T 
186 
Regal 
TABLE 1 
Crocodilia 
Caiman sclerops (Flanigan et al., 1973) 
C. latirostris (Peyrethon and Dusan- 
Peyrethon, 1969) 
Snakes 
Python saebe (Peyrethon and Dusan- 
Peyrethon, 1969) 
Lizards 
Chameleo jacksoni (Tauber et al., 1966) 
C. melleri (Tauber et al., 1966) 
Ctenosaura pectinata (Tauber et al., 1968; 
Flanigan, 1973) 
Iguana iguana (Peyrethon and Dusan- 
Peyrethon, 1969; Flanigan, 1973) 
Sceloporus olivaceus (Hunsaker and 
Lansing, 1962) 
Turtles 
Caretta caretta (Susie, 1972) 
Emys orbicularis (Karmanova et al., 1972; 
Vasilescu, 1970) 
Geochelone carbonaria (Flanigan, 1974; 
Hartse and Rechtschaffen, 1974) 
Terrapene Carolina (Flanigan et al., 1974) 
Testudo denticulata (Walker and Berger, 
1973) 
Testudo marginata (Hermann et al., 1964) 
Heart Rate 
Cowles and Phelan (1958) could not detect 
any clear evidence of fear in rattlesnakes 
unless they were touched or could detect 
movement. The authors monitored heart 
rates as an index of the arousal caused by 
noxious odors and found an increase. Experi- 
ence shows that heart rate might be used 
as an objective index of arousal for species 
where behavioral criteria are ambiguous or 
difficult to detect. Sassaman (1974) found 
heart rate to be a useful indicator of response 
in studies on social behavior in iguanid and 
agamid lizards. Even with this technique, 
however, caution is advised. Belkin (personal 
communication) reports that in captive green 
iguanas {Iguana iguana) there is a decrease 
of the heart rate as part of a “fear” response. 
The hog-nosed snake has a slower heart rate 
during death feigning (McDonald, 1974). All 
available information points to a need for 
more study of indices of arousal and caution 
in using those now available. 
ACTIVITY RHYTHMS AND 
TEMPERATURE REGULATION 
The classic paradigm for the regulation of 
motor activity levels in reptiles derives from 
the studies of Cowles and Bogert (1944) and 
Bogert (1949) on desert reptiles. Lizards 
emerge in the morning and orient to the 
sun. Their body temperatures rise through a 
basking range of temperatures until they be- 
come alert and active in an activity range. 
In this activity range, various physiological 
and behavioral processes are at or near an 
optimum (Dawson, 1975). The level of be- 
havioral arousal is regarded as temperature 
dependent. 
Endogenous biological rhythms are known 
to determine locomotor activity in rep- 
tiles under constant conditions (Barden, 
1942; Brett, 1971; Bustard, 1970; Cloudsley- 
Thompson, 1965, 1970; Evans, 1966, 1967; 
Gourley, 1972; Heath, 1962; Heckrotte. 1962; 
Hoffman, 1960; Regal, 1968; Norris and 
Kavanau, 1966; Mangelsdorf and Hauty, 
1972; Marx and Kayser, 1949; Mautz and 
Case, 1974; Underwood and Menaker, 1970). 
Here, the level of arousal appears to be time 
dependent. 
To reconcile the apparent thermal and 
temporal inconsistency, one must envision a 
system in which temperature and biological 
rhythms interact to control activity and 
alertness in lizards. 
We know little about control mechanisms 
of locomotor activity cycles in lizards. More 
is known about a rhythm of temperature 
preference (Regal, 1967, 1968, 1974; Myhre 
and Hammel, 1969 ; Gehrmann, 1971 ; Spel- 
lerberg, 1974; Hutchison and Kosh, 1974; 
Engbretson and Hutchison, 1976). Brain 
lesions in the posterior hypothalamus involv- 
