Long-term population trends in seven Antarctic seabirds at Pointe Géologie (Terre Adélie) Human impact compared with environmental change

Antarctic seabird populations have been much studied over the last decades as bioindicators of the nature of variability in the Southern Ocean marine ecosystem, and most attention has been focused on the role of food supply and the extent of sea ice. In addition, the rapid spread of tourism and the activities of researchers since the early 1960s have raised questions related to their real and potential impact on bird populations. Our data sets start in 1952 for several species of Antarctic seabirds and this study documents the trends over a 14-year period (1985–1999) in seven species breeding on Pointe Géologie archipelago (Terre Adélie, Antarctica). This is the first study where the direct impact of destruction of breeding sites (for building of an airstrip) is examined and where such long-term populations trends have been assessed in such a number of Antarctic species at one site. Trends from 1985 show that for the whole archipelago and when excluding islands destroyed, Adélie penguins and south polar skuas were the only species to show a significant increase (>3.5% annual change). The others species showed opposite trends, three increasing slightly (southern fulmars +0.4%, cape petrels +2.3%, snow petrels +0.9%) and two decreasing (emperor penguin −0.9%, southern giant petrel −3.9%). Three species particularly affected by the destruction of their breeding habitat (Adélie penguin, cape petrel, snow petrel) showed the capability to restore their populations. The availability of food and nesting sites is discussed in relation to environmental change. Species feeding on krill (Adélie penguins and cape petrels) increased more than other species; however, decrease of ice cover can increase availability of nesting sites. The importance of long-term studies is shown when assessing the role of human activities in Antarctica compared to larger-scale changes. Accepted: 18 September 2000     

First census of breeding seabirds between Cap Bienvenue (Terre Adélie) and Moyes Islands (King George V Land), Antarctica: new records for Antarctic seabird populations

Breeding population sizes of penguins, fulmarine etrels and skuas were estimated for the first time on a major part of the Terre Adélie coast and a section of the King George V Land coast during the 1997/1998 austral summer. We counted 106,400 breeding pairs and 12,400 Adélie penguin (Pygoscelis adeliae) chicks by direct counts, and 6960 breeding pairs from aerial photographs. Minimum breeding populations for other species are (direct counts): Antarctic fulmar (Fulmarus glacialoides) 6861 pairs, Antarctic petrel (Thalassoica antarctica) 4574 pairs, cape petrel (Daption capense) 194 pairs, snow petrel (Pagodroma nivea) 767 pairs, south polar skua (Catharacta maccormicki) 129 pairs and subantarctic skua (Catharacta lonnbergi) 1 breeding bird. We discovered 29 new seabird breeding locations in King George V Land, including 6 Antarctic fulmar, 4 Antarctic petrel, 3 cape petrel, 6 snow petrel and 10 south polar skua colonies. The largest colonies found contained up to 4205 breeding pairs of Antarctic fulmars. Population sizes of all species obtained in this study are higher than those found during previous partial surveys. Although these differences are in great part due to differences in survey methods, they also reflect real population changes. Our minimum population sizes obtained for a small portion of the Antarctic coast (<2%) suggest an underestimation of the estimated world breeding populations for several species of Antarctic seabirds. Accepted: 28 August 1998     

Changes in egg and body temperature indicate triggering of egg desertion at a body mass threshold in fasting incubating blue petrels (Halobaena caerulea)

The triggering of transitory egg desertion in fasting and incubating blue petrels (Halobaena caerulea, nocturnal burrowing seabirds living in the subantarctic region) was investigated by continuously monitoring both body temperature (T _sto) and egg temperature (T _egg) with a telemetry system, and by measuring body mass (BM) loss. The birds were kept captive in their burrow and incubated day and night without any interruption; there was no day-night cycle in T _sto and T _egg, which averaged 39.9 °C and 32.0 °C, respectively. There was no evidence of hypothermia as a way to save energy in this fasting situation. Egg desertion occurred at night and was an abrupt and definitive phenomenon reflected by a simultaneous fall in T _egg and a peak in T _sto. After egg desertion, a distinct day-night cycle of body temperature was observed, T _sto being 0.6 °C higher during night-time (P < 0.05), probably reflecting increased nocturnal activity. BM at egg desertion averaged 166.7 ± 3.8 g in telemetered birds and 164.4 ± 1.6 g in␣a group of free-living birds. Throughout fasting, the␣specific daily BM loss remained at 46 ± 1 g · kg⁻¹ · day⁻¹, but increased sharply below a critical BM of 160.0 ± 2.5 g. Thus, fasting incubating blue petrels spontaneously desert their egg when reaching a BM threshold. This BM is very close to a critical value in fasting birds and mammals that corresponds to a critical depletion of fat stores and to a shift from lipid to protein utilization. This strongly suggests that such a metabolic shift triggers behavioural changes leading to egg desertion and refeeding, which is of great relevance to the understanding of the long-term control of food intake and BM. Accepted: 16 July 1998     

Torpor and thermal energetics in a tiny Australian vespertilionid,the little forest bat (<Emphasis Type="Italic">Vespadelus vulturnus</Emphasis>)

Data on thermal energetics for vespertilionid bats are under-represented in the literature relative to their abundance, as are data for bats of very small body mass. Therefore, we studied torpor use and thermal energetics in one of the smallest (4 g) Australian vespertilionids, Vespadelus vulturnus. We used open-flow respirometry to quantify temporal patterns of torpor use, upper and lower critical temperatures (T _uc and T _lc) of the thermoneutral zone (TNZ), basal metabolic rate (BMR), resting metabolic rate (RMR), torpid metabolic rate (TMR), and wet thermal conductance (C _wet) over a range of ambient temperatures (T _a). We also measured body temperature (T _b) during torpor and normothermia. Bats showed a high proclivity for torpor and typically aroused only for brief periods. The TNZ ranged from 27.6°C to 33.3°C. Within the TNZ T _b was 33.3±0.4°C and BMR was 1.02±0.29 mlO₂ g⁻¹ h⁻¹ (5.60±1.65 mW g⁻¹) at a mean body mass of 4.0±0.69 g, which is 55 % of that predicted for a 4 g bat. Minimum TMR of torpid bats was 0.014±0.006 mlO₂ g⁻¹ h⁻¹ (0.079±0.032 mW g⁻¹) at T _a=4.6±0.4°C and T _b=7.5±1.9. T _lc and C _wet of normothermic bats were both lower than that predicted for a 4 g bat, which indicates that V. vulturnus is adapted to minimising heat loss at low T _a. Our findings support the hypothesis that vespertilionid bats have evolved energy-conserving physiological traits, such as low BMR and proclivity for torpor.     

Occurrence of the flea Glaciopsyllus antarcticus and avian lice in central Dronning Maud Land

The flea Glaciopsyllus antarcticus is endemic to the Antarctic continent, where it is known to parasitise a number of seabird species. This paper reports the occurrence of the flea and two species of lice from snow petrel (Pagodroma nivea) colonies in central Dronning Maud Land, Antarctica, and extends considerably the recorded distribution of the flea. Flea adults, pupae and larvae were recovered from 10 of 11 samples of organic material collected from snow petrel nests at Svarthamaren (71°53^′S, 05°10^′E) in the Mühlig-Hofmannfjella. Specimens of two philopterid lice species, Saemundssonia antarctica and Pseudonirmus charcoti, were recovered from three of these samples. Specimens of the Antarctic flea and of the louse S. antarctica were recovered from carcasses of snow petrel chicks collected both at Svarthamaren and Robertskollen (71°28^′S, 03°15^′W) in the northern Ahlmannryggen; the louse Pseudonirmus charcoti was recovered from Robertskollen only. Received: 30 January 1996 / Accepted: 28 April 1997     

An extreme inland breeding locality of snow petrels (Pagodroma nivea) in the southern Prince Charles Mountains, Antarctica

Bird observations were made as part of a preliminary biological survey of the southern half of the Mawson Escarpment in the southern Prince Charles Mountains, Mac.Robertson Land between 26 January and 4 February 1998. A new breeding colony of snow petrels (Pagodroma nivea) is described, together with details of individual snow petrel sightings. At 440 km from the coast, the snow petrel colony is the furthest inland of any confirmed breeding site for this species. Accepted: 1 May 2000     

Exploitation of inland-breeding Antarctic petrels by south polar skuas

During the austral summer of 1996/1997 we studied south polar skuas at Svarthamaren, Dronning Maud Land, Antarctica, where the world's largest known colony of Antarctic petrels is found. Our censuses suggested approximately 250 full-grown skuas and 140,000 breeding pairs of petrels were present. During their breeding season, skuas did not visit the open sea at least 200 km from the site; they relied entirely on prey caught and scavenged from the petrel colony. Because the site is so isolated, we asked whether the prey (petrels) had swamped the predators (skuas), or whether there was evidence that predator numbers were limited by the size of the prey population. Particularly at the end of the petrel incubation period, we found a close correspondence between the energy required by adult skuas and their chicks, ascertained from time budget studies, and the rate at which petrel eggs disappeared from the colony. This suggests that, in this closed system, the predator population was limited by the prey population, and that predator swamping was not an advantage that petrels gained by nesting in this remote location. Received: 12 April 1999 / Accepted: 30 June 1999     

Distribution and abundance of Wilson’s storm petrels Oceanites oceanicus at two locations in East Antarctica: testing habitat selection models

Over the last decades, Antarctic seabird populations have been studied as bioindicators of the variability in the Southern Ocean marine ecosystem. Little information is available on the distribution and abundance of Wilson’s storm petrel (Oceanites oceanicus) in East Antarctica although the bioindicator value of this species has been investigated. Regional surveys were conducted at two coastal locations, Casey (66°S, 110°E) and Mawson (67°S, 62°E), to locate Wilson’s storm petrel nests using systematic searches in sites selected with a balanced random sampling design. Conducted in ice-free areas of similar size, searches located 553 Wilson’s storm petrel nests at Mawson and 630 at Casey. Comparable densities were observed between locations but regional estimates suggest that Wilson’s storm petrels are more abundant at Casey. Habitat preferences of Wilson’s storm petrels were investigated using resource selection functions based on Generalized Additive and Linear Models (GAMs and GLMs), which allow their ecological niche to be graphically and quantitatively described. The orientation of nests in relation to the prevailing winds was identified as a determinant of nest distribution at both locations. However, selected rock substrate types differed between Mawson and Casey. Snow was confirmed to constrain the spatial distribution of nests, especially at Casey where snow precipitations and accumulation are more common in summer, confirming the results of previous temporal surveys focusing on breeding success. At the southern edge of its geographic distribution, the Wilson’s storm petrel may be subject to more obvious climate related habitat changes in East Antarctica. Such models may provide valuable information to detect the potential effect of climate variations on this species and others, in the context of a broad Antarctic ecosystem monitoring.     

One House Two Families: Petrel Squatters Get a Sniff of Low‐Cost Breeding Opportunities

Burrowing is a widespread nesting behaviour, found in vertebrates and invertebrates. It is particularly common in small procellariiform seabirds such as blue petrels (Halobaena caerulea) and Antarctic prions (Pachyptila desolata), two closely related petrel species. However, digging a burrow is costly and alternative strategies may evolve. Accordingly, blue petrel males can adopt two alternative nesting strategies: digging a new burrow or squatting in an empty one. Importantly, a blue petrel squatter arriving at the colony to breed is more likely to find empty Antarctic prion burrows than empty blue petrel burrows, since the former species only start breeding a month later. However, squatting in a prion’s burrow is risky for blue petrels as the legitimate owner very often returns and claims the burrow back, thus ruining the squatter’s breeding attempt. We present here results of a survey of two sympatric colonies of blue petrels and Antarctic prions on Kerguelen Island. Our data show that blue petrel squatters preferentially occupy blue petrel empty burrows. To investigate potential underlying mechanisms behind this preference, we used a simple Y‐maze design to show that blue petrels can discriminate and prefer their specific odour over the prion odour. Our results confirm the existence of alternative burrowing strategies in blue petrels and suggest that squatters could use olfaction to avoid the less suitable Antarctic prion burrows.     

Variations of snow petrel breeding success in relation to sea-ice extent: detecting local response to large-scale processes?

Demographic parameters were estimated for snow petrels Pagodroma nivea nesting at the study colony of Reeve Hill near Casey station, Antarctica between 1984 and 2003. Average breeding success for the colony varied from 18.2% to 76.5%. Breeding effort, hatching and fledging success were subject to a high interannual variability. We examined the influence of regional sea-ice extent on the breeding performance of snow petrels at Reeve Hill. Fewer birds were breeding when sea-ice had been extensive during April–May. Overall breeding success and fledging success were improved during years with extensive sea-ice cover in winter. Successful breeding effort and breeding success were depressed when there was extensive sea-ice cover during January–February. Sea surface temperatures also correlated to snow petrel breeding performance parameters. Previous work showed that large-scale climatic events (ENSO, Antarctic circumpolar wave) and the related sea-ice cover around the Antarctic might affect the lower trophic levels of the marine environment and consequently food availability for snow petrels. A comparison with the long-term study conducted at Ile des Pétrels (Terre Adélie) suggests that despite similarities in the underlying biological processes that control snow petrel breeding performance, the nature of the correlation of large-scale environmental factors with breeding performance differs substantially between the two colonies, probably because of the confounding effects of other environmental factors acting at a local scale (local weather, nest quality), which also affect bird body condition.     

Seasonal variations in basal metabolic rate, lower critical temperature and responses to temporary starvation in the arctic fox (Alopex lagopus) from Svalbard

Metabolic rates of four resting, post-absorptive male adult summer- and winter-adapted captive arctic foxes (Alopex lagopus) were recorded. Basal metabolic rates (BMR) varied seasonally with a 36% increase from winter to summer, while body mass was reduced by 17% in the same period. The lower critical temperature (T _1c) of the winter-adapted arctic fox was estimated to −7°C, whereas T _lc during summer was 5°C. The similarity of these values, which are much higher than hitherto assumed (e.g. Scholander et al. 1950b), is mainly due to a significantly (P<0.05) lower BMR in winter than in summer. Body core (stomach) temperature was stable, even at ambient temperatures as low as −45°C, but showed a significant (P<0.05) seasonal variation, being lower in winter (39.3±0.33°C) than in summer (39.8±0.16°C). The thermal conductivity of arctic fox fur was the same during both seasons, whereas the thermal conductance in winter was lower than in summer. This was reflected in an increase in fur thickness of 140% from summer to winter, and in a reduced metabolic response to ambient temperatures below T _lc in winter. Another four arctic foxes were exposed to three periods of forced starvation, each lasting 8 days during winter, when body mass is in decline. No significant reduction in mass specific BMR was observed during the exposure to starvation, and respiratory quotient was unchanged at 0.73±0.02 during the first 5 days, but dropped significantly (P<0.05) to 0.69±0.03 at day 7. Locomotor activity and body core (intraperitoneal) temperature was unaltered throughout the starvation period, but body mass was reduced by 18.5±2.1% during these periods. Upon re-feeding, locomotor activity was significantly (P<0.05) reduced for about 6 days. Energy intake was almost doubled, but stabilised at normal levels after 11 days. Body mass increased, but not to the level before the starvation episodes. Instead, body mass increased until it reached the reduced body mass of ad libitum fed control animals. This indicates that body mass in the arctic fox is regulated according to a seasonally changing set point.     

Field metabolic rates and water uptake in the blossom-bat Syconycteris australis (Megachiroptera)

Blossom-bats, Syconycteris australis (18 g) are known to be highly active throughout the night. Since this species frequently enters torpor, we postulated that their use of heterothermy may be related to a high energy expenditure in the field. To test this hypothesis we measured field metabolic rates (FMR) of S. australis at a subtropical site using the doubly labelled water (DLW) method. We also measured DLW turnover in captive animals held at constant ambient temperature (T _a) with ad libitum food to estimate whether T _a and food availability affect energy expenditure under natural conditions. The FMR of S. australis was 8.55 ml CO₂ g⁻¹h⁻¹ or 76.87 kJ day⁻¹ which is 7.04 times the basal metabolic rate (BMR) and one of the highest values reported for endotherms to date. Mass-specific energy expenditure by bats in the laboratory was about two-thirds of that of bats in the field, but some of this difference was explained by the greater body mass in captive bats. This suggests that foraging times in the field and laboratory were similar, and daily energy expenditure was not strongly affected by T _a or ad libitum food. Water uptake in the field was significantly higher than in the laboratory, most likely because nectar contained more water than the laboratory diet. Our study shows that S. australis has a FMR that is about double that predicted for its size although its BMR is lower than predicted. This supports the view that caution must be used in making assumptions from measurements of BMR in the laboratory about energy and other biological requirements in free-ranging animals. Accepted: 4 January 1999     

Thermal ecology of the Australian agamid Pogona barbata

This study compares the thermal ecology of male bearded dragon lizards (Pogona barbata) from south-east Queensland across two seasons: summer (1994–1995) and autumn (1995). Seasonal patterns of body temperature (T _b) were explored in terms of changes in the physical properties of the thermal environment and thermoregulatory effort. To quantify thermoregulatory effort, we compared behavioral and physiological variables recorded for observed lizards with those estimated for a thermoconforming lizard. The study lizards' field T _bs varied seasonally (summer: grand daily mean (GDM) 34.6 ± 0.6°C, autumn: GDM 27.5 ± 0.3°C) as did maximum and minimum available operative temperatures (summer: GDM T _max 42.1 ± 1.7°C, T _min 32.2 ± 1.0°C, autumn: GDM T _max 31.7 ± 1.2°C, T _min 26.4 ± 0.5°C). Interestingly, the range of temperatures that lizards selected in a gradient (selected range) did not change seasonally. However, P. barbata thermoregulated more extensively and more accurately in summer than in autumn; lizards generally displayed behaviors affecting heat load nonrandomly in summer and randomly in autumn, leading to the GDM of the mean deviations of lizards' field T _bs from their selected ranges being only 2.1 ± 0.5°C in summer, compared to 4.4 ± 0.5°C in autumn. This seasonal difference was not a consequence of different heat availability in the two seasons, because the seasonally available ranges of operative temperatures rarely precluded lizards from attaining field T _bs within their selected range, should that have been the goal. Rather, thermal microhabitat distribution and social behavior appear to have had an important influence on seasonal levels of thermoregulatory effort. Received: 28 April 1997 / Accepted: 29 December 1997     

Seasonal variation in thermal energetics of the Australian owlet-nightjar (Aegotheles cristatus)

Many birds living in regions with seasonal fluctuations in ambient temperatures (T_a) typically respond to cold by increasing insulation and adjusting metabolic rate. Seasonal variation in thermal physiology has not been studied for the Caprimulgiformes, an order of birds that generally have basal metabolic rates (BMR) lower than predicted for their body mass. We measured the metabolic rate and thermal conductance of Australian owlet-nightjars (Aegotheles cristatus) during summer and winter using open-flow respirometry. Within the thermoneutral zone (TNZ; 31.3 to 34.8 °C), there was no seasonal difference in BMR or thermal conductance (C), but body temperature was higher in summer- (38.2 ± 0.3 °C) than winter-acclimatized (37.1 ± 0.5 °C) birds. Below the TNZ, resting metabolic rate (RMR) increased linearly with decreasing T_a, and RMR and C were higher for summer- than winter-acclimatized birds. The mean mass-specific BMR of owlet-nightjars (1.27 mL O₂ g^− 1 h^− 1) was close to the allometrically predicted value for a 45 g Caprimulgiformes, but well below that predicted for birds overall. These results suggest that owlet-nightjars increase plumage insulation to cope with low winter T_a, which is reflected in the seasonal difference in RMR and C below the TNZ, rather than adjusting BMR.     

Daily torpor and energetics in a tropical mammal, the northern blossom-bat Macroglossus minimus (Megachiroptera)

Little is known about torpor in the tropics or torpor in megachiropteran species. We investigated thermoregulation, energetics and patterns of torpor in the northern blossom-bat Macroglossus minimus (16 g) to test whether physiological variables may explain why its range is limited to tropical regions. Normothermic bats showed a large variation in body temperature (T _b) (33 to 37 °C) over a wide range of ambient temperatures (T _as) and a relatively low basal metabolic rate (1.29 ml O₂ g⁻¹h⁻¹). Bats entered torpor frequently in the laboratory at T _as between 14 and 25 °C. Entry into torpor always occurred when lights were switched on in the morning, independent of T _a. MRs during torpor were reduced to about 20–40% of normothermic bats and T _bs were regulated at a minimum of 23.1 ± 1.4 °C. The duration of torpor bouts increased with decreasing T _a in non-thermoregulating bats, but generally terminated after 8 h in thermoregulating torpid bats. Both the mean minimum T _b and MR of torpid M. minimus were higher than that predicted for a 16-g daily heterotherm and the T _b was also about 5 °C higher than that of the common blossom-bat Syconycteris australis, which has a more subtropical distribution. These observations suggest that variables associated with torpor are affected by T _a and that the restriction to tropical areas in M. minimus to some extent may be due to their ability to enter only very shallow daily torpor. Accepted: 22 September 1997     

Thermal comfort modelling of body temperature and psychological variations of a human exercising in an outdoor environment

Human thermal comfort assessments pertaining to exercise while in outdoor environments can improve urban and recreational planning. The current study applied a simple four-segment skin temperature approach to the COMFA (COMfort FormulA) outdoor energy balance model. Comparative results of measured mean skin temperature ( [`(T)]\nolimits<sub>Msk</sub> \mathop{{\bar{T}}}\nolimits_{{Msk}} ) with predicted [`(T)]\nolimits_sk \mathop{{\bar{T}}}\nolimits_{{sk}} indicate that the model accurately predicted [`(T)]\nolimits<sub>sk</sub> \mathop{{\bar{T}}}\nolimits_{{sk}} , showing significantly strong agreement (r = 0.859, P < 0.01) during outdoor exercise (cycling and running). The combined 5-min mean variation of the [`(T)]\nolimits_sk \mathop{{\bar{T}}}\nolimits_{{sk}} RMSE was 1.5°C, with separate cycling and running giving RMSE of 1.4°C and 1.6°C, respectively, and no significant difference in residuals. Subjects’ actual thermal sensation (ATS) votes displayed significant strong rank correlation with budget scores calculated using both measured and predicted [`(T)]\nolimits<sub>sk</sub> \mathop{{\bar{T}}}\nolimits_{{sk}} (r <sub>s</sub>  = 0.507 and 0.517, respectively, P < 0.01). These results show improved predictive strength of ATS of subjects as compared to the original and updated COMFA models. This psychological improvement, plus [`(T)]\nolimits_sk \mathop{{\bar{T}}}\nolimits_{{sk}} and T _c validations, enables better application to a variety of outdoor spaces. This model can be used in future research studying linkages between thermal discomfort, subsequent decreases in physical activity, and negative health trends.     

Diet and prey consumption of Antarctic petrels Thalassoica antarctica at Svarthamaren, Dronning Maud Land, and at sea outside the colony

The diet of the Antarctic petrel Thalassoica antarctica was studied during two seasons at Svarthamaren, an inland colony in Dronning Maud Land, Antarctica, and in the pack ice off the coast of Svarthamaren. The most important food (wet mass) at Svarthamaren was crustaceans (67%), fish (29%) and squid (5%); however, individuals collected in the pack ice took mostly fish (87%). The prey composition and lengths of prey are comparable to what has been documented in other studies on this species. Estimates of food consumption by birds breeding at Svarthamaren (ca. 250,000 pairs) suggest that approximately 6500 tonnes of crustaceans, 2800 tonnes of fish and 435 tonnes of squid are consumed during the breeding season. The annual consumptions of these birds are estimated to be 34,100 tonnes of crustaceans, 14,700 tonnes of fish, and 2300 tonnes of squid. Satellite telemetry data indicate that Antarctic petrels from Svarthamaren may fly more than 3000 km during one foraging trip, and thus may cover a huge ocean area to obtain their prey. Received: 1 September 1997 / Accepted: 3 February 1998     

Effects of temperature on mitochondrial function in the Antarctic fish Trematomus bernacchii

Effects of temperature on O₂ consumption by mitochondria of the Antarctic fish Trematomus bernacchii were compared with effects obtained with mitochondria from tropical (Sarotheridon mossambica) and temperate zone fishes (Sebastes carnatus and Sebastes mystinus). Arrhenius plots of O₂ consumption versus temperature exhibited slope discontinuities (“breaks”) at temperatures (Arrhenius break temperatures: ABTs) reflective of the species' adaptation temperatures. The ABT for mitochondria of T. bernacchii is the lowest reported for any animal and is ∼12 °C below the value predicted by a regression equation based on ABT data for several invertebrates and fishes. The temperature at which the acceptor control ratio (ACR), an index of efficiency of coupling of electron transport to synthesis of ATP, began to decrease with rising temperature also reflected adaptation temperature. The decrease in ACR with rising temperature began at ∼18 °C for mitochondria of T. bernacchii, in contrast to ∼35 °C for mitochondria of Sarotheridon mossambica. Maintaining T. bernacchii at 4 °C for 2 weeks led to no changes in ABT or in the response of ACR to temperature. The thermal sensitivities of mitochondria of T. bernacchii reflect the high level of cold adaptation and stenothermy that is characteristic of Antarctic Notothenioid fishes. Accepted: 5 January 1998     

Body temperatures in free-flying pigeons

We examined the relationship between body temperature (T_b) of free flying pigeons and ambient water vapor pressure and temperature. Core or near core T_b of pigeons were measured using thermistors inserted into the cloaca and connected to small transmitters mounted on the tail feathers of free flying tippler pigeons (Columba livia). Wet and dry bulb temperatures were measured using modified transmitters mounted onto free-flying pigeons. These allowed calculation of relative humidity and hence water vapor pressure at flight altitudes. Mean T_b during flight was 42.0 ± 1.3 °C (n = 16). Paired comparisons of a subset of this data indicated that average in-flight T_b increased significantly by 1.2 ± 0.7 °C (n = 7) over that of birds at rest (t = −4.22, P < 0.05, n = 7) within the first 15 min of takeoff. In addition, there was a small but significant increase in T_b with increasing ambient air (T_a) when individuals on replicate flights (n = 35) were considered. Inclusion of water vapor pressure into the regression model did not improve the correlation between body temperature and ambient conditions. Flight T_b also increased a small (0.5 °C) but significant amount (t = 2.827, P < 0.05, n = 8) from the beginning to the end of a flight. The small response of T_b to changing flight conditions presumably reflects the efficiency of convection as a heat loss mechanism during sustained regular flight. The increase in T_b on landing that occurred in some birds was a probable consequence of a sudden reduction in convective heat loss. Accepted: 2 February 1999     

Thermogenic responses to body cooling during fever induced by Staphylococcus aureus cell walls in rabbits

Hypothalamic temperature (T _hypo) and metabolic heat production (M) were measured in seven conscious rabbits injected intravenously with either saline or with Staphylococcus aureus, (8 · 10⁷ cell walls · kg⁻¹) while being subjected to a 3-h period of ramp-like total body cooling using a chronically implanted intravascular heat exchanger. In pyrogen-injected animals cooling started (1) at the time of injection or (2) 70 min after injection. In (1) the fall in T _hypo induced by heat extraction was similar (1.0 °C) in afebrile and febrile animals. In (2) there was a transient increase in T _hypo of about 0.5 °C at a time corresponding to the start of fever resulting in a significantly smaller fall in T _hypo at the end of the 3-h cooling period (0.5 °C vs 0.9 °C, P < 0.05, n = 5). At this time in both (1) and (2) M was lower than theoretically expected from the increase in shivering threshold during fever. However, most of this effect can be explained when available data showing a decrease in thermosensitivity during S. aureus-induced fever are taken into account. After cessation of cooling in both groups of febrile animals T _hypo rose to about 1 °C higher than the precooling level, which is comparable to the fever level in a separate series of experiments with S. aureus injection without cooling (1.2 °C). Accepted: 23 September 1997