Some physiological consequences of estivation by freshwater crocodiles, Crocodylus johnstoni

K. Christian, B. Green, R. Kennett

    Research output: Contribution to journalArticleResearchpeer-review

    Abstract

    Estivating crocodiles were studied at their dry season refuge in northern Australia over six years. The crocodiles spent three or four months a year underground without access to water. Doubly labeled water was used to measure field metabolic rates and water flux, and plasma and cloacal fluid samples were taken at approximately monthly intervals during some years to monitor the effects of estivation with respect to the accumulation of nitrogenous wastes and electrolyte concentrations. Estivating crocodiles expended a mean of 26.1 kJ kg-1 day-1. Although environmental and, hence, body temperatures increased with increasing time in estivation, water efflux decreased with increasing time in estivation to 9.3 mL kg-1 day-1, which was only 23% of the flux rate of crocodiles in water before estivation (40.2 mL kg-1 day-1). The absolute size of body water pools declined proportionately with body mass and body solids; thus the crocodiles were not dehydrated even after three months without access to water. With increasing time in estivation, the following parameters increased in the cloacal fluid: osmolality, potassium, and magnesium; and the following increased in the blood plasma: osmolality, and protein concentration. Electrolytes in plasma were highest when the crocodiles were in the water and late in the estivation period. Freshwater crocodiles do not appear to have any specific adaptations for estivation, but given an adequate refuge, they can survive many months without access to water.
    Original languageEnglish
    Pages (from-to)1-9
    Number of pages9
    JournalJournal of Herpetology
    Volume30
    Issue number1
    DOIs
    Publication statusPublished - 1996

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    estivation
    Crocodylus
    crocodiles
    water
    plasma
    refuge
    electrolyte
    osmolality
    electrolytes
    fluid
    body temperature
    crocodile
    body mass
    blood plasma
    dry season
    magnesium
    body water
    potassium
    blood
    protein

    Cite this

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    title = "Some physiological consequences of estivation by freshwater crocodiles, Crocodylus johnstoni",
    abstract = "Estivating crocodiles were studied at their dry season refuge in northern Australia over six years. The crocodiles spent three or four months a year underground without access to water. Doubly labeled water was used to measure field metabolic rates and water flux, and plasma and cloacal fluid samples were taken at approximately monthly intervals during some years to monitor the effects of estivation with respect to the accumulation of nitrogenous wastes and electrolyte concentrations. Estivating crocodiles expended a mean of 26.1 kJ kg-1 day-1. Although environmental and, hence, body temperatures increased with increasing time in estivation, water efflux decreased with increasing time in estivation to 9.3 mL kg-1 day-1, which was only 23{\%} of the flux rate of crocodiles in water before estivation (40.2 mL kg-1 day-1). The absolute size of body water pools declined proportionately with body mass and body solids; thus the crocodiles were not dehydrated even after three months without access to water. With increasing time in estivation, the following parameters increased in the cloacal fluid: osmolality, potassium, and magnesium; and the following increased in the blood plasma: osmolality, and protein concentration. Electrolytes in plasma were highest when the crocodiles were in the water and late in the estivation period. Freshwater crocodiles do not appear to have any specific adaptations for estivation, but given an adequate refuge, they can survive many months without access to water.",
    keywords = "Alligator, Crocodylidae (all crocodiles), Crocodylus johnsoni",
    author = "K. Christian and B. Green and R. Kennett",
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    language = "English",
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    Some physiological consequences of estivation by freshwater crocodiles, Crocodylus johnstoni. / Christian, K.; Green, B.; Kennett, R.

    In: Journal of Herpetology, Vol. 30, No. 1, 1996, p. 1-9.

    Research output: Contribution to journalArticleResearchpeer-review

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    T1 - Some physiological consequences of estivation by freshwater crocodiles, Crocodylus johnstoni

    AU - Christian, K.

    AU - Green, B.

    AU - Kennett, R.

    PY - 1996

    Y1 - 1996

    N2 - Estivating crocodiles were studied at their dry season refuge in northern Australia over six years. The crocodiles spent three or four months a year underground without access to water. Doubly labeled water was used to measure field metabolic rates and water flux, and plasma and cloacal fluid samples were taken at approximately monthly intervals during some years to monitor the effects of estivation with respect to the accumulation of nitrogenous wastes and electrolyte concentrations. Estivating crocodiles expended a mean of 26.1 kJ kg-1 day-1. Although environmental and, hence, body temperatures increased with increasing time in estivation, water efflux decreased with increasing time in estivation to 9.3 mL kg-1 day-1, which was only 23% of the flux rate of crocodiles in water before estivation (40.2 mL kg-1 day-1). The absolute size of body water pools declined proportionately with body mass and body solids; thus the crocodiles were not dehydrated even after three months without access to water. With increasing time in estivation, the following parameters increased in the cloacal fluid: osmolality, potassium, and magnesium; and the following increased in the blood plasma: osmolality, and protein concentration. Electrolytes in plasma were highest when the crocodiles were in the water and late in the estivation period. Freshwater crocodiles do not appear to have any specific adaptations for estivation, but given an adequate refuge, they can survive many months without access to water.

    AB - Estivating crocodiles were studied at their dry season refuge in northern Australia over six years. The crocodiles spent three or four months a year underground without access to water. Doubly labeled water was used to measure field metabolic rates and water flux, and plasma and cloacal fluid samples were taken at approximately monthly intervals during some years to monitor the effects of estivation with respect to the accumulation of nitrogenous wastes and electrolyte concentrations. Estivating crocodiles expended a mean of 26.1 kJ kg-1 day-1. Although environmental and, hence, body temperatures increased with increasing time in estivation, water efflux decreased with increasing time in estivation to 9.3 mL kg-1 day-1, which was only 23% of the flux rate of crocodiles in water before estivation (40.2 mL kg-1 day-1). The absolute size of body water pools declined proportionately with body mass and body solids; thus the crocodiles were not dehydrated even after three months without access to water. With increasing time in estivation, the following parameters increased in the cloacal fluid: osmolality, potassium, and magnesium; and the following increased in the blood plasma: osmolality, and protein concentration. Electrolytes in plasma were highest when the crocodiles were in the water and late in the estivation period. Freshwater crocodiles do not appear to have any specific adaptations for estivation, but given an adequate refuge, they can survive many months without access to water.

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