Critical thermal maxima of turtles: Validity of body temperature

Bushes protect tortoises from lethal overheating in arid areas of Morocco

“…The precise lethal body temperatures (critical thermal minima and maxima) of the studied species are unknown, and we did not attempt to measure them for ethical reasons. Based on studies performed on reptile species including chelonians (Hutchison et al 1966;Webb & Witten 1973;reviews in Bartholomew 1982;Lillywhite 1987;Peterson et al 1993), we confidently estimated that exposure to prolonged periods (> 1 hour) of ambient temperatures of 40 • C are unsafe, and that a prolonged central body temperature > 38 • C precipitates dehydration and can be eventually lethal (there is no record of reptiles surviving an elevation of body temperature > 44 • C). Most reptiles can easily tolerate ambient temperature close to 0 • C for prolonged time periods, critical lower body temperatures are generally markedly negative (Bartholomew 1982).…”

“…Based on studies performed on reptile species including chelonians (Hutchison et al . 1966; Webb & Witten 1973; reviews in Bartholomew 1982; Lillywhite 1987; Peterson et al . 1993), we confidently estimated that exposure to prolonged periods (> 1 hour) of ambient temperatures of 40 °C are unsafe, and that a prolonged central body temperature > 38 °C precipitates dehydration and can be eventually lethal (there is no record of reptiles surviving an elevation of body temperature > 44 °C).…”

“…Most reptiles can easily tolerate ambient temperature close to 0 °C for prolonged time periods, critical lower body temperatures are generally markedly negative (Bartholomew 1982). We emphasize that we distinguish central (internal) body temperature, from external (cutaneous) body temperatures, which can momentarily reach values > 40 °C or < –5 °C without visible damage, especially in relatively large species such as terrestrial chelonians (McGinnis & Voigt 1971; Webb & Witten 1973). The main consequence of focusing on critical minimum and maximum body temperatures is the straightforwardness of the analyses: no individual can survive a single episode of prolonged overheating (for example >45 °C for one hour).…”

Bushes protect tortoises from lethal overheating in arid areas of Morocco

“…The precise lethal body temperatures (critical thermal minima and maxima) of the studied species are unknown, and we did not attempt to measure them for ethical reasons. Based on studies performed on reptile species including chelonians (Hutchison et al 1966;Webb & Witten 1973;reviews in Bartholomew 1982;Lillywhite 1987;Peterson et al 1993), we confidently estimated that exposure to prolonged periods (> 1 hour) of ambient temperatures of 40 • C are unsafe, and that a prolonged central body temperature > 38 • C precipitates dehydration and can be eventually lethal (there is no record of reptiles surviving an elevation of body temperature > 44 • C). Most reptiles can easily tolerate ambient temperature close to 0 • C for prolonged time periods, critical lower body temperatures are generally markedly negative (Bartholomew 1982).…”

“…Based on studies performed on reptile species including chelonians (Hutchison et al . 1966; Webb & Witten 1973; reviews in Bartholomew 1982; Lillywhite 1987; Peterson et al . 1993), we confidently estimated that exposure to prolonged periods (> 1 hour) of ambient temperatures of 40 °C are unsafe, and that a prolonged central body temperature > 38 °C precipitates dehydration and can be eventually lethal (there is no record of reptiles surviving an elevation of body temperature > 44 °C).…”

“…Most reptiles can easily tolerate ambient temperature close to 0 °C for prolonged time periods, critical lower body temperatures are generally markedly negative (Bartholomew 1982). We emphasize that we distinguish central (internal) body temperature, from external (cutaneous) body temperatures, which can momentarily reach values > 40 °C or < –5 °C without visible damage, especially in relatively large species such as terrestrial chelonians (McGinnis & Voigt 1971; Webb & Witten 1973). The main consequence of focusing on critical minimum and maximum body temperatures is the straightforwardness of the analyses: no individual can survive a single episode of prolonged overheating (for example >45 °C for one hour).…”

Observations and comments on the body temperatures of some New Zealand reptiles

“…But should rectal or brain temperature be measured and accepted as representative of the body? The question arises because several studies have shown differences between the two (Heath 1964a, Campbell 1969, Webb et al 1972, Webb & Whitten 1973, with significantly more precise regulation of brain temperature (Hammel et al 1967, Crawford 1972. Heatwole (1970) suggested that head temperature is a more accurate indicator of PBT than cloacal temperature.…”

Effect of the rate of temperature increase of the dynamic method on the heat tolerance of fishes

“…As an example, until 2004 the Cambridge Scientific Abstracts Database contained 197 citations referring to ''critical thermal maximum''; of these only five specifically referred to ''heating and/or warming rates''. Out of these five one did not provide any comparison of thermal tolerances among heating rates (Gomez, 1990) and another was based on the rate of temperature penetration in the body of turtles (Webb and Witten, 1973). Our precarious understanding about the effect of the heating rate on thermal tolerance is particularly critical given the broad range of heating rates used so far.…”

Bushes protect tortoises from lethal overheating in arid areas of Morocco

“…The precise lethal body temperatures (critical thermal minima and maxima) of the studied species are unknown, and we did not attempt to measure them for ethical reasons. Based on studies performed on reptile species including chelonians (Hutchison et al 1966;Webb & Witten 1973;reviews in Bartholomew 1982;Lillywhite 1987;Peterson et al 1993), we confidently estimated that exposure to prolonged periods (> 1 hour) of ambient temperatures of 40 • C are unsafe, and that a prolonged central body temperature > 38 • C precipitates dehydration and can be eventually lethal (there is no record of reptiles surviving an elevation of body temperature > 44 • C). Most reptiles can easily tolerate ambient temperature close to 0 • C for prolonged time periods, critical lower body temperatures are generally markedly negative (Bartholomew 1982).…”

“…Based on studies performed on reptile species including chelonians (Hutchison et al . 1966; Webb & Witten 1973; reviews in Bartholomew 1982; Lillywhite 1987; Peterson et al . 1993), we confidently estimated that exposure to prolonged periods (> 1 hour) of ambient temperatures of 40 °C are unsafe, and that a prolonged central body temperature > 38 °C precipitates dehydration and can be eventually lethal (there is no record of reptiles surviving an elevation of body temperature > 44 °C).…”

“…Most reptiles can easily tolerate ambient temperature close to 0 °C for prolonged time periods, critical lower body temperatures are generally markedly negative (Bartholomew 1982). We emphasize that we distinguish central (internal) body temperature, from external (cutaneous) body temperatures, which can momentarily reach values > 40 °C or < –5 °C without visible damage, especially in relatively large species such as terrestrial chelonians (McGinnis & Voigt 1971; Webb & Witten 1973). The main consequence of focusing on critical minimum and maximum body temperatures is the straightforwardness of the analyses: no individual can survive a single episode of prolonged overheating (for example >45 °C for one hour).…”

Observations and comments on the body temperatures of some New Zealand reptiles

“…But should rectal or brain temperature be measured and accepted as representative of the body? The question arises because several studies have shown differences between the two (Heath 1964a, Campbell 1969, Webb et al 1972, Webb & Whitten 1973, with significantly more precise regulation of brain temperature (Hammel et al 1967, Crawford 1972. Heatwole (1970) suggested that head temperature is a more accurate indicator of PBT than cloacal temperature.…”

Effect of the rate of temperature increase of the dynamic method on the heat tolerance of fishes

“…As an example, until 2004 the Cambridge Scientific Abstracts Database contained 197 citations referring to ''critical thermal maximum''; of these only five specifically referred to ''heating and/or warming rates''. Out of these five one did not provide any comparison of thermal tolerances among heating rates (Gomez, 1990) and another was based on the rate of temperature penetration in the body of turtles (Webb and Witten, 1973). Our precarious understanding about the effect of the heating rate on thermal tolerance is particularly critical given the broad range of heating rates used so far.…”

Bushes protect tortoises from lethal overheating in arid areas of Morocco

“…The precise lethal body temperatures (critical thermal minima and maxima) of the studied species are unknown, and we did not attempt to measure them for ethical reasons. Based on studies performed on reptile species including chelonians (Hutchison et al 1966;Webb & Witten 1973;reviews in Bartholomew 1982;Lillywhite 1987;Peterson et al 1993), we confidently estimated that exposure to prolonged periods (> 1 hour) of ambient temperatures of 40 • C are unsafe, and that a prolonged central body temperature > 38 • C precipitates dehydration and can be eventually lethal (there is no record of reptiles surviving an elevation of body temperature > 44 • C). Most reptiles can easily tolerate ambient temperature close to 0 • C for prolonged time periods, critical lower body temperatures are generally markedly negative (Bartholomew 1982).…”

“…Based on studies performed on reptile species including chelonians (Hutchison et al . 1966; Webb & Witten 1973; reviews in Bartholomew 1982; Lillywhite 1987; Peterson et al . 1993), we confidently estimated that exposure to prolonged periods (> 1 hour) of ambient temperatures of 40 °C are unsafe, and that a prolonged central body temperature > 38 °C precipitates dehydration and can be eventually lethal (there is no record of reptiles surviving an elevation of body temperature > 44 °C).…”

“…Most reptiles can easily tolerate ambient temperature close to 0 °C for prolonged time periods, critical lower body temperatures are generally markedly negative (Bartholomew 1982). We emphasize that we distinguish central (internal) body temperature, from external (cutaneous) body temperatures, which can momentarily reach values > 40 °C or < –5 °C without visible damage, especially in relatively large species such as terrestrial chelonians (McGinnis & Voigt 1971; Webb & Witten 1973). The main consequence of focusing on critical minimum and maximum body temperatures is the straightforwardness of the analyses: no individual can survive a single episode of prolonged overheating (for example >45 °C for one hour).…”

Observations and comments on the body temperatures of some New Zealand reptiles

“…But should rectal or brain temperature be measured and accepted as representative of the body? The question arises because several studies have shown differences between the two (Heath 1964a, Campbell 1969, Webb et al 1972, Webb & Whitten 1973, with significantly more precise regulation of brain temperature (Hammel et al 1967, Crawford 1972. Heatwole (1970) suggested that head temperature is a more accurate indicator of PBT than cloacal temperature.…”

Effect of the rate of temperature increase of the dynamic method on the heat tolerance of fishes

“…As an example, until 2004 the Cambridge Scientific Abstracts Database contained 197 citations referring to ''critical thermal maximum''; of these only five specifically referred to ''heating and/or warming rates''. Out of these five one did not provide any comparison of thermal tolerances among heating rates (Gomez, 1990) and another was based on the rate of temperature penetration in the body of turtles (Webb and Witten, 1973). Our precarious understanding about the effect of the heating rate on thermal tolerance is particularly critical given the broad range of heating rates used so far.…”