TY - JOUR
T1 - Thermal preferences of hatchling saltwater crocodiles (Crocodylus porosus) in response to time of day, social aggregation and feeding
AU - Brien, Matthew
AU - Webb, Grahame
AU - Gienger, Christopher
AU - Lang, Jeffrey
AU - Christian, Keith
PY - 2012/12
Y1 - 2012/12
N2 - Three month old hatchling Crocodylus porosus with data loggers in their stomachs were placed
in thermal gradients, in isolation (N=16) and in groups of 4 (N=8 groups; 32 individuals). Mean Tb and
variation in Tb (SD) was not different whether individual crocodiles
in isolation were fasted or fed, or if individuals were housed in isolation (I) or in groups (G). However,
individuals in isolation (N=16) maintained slightly lower Tbs than those in
groups (N=32) during the early morning (06:00–11:00 h). The overall
mean Tb recorded for fasted individuals in the isolated and
group treatments (N=48) was 30.9±2.3 °C SD, with 50% of Tbs (Tset) between
29.4 °C and 32.6 °C, and a voluntary maximum and minimum of
37.6 °C and 23.2 °C respectively. During the day (11:00–17:00 h),
individuals in isolation and in groups selected the warmer parts of the
gradient on land, where they moved little. Outside of this quiescent period
(QP), activity levels were much higher and they used the water more. There was
a strong diurnal cycle for fasted individuals in isolation and in groups, with Tbduring the QP
(31.9±2.09 °C; N=48) significantly higher than during the non-quiescent
period (NQP: 30.6±2.31 °C). Thermal variation (SD) in Tb was
relatively stable throughout the day, with the highest variation at around dusk
and early evening (18:00–20:00 h), which coincided with a period of
highest activity. The diurnal activity cycle appears innate, and may reflect
the need to engage in feeding activity at the water's edge in the early evening,
despite ambient temperatures being cooler, with reduced activity and basking
during the day. If so, preferred Tb may be more accurately defined as the mean Tb during the
QP rather than the NQP. Implications for the thermal environment best suited
for captive C. porosus hatchlings are discussed.
AB - Three month old hatchling Crocodylus porosus with data loggers in their stomachs were placed
in thermal gradients, in isolation (N=16) and in groups of 4 (N=8 groups; 32 individuals). Mean Tb and
variation in Tb (SD) was not different whether individual crocodiles
in isolation were fasted or fed, or if individuals were housed in isolation (I) or in groups (G). However,
individuals in isolation (N=16) maintained slightly lower Tbs than those in
groups (N=32) during the early morning (06:00–11:00 h). The overall
mean Tb recorded for fasted individuals in the isolated and
group treatments (N=48) was 30.9±2.3 °C SD, with 50% of Tbs (Tset) between
29.4 °C and 32.6 °C, and a voluntary maximum and minimum of
37.6 °C and 23.2 °C respectively. During the day (11:00–17:00 h),
individuals in isolation and in groups selected the warmer parts of the
gradient on land, where they moved little. Outside of this quiescent period
(QP), activity levels were much higher and they used the water more. There was
a strong diurnal cycle for fasted individuals in isolation and in groups, with Tbduring the QP
(31.9±2.09 °C; N=48) significantly higher than during the non-quiescent
period (NQP: 30.6±2.31 °C). Thermal variation (SD) in Tb was
relatively stable throughout the day, with the highest variation at around dusk
and early evening (18:00–20:00 h), which coincided with a period of
highest activity. The diurnal activity cycle appears innate, and may reflect
the need to engage in feeding activity at the water's edge in the early evening,
despite ambient temperatures being cooler, with reduced activity and basking
during the day. If so, preferred Tb may be more accurately defined as the mean Tb during the
QP rather than the NQP. Implications for the thermal environment best suited
for captive C. porosus hatchlings are discussed.
U2 - 10.1016/j.jtherbio.2012.08.003
DO - 10.1016/j.jtherbio.2012.08.003
M3 - Article
SN - 0306-4565
VL - 37
SP - 625
EP - 630
JO - Journal of Thermal Biology
JF - Journal of Thermal Biology
IS - 8
ER -