Body-Temperature and Diurnal Activity Patterns in the Platypus (Ornithorhynchus-Anatinus) During Winter

Grigg, G. C.; Beard, Laura; Grant, Tom; Augee, M. L.

doi:10.1071/zo9920135

Cited by 39 publications

(30 citation statements)

References 10 publications

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“…The platypus has very dense fur which retains a high insulative value in water, and a number of vascular adaptations which reduce heat loss, but even so at water temperatures below 20°C heat loss of resting platypuses is double that in air at the same temperature (Grant and Dawson, 1978; Bethge et al, 2001). Metabolic rate further increases during foraging activity (Fish, 2000; Bethge et al, 2001), but even when foraging at water temperatures very close to freezing, platypuses maintain their body temperature within the normal range (Grigg et al, 1992), which means that heat loss is being matched by increased heat production. Even in the coldest water platypuses forage on average about 12 h/day (Bethge et al, 2009), and these sustained high levels of energy expenditure have selected for a higher BMR than the terrestrial echidna.…”

Section: Metabolic Rate and Body Temperaturementioning

confidence: 99%

Energy Homeostasis in Monotremes

Nicol

2017

Front. Neurosci.

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In 1803, the French anatomist Étienne Geoffroy Saint-Hilaire decided that the newly described echidna and platypus should be placed in a separate order, the monotremes, intermediate between reptiles and mammals. The first physiological observations showed monotremes had low body temperatures and metabolic rates, and the consensus was that they were at a stage of physiological development intermediate between “higher mammals” and “lower vertebrates.” Subsequent studies demonstrated that platypuses and echidnas are capable of close thermoregulation in the cold although less so under hot conditions. Because the short-beaked echidna Tachyglossus aculeatus, may show very large daily variations in body temperature, as well as seasonal hibernation, it has been suggested that it may provide a useful model of protoendotherm physiology. Such analysis is complicated by the very significant differences in thermal relations between echidnas from different climates. In all areas female echidnas regulate Tb within 1°C during egg incubation. The lactation period is considered to be the most energetically expensive time for most female mammals but lactating echidnas showed no measurable difference in field metabolic rate from non-lactating females, while the lactation period is more than 200 days for Kangaroo Island echidnas but only 150 days in Tasmania. In areas with mild winters echidnas show reduced activity and shallow torpor in autumn and early winter, but in areas with cold winters echidnas enter true hibernation with Tb falling as low as 4.5°C. Monotremes do not possess brown adipose tissue and maximum rates of rewarming from hibernation in echidnas were only half those of marmots of the same mass. Although echidnas show very large seasonal variations in fat stores associated with hibernation there is no relationship between plasma leptin and adiposity. Leptin levels are lowest during post-reproductive fattening, supporting suggestions that in evolutionary terms the anorectic effects of leptin preceded the adiposity signal. BMR of platypuses is twice that of echidnas although maximum metabolism is similar. High levels of thyroid hormones in platypuses may be driving metabolism limited by low body temperature. Monotremes show a mosaic of plesiomorphic and derived features but can still inform our understanding of the evolution of endothermy.

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Section: Metabolic Rate and Body Temperaturementioning

confidence: 99%

Energy Homeostasis in Monotremes

Nicol

2017

Front. Neurosci.

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“…During winter/spring echidnas were still being recruited to the study (Table 1) so data acquired directly were sparse and were supplemented by interpolation and deduction, as in Grigg et al (1992b). For example, a signal that varied from hour to hour as recorded by a stationary scanner was interpreted as coming from a moving, active echidna whereas a signal that remained constant in strength (relative to any background noise) over several hours was interpreted as originating from a stationary (if not inactive) echidna.…”

Section: Methodsmentioning

confidence: 99%

Patterns of activity and inactivity in echidnas (Tachyglossus aculeatus) free-ranging in a hot dry climate: correlates with ambient temperature, time of day and season

Brice¹,

Grigg²,

Beard³

et al. 2002

Aust. J. Zool.

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Echidnas occur throughout Australia. They exhibit daily fluctuations in body temperature (T b ) and use torpor to various degrees throughout much of their range. Echidnas elsewhere are commonly diurnal except during hot weather. This study used temperature-sensitive radio-transmitters to investigate the activity patterns and temperature relations of echidnas in the relatively hot, dry climate of south-west Queensland with respect to temperature and photoperiod.During activity, echidnas were characterised by rising, but not necessarily high, T b s. Activity was seen only within an ambient temperature range (as measured in a nearby Stevenson Screen: T ss ) of 9-33°C so that activity was seen during the day and at night during the cool weather but only at night in summer. Echidnas used caves, burrows and logs when inactive. T b s of inactive echidnas declined except when affected by rising ambient temperatures, as determined within these shelters (T a ). In summer, T b s of echidnas in these shelters changed little or rose with increasing T a to levels even higher than in active echidnas.Torpor was used by echidnas for periods up to nine days during winter and occasionally for up to one day during summer. Due to the difficulty of identifying the occurrence of torpor from T b alone in warm conditions, the possibility that echidnas utilise torpor for less than one day remains inconclusive. Nevertheless, at least five bouts of torpor were identified in four (of eight) echidnas during winter/spring and two bouts of torpor from two echidnas in summer.Z O 0 1 0 8 0 A c t i v i t y p a t t e r n s i n e c h i d n a s P . H . B r i c e e t a l .

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“…by night during winter and by day during summer. Additionally, body temperature (which varies markedly on a daily cycle: Grigg et al 1989Grigg et al , 1992a) and variability of signal strength (Grigg et al 1992b) were a reasonable guide to whether an individual was active or at rest. Sheltered echidnas were often well hidden, but could be located to within 0.5 m using the radio-tracking equipment and did not need to be disturbed in order to get an accurate assessment of the shelter in use and the relevant entrance.…”

Section: Location and Description Of Shelter Sites Used By Echidnasmentioning

confidence: 99%

Shelter selection and home range of echidnas, Tachyglossus aculeatus, in the highlands of south-east Queensland

Wilkinson¹,

Grigg²,

Beard³

1998

Wildl. Res.

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We recorded physical attributes of sites used for daily shelter or as hibernacula by nine echidnas, Tachyglossus aculeatus, living on a sheep-grazing property in south-eastern Queensland. Home ranges were also determined. For daily shelter sites, echidnas most often used hollow logs and depressions under the roots of fallen trees. Daily shelters were found more often on north-facing slopes and usually provided >90% cover. Hibernation sites always provided 100% cover but, in contrast to daily sites, were distributed randomly in relation to the slope of the terrain. Rabbit burrows, which offer much better thermal buffering than hollow logs, were used most commonly as hibernacula. There were differences between individuals in the type of shelter they used and, moreover, echidnas did not use shelter sites in proportion to what was available, indicating that choice was being exercised. Re-use of sites occurred non-randomly, implying that echidnas can recognise previously used shelters and probably have a learned familiarity with their living area. Home ranges varied between 20.6 ha and 93.3 ha (mean = 49.8, s.d. = 25.4), overlapped with those of other echidnas and correlated positively with body weight.

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Body-Temperature and Diurnal Activity Patterns in the Platypus (Ornithorhynchus-Anatinus) During Winter

Cited by 39 publications

References 10 publications

Energy Homeostasis in Monotremes

Energy Homeostasis in Monotremes

Patterns of activity and inactivity in echidnas (Tachyglossus aculeatus) free-ranging in a hot dry climate: correlates with ambient temperature, time of day and season

Shelter selection and home range of echidnas, Tachyglossus aculeatus, in the highlands of south-east Queensland

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