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Behavior of the zebra-tailed lizard during a total solar eclipse.

ABSTRACT. -- The behavior of ten Callisaurus draconoides in a 20 [m.sup.2] enclosure of natural microhabitat in Baja California Sur, Mexico, were monitored five days prior to and during a total solar eclipse on 11 July 1991. During the eclipse, lizard behavior was similar to that following sunset, but the short time-span of the eclipse did not allow all the lizards to assume sleeping shelters. Key words: behavior; Callisaurus draconoides; eclipse; lizard; Mexico.

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The changed behavior of birds (Elliot and Elliot, 1974), chimpanzees (Branch and Gust, 1986), rodents (Advani, 1981) and fishes (Pandey and Shukla, 1982) has been observed during solar eclipses, but similar data are not available for lizards. The zebra-tailed lizard, Callisaurus draconoides, is a medium-sized (55-75 millimeters snout-vent length) inhabitant of North American deserts (Asplund, 1967; Vitt and Ohmart, 1977; Stebbins, 1985). The purpose of this study is to report the behavioral changes of C. draconoides during a total solar eclipse.

MATERIALS AND METHODS

The study was conducted at "El Comitan", 17 kilometers west of La Paz, Baja California Sur, Mexico (24[degrees]08' N; 110[degrees]12' W). The area is a coastal lowland with loam-sandy soils covered with a xerophitic-scrub (Leon De la Luz and Troyo, 1985), composed mainly of the cacti Pachycereus pringlei, Macharocereus gummosus and the shrubs Jatropha cinerea and Fouqueria diguetti. The average annual temperature is 23.6[degrees]C, and the mean annual precipitation is 181 millimeters concentrated mostly in August and September (Hastings and Humprey, 1969; Garcia, 1983).

Ten adult Callisaurus draconoides from this desert scrub habitat were placed in a 20 [m.sup.2] enclosure (of similar habitat) surrounded by a metal wall 40 centimeters high. We monitored the behavior of the lizards twice daily, from 1034 to 1314 hr (the time interval of the eclipse on 11 July 1991) and at sunset (1909 hr) for five days prior to the eclipse.

On 11 July 1991 we recorded environmental characteristics at 10-minute intervals (Table 1) and continuously recorded the behavior of the individuals from 0909 to 1404 hr (Table 2). Air and soil temperatures, in both shade and sun were recorded with a remote sensor electronic thermometer (CIB-3), the incident and reflected solar radiation with a pyranometer, the humidity of the air with an electronic hygrometer (CIB-18), and the wind direction and speed with an anemometer.

RESULTS

Between 1000 and 1200 hrs during the five days before the eclipse, lizards avoided the open soil and spent most of their time in the shade of shrubs and rocks. The mean soil and air temperatures in the shade were 41.4[degrees]C, and 36.8[degrees]C, respectively. In direct sun, the mean temperature of the soil was 49.8[degrees]C, and the mean air temperature was 39.6[degrees]C.

After sunset, prior to the eclipse, the lizards retreated into sleeping shelters. They buried themselves at depths 1.2 to 2.5 centimeters below the loam-sandy soil surface (littered with leaves and debris) and near or underneath shrubs. At sunset the mean temperature of the soil in the shade was 38.7[degrees]C, and the mean air temperature was 31.2[degrees]C.

Changes in environmental factors were recorded during the eclipse (Table 1). Sudden decreases occurred in incident and reflected solar irradiation with the onset of the eclipse, but air and soil temperatures decreased slowly. Wind speed and humidity increased slightly and wind direction exhibited little change during total eclipse (6 min, 27 sec).

Table 2 shows the behavior of lizards during the eclipse period. These data are summarized in Fig. 1.

DISCUSSION

During the solar eclipse C. draconoides exhibited various postures associated with behavioral thermoregulation (Heath, 1965; DeWitt, 1971; Muth, 1977) and two lizards performed activities similar to those observed during sunset, i.e., they buried themselves below the soil surface (Grenot et al., In Press). However, the other eight lizards only became motionless, with eyes closed and bodies flat against the substrate.

[FIGURE 1 OMITTED]

The two buried lizards emerged from their subterranean retreats and became active following the eclipse, resuming behavior similar to that during the early hours of morning. However, because of the sudden increase of temperature and radiation from the nearly directly overhead sun, the lizards almost immediately took refuge in shaded places.

We conclude that, like other animal species (Delye, 1973; Lescure, 1975), individuals of C. draconoides became confused by a total solar eclipse and proceeded to perform the same behaviors as normally exhibited at the end of the day, during sunset. However, probably because of the short time-period of the total solar eclipse (6 min, 27 sec), most of the individuals (80%) failed to burrow into a subterranean sleeping shelter before the sunlight reappeared.
TABLE 1. Environmental characteristics recorded at the study site during
the total solar eclipse of July 11, 1991.

Hour Temperature ([degrees]C) Humidity Incident Reflected
 Air Soil rad. rad.
 shade sun shade sun % (w/[m.sup.2]) (w/[m.sup.2])

0909 32.3 34.7 36.5 43.3 33.7 499.9 99.1
0919 32.9 35.5 37.0 43.8 33.3 525.3 101.9
0929 33.3 36.0 37.5 44.8 32.9 550.2 105.8
0939 33.9 37.0 38.2 45.5 32.5 574.1 110.2
0949 34.5 37.7 38.4 46.1 32.1 596.3 114.5
0959 35.0 37.9 39.6 46.9 31.7 617.7 115.1
1009 35.8 38.9 39.9 47.9 31.3 638.2 119.1
1019 35.8 39.1 41.0 48.6 31.3 659.0 122.8
1029 36.4 39.1 41.4 49.4 31.3 677.4 123.5
1039 36.8 39.9 41.3 49.2 31.3 672.2 122.4
1049 36.8 39.7 41.9 49.0 32.1 630.3 112.5
1059 37.0 40.1 42.3 48.5 32.1 563.9 99.3
1109 37.0 40.1 42.5 48.0 32.5 475.2 82.3
1119 37.0 40.1 42.7 47.1 32.9 370.7 62.3
1129 36.6 39.9 42.1 46.9 33.3 255.0 41.1
1139 36.2 39.5 42.0 46.7 33.3 137.7 20.1
1149 35.4 38.8 42.0 46.3 34.1 30.3 1.2
1159 34.9 37.3 41.7 46.2 34.1 0.0 0.0
1209 34.3 36.8 41.0 45.5 34.1 57.2 5.9
1219 34.1 36.8 41.3 47.0 32.9 183.3 28.7
1229 34.1 37.0 41.2 47.6 31.7 304.1 50.5
1239 34.3 37.2 41.2 48.3 32.5 431.1 73.2
1249 34.7 37.8 41.0 48.6 32.5 548.4 94.5
1259 35.2 38.3 41.0 48.9 32.9 649.8 112.8
1309 35.8 39.0 41.3 48.8 33.3 730.7 127.9
1319 36.6 39.6 41.6 49.2 33.3 782.8 137.4
1329 37.2 40.2 41.7 49.3 34.9 790.6 136.9
1339 37.2 40.4 41.7 49.4 33.3 785.2 136.7
1349 37.4 40.5 41.9 49.2 36.4 774.3 133.0
1359 36.6 40.1 41.8 49.0 38.4 765.1 132.3
1404 36.4 40.0 41.9 49.1 39.2 758.7 132.3

Hour Wind Wind
 speed dir.

0909 1.0 SW
0919 2.8 SW
0929 1.7 SW
0939 2.0 SW
0949 1.5 SW
0959 0.7 SW
1009 2.1 W
1019 0.6 SW
1029 1.1 SW
1039 1.5 SW
1049 1.3 SW
1059 1.2 W
1109 0.8 SW
1119 0.8 SW
1129 1.1 NW
1139 1.1 SW
1149 1.1 W
1159 1.4 W
1209 1.5 W
1219 2.0 W
1229 1.6 W
1239 1.3 W
1249 1.7 W
1259 1.3 W
1309 0.8 W
1319 0.8 SW
1329 1.2 SW
1339 0.6 SW
1349 1.1 SW
1359 1.4 SE
1404 1.7 SW

TABLE 2. Behavior of the lizards during the total solar eclipse of July
11, 1991.

Hour Behavior recorded

10:00 Excepting lizard 7, which was on the sand directly under the sun
 and lizard 4 which had its forelegs on a small rock vertically
 positioned, all other individuals were located under the shade of
 shrubs and small rocks.
10:05 Lizard 3 moved 52 cm from below a shrub in the shade to a shaded
 place near a rock (pattern #1). Movements were fast out of the
 shade, but when it reached the shade the movements became
 sluggish. All the other individuals are practically without
 movement, sluggish in the shade.
10:08 Lizard 5 moves quickly 10 cm out of the shade and catches a small
 cricket and proceeds to eat it under the sun and moving the head
 vigorously from one side to the other.
10:09 Lizard 9 moved (pattern #1) 65 cm from one shaded point to
 another.
10:12 Lizard 7 moved 34 cm to the shade of a shrub. When it reached the
 shade it became sluggish.
10:14 Lizard 5 returned 15 cm to the shade.
10:34 Lizard 8 moved 40 cm from one shaded place to another
 (pattern #1).
10:58 Lizard 6 moved fast 30 cm to an open space and proceeded to eat a
 small hemipteran but the lizard did not perform vigorous
 movements of the head from side to side. Lizard 6 stayed in the
 sun.
11:16 Lizard 4 became flattened in the same position on a rock.
11:18 Lizard 2 closed its eyes.
11:20 Lizard 4 closed its eyes.
11:23 Lizard 8 buried itself under the soil exactly where it was. It
 buried itself under the soil by moving quickly all legs and
 moving the body from one side to other (pattern #2).
11:27 Following pattern #2 lizard 9 proceeds also to bury itself where
 it was lying. In both cases the lizards were finally located
 about 2 cm below the soil surface.
11:34 Two of the 10 lizards were buried below the soil; one was
 flattened to a rock and the other 7 were motionless with their
 bodies flat to the soil, with the eyes closed and underneath
 shrubs.
11:40 There was no movement.
12:17 All lizards same as at 11:34.
12:20 Lizard 2 moved 3 cm.
12:26 Lizard 5 executed pushups in the place where it was located.
12:28 Lizard 9 emerged to the surface.
12:36 Lizard 8 emerged to the surface.
12:40 Three lizards were active and the other 7 had their eyes open but
 were still motionless.
12:42 Excepting lizard 4 all the lizards move to the shade of shrubs
 and rocks.
12:54 All lizards are in shade, awake but inactive.


ACKNOWLEDGMENTS

This study was supported by the Centro de Investigaciones de Baja California Sur and the Consejo Nacional de Ciencia y Tecnologia of Mexico. We thank the Climatic Fluctuations Group of Centro de Investigaciones Biologicas de B.C.S. for providing the data of environmental characteristics during the eclipse and two anonymous reviewers for their valuable comments and suggestions on an earlier draft of the manuscript. Thanks go to L. Arriaga, P. Ortega, F. Alvarez, F. Vega, H. Romero, D. Vega, M. F. Vega, Fam. Diaz and G. Galilei for their patience during the experiment and to V. Hirales and L. Vazquez for typing the manuscript.

LITERATURE CITED

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Alvarez, M. 1991. Eclipse total de sol, 11 de Julio de 1991. Conciencia. Fac. Cienc. Univ. Auton. Baja Calif. Sur., 17 pp.

Asplund, K. 1967. Ecology of lizards in the relictual Cape flora, Baja California. Amer. Midl. Nat., 77:462-475.

Branch, J., and D. Gust. 1986. Effect of solar eclipse on the behavior of a captive group of chimpanzees (Pan troglotydes). Amer. J. Primatol., 11:367-373.

Delye, G. 1973. Observations sur le comportement des fourmis pendant une eclipse totale de soleil. C. R. Acad. Sc. Paris, 277:1533-1535.

DeWitt, C. B. 1971. Postural mechanisms in the behavioral thermoregulation of a desert lizard Dipsosaurus dorsalis. J. Physiol., 63:242-245.

Elliot, J. A., and G. H. Elliot. 1974. Observations on bird singing during a solar eclipse. Canadian Field Nat., 88:213-217.

Garcia, E. 1983. Apuntes de Climatologia. Universidad Nacional Autonoma de Mexico. Mexico, 153 pp.

Grenot, C. S. Alvarez-Cardenas and A. Ortega-Rubio (In Press). Sur le Comportement Thermoregulateur et les Sites Nocturnes de Repos de quelques Lezards de Basse Californe. Society Herpetologique de France.

Hastings, J. R., and R. R. Humprey. 1969. Climatological data and statistics from Baja California. Tech. Rep. Meteor. Climat. Arid Reg. No. 18. Inst. Atmosph. Phys. Univ. Arizona. Arizona, 96 pp.

Heath, J. E. 1965. Temperature regulation and diurnal activity in horned lizards. Univ. Calif. Publ. Zool., 64:97-136.

Leon De la Luz, J. L., and E. Troyo. 1985. Evaluacion de un novedoso sistema de riego en Baja California Sur. Pp. 100-103 in Proc. of I Conferencia Internacional sobre uso y preservacion de los recursos Biologicos Marinos y de zonas aridas. La Paz, Mexico.

Lescure, J. 1975. The effect of a total sun eclipse on the vocal behavior of some amphibians. Copeia, 1975:764-765.

Muth, A. 1977. Body temperatures and associated postures of the zebra tailed lizard, Callisaurus draconoides. Copeia, 1977:122-125.

Pandey, K. and P. J. Shukla. 1982. Behavioural studies of freshwater fishes during a solar eclipse. Env. Biol. Fishes, 7:63-64.

Stebbins, R. 1985. A Field Guide to Western Reptiles and Amphibians. Houghton Mifflin Co. Boston, 336 pp.

Vitt L. J., and R. D. Ohmart. 1977. Ecology and reproduction of lower Colorado River lizards: I Callisaurus draconoides (Iguanidae). Herpetologica 33:214-222.

ALFREDO ORTEGA-RUBIO, PATRICIA GALINA-TESSARO, AND SERGIO ALVAREZ-CARDENAS

Centro de Investigaciones Biologicas de Baja California Sur, Apdo. Postal No. 128, La Paz, BCS Mexico
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Author:Ortega-Rubio, Alfredo; Galina-Tessaro, Patricia; Alvarez-Cardenas, Sergio
Publication:The Texas Journal of Science
Geographic Code:1MEX
Date:May 1, 1994
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