Maintenance of Temperature of Crocodile Nests (Reptilia, Crocodilidae)

Magnusson, William E.

doi:10.2307/1563479

Cited by 21 publications

(13 citation statements)

References 3 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…First, it is known that nest temperatures fluctuate and the values given in Figs 2-5 are only the average values for the temperature-sensitive period of sex determination. These agree well with previous reports of nest temperatures for Alligator mississippiensis (McIlhenny, 1935;Joanen, 1969;Chabreck, 1973;Deitz & Hines, 1980), Crocodylus porcms (Webb et al, 1977;Magnusson, 1979), Caiman crocodilus crocodilus (Staton & Dixon, 1977) and Crocodylus niloticus . These previous studies were all relatively crude averages and up to now no-one has attempted to carefully record temperatures at several different locations within a nest.…”

Section: Discussionsupporting

confidence: 92%

“…Since alligators cannot be reliably sexed by the external cloaca1 method until they are 1.5 years of age (Joanen & McNease, 1978), the hatchlings were raised to that age in controlled environmental chambers under identical conditions of heat, light, feeding, etc. (Joanen & McNease, 39746, 1976, 1977, 1979. At 1.5 years the alligators were weighed, measured (tip ofsnout to tip of tail) and sexed externally, representative animals being killed, fixed and sexed by internal dissection and histological examination.…”

Section: Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Temperature‐dependent sex determination in Alligator mississippiensis

Ferguson¹,

Joanen

1983

Journal of Zoology

174

View full text Add to dashboard Cite

The structure of the reproductive systems of hatchling and 1 ‐year‐old alligators was investigated macroscopically and histologically. Sex is fully determined at the time of hatching and irreversible thereafter. Constant temperature laboratory experiments revealed that the sex of Alligator miuissippiensis is determined by the temperature of egg incubation, 30°C or below producing females, and 34°C or above, males. Experiments in which eggs were shifted from female‐producing temperatures to male‐producing temperatures and vice versa at weekly intervals during incubation demonstrated that the temperature‐sensitive period for sex determination is around 20 and 35 days after egg laying. In the wild, temperature probes were placed in alligator nests constructed in three different habitats: wet marsh, dry marsh and levee (elevated firm ground). The position of the eggs in the nests were mapped at 60 days incubation and the sex of the enclosed hatchlings correlated with the nest temperatures at that site. Levee nests were hot (34°C) and hatched approximately 100% males. Wet marsh nests were cool (30°C) and hatched approximately 100% females. Dry marsh nests had an intermediate temperature profile, the hottest location (34°C) being the top centre of the nest. Males developed from eggs in this location and females from eggs around the periphery and base of the nest. The sex ratio in dry marsh nests was five females to one male. The natural sex ratio at hatching was determined for a large area of representative habitat for four consecutive years and averaged five (±0.7) females to one male. Females hatched from eggs incubated at 30°C weighed more than males hatched from eggs incubated at 34°C because the former contained more absorbed abdominal yolk. These extra energy reserves enable females to grow faster and become larger than males in the early years of life. This means that heavy females become sexually mature ahead of either light females or light males, and because of the reproductive lifestyle of alligators, this early maturity constitutes a selective biological advantage for the evolution of temperature‐dependent sex determination in Alligator mississippiensis. The occurrence of temperature‐dependent sex determination in alligators has wide‐ranging implications for embryological, teratological, molecular, phylogenetic, conservation and farming studies.

show abstract

Section: Discussionsupporting

confidence: 92%

Section: Methodsmentioning

confidence: 99%

Temperature‐dependent sex determination in Alligator mississippiensis

Ferguson¹,

Joanen

1983

Journal of Zoology

174

View full text Add to dashboard Cite

show abstract

“…Crocodilians are dimorphic in their nesting habits (Greer, 1971), with some species building mound nests and others excavating hole nests (Greer, 1970(Greer, , 1971Webb et al, 1983;Ferguson, 1985). Both types of nests provide ideal temperature, humidity (Chabreck, 1973;Magnusson, 1979;Ferguson and Joanen 1983;Lutz and Dunbar-Cooper 1984;Ferguson, 1985) and appropriate levels of oxygen for gas exchange (Grigg et al, 2010). Once thought to be hole nesters (Barbour and Ramsden, 1919;Varona, 1966;Greer, 1970;Varona, 1986), C. rhombifer, are now known to utilize both hole and mound nests (Thorbjarnarson, 1996).…”

Section: Discussionmentioning

confidence: 99%

Age, fertility and reproductive behavior in cuban crocodiles,Crocodylus rhombifer, at the smithsonian's national zoological park

Augustine

Watkins

2015

Zoo Biology

View full text Add to dashboard Cite

The Smithsonian's National Zoological Park (NZP) has a long history with Cuban crocodiles, Crocodylus rhombifer, beginning in 1900's when the first animals arrived at the NZP. Today, the Zoo has two breeding groups of C. rhombifer and has observed and analyzed reproductive behavior and fertility rates over the last three years. Fertility rates were determined initially by observing the formation of an opaque band that forms on the shell of a fertile egg, called banding. The fertility rates by banding were later compared to the observation made after opening the eggs to verify fertility. In addition to tracking fertility, nesting and agonistic behavior were also observed. Several notable observations were documented over the same period. These included a male predating a nesting female's eggs, increased aggression between two females housed together, the continued development of a partially banded egg, and the discovery of 19 additional egg shells post oviposition by both females in the enclosure. Here we discuss the nest phenology, fertility and behavior of the five exhibited C. rhombifer at the Smithsonian's National Zoological Park over a 3-year period. Zoo Biol. 34:278-284, 2015. © 2015 Wiley Periodicals Inc.

show abstract

“…In this context, it is important to understand temperature regimes in wild nests of crocodilians and corresponding hatchling sex ratios and characteristics. Temperature of wild crocodilian nests is not constant, but fluctuates depending on several factors including metabolic heat produced by embryo development, environmental temperature, vegetation cover, solar radiation, nest material, rainfall regime and tropical cyclones Ewert and Nelson, 2003;He et al, 2002;Leslie and Spotila, 2001;Magnusson, 1979;Thorbjarnarson et al, 2001). Female behaviour mediated nest site selection, nesting date and nest construction can also influence variation in nest temperatures (Ferguson, 1985;Valenzuela, 2001).…”

Section: Introductionmentioning

confidence: 99%

Microclimate of American crocodile nests in Banco Chinchorro biosphere reserve, Mexico: Effect on incubation length, embryos survival and hatchlings sex

Charruau

2012

Journal of Thermal Biology

View full text Add to dashboard Cite

Maintenance of Temperature of Crocodile Nests (Reptilia, Crocodilidae)

Cited by 21 publications

References 3 publications

Temperature‐dependent sex determination in Alligator mississippiensis

Temperature‐dependent sex determination in Alligator mississippiensis

Age, fertility and reproductive behavior in cuban crocodiles,Crocodylus rhombifer, at the smithsonian's national zoological park

Microclimate of American crocodile nests in Banco Chinchorro biosphere reserve, Mexico: Effect on incubation length, embryos survival and hatchlings sex

Contact Info

Product

Resources

About