Temperature-sensitive Radio Transmitters Research Articles

Daily Torpor in a Free-ranging Goatsucker, the Common Poorwill (Phalaenoptilus nuttallii)

Numerous laboratory studies show that common poorwills (Caprimulgidae: Phalaenoptilus nuttallii) are capable of entering daily torpor when deprived of food. Using temperature-sensitive radio transmitters, I measured the skin temperature of free-ranging birds under natural conditions to test three hypotheses about the use of torpor by poorwills. I predicted that (1) poorwills would enter torpor only in "energy emergencies" (defined as birds with low body mass), (2) only the nonincubating or brooding member of a pair would use torpor during the breeding season, and (3) poorwills would be less likely to enter torpor on moonlit nights when longer periods of activity can be sustained. My results show that adult poorwills of both sexes enter torpor regularly in April, May, and September, but not during the breeding season. I found no evidence that torpor was used only in energy emergencies or that the lunar cycle influenced the use of torpor. Skin temperatures regularly dropped below 10°C and in one instance fell below 3 C. On one occasion an individual bird remained torpid for at least 36 h. I found limited evidence suggesting that the temperature at twilight, but not insect abundance, can be used to predict whether birds will remain active or enter torpor.

Thermal and Behavioral Respones to Feeding in Free-Ranging Turtles, Chelydra serpentina

Using temperature-sensitive radio transmitters, we tested the hypothesis that recently fed snapping turtles (Chelydra serpentina) would inhabit warmer microhabitats than would unfed individuals. We used free-ranging adult turtles from a population in Ontario, Canada near the northern limit of the species' distribution. In late July 1989, four radio-transmittered adults were fed by hand and their sub- sequent behavior and ambient temperature were recorded. Seven other radio-tagged individuals served as a control group. Following feeding, experimental turtles did not bask or experience an increase in habitat temperature, nor did they experience significantly warmer temperatures than did unfed controls. Instead, fed turtles buried themselves in the substrate and were less active and remained in shallower water than the control group. We conclude that in this population turtles do not use basking and thermophilic behavior to accelerate their rate of digestion.

Endotoxin induced prolonged fever in rats

1. 1.| E. coli endotoxin (3.0 mg/kg) was injected intraperitoneally (i.p.) at 09:00 h for one group and 17:00 h for a second group of male Wistar rats. 2. 2.|Deep body temperature ( T b) was monitored with a small temperature sensitive radiotransmitter located in the abdomen. 3. 3.|After 2–4 h latency the endotoxin injections resulted in elevated T b in both groups for a period of more than 24 h. 4. 4.|The results indicate that male Wistar rats will develop prolonged fever after a single i.p. injection of E. coli endotoxin.

Daily and seasonal cycles of body temperature and aspects of heterothermy in the hedgehog Eriuaceus europaeus.

Summary. Intra-abdominal temperature-sensitive radio transmitters were used to collect more than 350 sets of body temperature (Tb) data from 23 captive adult hedgehogs over a 3-year period. Each data set comprised measurements made every 1/2 h for 24-h periods. Between 20 and 60 such data sets were recorded every calendar month, and a total of 17400 measurements of Tb were collected. The hedgehogs were exposed to natural environmental conditions at 57 ⁰N in NE Scotlad. Hedgehogs showed seasonal changes in mean daily euthermic Tb, with a July maximum of 35.9±0.2 ⁰C a September minimum of 34.7± 0.9 ⁰C and a marked circadian Tb cycle that correlates closely with photoperiod Maximal Tb occurred within 2 h of midnight and this pattern of nocturnal maximum and diurnal minimum Tb was most marked between April and September. The circadian Tbcycle was least correlated with photoperiod during winter. Hibernal Tb during winter correlated with ambient temperature (Ta), it was maximal in September(17.7± 1.0 ⁰C and minimal in December (5.2±0.9 ⁰C Apart from the tracking of Ta and Tb during hibernalb outs, with a time-lag of 4-6 h, circadian rhythmicity of hibernal Tb was not evident. However, the Tb of hibernating hedgehogs rose significantly when Ta fell below-5 ⁰C although the animals did not neccessarily arouse.Although hibernal bouts occurred between September and April, 89.5% of such bouts were recorded between November and February. The mean time of entry into hibernation was 01:45 ±5./h GMT while the mean time of the start of spontaneous arousal from hibernation was 11 : 53 ± 4.8 h GMT. Therefore, during hibernation hedgehogs were either fully aroused at night,when euthermic hedgehogs have maximal Tb, or in deep hibernation around midday, when euthermic hedgehogs have minimal Tb. Since wild hedgehogs will feed during spontaneous arousal from hibernation, these timings are probably adaptive, and suggest that entry into, and arousal from, hibernation may be extensions of circadian cyclicity. Spontaneous bouts of transient shallow torpor (TST) were recorded throughout the year, with nearly 80% of observations occurring during August and September, at the start of the hibernal period. TST bouts lasted for 4.9±2.9 h, with T b falling to 25.8±3.1 ⁰C Only 20% of TST bouts immediately preceded hibernation and their duration did not correlate with Ta or body mass. TST bouts started at O6:51± 4.7 h GMT, significantly later than entry into hibernation, and ended at 13:04±5.4 h GMT. The function of TST bouts is unclear,but they may be preparation for the hibernation season or a further energy conservation strategy. When arousing from hibernation hedgehogs warmed at a rate of 1.9±0.4⁰C -1, and when entering hibernation cooled at 7.9±1.9 ⁰C h- 1. Warming rates were slightly higher during mid-winter when Tb and body mass were minimal, but cooling rates were 44% higher at the end of the hibernal period compared to the start. Cooling and warming rates were strikingly similar to those measured in hedgehogs at 31 ⁰N These results demonstrate that thermoregulation in the hedgehog is closely regulated and changes on a seasonal basis, in meeting with requirements of surviving food shortages and low temperature during winter.

Hibernating patterns of free-ranging Columbian ground squirrels.

The patterns of torpor and euthermy during hibernation was documented for 28 free-ranging Columbian ground squirrels (Spermophilus columbianus) fitted with temperature-sensitive radio transmitter collars. Adult males began hibernation earlier, were euthermic for a greater proportion of the hibernating season and emerged earlier than other age and sex classes. The patterns of hibernation of adult females did not differ significantly from those of juveniles. Emergence from the hibernaculum was preceded by a long (3-12 d) euthermic interval in adult males but not in adult females or juveniles. Changes in soil temperature did not appear to initiate emergence. The greater time spent euthermic by adult males is interpreted as a significantly greater energy cost of hibernation for adult males than for other age and sex classes. The benefits offsetting these costs may be increased reproductive potential in spring and avoidance of predation in late summer.

Seasonal shifts in the thermoregulatory behaviour of australian blacksnakes, Pseudechis porphyriacus (serpentes: elapidae)

1. 1.Activity patterns, movements and thermoregulation of 27 adult blacksnakes containing miniature temperature-sensitive radiotransmitters were monitored in spring and summer in a montane area of eastern Australia. 2. 2.Within each season, mean selected body temperatures were similar in the two sexes, regardless of reproductive status. 3. 3.In spring, male temperatures tended to be more variable than those of females, because the long-range movements of males precluded precise thermoregulation. 4. 4.Although ambient (air) temperatures were higher in summer than in spring, the reverse was true of body temperatures: both male and female snakes were approx. 5°C cooler in summer than in spring. 5. 5.Snakes were less active in summer than in spring, and were cooler in summer even when they were active. 6. 6.We attribute the decreased activity levels in summer to drought, which apparently depressed availability of prey (frogs), and hence foraging by the snakes. Under such circumstances, the metabolic costs of maintaining high body temperatures may exceed the likely benefits of unproductive foraging.

Freeze avoidance in a mammal: body temperatures below 0 degree C in an Arctic hibernator.

Hibernating arctic ground squirrels, Spermophilus parryii, were able to adopt and spontaneously arouse from core body temperatures as low as -2.9 degrees C without freezing. Abdominal body temperatures of ground squirrels hibernating in outdoor burrows were recorded with temperature-sensitive radiotransmitter implants. Body temperatures and soil temperatures at hibernaculum depth reached average minima during February of -1.9 degrees and -6 degrees C, respectively. Laboratory-housed ground squirrels hibernating in ambient temperatures of -4.3 degrees C maintained above 0 degree C thoracic temperatures but decreased colonic temperatures to as low as -1.3 degrees C. Plasma sampled from animals with below 0 degree C body temperatures had normal solute concentrations and showed no evidence of containing antifreeze molecules.

Thermoregulation of Free-Ranging Diamond Pythons, Morelia spilota (Serpentes, Boidae)

Temperature-sensitive radiotransmitters were implanted in 18 free-ranging diamond pythons (Morelia spilota), and the snakes monitored for 4-34 mo. Body temperatures rose during a period of morning basking to between 28 and 30 C then fell gradually until the following morning. Unlike many other heliothermic reptiles, diamond pythons generally showed only one period of basking each day. Overt shuttling behavior did not occur, but behavioral modifications such as postural adjustments and the use of insulated microhabitats were used to reduce the rate of heat loss. Body temperatures were lower on cloudy days than on clear days, mainly because of reduced opportunities for basking. Mean body temperatures on clear days were lower in winter than in other seasons, mainly because of higher cooling rates. On clear days, snakes under cover were relatively cool (mean ? SD = 23.6 ? 5.35 C), and much warmer when they were active (27.7 ? 4.26 C). On cloudy days, body temperatures were lowest when snakes were coiled in the open (20.9 + 3.00 C) and highest when snakes were basking (25.4 ? 3.93 C) and moving (25.4 ? 4.08 C). Thermoregulation of large terrestrial snakes may be profoundly influenced by their high but variable thermal inertia: low heating rates militate against shuttling heliothermy, but behavioral and physiological control of cooling rates confers an ability to remain relatively warm even when ambient temperatures fall rapidly. In nocturnal ambush predators like the diamond python, heatconserving behaviors (coiling immobile in sheltered microhabitats) are compatible with foraging and may extend the range of times and ambient temperatures over which the snake can capture prey.

Social thermoregulation during hibernation in alpine marmots (Marmota marmota).

Body temperature (Tb) of socially hibernating alpine marmots, a pair and two family groups, was monitored continuously from October to March with implanted temperature-sensitive radiotransmitters. At the same time, the animals' behaviour was observed. The recurrent entrances into and arousals from hibernation were highly synchronised within groups. Group members always lay huddled together when euthermic and also when torpid with a few exceptions at higher ambient temperatures (Ta). Body contact with euthermic nestmates warmed torpid marmots passively. The Tb of animals reentering hibernation did not fall to values close to Ta as long as euthermic group members were present. Although animals presumably save energy through social thermoregulation, especially when euthermic, these benefits are not necessarily mutual among group members. Differences in thermoregulatory behaviour of individuals described in this study could be responsible for differential weight losses during winter as found in the natural habitat (Arnold 1986).

Thermophilic response to feeding of the diamond python, Morelia s. spilota (Serpentes: Boidae)

1. 1. Miniature temperature-sensitive radiotransmitters were implanted surgically into eighteen adult diamond pythons and thermoregulation of these snakes studied in a large thermal gradient in the laboratory. 2. 2. Unfed diamond pythons selected temperatures in the range 26–33°C. Selected body temperature changed after feeding, with mean temperatures generally increasing by 2–5°C, and variances decreasing significantly in most snakes. 3. 3. Selected body temperatures in the laboratory were similar to maximum body temperatures achieved when basking in the field. 4. 4. Pythons without access to a heat source showed no elevation in body temperature after feeding, indicating that the thermophilic response to feeding in this species is achieved behaviorally, not physiologically.

Radiotracking Hybrid Striped Bass in Spring Lake, Illinois, to Determine Temperature and Oxygen Preferences

Abstract Twelve hybrid striped bass (striped bass Morone saxatilis ♀ x white bass M. chrysops ♂) in 101-hectare Spring Lake, Illinois, had temperature-sensitive radio transmitters implanted in April and May 1985 to determine their temperature and oxygen preferenda. Tagged fish, which were monitored weekly from April 25 to September 30, 1985, ranged widely during most of the tracking period. Overall average movements were greater than 25 m/h 56% of the time. During summer stratification, however, fish concentrated in the deeper section of the lake between the old and new dams and moved only 27 m/h during this time, as opposed to 61 m/h before it. During stratification, the fish were confined to a narrow layer of water just above the zone of oxygen depletion, where water temperatures were consistently 2-3°C cooler than near the surface. Fish appeared to prefer oxygen concentrations above 2 mg/L, which often forced them into water temperatures as high as 27°C.

Daily Variation in the Body Temperatures of Free‐Ranging Garter Snakes

This study describes how the body temperatures (Tb) of individual garter snakes varied on a daily basis under field conditions. Temperature—sensitive radio transmitters were surgically implanted into 10 Thamnophis elegans vagrans in eastern Washington. The snakes were released and monitored at 15—min intervals for periods of up to several days from June 1979 to May 1980. Operative environmental temperatures were estimated with painted metal models and were used to indicate possible Tb's. The combination of telemetered body temperatures with operative temperature data permitted detailed description of Tb variation and evaluation of the relative importance of the physical environment and behavior in determining that variation. The physical environment usually prevented the snakes from attaining preferred (selected) Tb's and thus limited when and where they could be active and potentially reduced their physiological performance. On cool days or at night, when operative temperatures (Te) were <15°C, the snakes remained underground and body temperatures changed gradually. On moderate days (15° < Te < 30°), the snakes usually emerged but were unable to maintain preferred body temperatures, and Tb variation was marked. On warm days (Te > 30°), the snakes selected Tb's within their preferred temperature range, and variation in Tb was small (e.g., range = 28.0°—32.5° X = 29.9°, SD = 1.32°). The snakes stayed within their preferred temperature range >90% of the time when Te > 30°. Their high thermoregulatory precision and thermal utilization presumably maintained high levels of physiological performance on warm days. Delays in emergence accounted for most instances in which the snakes did not utilize available thermal opportunities.

Effect of environmental stimuli on the core temperature of nervous dogs

Temperature sensitive radio transmitters were implanted into the abdominal cavities of two substrains of pointer dogs to monitor the core temperature during a 12:12 L/D cycle. The results obtained from dogs of a nervous, person-aversive strain were best described by a partially-rectified sine curve, with well defined maxima during the light period. When similarly tested in a situation with minimal diurnal stimulation, the variation in temperatures was reduced. Temperatures of normal pointer dogs, kennel-mates of the nervous dogs, fluctuated very little by comparison. Their data fitted a straight line about as well as a sine curve.

Movements and Temperature Relationships of Timber Rattlesnakes (Crotalus horridus) in Northeastern New York

ABSTRAC. -Five adult timber rattlesnakes (Crotalus horridus) were tracked using temperaturesensitive radio transmitters during their movements away from a den and on summer habitat. The snakes dispersed a mean of 504 m ( Q $ 280 m, 8 1400 m) and gained a mean of 102 m in elevation. One gravid female was relatively sedentary (39 m/move) between 20 June-5 August. Non-gravid females moved farther. Immediately after ecdysis movements of three snakes were suddenly extensive. Two females appeared to use the same migratory routes returning to the den in autumn as they did at spring egress. Minimum and maximum voluntary temperatures were 12.5 and 33.3?C, respectively. The overall mean body temperature (TB) was 26.9?C (N = 157). On the surface in clear weather, TB averaged 30.1?C while mean air temperature (TA) was 26.0 and substrate (Ts) 20.6?C. On the surface in cloudy weather and underground in clear weather, mean TB was 27.8?C. Snakes underground in cloudy weather had a mean TB of 20.2?C, not significantly different from mean TA and Ts. Thermoregulation was accomplished by moving in and out of rock crevices and by moving slightly within the sunshade interface in grassy-shrub locations. Body color, reproductive condition, stage of ecdysis, and feeding are four factors that may have important effects on thermal relationships of C. horridus. Controlled experiments to examine these factors are needed.

Body Temperatures of Incubating versus Non-Incubating Roadrunners

Core temperatures of free-living Roadrunners (Geococcyx californianus) were monitored with temperature-sensitive radio transmitters. Breeding males were found to perform all of the nocturnal incubation and to maintain normothermic body temperatures at night. Body temperatures of females and non-breeding males dropped at night to as low as 330C, depending on the ambient temperature. Facultative, short-term hypothermia appears to be a regular energysaving feature of this species that is conspicuously not employed by the nocturnal incubator. Most birds exhibit a circadian pattern of body temperature, involving a reduction of 1 to 30C during the nighttime hours (Dawson 1954, Aschoffand Pohl 1970). Lower nocturnal body temperatures appear to be due to reduced motor activity and other cyclic phenomena of sleep, since nocturnally active birds show a reversal of the pattern, i.e., lower diurnal body temperatures. Only a handful of species exhibit true hypothermia, defined operationally as a reduction of body temperature below 360C that may or may not involve torpor (Dawson and Hudson 1970). Facultative hypothermia is generally argued to be an energy-saving adaptation in response to periodic food shortages and/or excessively low ambient temperatures (Calder and King 1974). Species that exhibit hypothermia include nectar-feeding hummingbirds, aerial insectivores such as caprimulgids, swallows and swifts, small passerines overwintering in cold climates, and a few tropical species such as anis and colies (Dawson and Hudson 1970, Calder and King 1974). It has been argued that short-term hypothermia should occur only in small animals due to the theoretically prohibitive effects of thermal inertia and high rewarming cost for large animals (Calder and King 1974), yet vultures are known to lower body temperatures to 340C. Hypothermia is a complex phenomenon for which the costs and benefits are still poorly understood. The constraints that hypothermia places on breeding birds have not been explored. In particular, incubation and hypothermia may not be compatible. Incubating hummingbirds have generally been found to maintain normothermic body temperatures at night except during unusual cold (Calder 1971, Vleck 1982). Egg temperatures fall well below normal incubation temperatures during these lapses into hypothermia. It is not clear whether non-incubators under similar conditions would show the same or different responses. If incubators typically maintain high body temperatures under conditions when non-incubators show hypothermia, then incubation may be metabolically expensive. Furthermore, the female of a facultatively hypothermic species may be energetically constrained during incubation if she has laid a large clutch of eggs and must recuperate depleted reserves via hypothermia. Thus facultative hypothermia may have important implications for both clutch size and the sex that performs the incubation. The Roadrunner (Geococcyx californianus) is a large (350 g) cuckoo that has been reported to lower its body temperature under stressful conditions and to warm up by sunning (Ohmart and Lasiewski 1971). Hypothermic birds have been found to conserve a significant amount of energy compared to normothermic birds at the same ambient temperature. The Roadrunner is also among the few species in which the male performs most of the incubation, especially at night (Calder 1967, Ohmart 1973, Skutch 1976). In order to obtain a better understanding of the breeding energetics of this unusual bird, I monitored the body temperatures of free-living Roadrunners using radio-telemetry techniques while simultaneously following breeding activities. I here report significant differences in body temperature for Roadrunners as a function of sex and

Field Surgical Techniques for Implanting Temperature-Sensitive Radio Transmitters in Grizzly Bears

Field Surgical Techniques for Implanting Temperature-Sensitive Radio Transmitters in Grizzly Bears

Torpor Patterns and Microenvironment of the Eastern Chipmunk, Tamias striatus

Four chipmunks ( Tamias striatus ), implanted with temperature-sensitive radio transmitters, were released into outdoor artificial burrow systems in southeastern Michigan. These systems closely approximated natural burrows in design and dimensions. Torpor patterns, ambient temperatures, and the concentrations of oxygen and carbon dioxide within the burrows were monitored throughout the winter. One animal remained euthermic at all times. The others underwent frequent periods of shallow torpor between December and February. Duration of the torpor cycles was usually less than 24 h, and the mean minimum body temperature during torpor was 16.6°C. The lowest body temperature recorded was 10°C. Nest temperatures during this period were between 2 and 5°C. The nest temperatures were highly stable on a daily basis and never fell below 2°C, whereas temperatures above the surface were frequently below — 10°C. Gaseous composition within the burrows was unstable. Mean oxygen and carbon dioxide concentrations were 17.8 and 3.2%, respectively, but oxygen concentrations as low as 14.4% and carbon dioxide concentrations as high as 6.4% were recorded.

Heterothermy in Free‐Ranging Abert's Squirrels (Sciurus Aberti)

Body temperatures (T_b) of 7 free—ranging Abert's squirrels were monitored by intraperitoneally implanted temperature sensitive radio transmitters. Relationships between Tb, activity, solar exposure, ambient air temperature (T_a), and weather conditions were examined. T_b values ranged from 35.2 to 41.1 degrees C (° = 39.0 degrees C) and varied with behavior. A hyperthermic condition during both summer and winter developed during bouts of intense activity and the degree of hyperthermia was related to intensity of activity. Immediately following intense activity, squirrels sought shade in a tree to facilitate cooling. Squirrels exhibited hypothermia in the nest during the day and night. A diurnal rhythm of Tb was observed in free—ranging squirrels when in the nest and similar rhythms of T_b and O_2 consumption rate (V_(O_2)) were observed in laboratory squirrels. Basking was common on winter afternoons and upon emergence from the nest in the morning throughout the year, resulting in elevated Tb values. Position of the tail appeared to moderate solar irradiation striking the squirrel during basking. When positioned dorsally, the tail increased reflectance. Wind and rain significantly reduced Tb in squirrels outside the nest. The relationship between Tb and Ta was subtle and difficult to ascertain in the field. In the laboratory, Tb decreased in response to falling Ta and subsequently metabolic expenditures were depressed from the expected. The mean field Tb during summer and early fall was significantly higher than during winter or spring and may indicate seasonal acclimatization. Squirrels in the field did not cache substantial quantities of food. They foraged daily and were active during all seasons, including inclement winter weather. Fresh snow appeared to restrict movements. Squirrels were seldom outside of the nests at Ta values < —10°C. Laboratory experiments established a thermoneutral zone between 29° and 35°C. Within the zone the Vo2 was 0.69 ml O2 (g h)—1 (standard temperature and pressure, dry) or 104% of the predicted weight specific value. The curve of thermogenesis is best described by a polynomial regression due to shifts in Vo2 caused by changes in Tb in response to falling Ta. The lower lethal limit was near —20 degrees C.

Postirradiation Hibernation and Radiation Response of Ground Squirrels: Telemetry Surveillance

Temperature sensitive radio transmitters were implanted in the abdominal cavity of ground squirrels, Citellus tridecemlineatus. A 72-channel telemetry receiver system was constructed to monitor the hibernation patterns, as reflected in body temperature changes, of 72 squirrels given 1250 rads60 Co gamma radiation and 20 nonirradiated controls. Forty-eight squirrels were irradiated while torpid and 24 while active. These groups were equally divided into three postirradiation groups, one group each being maintained for 8 weeks at temperature environments, 5, 13, and 23°C. The results showed the highest levels of survival among squirrels irradiated while torpid and that additional increase in survival may have occurred due to postirradiation hibernation. No significant effect was noted relating to the three postirradiation environments.

Monitoring Activity of Small Mammals by Temperature‐Telemetry

A temperature—sensitive radio transmitter for small mammals is described. Its range was 200 meters, and it provided valuable information about movements of small mammals in and out nests. The only limitation is that the nest or burrow temperature must differ from that of ambient air by at least 3°C.