Regulated torpor and unregulated hypothermia are both characterized by substantially reduced body temperature (Tb) metabolic rate (MR), but they differ physiologically. Although the remarkable, medically interesting adaptations accompanying (e.g., tolerance for cold ischemia, absence of reperfusion injury, disuse atrophy) often do not apply to in homeothermic species such as humans, terms "torpor" "hypothermia" used interchangeably literature. To determine how these states functionally...

We report on the occurrence and context of female song in color-marked Song Sparrow (Melospiza melodia) population resident Mandarte Island, British Columbia. Sonograms three females showed that structure varied, but was usually less complex than males. At least one female's within male range complexity could have been mistaken for a had sex bird unknown. Another sang at two distinct types. Further, songs recorded were similar to those elsewhere from wild captive implanted with testosterone....

Models of sexual selection propose that exaggerated secondary ornaments indicate a male's own fitness and the his offspring. These hypotheses have rarely been thoroughly tested in free‐living individuals because overall fitness, as opposed to components, is difficult measure. We used 20 years data from song sparrows (Melospiza melodia) inhabiting Mandarte Island, British Columbia, Canada, test whether repertoire size, trait, predicted measures male or offspring fitness. Males with larger...

Continuous records of nighttime O₂ consumption (V̇o2) from rufous hummingbirds (Selasphorus rufus) were used to determine during normothermic rest, entry into torpor, steady-state and arousal torpor over a range air temperatures (Ta)from −1° 24° C. Whereas occurred anytime the first 9.5 h 12-h night, arousals consistently initiated within 2.5 end night in absence known environmental cues. During V̇o2 was inversely related Ta entire temperature range. reached its lowest value at approximately...

Torpor bouts of mammalian hibernators are generally shorter at the beginning and end consistently longer during main part hibernation season. Because it is not known why duration torpor changes season, we studied this phenomenon in two sciurid rodents: Spermophilus saturatus (200–300g) Eutamias amoenus (45-60g). We examined seasonal change bout a constant air temperature (Ta) 2° C relation to (1) minimum body (minimum Tb) which animals could be experimentally cooled before they maintained Tb...

In a study designed to determine seasonal patterns of body mass and torpor in Rufous Hummingbirds (Selasphorus rufus), birds were maintained for 12 months the laboratory on photoregime approximating that experienced by free-living birds. Ambient temperature cycled from 20°C during day 5°C at night. Body mass, torpor, rates nighttime oxygen consumption measured under conditions ad libitum feeding LD 12:12 autumn (when are normally migrating south), spring (during molt), 16:8 summer. Both use...

Hummingbirds depend on floral nectars for energy. This entails a significant water excess which is eliminated in chronic diuresis. In the eight species from we obtained urine samples, solutes were conserved by reducing osmotic concentrations to approximately one-fifth of plasma levels. Sodium and potassium salts accounted one-half one-third concentration urine. These can be replaced mostly trace amounts nectars. Data field, laboratory, literature are combined account salt exchanges...

Daily food consumption of captive Rufous Hummingbirds (Selasphorus rufus) was restricted during two different seasons to determine the effect chronically reduced intake on body mass and role nocturnal torpor in promoting changes mass. 70-90% ad libitum levels for 15 days spring 30 summer. In spring, all birds (n = 4) showed increases both use restriction, although energy saved by using sufficient compensate lost through restriction only birds. As soon as feeding resumed, three four a decline...

This article provides instructors with guidelines for teaching simple experimental design the comparison of two treatment groups. Two designs specific examples are discussed along common misconceptions that undergraduate students typically bring to experiment process. Features maximize power and minimize effects interindividual variation, thus allowing reduction sample sizes, described. Classroom implementation emphasizes student-centered learning is suggested, thought questions, designed...

Entrainment of circannual rhythms body mass and reproduction was monitored for 3 years in female golden-mantled ground squirrels maintained a simulated natural photoperiod. Both pinealectomized pinealintact generated estrus, but only the intact animals entrained these to period 365 days. In second third after treatment, rhythm significantly shorter than days squirrels, variance tau among greater squirrels. Asimilar pattern evident reproduction, which phase-disrupted intacts. Seasonal changes...

Laboratory exercises in which students examine the human diving response are widely used high school and college biology courses despite experience of some instructors that is unreliably produced classroom. Our with this exercise demonstrates bradycardia associated a robust effect can easily be measured by without any sophisticated measurement technology. We discuss measures maximize success reducing individual variation, designing experiments minimally affected change over time, collecting...

This investigative laboratory exercise uses the different relations between ambient temperature and metabolic rate in endotherms ectotherms as a core concept to answer following question: What thermoregulatory mode is employed by chicken embryos? Emphasis placed on physiological concepts that can be taught with this exercise, including methods for measuring rates of oxygen consumption, relation consumption rate, influence differences both overall magnitude shape temperature. Included article...

Previous studies have shown that hibernators preparing for winter prefer a diet rich in unsaturated fat. This study was designed to determine if daily heterotherm, the Djungarian hamster (Phodopus sungorus), shows similar preference when given simultaneous access two diets, one saturated fat and other In experiments, hamsters had been exposed short days 8-10 weeks were 8°C 10 days. When half of these animals moved warm environment (26-29°C), they developed significantly lower than controls...