1978,1980, 1981,1982) demonstrated that food abundance is strongly correlated with precipitation and that variation in resource abundance is related to variation in life-history characteristics of U. ornatus. This could also be the case in the population of U . b. bicarinatus from Morelos. Larger size at hatching and larger adult males were found in the population from Michoacin than in the one from Morelos. These variations in life-history characteristics are most likely a demographic response to differences in the environment experienced by both populations. The reproductive activity period described here for U . b. bicarinatus is similar in length to the populations of U . ornatus (Dunham, 1982; Martin, 1977; Michel, 1976; Tinkle and Dunham, 1983; Van
[Vol. 51, No. 1
Loben Sels and Vitt, 1984) and U. graciosus (Vitt et al., 1978). The slightly extended period of reproductive activity in the population from Morelos appears to be a response to its environment. Temperature and photoperiod are correlated with gonadal size of males in both populations, as has been found in other reptiles (Duvall et al., 1982; Marion, 1982). Temperature and ~hotoperiodare known to influence the stimulation, maintenance, and regression of gonadal activity (Licht, 1984; Marion, 1982). Whereas follicular activity is correlated with photoperiod, precipitation, and temperature in Michoacin, this was not the case for Morelos. Rainfall may be the main factor that influences gonadal activity of females. In Morelos, the rainy season starts between March and April and finishes in November and is not as variable as in Michoacin. During the rainy season, productivity of insects is high and may directly influence the reproductive dynamics of the populations. The increase in vegetational growth supports a great diversity and abundance of herbivorous insects. This increase in resources provides abundant energy for insectivorous lizards. Several authors have suggested that a positive correlation exists between insect abundance and clutch frequency, clutch size, and reproductive potential in lizards (Ballinger, 1977, 1979; Dunham, 1982; Martin, 1977; Parker and Pianka, 1975).Cole (1954) pointed out that females could maximize their fitness by producing clutches early in their lives and early in the season. The abundance of resources produced in response to rainfall allows lizards a suitable period of maintenance and growth, but is mainly responsible for successful reproduction (Andrews et al., 1983; Ballinger, 1977; Lister and Garcia-Aguayo, 1992; Stamps and Tanaka, 1981). Data for both populations showed that most adult females produced one clutch and some laid two clutches. However, some individuals could have laid three clutches per season (Table 1). A similar pattern has been recorded in U . ornatus (Ballinger, 1977; Dunham, 1982; Michel, 1976; Tinkle and Dunham, 1983; Van Loben Sels and
March 19951
TABLE 1.-Means
HERPETOLOGICA
31
2 1 SD for reproductive characteristics of the populations of Urosaurus bicarinatus from Morelos and Michoacin.
Characteristics
Peak activity males Peak activity females Incubation Hatching First clutch size Second clutch size Reproductive potential SVL at hatching (mm) SVL at maturity (mm) SVL adult female (mm) SVL adult males (mm)
Morelos
Michoah
spring-summer spring-summer summer summer-fall 7.7 t 1.8 (3-11; n = 23) 7.8 t 2.4 (3-8; n = 5) 15.5 23 -+ 2.0 (20-25; n = 6) 40
27 (40-53)
51 (41-65)
Vitt, 1984). The reproductive potentials in the populations from Morelos and Michoacin were 15.5 and 13.0 eggs, respectively assuming two clutches, somewhat more than for U . ornatus (Van Loben Sels and Vitt, 1984). Urosaurus b. bicarinatus clearly belongs to a group of lizards in which members have short lives, early maturity, and multiple clutches (Tinkle et al., 1970). Several studies have suggested that U. ornatus is r-selected, although in some years it exhibits life-history characteristics that suggest that it is K-selected (Ballinger, 1976, 1977; Tinkle and Dunham, 1983). Given the life-history characteristics of the populations of U. b. bicarinatus from Morelos and Michoacin, it would be characterized as r-selected. In general, the reproductive pattern, as well as reproductive activity period, clutch size, clutch frequency, reproductive potential, SVL at hatching, and SVL at maturity, exhibited by both populations of U . b. bicarinatus are similar to other, phylogenetically related North America lizards (Ballinger,1977;Dunham, 1981,1982; Tinkle and Dunham, 1983). Thus, we suggest that the reproductive patterns of both populations are due both to phylogenetic conservatism (Miles and Dunham, 1992; Shine and Charnov, 1992) and to environmental factors (Dunham, 1982).
RESUMEN La biolOgia re~rOductiva de dOs poblaciones de la lagartija arboricola Urosaurus b. bicariuntus fui?estudiada durante 1980-
spring-summer spring-summer summer summer-fall 7.2 t 1.6(3-7; n = 8) 5.8 t 1.1 (3-7; n = 8) 13.0 25 -t 2.3 (21-27; n = 11) 40 47 (40-51) 53 (41-61)
1984. Una de las poblaciones se localiza en la parte alta de la Cuenca del Rio Balsas, en el Estado de Morelos y la otra en la parte baja, en el Estado de Michoacin. Los datos fueron obtenidos de especimenes colectados en el campo y de colecciones de museos. Hembras y machos de ambas poblaciones presentaron un patr6n reproductivo de fines de la primavera y verano. Los machos mostraron actividad reproductora y volumen testicular miximo a fines de la primavera y verano en Michoacin y durante toda la primavera y verano en la poblacibn de Morelos. La vitelogknesis se inicii, en abril, y la mayoria de las hembras de ambas poblaciones ovularon en verano. Los huevos son incubados en el verano y 10s nacimientos a fines de verano y a principios de otoiio. Los individuos alcanzaron la madurez sexual antes del afio. La media del tamafio de la nidada de 10s huevos en el oviduct0 fue de 7.7 2.4 y 6.7 1.8 en la poblaci6n de Morelos y Michoacin respectivamente.
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Acknowledgments.-We thank R. Castro-Franco (UAM) for allowing us to examine specimens under his care and B. Lister, R. Jaeger, D. Formanowicz, Jr., M. Benabib, E. Naranjo-Garcia, G. GutibrrezMaybn, M. Feria, and three anonymous reviewers for critical comments and suggestions on an earlier version of the manuscript. F. Villegas assisted with a graph.
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BALLINGER, R. E. 1976. Evolution of life history cin. Bol. Inst. Geografia, Universidad Nacional Au-
strategies: Implications of recruitment in a lizard t6noma de MBxico, Mexico 2:59-88.
population following density manipulations. SouthJAMES,C. D. 1991. Population dynamics, demogwest. Nat. 21:203-208. raphy, and life history of sympatric scincid lizards . 1977. Reproductive strategies: Food avail(Ctenotus) in Central Australia. Herpetologica 47: ability as a source of proximal variation in a lizard. 194-210. Ecology 58:628-635. JONES,S. M., R. E. BALLINGER, AND W. P. PORTER. . 1979. Intraspecific variation in demogra1987. Physiological and environmental sources of phy and life history of the lizard. Sceloporus jarrovi variation in reproduction: Prairie lizards in a food along an altitudinal gradient in southeastern Aririch environment. Oikos 48:325-335. zona. Ecology 60:901-909. LICHT, P. 1984. Reptiles. Pp. 206-282. In G. E.
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Herpetologica, 51(1), 1995, 3 3 3 8
O 1995 by The Herpetologists' League, Inc.
FECAL SCENT MARKING IN THE WESTERN BANDED
GECKO (COLEONYX VARIEGATUS)
GEOFFREY C.
CARPENTER',^ AND
DAVIDDUVALL'.~
'Department of Zoology and Physiology, University of Wyoming, Laramie, WY 82071, USA ABSTRACT:We examined the phenomenon of feces confinement in western banded geckos (Coleonyx oariegatus). Discrete "defecatoria" (preferred defecation sites) were observed for both males and females housed individually. Lizards tended to establish defecatoria away from their own diurnal resting sites as well as areas marked by conspecifics. Geckos formed more compact defecatoria when introduced into an arena marked by a member of the opposite (versus the same) sex, suggesting the presence of sex-specific fecal cues. Responses to extracts of feces suggest that chemical cues are important in mediating defecation patterns and that geckos are able to recognize the scent of their own feces. Defecatoria may serve to reduce predation pressure or as social "signposts" where geckos obtain information concerning conspecifics. Key words:
Coleonyx uariegatus; Chemical signal; Eublepharinae: Gecko
CHEMICAL signals are important in the spacing and social behavior of a variety of animals (Gosling, 1982; Stoddard, 1980). Many reptiles rely on the use of such signals in their life histories (reviewed by Mason, 1992), and lizards are no exception.
For example, chemical cues are utilized by the skink Eumeces laticeps in discrimination of prey odors (Cooper and Vitt, 1986a, 1989), eliciting male courtship behavior (Cooper et al., 1986), and species identification (Cooper and Vitt, 1986b,c). Cooper (1989) concluded that the autarchoglossans Heloderma suspectum and PRESENT ADDRESS: Department of Biology, Col- Varanus exanthema ticus rely on discrimorado State University, Fort Collins, CO 80523, USA. ination of prey odors in their foraging ac"RESENT ADDRESS: Life Sciences Program (2352), Arizona State University West, P.O. Box 37100, Phoe- tivities. Western banded geckos (Coleonyx variegatus) use chemical cues in sexual nix, AZ 85069-7100, USA.
