Thermal preferences of hatchling saltwater crocodiles (Crocodylus porosus) in response to time of day, social aggregation and feeding

Matthew Brien, Grahame Webb, Christopher Gienger, Jeffrey Lang, Keith Christian

    Research output: Contribution to journalArticleResearchpeer-review

    Abstract

    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.

    Original languageEnglish
    Pages (from-to)625 -630
    Number of pages6
    JournalJournal of Thermal Biology
    Volume37
    Issue number8
    DOIs
    Publication statusPublished - Dec 2012

    Fingerprint

    Crocodylus porosus
    Alligators and Crocodiles
    Agglomeration
    Hot Temperature
    heat
    diurnal activity
    Water
    coolers
    temperature profiles
    Thermal gradients
    Activity Cycles
    ambient temperature
    stomach
    Stomach
    Temperature
    water

    Cite this

    @article{1e07361441184c208566a7148123b1e1,
    title = "Thermal preferences of hatchling saltwater crocodiles (Crocodylus porosus) in response to time of day, social aggregation and feeding",
    abstract = "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.",
    author = "Matthew Brien and Grahame Webb and Christopher Gienger and Jeffrey Lang and Keith Christian",
    year = "2012",
    month = "12",
    doi = "10.1016/j.jtherbio.2012.08.003",
    language = "English",
    volume = "37",
    pages = "625 --630",
    journal = "Journal of Thermal Biology",
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    Thermal preferences of hatchling saltwater crocodiles (Crocodylus porosus) in response to time of day, social aggregation and feeding. / Brien, Matthew; Webb, Grahame; Gienger, Christopher; Lang, Jeffrey; Christian, Keith.

    In: Journal of Thermal Biology, Vol. 37, No. 8, 12.2012, p. 625 -630.

    Research output: Contribution to journalArticleResearchpeer-review

    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

    VL - 37

    SP - 625

    EP - 630

    JO - Journal of Thermal Biology

    JF - Journal of Thermal Biology

    SN - 0306-4565

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    ER -