| | |
Summary: YET ANOTHER NOCTURNAL LIZARD WITH A LOW COST OF TRANSPORT IS THIS A GENERAL
PATTERN? K. Autumn* and C. Farley. University of California, Berkeley.
Nocturnal lizards are often active at temperatures well below their thermal optima. This means that
nocturnality can impose a thermal handicap that dramatically reduces the range of sustainable
speeds. We test the hypothesis that nocturnal lizards have greater performance at low temperatures
than do similar diurnal lizards. This study investigates two possible mechanisms for increased en-
durance at low temperatures in the Banded gecko, Coleonyx variegatus: 1) The minimum cost of
transport (Cmin) could be lower in C. variegatus than in a diurnal lizard of the same mass. A lower
Cmin would increase the range of sustainable speeds by increasing the maximum aerobic speed
(MAS) without increasing the maximal rate of oxygen consumption (V_
O2max). 2) V_
O2max could
be greater at low temperature in C. variegatus than in a diurnal lizard of the same mass. During
exercise on a treadmill, Cmin in C. variegatus was less than half of the predicted Cmin for diurnal
lizards, and is below the 95% confidence limits of the allometry for diurnal lizards. This low Cmin
increases the MAS and allows greater endurance at low temperature. V_
O2max was not unusually
high at 25_C in C. variegatus. This is the same pattern found in Teratoscincus przewalskii, a noc-
turnal gecko that is active at very low temperatures (15_C). The fact that two distantly related noc-
turnal geckos have unusually low Cmin may be indicative of a general phylogenetic pattern
|
