Asiatic Herpetological Research

1997

Vol. 7. pp. 153-165

Varied and Fluctuating Foraging Modes in Nocturnal Lizards of the Family

Gekkonidae

Yehudah L. Werner

1 -Shigeru Okada 2 Hidetoshi Ota 3,,

Gad Perry 4 and Shoji

TOKUNAGA 5
Department of Evolution, Systematics and Ecology, The Alexander Silberman Institute of Life Sciences, The

Hebrew University of Jerusalem. 91904 Jerusalem, Israel; Kagoshima Environmental Research & Services, 2-7
Masago-cho, Kagoshima-shi, Kagoshima 890, Japan; Tropical Biosphere Research Center and Department of
Biology. University of the Ryukyus, Nishihara, Okinawa 903-01 .Japan; Department of Zoology, University ofTexas, Austin, TX 78712-1064. USA;1

Department of Public Health. School of Medicine, Kyushu University, 3-1Maidashi, Higashi-ku, Fukuoka SI 2. Japan

Abstract. -Heliothermic lizards have been used as model organisms in studies of foraging mode, although their

behavior is generally complicated by thermoregulation. Tropical nocturnal gekkonid lizards could be bettermodels than temperate diurnal lizards. In several recent reviews, gekkonids have been considered to be sit-andwait (ambush) predators. Observation of Gekko hokouensis, G. japonicus and Teratoscincus roborowskii in thefield on warm nights revealed that by the measure of moves-per-minute they are sit-and-wait (SW)predators butby the measure of percent-time-moving G. hokouensis is widely-foraging (WF), as is Coleonyx variegatus,
according to the literature. The behavior of individuals of all three species combines to varying extent both SW

andWF modes. This observation accords with recent reports of foraging behavior in G. gecko and Stenodactvlus

doriae. Reexamination of the original literature sources quoted in recent reviews showed that these sources had

WF

or mixed strategists. The fluctuating foraging mode ofalready qualitatively described many geckos as either
geckos presumably enables these noctural visual predators to locate stationary prey and. without wasting

WF modes may depend on the
SW predators, their relative clutch

locomotor energy, to locate mobile prey. The option to employ both SW andabsence of competition. Although geckos as a group had been believed to bemass (RCM) had often been believed to be as small as in WF lizards. More recently, several geckos were showntohave larger RCMs. Hence geckos, rather than having a paradoxically low RCM. areintermediatein fact

between SW and WF lizard groups in both RCM and foraging mode.

Key words: Reptilia, Lacertilia, Gekkonidae, Gekko hokouensis, Gekko japonicus, Teratoscincus roborowskii,
China, Japan, foraging mode, nocturnality. relative clutch mass.

Introduction

assumptions that there

Ever since they were first coined by Pianka (1966).
the terms "sit-and-wait"(SW) and "widely foraging"(WF) have been used extensively to describe foraging
behavior. Often they have been considered alternative
states of adichotomy (Pianka. 1986; McLaughlin.
1989; Etheridge and Wit. 1993; and references in

Pietruszka, 1986). while some authors have viewed
them as extremes of a continuum (Pianka. 1974:203;

Pietruszka, 1986; Perry etal.,1990). Although Vittand Congdon (1978) and Vitt (1990) recognized thepossibility of acontinuum of foraging modes, theirSW

WF

foragers)

areandlizpapers highlight differences between
ards. Implicit in the use of these terms (or the equivalent"ambush"and"active"theislittleintraspecific or intra

individual variation in foraging behavior.

Lizards have been used often as models for studying the foraging behavior of animals in the field. The
two commonest coins for quantification and compari-son have been the "percent time moving"! PTM) and"movements per minute" (MPM, see below) (Hueyand Pianka, 1981; Perry et al., 1990).

Going by such
eitherSW or WF.

isthe foraging mode,
usually considered typical of ayardsticks,

whole lizard family. Thus, Agamidae, Anguidae andlguanidae (s.L), unless herbivorous, areSW foragers,

whereas almost all Lacertidae, Scincidae, Teiidae andVaranidae are
et al..

WF (Huey and Pianka. 1981; Dunham

1988; Green and King, 1993; Cooper. 1994a, b).

Asiatic Herpetological ResearchVol. 7, p. 154

The

1997

underlying this classification obviously presuppose that the observations quantified hadments per minute", the average number of times,
during one minute, that a lizard changed its locomo-been free of socially-motivated (Regal, 1983:1 16) andtory state from "stationary" to "moving";of thennoregulation-related (Anderson, 1993) behav-

cent time moving" percentage of the total time, thatthe animal spent locomoting; percra. percents of ra;

studies

Whereas it is relatively easy to account for theformer (Kingsbury, 1989), it is often difficult to comior.

rostrum-anusra.

("snout- vent")

PTM, "per-length(Werner,1971); RCM. relative clutch mass, ratio of total clutch

pletely exclude the latter when observing diurnal
poikilotherms such as lizards. Nocturnal lizards suchmass to total maternal mass, including the clutch (Vittas geckos can thus provide superior models of forag-

and Price, 1982); SD, standard deviation; SW,

ing mode if observed in a climate with stable night

and-wait" predator; WF, "widely ranging forager".

"sit-

temperatures approximating those preferred by the

Data Collection

lizards.

The Gekkonidae have traditionally been considered

SW predators (Pianka. 1986:48; Dunham etal..

1988:513), and this view appears somewhat supported

by recent observations on Gekko gecko (Stanner et al..

However, Coleonyx variegatus employs anintermediate stragtegy (Kingsbury. 1989) and someothers have recently been counted as active foragers
in press).

(Cooper, 1994a,b).

Thus it remains unclear whether

Environmental factors such as illumination can affectthe activity of nocturnal geckos (Frankenberg. 1979:

Frankenberg and Werner, 1979; Bouskila et al., 1992;
Petren et al., 1993). We therefore detail the circumstances of the observations.

Observations were made at night by one observer
carrying an electric torch with a removable cover of
red cellophane paper (two layers). When the torch was

the Gekkonidae are characterized by a given foraging

held on the observer's forehead, Teratoscincus couldmode, as are other lizard families, and. if so, what thatbe located on the ground by their reflecting reddish
eyeshine. With both Gekko species, which were

foraging mode is.

This issue is of particular interest because whereas

observed mainly on walls, this method was superflu-

m for Tera-

SW lizards usually have greater relative clutch masses

ous. Searching began at a distance (>20

(RCMs) than WF lizards (Vitt and Congdon,

toscincus; less for the Gekko species) with white light.

1978).

geckos tend to have RCMs similar to those of WF
Lizards (Vitt and Price, 1982: figs.
and 3). This1

putative paradox cannot be explained fully as an adap-

The main observations were made from 3-10 m,
depending on species and situation, with red light. We
endeavoured to observe each individual for 30 min-tation of geckos to life in crevices (Vitt, 1981): small

utes; finally the gecko was approached and examined.

RCMs occur also in cursorial, arenicolous species ofIn all three species,

geckos (Vitt and Price, 1982: Werner, 1989): in someof these this could be a phylogenetic constraint (Vitt.

individuals was towards the observer, hence presum-

1986: Stearns, 1992) but presumably at leastprimitive group of Eublepharinae (Kluge.

in the1967:

Werner. 1972) this would not be the case. Hence additional

data on the foraging

modes of geckos

are

ably

the

Therefore, we report here on the foraging behavior

observer did not affect them(following

Anderson. 1993).

To enable prompt photography, the observer carcamera (Leica M3 with 135 mm lens)ried a readywith flash and mostly Agfachrome Professional 200

ASA

needed.

some of the locomotion of thefilm.

Air temperature

Miller- Weber

mercury

was recorded with athermometer("Schultheis"m above ground (for Teratoscincus also cmof three nocturnal geckos in the eastern Asian sum-

type)mer, Gekko hokouensis, G.japonicus, and Teratoscin-above ground, and substrate temperature was also
taken). Illumination was recorded with a Lunasix-3

cusroborowskii.

Wepay particular attention

to

1

1

intraspecific variation, which has been reported in the(Gossen) light meter.

foraging behavior of some other lizards (Pianka et al„
1979; Kingsbury. 1989: Perry. 1996). and to intra-

recorded into a microcassette recorder (Panasonicindividual

variation,

a

topic

which has not beenaddressed previously.

Materials and Methods
Abbreviations and Definitions
CV, coefficient of variation (standard deviation as percent of mean); FM. foraging mode: MPM, "move-Observations

andenvironmental

data

were

RN-102). When the information was transcribed on
paper, detailed time data were derived from a clock
synchronized with recorded times. Because the speedsof recording and playback varied with battery
strength, care was taken to use equivalent batteries.

Asiatic Herpetological Research

199732.7).

Vol. 7, p. 155

We followed this methodology for approx. half

the data of Gekko hokouensis, which included appropriate time statements.
In the remainder of G. hokouensis data, the obser-

vations had been grouped per half-minute periods,
leaving precise durations unknown. These records

were scanned automatically by the NOTITA computer

program (N. Werner & H. Dreher, in MS) which constructed a quantitative table, from which some summarising statistics were derived by the
Excel program.

Study site for Gekko hokouensis at the
Chinen Castle ruins, near Chinen, Okinawa Island,
Figure 1

Microsoft

We do not use velocity as a descriptor of FM.

(Huey and Pianka. 1981; Magnusson
Anderson.

Japan (4 August 1992).

1993)

becausevelocity

1985;

et

al.,

is

generallyaffected by body size (Avery et al., 1987b).

Species, Environments and Observations

Data Processing and Presentation
Geographical grid references of towns, for macroecological evaluation, are from the Times Atlas of theWorld (1967).
Observations suspected of reflecting social

Gekko hokouensis Pope, 1928. Gekko
males attain 59.8

hokouensis

mm ra (mean53.9) and females 65.4

mm ra (mean 54.8) on Okinawa Island (Ota. unpublished data).

inter-

actions or observer effect were excluded. The proxim-

Study site. G. hokouensis was studied at the Chinen

ity of an observer may suppress the activity of lizards

Castle ruins near Chinen (26° 07'N. 127° 49'E), south-(Sugerman and Hacker, 1980) or stimulate excessive

ern

activity (Regal. 1983).

To enable comparison with previous data (Hueyand Pianka. 1981: Perry et al, 1990). we use MPM
and PTM to assess FM. These depend on the definition of discrete locomotor states, although the activityof the animals may constitute a continuum of patterns(Regal. 1983:1 15). We coarsely classified all postures
and actions as "stationary" or "moving". "Stationary"

included the time during which the gecko remained in

same

the

place, perhaps moving its head, jaws,
limbs
or tail, or even shifting its posture by
tongue,180°, as long as it did not move towards another loca-"Moving" included crawling, walking, running,jumping and jerking forwards.

tion.

A complication arose from frequent brief pauses

Okinawa Island. Japan (. 1). Most observations
were made on geckos on and in a small modem but
uninhabited

concrete-blockbuilding

trees (fig. 1); few observations

among

large

were made on geckos

on the trees. None of the other gecko species occurring on Okinawa (Ota. 1989) was encountered in the

study site.

Procedure and conditions. On

fivenightsbetween28 July and 4 August 1992, observations started
between 1850 h (at which time the illumination was

down to 700 lux) and 2015 h (sunset was approx. at1915 h), and lasted as long as geckos were active on

Throughout the observations, the sky
was mostly at least half overcast, hiding the moon
the building.

which was waxing, in its first quarter. Air temperature
varied only between 26.0 and 28.1° C.

On the firstduring locomotion in Gekko hokouensis. We found anight, observations were made by a team of two; on

precedent in Avery et al. (1987a, b), who analyzed thelocomotion of four lacertid species by videotape.

the later nights, the two observers functioned as separate teams. Observations were made from distances of"Standard" locomotion (neither fleeing nor chasing),

3-5 m, so that behaviour was seen in detail. Observa-

presumably representing foraging behavior, comprised 88-143 bursts of movement per minute, each oftion time totalled 27.25 team-hours.

0.25-0.56 sec. The intervening pauses lasted 0.120. 7 sec. and occupied 18-40% of the time. In the FM

Observations. Of 63 geckos recorded, only 12 could
be followed for >30 min. These showed varied move-1of female Podarcis siculain

Avery (1991)
defined as 'movement' a bout of locomotion separated

ment patterns.

nature,Bouts during which the geckos were stationary,
min to > 15 min. While stationary, gec-from others by pauses of >1 second. Thus defined,

lasted from <1movement duration

10.9 sec;

kos often turned their head (to one side or another, or

pause duration averaged 22.4 sec (MPM= 1.8; PTM=

back to the straight position, up to twice per minute).

inP.

sicula averaged

Table 1.

1997

Asiatic Herpetological ResearchVol. 7. p. 156

Measures of foraging mode in the geckos studied. Species means are based on samples

described or quoted in the text.
Species

Minutes observed

X

X

SD

37.8

.

25.44

11.97

25.5

(0.18-0.65)

0.15

12.32

(4-43)

Teratoscincus roborowskii

SD(Range)

0.15

0.35

7.15

(30.5-53.5)

G japonicus n=12

X

SD
(Range)(Range)Gekko hokouensis n=12

% of time moving

Moves/minute(5.1-51.5)

8.94

0.2

(0.00-2 82(1.5-36.03)

14.8

8.83

0.8

0.44

9.7

(0.0-50.0)(0.00-0.75)

8.81

14.7

(0.0-50.0)

1

Duration (seconds) of a single-

Move

Stationary pause

Gekko hokouensis n=12

150.2

50.2

74.1

(1-375)(5-1050)
G. japonicus n=12

856.6

818.7

385.0

38.6

34.7

(1-150)(2-2580)
Teratoscincus roborowskii n=\

29.9

296.3

23.0

13.2

(1-150)(1-1800)

turned the whole body to another direction (up to once

minute. Following Avery et al. (1987a, b; see Materi-per four minutes), or waved or vibrated the tail (up toonce in seven minutes). Licking the lips could occur

als

at any time (usually up to once per minute).

as one bout of moving, or "move". But "micromoves"

Gecko movements between stationary bouts took
three major forms: (a) Normal walking or running,
usually for a distance of 5-100 cm at a time.

Crawling: the geckos sometimes advanced,
with or without pauses, by a slow "crawl", at a speed(b)and Methods) we classify each sequence of locomotion by "micromoves". including its brief pauses,
could also occur singly or widely spaced, and thenwere reckoned separately.

On the basis of these definitions of "moves", theirstatistics are summarized in Table

1.

The sex of twelve females was verified by captureof about 1 cm/min. We saw no evidence that this wasor was evident due to obvious gravidity but the sex of

consistently related to the gecko having detected aprey item.

only four males was ascertained by capture. Males
appeared to be a little more active than females but the(c) Interrupted

locomotion: a sequence of forward

movements by 1-2 cm each ("micromoves"). at a rateof usually 2-12 (rarely up to 72) "micromoves" perdifference

was not

statisticallysignificant(MPM:

males, X=0.46; females, X=0.32; t-test p=0.06).

Vol. 7, p. 157

Asiatic Herpetological Research

1997

Gekko japonicus (Dumeril ef Bibron, 1836). Gekko
japonicus males reach 65 mm ra (mode 60 mm), andmm ra (mode 61 mm) (Tokunaga

females reach 70

Teratoscincus roborowskii Bedriaga, 1905
Teratoscincus roborowskii was synonymized byPope 1935:458) with T. scincus but is in the process(

L984:fig.l).

of being validated by J. R. Macey et al. (see Autumn

Stuclv site. G. japonicus was studied on the Hakozaki

and Han. 1989). The species is arenicolous and its
toes lack adhesive pads; males up to 87
ra,campus of Kyushu University. Fukuoka (33° 39'N.
130° 21'E). Kyushu Island. Japan, where the investigations of Tokunaga 1984) had been conducted. The(

geckos were on various buildings and sheds, especially in portions of walls or passage ceilings lit byincasndescent or fluorescent lamps or by nearby street

lamps. G. japonicus is the only gecko species in thisstudy site (Nakamura and Ueno. 1963; Tokunaga,
1984). and no other reptiles were encountered during
the observations.

Procedure and conditions.

During three nights, 9-females up to 80

mm
mm ra (from 30 adults in the Califor-

nia Academy of Sciences, courtesy J. Vindum).

Study site. T. roborowskii was studied near Turpan(42°55'N, 89°06'E), Xinjiang Uygur Autonomous
Region, People's Republic of China (on the Turpanof the Turpan SixMinJiaohe road, approx. 4.5 km

Warets Mosque; 3km E of Jiaohe Ancient City).

Located on the margin of the Turpan Depression (150 m), this area has a total annual precipitation average of 16.6mm (Turpan Weather Bureau data). The

August 1992, observations by one observer started
between 1915 h, when the illumination was 44 lux.

daily maximum air temperature ranged up to 45°C inand 2030 h (sunset, approx. 1910 h; end of twilight.

aged only 40°C during the study period.

approx. 2040 h), but had to be ended for logistic reasons by 2300 h. while geckos were still active.

The study site comprised long-abandoned fields ofblackish sand at the foot of hills with undisturbed veg-

Throughout the observations the sky was overcast;sometimes a slight drizzle rained. The mostly-hidden

etation described by

1

1

moon was waxing in its second quarter. Light intensiwhere most geckos were observed ranged from
0.35 to 1000 lux. Some geckos were in the lit areasties

and others in nearby shaded situations. At the times

September 1987 (Autumn & Wang, 1988) but aver-Autumn & Wang (1988). The

sand was soft in some places, hard packed in others,

and retained remnants of furrows, ditches and wells.
Plant coverage comprised only two small shrub species and by estimate varied between patches from 2%

were conducted, air tempera-

80%. Rainfall had exceeded the average - during
the first half of the year 1.1.-9.VII.92), 21.8 mm had

ranged from 27.2°C down to 24.5°C. These
three nights followed two very rainy nights, when thealready acummulated (Turpan Weather Bureau data).
In addition to the trees lining the road, some small

the daily observationsturessite had been on the margin of a typhoon. The

geckoswere observed from distances of 5-8 m, so that finedetails were missed. Observation time totalled 7.5 h.

Observations. Of 20 geckos recorded, only 7 couldto(stands of small Tamarix sp. trees occurred in the area.

Other than the Teratoscincus encountered at night,
the only reptiles seen on the site were the diurnal liz-

be followed for >25 min; the 12 observed for >4 minards Phrynocephalus axillaris (Agamidae) and Eremias velox (Lacertidae). Some individuals of bothbehaved variably: three remained stationary through-species, especially of Eremias, were still active in theout (up to 43 min) whereas others alternated moving

last

and pausing, usually moving less frequently than once
every ten minutes, and spending up to 10% of theirtime in locomotion; but one spent 50% of the time

moving (Table

1).

There appeared to be some intra-

example gecko no. 13 wasonce stationary for 15 min. whereas its other 7 stationindividual variation; forary bouts all lasted <4 min.

The individuals were not sexed because most were&daylight after sunset. According to Autumn
Wang (1988) Psammophis lineolatus (Colubridae)

may also occur on the site. These authors pointed out
the simplicity-in-principle of flora and herpetofaunaon the site and in Chinese deserts in general.

Procedure and conditions.

On

four

6-10

nights,July 1992, observations (by one observer) started at
2125-2200 h (Beijing time: sunset. 2135 h), i.e.,

activebefore the geckos emerged for their nocturnal activity
on the surface: but had to be ended for administrative
reasons at 0001-0030 h. while the geckos were stillthan usual during these observations due to the rainy

active. The moon was about 1/2 full (waxing), the sky

summer 1992 themean daily temperatures were 2-3°C below the 30-

mostly 4/8 cloudy; when gecko activity was high, thelux.
illumination was of the order of magnitude ofyear average (Fukuoka Meteorological Observatory

Temperature differed little between sand surface, airrecords).

cm above ground and air

high on walls.

Comment. The geckos may have been
weather and the cool season

-

in

less

1

1

1

m above ground; the over-1997

Asiatic Herpetological ResearchVol. 7. p. 158

Individuals were not sexed because this species

autotomizes the skin when held, as described for Teratoscincus scincus by Bauer et al. (1993).

Comment. Thus these geckos are not simply "active
foragers" as has been described for Teratoscincus
przewalskii (Semenov and Borkin, 1992).

Discussion
Figure 2.

Teratoscincus roborowskii. half-grown indi-vidual, scouting from the entrance of its burrow (Tur-The Foraging Mode of Gekkonid Species
For lizards. SW andpan, 2235 h, 8 July 1992).

arange during observations was 26.5-34.4°C. The
wind varied from absent to fairly strong for shortall

FM continuum:(

1

WF appear to be the extremes ofBoth SW and WF are practiced)

differently by different lizard species, which combine
anddifferent
values; (2) Some lizard spe-

MPM

cies vary their

PTM
FM during the day or during the year

times, commonly blew from the north, and sometimes(Pietruszka. 1986); (3) the intermediate

was noticeably warm. In the darkness, at distances ofmostly approx. 10 m, gecko behavior was assessed

edly shifting the position for stationary scanning foreyeshine. Observation time
totalled lOh 20' but as the torch became effective only

more

from

at

their

returnedtime
approx. 2210 h, the effective observation

approximated only 8h 20'.

by Regal (1983:113-114). or,

prey, called "cruising"less,"saltatory"

aptly,

occurs also

in lizards

O'Brienby(Moremond.
andmerriami

On each night, the earliest gecko wasminafter sunset, after a search of 10-60
40-65
spottedmin. Thereafter, the finding of each successive individual usually required 0.5-5 min.

erallysand temperature 30.5°C and air temperature (1 cm)
31.3°C, had a rectal temperature of 30.2°C.

animals
Time budgets were calculated for the>and not90
sec
observed (despite the vegetation) for1

1

suspected of having been affected by the observer(Table ). Of 28 individuals discovered at a distance,
1

only three were moving when spotted. This value of
10.7% of the animals moving when discovered isclose to the 8.8

PTM calculated for the species (Table(1989),

al.

ornatus

Urosaurus(Iguanidae) switched from distinct

One individual, caught at 231 Oh on 9.VII.92 withet1979). Neverthe-

SW and WF are definite foraging techniques:

Sceloporus

Observations.

FM, repeat-

WF to distinct SW

when food was scarce (Dunham. 19S3). Indeed, gen-SW the optimal strategy for motile prey, andWF the optimal strategy for stationary prey (Gerritsen
isand Strickler. 1977).
In lacertid lizards thetwo FM measures. MPM

and PTM, usually yield the same verdict as to whether
values of < 1-2 anda species is SW or WF, i.e..

MPM

PTM values of <15 indicate SW; MPM of > 1.5-2 andPTM of >30 indicate WF (Huey and Pianka. 1981;
aver-

Perry et al.. 1990). By either index the species
ages of Gekko japonicus and of Teratoscincus

roborowski (Table

1)

indicate that these geckos are

SW foragers. The observations of Stanner et al. (inwith thepress) of Gekko gecko also are compatible
a
(0.04
of
this
predator
being
speciessuggestion

SW

1).

Individual foraging behavior was highly variable

MPM. 4.37 PTM). However, the third species studied

SW only inMPM

two extreme patterns appeared to be dominant:several animals remained stationary throughout an

here,

observation period of 10-15 min; others kept alternat-tion in Coleonyx variegatus is very similar, with 0.57

but

ing between standing and walking at intervals ofsec (rarely <1 or >60 sec).

1-7

Two individuals (a half-grown individual spottedon 8. VII at 223 h and a subadult spotted on 9. VII at
2327 h) were sitting with only their fore-parts out of1

the openings of their burrows (fig. 2). One retained
this position for 36 min. then ran out and away (theother was disturbed by the observer after 14 min, andretreated downitshole).

When looking out from theburrow, these geckos may have been

Ptenopus (Huey and Pianka, 1981 ).

SW scouting likeGekko hokouensis,

is

its

mean, and is WF, or nearly so. in its PTM. The situa-

MPM but 34 PTM (Kingsbury, 1989).
Thus by the index of MPM. all five gecko species
for which at least some quantitative data exist, arepredators. But the index ofSW

PTM is probably ecologi-

because

cally

more

energyinvestment in foraging, and by this index threesignificant,itpartlyreflects

WF. Moreover, thespecies are SW, whereas two arediet of Ptyodactylus guttatus indicates that this spe-

more widely than previously believed
and Borkin(Perry and Brandeis. 1992). and Semenovcies forages(1992) have stated that Teratoscincus przewalskii is a

1997

Vol. 7. p. 160

Asiatic Herpetological Research

1997

Recently Arnold 1993) listed the forgaing modesof seven gecko taxa: he considered four species oftage point in the dark, and during 280 min of observa-

Pristurus and Quedenfeldtia trachyblepharus passive

MPM. 2.5 PTM). In the second night(

feeders,

celerrimusP.

acruising

forager,

and

tion

moved only 8 times, within only 40 cm (0.03

at an

it

stationed itself

illuminated window and was more active: during

Gonatodes active foragers, although he provided no

640 min it moved 29 times (10 of these, eating); by

quantitative databy either of the two indices mentioned above. Hence by the criteria developed forthese movements, which totalled 40 min. it loeomoted

other lizards (especially Lacertidae), of the seventeen

nearly 50 meters (0.05 MPM. 6.25 PTM). (3) Preliminary observations of Hemidactylus turcicus (Perry,gekkonoid species whose FMs have been quantified

unpublished) also show great variability in FM.

or described, only eight are strict

tend in varying degree to

SW predators: nine

WF strategies. This agrees inprinciple with the recent survey of Cooper ( 1994a. b)

who counted 52 species as SW and 8 as having WF or

No similar variability has been reported by Kingsbury (1989) from Coleonyx variegatus, so currently
the combination of
andbehaviors is known

WF

SW

only from gekkonine geckos.

mixed strategies.

This heterogeneity resembles that reported in Lac-

The Structure and Sources of the Variable FM
of Geckos
Previous studies of lizard FM have found intraspecificerta laevis (Lacertidae). in which during observation

periods of five minutes, most individuals were either
completely stationary or rather active (Perry et al.,1990).

variation, which varied in extent even among the spe-

cies within a family in one region. Among Lacertidae

CV of MPM ranged from 10.0%

in the Kalahari, thein Ichnotropis squamulosa tooocellata and that of

105.8% in Eremias line-

PTM ranged from 10.4% in

Nucras tessellata to 81.1%

in

Eremias lineoocellata(Table 2; Huey and Pianka. 1981 ). In the gecko Cole-onyx variegatus, males
greater distance per hour
(9.4 m/hr), although

in

moved

a

7.6 m/hr) than did females

1(

an enclosure

Unless random, such heterogeneity could result
from three factors, which are not mutually exclusive.
(1)

FM may change with age: in two species of Ich-

notropis (Lacertidae). as well as in Yaranus komoare WF whereas the adultsSW
behavior
partly adopt(Broadley, 1979; Auffenthe juveniles

doensis,berg,1981). But

allthe data discussed

above were

derived from adults and subadults.

MPM were equal (0.57) (Kings-(2) There are precedents for a sexual difference in

FM of lizards of other families, usually with males

bury, 1989). In Anolis polylepis, Perry (1996) foundthesignificant differences in foraging behavior between

more active than females, by one measure or anothermales, females and juveniles. But we are unaware of(Pietruszka. 1986; Anderson. 1993; Perry, 1996). In

any attention given to intraindividual variation in FM.

Coleonyx variegatus, Kingsbury (1989) found that,
although males and females moved equally fre-

The three species reported here share great behavioral variability, as shown also (in two of them) by thehigh CVs of

MPM and of PTM (Table 2). In each spe-cies, some individuals appeared to be very stationary,

quently, males moved longer distances each time.
This confirmed the earlier observation by Cooper etal.( 1985).

that males were more active (exposed) thansometimes throughout the whole observation time
Other individuals were so active that they
(Tablefemales.

could not be observed throughout the intended period.

alus mystaceus (Agamidae): males scout

Single consecutive movement (or bouts of rapid alternations of standing and moving) lasted several min-perched in presumably territory-guarding situations,whereas females are(Polynova and Lobachev,

maximum PTM
observed in individuals approximated 50% in two ofquoted by Ananjeva and Tsellarius, 1986). Perry1996) found a similarly reversed sexual difference inthe species (Table

Anolis polylepis.

1

A reverse sexual difference occurs in Phrynoceph-).

utes at themost (Table

1

1

)

but the).

Similar variability occurs in three other geckos forwhich some data are available.

(

1

)

The arenicolous

SW while

WF(

Of the geckos reported here. Gekko hokouensis
males may have been a little more active than females.

Stenodactylus doriae in the Arava Valley, Israel: during 30 min observation periods, some individuals

As explained above. G. japonicus and Teratoscincus

remain stationary throughout, whereas others movelaevisabout actively (Werner, pers. obs.; Bogin, 1993). (2)behavior patterns were related to sex (Perry

The adult Gekko gecko individual briefly observed by

1990).

Stanner etal.

(in press)

variably: In thefirstnear Bangkok also behaved

night

it

perched itself on a van-rohorowskii individuals were not sexed. In Lacerta
itislikewise

unknown whether the different(3) Species averages

mask

intraspecific

of

et

al..

MPM and PTM always

variation.

With

the

usual

short

Asiatic Herpetological Research

1997

observation bouts per individual, it remains unknown

whether the variation is inter- or intra-individual. The

Vol. 7. p. 161

prey while reducing the costs associated with locomotion (e.g.. energy expenditure and detection by preda-

This

would

behavior of otherlonger observation bouts applied here, revealed individuals that switched from stationary to active behav-tors).

ior or vice versa. Because of the variations in the stylefood shortage or increased food requirements (Curio,

and speed of the active behaviour, it seems that the
animals were then foraging and not shifting to new

1976:20.27).

SW stations;(O'Brien

et

i.e..

al.,

this

1989).

was not

But conceivably the brief

The segregation of diurnal lizards in a community into1989), so that in these species theperiods are actually saltatory foraging.

WF

As the data

G. gecko and S. doriae, seem to methodically practice

FM alternating SW and WF bouts.

Huey and Pianka (1981) summarized theoretical predictions and observations to the effect that an increasein food availability should result in an increase in for-WF

as well as
species. Moreaging velocity, inthat
Dunhamfoundover,(1983)
Sceloporus merriami

and Urosaurus ornatus switched from a

WF to a SW

foraging tactic during periods of low resource abundance.
If thisprinciple were applicable to the fluctuating

FM of geckos, a reversed "giving-up time" principle(Green, 1987) would be indicated: a gecko forages
actively, till the lack of prey causes it to switch to theenergetically cheaper SW strategy. When its patienceisrewarded with prey, it "can afford to try its luck"

and resumes the

WF strategy.

We suggest that some geckos fluctuate between
kos are visual hunters despite the poor light in whichmost operate. They seem to cope with this handicap
having larger eyes if nocturnal and also (2) if
foraging cursorially. without scouting from vantage(

1)

points(Werner,1969):

stretch-limbed, posture

(3)
(if

1981:995). This dimension of resource partitioning

comes in addition to the many reviewed by Schoener
1974). The species reported here, Gekko hokouensis,
G. japonicus and Teratoscincus roborowskii, were
each the sole nocturnal lizard species observed in thepress)

itwas associated only with Hemidactylus

frenatus, two orders of magnitude smaller (>l()0g and<10g, respectively). Where Stenodactylus doriae wasobserved (Bogin. 1933) the area carrying its dense
population (Bouskila. 1987) contains very few individuals of other cursorial geckos. It would be instruc-

FM where a number of gecko species
forage together. The comparison should be madewithin the Gekkonidae so as to minimize the confu-

tive to observe

sion of ecological and phylogenetic factors (Dunhamand Miles, 1985; Huey and Bennett. 1986).

FM and Relative Clutch MassSW

has been stated that geckos, believed to be
lizards
predators, have small RCM, compared toItSWof other families (Vitt and Price. 1982;

Vitt.

1986).

However, on the one hand. Werner 1989) has alreadypointed out that the RCM of geckos is actually some(the two FMs irrespective of momentary success. Gec-bytitioning (Pianka et al., 1979:87-88; Huey and Pianka,

area. Where G. gecko was observed (Stanner et al., in

Function of the Fluctuating FM in Geckos

SW

SW and WF species presumably aids in resource par-(now stand, the three species reported here, as well asa fluctuating

The employment of both SW and WF modes bythese geckos may be related to lack of competition:

Lacerta spp. (Avery et al.. 1987a. b; Avery. 1991).
indeed serve for "snapshot scanning" as suggested by(theforaging

saltatorypauses during WF in G. hokouensis, and also in the

O'brien et al.

parallelanimals which vary their foraging tactics at times ofbyforaging

cursorial),

the

in

erect,

better toview their surroundings (Werner and Broza. 1969);
and (4) by being more active, WF. in the better-illumi-

what larger than generally believed, being intermediate between those typical of

the other hand,

WF and SW lizards. On

we have shown here that the FM of

geckos is not as strictly SW as generally stated but
contains

WF components to varying extent. Hence

geckos, rather than having a paradoxically low RCM.
lizardandare in fact intermediate between

SW

WF

groups in both their FM and RCM.

Werner and Frankenberg

(

1

989

)

have shown that

nated times of night (at least in some species) (Fran-

among lizard species, the correlation of the RCM tokenberg and Werner. 1979: Bouskila et al.. 1992). The
last phenomenon seems to parallel the observation of

the relative body size of the female (female ra as per-Dunham (1983) quoted above: when food is moreSW

apparent, foraging becomes more active.

ing

cent of male ra). depends on the

FM of the species: mpredators(Agamidae.
Iguanidae), the larger the female

We hypothesize that (5) by alternatingly employ-

SW and WF strategies, some geckos, foraging

ertidae. Scincidae), the larger thebilitvof encountering stationary as well as mobile

compared to theRCM. But in WF species (Lac-male, the greater thewhen the range of vision is short, increase their proba-

Chamaeleonidae.
isthe male), the smaller thefemale (relative to

RCM. Interestingly, therelationship among gekkonidae tends to be as among

1997

Asiatic Herpetological ResearchVol. 7, p. 162

WF species (Werner, 1996). Moreover, Vitt (1990) has
among sympatric caatinga lizards,

pointed out thatlian

Museum, and later by Dr. Jim Saunders, Univer-sity of Pennsylvania, Philadelphia.

geckos differ from typical SW species in possessing
continual rather than seasonal reproduction. The last

two observations seem to further support the notionthat geckos should not be considered strict

SW preda-

tors.

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