Behavioral and Physiological Thermoregulation of Crocodilians

Smith, E. Norbert

doi:10.1093/icb/19.1.239

Cited by 70 publications

(53 citation statements)

References 18 publications

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“…Crocodiles are primarily aquatic, only leaving the water to bask and for nesting, so I defined types of behavioural postures by estimates of the proportion of a crocodile's dorsal and lateral surface area exposed from the water: 0% exposed (ϭdiving), 20%, 40%, 60%, 80%, and 100% exposed (ϭbasking). Smith (1979) described some putative "thermoregulatory" postures (without giving T b data) of alligators with respect to the water surface, and his "high float" category would be similar to 40% exposed, "common float" is similar to 20% exposed, and "complete submergence" is equivalent to diving as used here. Seebacher and Grigg (1997) reported two patterns of T b in C. johnstoni, thermoregulation and thermoconformity.…”

Section: Study Site and Sampling Methodsmentioning

confidence: 99%

Behavioural Postures and the Rate of Body Temperature Change in Wild Freshwater Crocodiles, Crocodylus johnstoni

Seebacher

1999

Physiological and Biochemical Zoology

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I recorded body temperature and behaviour of eight Crocodylus johnstoni in the wild over a 2-yr period in order to quantify the effect of posturing on body temperature and to provide a mechanistic explanation of how behaviour affects body temperature. Behaviour was categorised according to the proportion of a crocodile's surface area exposed from the water (0% exposed [ϭdiving] to 100% exposed [ϭbasking]). Crocodiles did not simply shuttle between the extremes of 100% exposed and diving but showed an array of intermediate postures. Rates of body temperature change were negative for exposures less than 40% and positive for 60%-100% exposed. This was due to the difference between operative temperature and body temperature, which was negative during diving but increased with the percentage of exposure, up to 25Њ-30ЊC during basking. For any particular posture, the rate of body temperature change decreased with increasing mass. Thermal time constants were shortest during diving and longest during basking. A heattransfer equation predicted the rate of body temperature change well, except that it underestimated the rate of body temperature change during 80% and 100% exposed. Exposing only a small part of their body when in water (20%) slowed heat loss considerably, allowing crocodiles to spend more time in the water while maintaining body temperature within their preferred body temperature range.

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Section: Study Site and Sampling Methodsmentioning

confidence: 99%

Behavioural Postures and the Rate of Body Temperature Change in Wild Freshwater Crocodiles, Crocodylus johnstoni

Seebacher

1999

Physiological and Biochemical Zoology

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“…Because American alligators may be active day or night depending on season and environmental temperature (Smith, 1979), it is difficult to judge their influence the activity patterns habitat use of either adult or juvenile Pterygoplichthys.…”

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confidence: 99%

Nocturnal and diurnal activity of armored suckermouth catfish (Loricariidae: Pterygoplichthys) associated with wintering Florida manatees (Trichechus manatus latirostris)

Nico¹

2010

Neotrop. ichthyol.

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Several Pterygoplichthys species, members of the Neotropical catfish family Loricariidae, have been widely introduced outside their native ranges. In this paper, I present observations on the diel activity pattern of non-native Pterygoplichthys, tentatively identified as P. disjunctivus, with respect to their attachment and grazing on endangered Florida manatees, Trichechus manatus latirostris. The study was conducted in December 2009 at Volusia Blue Spring, an artesianal spring system in the St. Johns River basin, Florida (USA). Supplemented by information gathered during previous visits to the spring site, this study revealed that adult Pterygoplichthys are active throughout the diel period (day, twilight and night). However, juvenile Pterygoplichthys were largely nocturnal and only at night did they consistently join adults in attaching to manatees. The juveniles generally remain hidden during the day, probably responding to presence of diurnal predators, mainly birds. Differences in diel behaviors among different Pterygoplichthys size classes in Florida are consistent with published observations on loricariids inhabiting clearwater streams within their native ranges.Várias espécies de Pterygoplichthys, siluriformes Neotropicais da família Loricariidae, tem sido largamente introduzidos além de suas áreas naturais de ocorrência. Neste artigo, eu apresento observações dos padrões de atividade diária de uma população não nativa de Pterygoplichthys, identificada tentativamente como P. disjunctivus, associados com a espécie ameaçada de peixe-boi nativa da Flórida, Trichechus manatus latirostris. O estudo foi conduzido em dezembro de 2009 em Volusia Blue Spring um sistema artesiano na bacia do rio St. John, Flórida (USA). Suplementado por informações reunidas durante visitas prévias ao sítio em análise, este estudo revelou que Pterygoplichthys adultos estiveram ativos durante a maioria dos períodos (dia, crepúsculo e noite). No entanto, jovens foram principalmente noturnos e somente a noite eles uniram-se aos adultos sobre os peixes-boi. No sistema estudado na Flórida, jovens de Pterygoplichthys geralmente permanecem escondidos durante o dia, provavelmente respondendo a presença de predadores visuais diurnos, principalmente aves. As diferenças observadas na atividade diária entre diferentes classes de tamanho são semelhantes ao descrito para certos loricariídeos que habitam cursos d'água de águas límpidas em suas áreas nativas de ocorrência.

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“…Meanwhile, the water levels were so low that the water temperature in the pond reached dangerously high levels during the day (e.g., 39°C in August, Table 2). Alligators may avoid overheated surface water by retiring to deeper water [16,28]. Therefore, for an alligator habitat, a certain minimum water level has to be maintained throughout the spring to autumn activity period of the animals.…”

Section: Discussionmentioning

confidence: 99%

“…Many studies have identified temperature as one of the main factors influencing crocodilians' ranging behavior, and the warmer season usually resulted in stronger movement and a larger home range [27][28][29][30][31]33]. Although temperature significantly influenced the movement of the two alligators, its influence on home-range variations of the two alligators in the three seasons was not significant (Table 5).…”

Section: Discussionmentioning

confidence: 99%

Testing reintroduction as a conservation strategy for the critically endangered Chinese alligator: Movements and home range of released captive individuals

et al. 2011

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The Chinese alligator (Alligator sinensis) is considered the most critically endangered crocodilian as a result of the near total loss of its habitat and its extremely small and fragmented wild populations. Plans for population recovery lie mostly with wetland restoration and the reintroduction of captive-reared animals. We carried out a first-trial release of 3 adult Chinese alligators (1♂, 2♀) into a pond at the Hongxing conservation site, Xuancheng, southern Anhui Province; the animals were radio-tracked from May to October in 2003. We hypothesized that after a period of adaptation, the alligators would establish definable home ranges. Two (1♂, 1♀) of the 3 alligators were monitored for the whole of the tracking period. The male had an annual home-range size of 7.61 hm 2 , and the female 4.00 hm 2 . Water temperature and pond water level were two important factors influencing the alligators' distributions, and daily movements. The radio-tracked alligators had overlapping home ranges, which notably included the one substantial island in the pond; that island is the only known nesting site of the local native wild alligators. Aggressive interactions between the released alligators and native wild alligators were observed during the breeding season around this island. All the three reintroduced alligators survived the winter of 2003 and were alive in the same pond in 2008. We concluded that the Hongxing conservation site provided a suitable habitat for the reintroduced alligators. However, the low water level in the pond resulting from farmland irrigation in August and September can be a substantial threat to the alligators' survival. Therefore, regulations on irrigation in summer and autumn are needed to balance the water needs of the alligators and agriculture.

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Behavioral and Physiological Thermoregulation of Crocodilians

Cited by 70 publications

References 18 publications

Behavioural Postures and the Rate of Body Temperature Change in Wild Freshwater Crocodiles, Crocodylus johnstoni

Behavioural Postures and the Rate of Body Temperature Change in Wild Freshwater Crocodiles, Crocodylus johnstoni

Nocturnal and diurnal activity of armored suckermouth catfish (Loricariidae: Pterygoplichthys) associated with wintering Florida manatees (Trichechus manatus latirostris)

Testing reintroduction as a conservation strategy for the critically endangered Chinese alligator: Movements and home range of released captive individuals

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