共查询到20条相似文献,搜索用时 31 毫秒
1.
2.
Juana M. Rivera‐Ordonez A. Justin Nowakowski Adrian Manansala Michelle E. Thompson Brian D. Todd 《Biotropica》2019,51(5):747-756
The conversion of natural habitats to human land uses often increases local temperatures, creating novel thermal environments for species. The variable responses of ectotherms to habitat conversion, where some species decline while others persist, can partly be explained by variation among species in their thermal niches. However, few studies have examined thermal niche variation within species and across forest‐land use ecotones, information that could provide clues about the capacity of species to adapt to changing temperatures. Here, we quantify individual‐level variation in thermal traits of the tropical poison frog, Oophaga pumilio, in thermally contrasting habitats. Specifically, we examined local environmental temperatures, field body temperatures (Tb), preferred body temperatures (Tpref), critical thermal maxima (CTmax), and thermal safety margins (TSM) of individuals from warm, converted habitats and cool forests. We found that frogs from converted habitats exhibited greater mean Tb and Tpref than those from forests. In contrast, CTmax and TSM did not differ significantly between habitats. However, CTmax did increase moderately with increasing Tb, suggesting that changes in CTmax may be driven by microscale temperature exposure within habitats rather than by mean habitat conditions. Although O. pumilio exhibited moderate divergence in Tpref, CTmax appears to be less labile between habitats, possibly due to the ability of frogs in converted habitats to maintain their Tb below air temperatures that reach or exceed CTmax. Selective pressures on thermal tolerances may increase, however, with the loss of buffering microhabitats and increased frequency of extreme temperatures expected under future habitat degradation and climate warming. Abstract in Spanish is available with online material. 相似文献
3.
The urban heat island effect, where urban areas exhibit higher temperatures than less‐developed suburban and natural habitats, occurs in cities across the globe and is well understood from a physical perspective and at broad spatial scales. However, very little is known about how thermal variation caused by urbanization influences the ability of organisms to live in cities. Ectotherms are sensitive to environmental changes that affect thermal conditions, and therefore, increased urban temperatures may pose significant challenges to thermoregulation and alter temperature‐dependent activity. To evaluate whether these changes to the thermal environment affect the persistence and dispersal of ectothermic species in urban areas, we studied two species of Anolis lizards (Anolis cristatellus and Anolis sagrei) introduced to Miami‐Dade County, FL, USA, where they occur in both urban and natural habitats. We calculated canopy openness and measured operative temperature (Te), which estimates the distribution of body temperatures in a non‐thermoregulating population, in four urban and four natural sites. We also captured lizards throughout the day and recorded their internal body temperature (Tb). We found that urban areas had more open canopies and higher Te compared to natural habitats. Laboratory trials showed that A. cristatellus preferred lower temperatures than A. sagrei. Urban sites currently occupied by each species appear to lower thermoregulatory costs for both species, but only A. sagreihad field Tb that were more often within their preferred temperature range in urban habitats compared to natural areas. Furthermore, based on available Te within each species' preferred temperature range, urban sites with only A. sagrei appear less suitable for A. cristatellus, whereas natural sites with only A. cristatellus are less suitable for A. sagrei. These results highlight how the thermal properties of urban areas contribute to patterns of persistence and dispersal, particularly relevant for studying species invasions worldwide. 相似文献
4.
Hot and not‐so‐hot females: reproductive state and thermal preferences of female Arizona Bark Scorpions (Centruroides sculpturatus)
下载免费PDF全文
![点击此处可从《Journal of evolutionary biology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
For ectotherms, environmental temperatures influence numerous life history characteristics, and the body temperatures (Tb) selected by individuals can affect offspring fitness and parental survival. Reproductive trade‐offs may therefore ensue for gravid females, because temperatures conducive to embryonic development may compromise females' body condition. We tested whether reproduction influenced thermoregulation in female Arizona Bark Scorpions (Centruroides sculpturatus). We predicted that gravid females select higher Tb and thermoregulate more precisely than nonreproductive females. Gravid C. sculpturatus gain body mass throughout gestation, which exposes larger portions of their pleural membrane, possibly increasing their rates of transcuticular water loss in arid environments. Accordingly, we tested whether gravid C. sculpturatus lose water faster than nonreproductive females. We determined the preferred Tb of female scorpions in a thermal gradient and measured water loss rates using flow‐through respirometry. Gravid females preferred significantly higher Tb than nonreproductive females, suggesting that gravid C. sculpturatus alter their thermoregulatory behaviour to promote offspring fitness. However, all scorpions thermoregulated with equal precision, perhaps because arid conditions create selective pressure on all females to thermoregulate effectively. Gravid females lost water faster than nonreproductive animals, indicating that greater exposure of the pleural membrane during gestation enhances the desiccation risk of reproductive females. Our findings suggest that gravid C. sculpturatus experience a trade‐off, whereby selection of higher Tb and increased mass during gestation increase females' susceptibility to water loss, and thus their mortality risk. Elucidating the mechanisms that influence thermal preferences may reveal how reproductive trade‐offs shape the life history of ectotherms in arid environments. 相似文献
5.
Williams CT Sheriff MJ Schmutz JA Kohl F Tøien Ø Buck CL Barnes BM 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2011,181(8):1101-1109
Precise measures of phenology are critical to understanding how animals organize their annual cycles and how individuals and
populations respond to climate-induced changes in physical and ecological stressors. We show that patterns of core body temperature
(T
b) can be used to precisely determine the timing of key seasonal events including hibernation, mating and parturition, and
immergence and emergence from the hibernacula in free-living arctic ground squirrels (Urocitellus parryii). Using temperature loggers that recorded T
b every 20 min for up to 18 months, we monitored core T
b from three females that subsequently gave birth in captivity and from 66 female and 57 male ground squirrels free-living
in the northern foothills of the Brooks Range Alaska. In addition, dates of emergence from hibernation were visually confirmed
for four free-living male squirrels. Average T
b in captive females decreased by 0.5–1.0°C during gestation and abruptly increased by 1–1.5°C on the day of parturition. In
free-living females, similar shifts in T
b were observed in 78% (n = 9) of yearlings and 94% (n = 31) of adults; females without the shift are assumed not to have given birth. Three of four ground squirrels for which
dates of emergence from hibernation were visually confirmed did not exhibit obvious diurnal rhythms in T
b until they first emerged onto the surface when T
b patterns became diurnal. In free-living males undergoing reproductive maturation, this pre-emergence euthermic interval averaged
20.4 days (n = 56). T
b-loggers represent a cost-effective and logistically feasible method to precisely investigate the phenology of reproduction
and hibernation in ground squirrels. 相似文献
6.
Weissenböck NM Arnold W Ruf T 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2012,182(2):311-319
Some mammals indigenous to desert environments, such as camels, cope with high heat load by tolerating an increase in body
temperature (T
b) during the hot day, and by dissipating excess heat during the cooler night hours, i.e., heterothermy. Because diurnal heat
storage mechanisms should be favoured by large body size, we investigated whether this response also exists in Asian elephants
when exposed to warm environmental conditions of their natural habitat. We compared daily cycles of intestinal T
b of 11 adult Asian elephants living under natural ambient temperatures (T
a) in Thailand (mean T
a ~ 30°C) and in 6 Asian elephants exposed to cooler conditions (mean T
a ~ 21°C) in Germany. Elephants in Thailand had mean daily ranges of T
b oscillations (1.15°C) that were significantly larger than in animals kept in Germany (0.51°C). This was due to both increased
maximum T
b during the day and decreased minimum T
b at late night. Elephant’s minimum T
b lowered daily as T
a increased and hence entered the day with a thermal reserve for additional heat storage, very similar to arid-zone ungulates.
We conclude that these responses show all characteristics of heterothermy, and that this thermoregulatory strategy is not
restricted to desert mammals, but is also employed by Asian elephants. 相似文献
7.
Habitat use and spatial fidelity of male South American sea lions during the nonbreeding period
下载免费PDF全文
![点击此处可从《Ecology and evolution》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Alastair M. M. Baylis Rachael A. Orben Daniel P. Costa Megan Tierney Paul Brickle Iain J. Staniland 《Ecology and evolution》2017,7(11):3992-4002
Conditions experienced during the nonbreeding period have profound long‐term effects on individual fitness and survival. Therefore, knowledge of habitat use during the nonbreeding period can provide insights into processes that regulate populations. At the Falkland Islands, the habitat use of South American sea lions (Otaria flavescens) during the nonbreeding period is of particular interest because the population is yet to recover from a catastrophic decline between the mid‐1930s and 1965, and nonbreeding movements are poorly understood. Here, we assessed the habitat use of adult male (n = 13) and juvenile male (n = 6) South American sea lions at the Falkland Islands using satellite tags and stable isotope analysis of vibrissae. Male South American sea lions behaved like central place foragers. Foraging trips were restricted to the Patagonian Shelf and were typically short in distance and duration (127 ± 66 km and 4.1 ± 2.0 days, respectively). Individual male foraging trips were also typically characterized by a high degree of foraging site fidelity. However, the isotopic niche of adult males was smaller than juvenile males, which suggested that adult males were more consistent in their use of foraging habitats and prey over time. Our findings differ from male South American sea lions in Chile and Argentina, which undertake extended movements during the nonbreeding period. Hence, throughout their breeding range, male South American sea lions have diverse movement patterns during the nonbreeding period that intuitively reflects differences in the predictability or accessibility of preferred prey. Our findings challenge the long‐standing notion that South American sea lions undertake a winter migration away from the Falkland Islands. Therefore, impediments to South American sea lion population recovery likely originate locally and conservation measures at a national level are likely to be effective in addressing the decline and the failure of the population to recover. 相似文献
8.
Gerhard Körtner A. Daniella Rojas Fritz Geiser 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2010,180(6):869-876
Many small desert dasyurids employ torpor almost daily during winter, because cold nights and low food availability impose
high energetic costs. However, in Western Australia the arid zone extends into tropical, coastal regions, where winter temperature
conditions are far less severe. We studied the thermal biology and activity patterns of free-ranging kaluta (~27 g), a dasyurid
restricted to these tropical spinifex deserts, during the Austral winter (June–July) and in addition quantified activity patterns
in captivity. Unlike most dasyurids, wild and captive kalutas were almost exclusively diurnal and retreated into underground
burrows during the night. Despite being active during the warmer part of the day, kalutas entered torpor daily. However, torpor
patterns differed remarkably between males and females. While females spent most of the night torpid at body temperatures
(T
b) as low as 21°C, close to soil temperature, males entered multiple short and shallow bouts (T
b > 25°C) during the night. Males also maintained higher T
bs during the early morning when active, occupied larger home ranges and covered greater distances while foraging than females.
Hence, males appear to expend more energy than the similar-sized females both while foraging and during the rest phase. We
propose that physiological as well as behavioural preparations for the September mating season that culminate in a complete
male die-off might already impose energetic costs on males during winter. 相似文献
9.
Wendy A. Wilson M. Justin O’Riain Robyn S. Hetem Andrea Fuller Linda G. Fick 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2010,180(7):1099-1110
The body temperature (T
b) of Cape ground squirrels (Xerus inauris, Sciuridae) living in their natural environment during winter has not yet been investigated. In this study we measured abdominal
T
b of eight free-ranging Cape ground squirrels over 27 consecutive days during the austral winter. Mean daily T
b was relatively stable at 37.0 ± 0.2°C (range 33.4 to 40.2°C) despite a marked variation in globe temperature (T
g) (range −7 to 37°C). Lactating females (n = 2) consistently had a significantly higher mean T
b (0.7°C) than non-lactating females (n = 3) and males. There was a pronounced nychthemeral rhythm with a mean active phase T
b of 38.1 ± 0.1°C and a mean inactive phase T
b of 36.3 ± 0.3°C for non-lactating individuals. Mean daily amplitude of T
b rhythm was 3.8 ± 0.2°C. T
b during the active phase closely followed T
g and mean active phase T
b was significantly correlated with mean active phase T
g (r
2 = 0.3–0.9; P < 0.01). There was no evidence for daily torpor or pronounced hypothermia during the inactive phase, and mean minimum inactive
phase T
b was 35.7 ± 0.3°C for non-lactating individuals. Several alternatives (including nocturnal huddling, an aseasonal breeding
pattern and abundant winter food resources) as to why Cape ground squirrels do not employ nocturnal hypothermia are discussed. 相似文献
10.
11.
El Ouezzani S Janati IA Magoul R Pévet P Saboureau M 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2011,181(2):299-309
The jerboa (Jaculus orientalis) has been described in the past as a hibernator, but no reliable data exist on the daily and seasonal rhythmicity of body
temperature (T
b). In this study, T
b patterns were determined in different groups of jerboas (isolated males and females, castrated males and grouped animals)
maintained in captivity during autumn and winter, and submitted to natural variations of light and ambient temperature (T
a). T
b and T
a variations were recorded with surgically implanted iButton temperature loggers at 30-min intervals for two consecutive years.
About half (6/13) of isolated female jerboas hibernated with a T
b < 33°C, with hibernation bouts interspersed with short periods of normothermy from November to February. Hibernation bout
durations were longer (4–5 days) than those of normothermia phases (1–4 days). During hibernation, the minimum T
b was low (T
bmin ~10.7°C). In contrast, one of the 12 isolated males showed short hibernation bouts of ca. 2 days late in the hibernation
season, February–March. The males had T
bmin values of 15.1°C. In contrast to predictions, no castrated males hibernated. When jerboas were grouped, females and males
exhibited concomitant torpor bouts. In males, the longest bouts were observed during the late hibernation season. These data
suggest complex regulation of hibernation in jerboas. 相似文献
12.
Luca Luiselli 《African Journal of Ecology》2005,43(1):64-69
Aspects of the thermal ecology of two sympatric hinge‐back tortoises, Kinixys erosa and Kinixys homeana, were studied in the rainforest zone of south‐eastern Nigeria (West Africa). There were no significant differences in mean body temperatures (Tb) among K. homeana males, K. homeana females, K. erosa males and K. erosa females. In both species, there was a significant correlation between Tb and air temperature (Ta), and the regression line of Ta plotted against Tb differed significantly from the line of ideal poikilothermy. These regressions did not differ significantly between sexes in either species. There were no significant differences in terms of mean Tb in K. homeana during the various day‐hour intervals, whereas the mean Tb of K. erosa varied significantly among the various daytime intervals, attaining the higher values at 11.01–15.00 and 15.01–19.00 hours. In both species, Tbs were nearly always below Tas, and the negative difference ‘Tb ‐ Ta’ increased with increasing Ta. The hourly‐time course of the difference between Tb and Ta showed significant differences in K. homeana (with the higher negative differences at 11.01–15.00 and 15.01–19.00 hours), whereas no such difference was observed in K. erosa. In general, tortoises of both species showed behavioural thermoregulation in their avoidance of overheating in tropical environments, taking advantage of shady forest environments. 相似文献
13.
Sexual size dimorphism (SSD) is a common phenomenon in animals. In many species females are substantially larger than males.
Because body size plays a central role in modulating the body temperature (T
b) of ectotherms, intersexual differences in body size may lead to important intersexual differences in thermoregulation. In
addition, because SSD is realized by differences in growth rate and because growth rate is strongly temperature dependent
in ectotherms, a conflict between male reproductive behaviour and thermoregulation may affect the expression of SSD. In this
study, we investigated the thermal implications of SSD in a reptile exhibiting spectacular female-biased SSD: the northern
map turtle (Graptemys geographica). Over three seasons, we collected >150,000 measurements of T
b in free-ranging adult and juvenile northern map turtles using surgically implanted miniature temperature loggers. Northern
map turtles exhibited seasonal patterns of thermoregulation typical of reptiles in northern latitudes, but we found that large
adult females experienced a lower daily maximum T
b and a narrower daily range of T
b than adult males and small juvenile females. In addition, despite more time spent basking, large adult females were not able
to thermoregulate as accurately as small turtles. Our findings strongly suggest that body size limits the ability to thermoregulate
accurately in large females. By comparing thermoregulatory patterns between adult males and juvenile females of similar body
size, we found no evidence that male reproductive behaviours are an impediment to thermoregulation. We also quantified the
thermal significance of basking behaviour. We found, contrary to previous findings, that aerial basking allows northern map
turtles to raise their T
b substantially above water temperature, indicating that basking behaviour likely plays an important role in thermoregulation. 相似文献
14.
D. B. Osmundson† 《Journal of fish biology》2006,68(5):1563-1588
Evidence for sexual size dimorphism (SSD) and its possible causes were examined in the endangered Colorado pikeminnow Ptychocheilus lucius, a large, piscivorous, cyprinid endemic to the Colorado River system of North America. Individuals representing 18–24% of the upper Colorado River population were captured, measured, sexed and released in 1999 and 2000. Differing male and female total length‐(LT) frequency distributions revealed SSD with females having greater mean and maximum sizes than males. Although both sexes exhibit indeterminate post‐maturity growth, growth trajectories differed. The point of trajectory divergence was not established, but slowed male growth might coincide with the onset of maturation. Differing growth rate was the dominant proximate cause of SSD, accounting for an estimated 61% of the observed difference in mean adult LT. The degree of SSD in adults, however, was also related to two other factors. Evidence suggests males become sexually active at a smaller size and earlier age than females; a 2 year difference, suggested here, accounted for an estimated 12% of the between‐sex difference in mean adult LT. Temporal shifts in gender‐specific survival accounted for an additional 27% of the observed between‐sex difference in mean adult LT. Estimated age distributions indicated a higher number of older females than older males and more younger males than younger females in the population during the period of sampling. Dissimilarity of age distributions was an unexpected result because the male : female population sex ratio was 1 : 1 and estimates of long‐term annual survival for adult males and females were equal (88%). Future assessments of SSD in this population are apt to vary depending on the prior history of short‐term gender‐specific survival. Without recognizing SSD, non‐gender‐specific growth curves overestimate mean age of adult females and underestimate mean age of adult males of given LT. Assuming age 8 years for first reproduction in males and age 10 years for females, the adult male : female ratio was estimated as 1·1 : 1 and mean adult age, or generation time, was estimated as 16·4 years for males and 18·4 years for females. 相似文献
15.
Cara E. Whalen Mary Bomberger Brown JoAnn McGee Larkin A. Powell Edward J. Walsh 《Ethology : formerly Zeitschrift fur Tierpsychologie》2019,125(12):863-875
Acoustic signals are often critical elements of mating displays, and lekking male greater prairie‐chickens (Tympanuchus cupido pinnatus) use their boom vocalization for this purpose. We quantified the acoustic characteristics of the boom chorus created by multiple male greater prairie‐chickens vocalizing simultaneously at leks in Brown County, NE, USA, in 2013 and 2014. We used these data to evaluate (a) the role of the boom chorus in prairie‐chicken breeding dynamics and (b) the impact of a wind energy facility on the acoustic signal of the boom chorus. We sampled the chorus using audio recorders placed in transects extending from leks; the chorus exhibited an average peak frequency of 297 ± 13 Hz. The mean chorus signal‐to‐noise ratio declined from 15.7 dB (50 m) to 2.6 dB (800 m), and wind speed and direction, topography, and relative humidity caused variation in signal‐to‐noise ratio at a given distance and location. Chorus recordings from leks within 1,000 m of a wind turbine had lower signal‐to‐noise ratio (βturbine = ?5.659, SE = 1.289) than leks farther from turbines. The chorus signal‐to‐noise ratio increased slightly with more males present on the lek (~0.1 dB for each additional male; βmales = 0.177; SE = 0.037) and considerably more as more females visited the lek (~1.4 dB for each additional female; βfemales = 2.498, SE = 0.235; βfemales2 = ?0.309, SE = 0.039). Our results provide support for the signal enhancement hypothesis that proposes the boom chorus is influenced notably by male–male competition for females on the lek, rather than functioning solely to advertise the presence of the lek to recruit females. Our results also suggest the choruses emanating from small leks have the greatest potential to be masked by anthropogenic (wind turbine) noise, which may affect the breeding success of male and female prairie‐chickens. 相似文献
16.
The aim of this work was to investigate the thermal biology of the Spix's yellow-toothed cavy (Galea spixii) from the hot and dry environment of the Brazilian Caatinga by infrared thermography and biophysical equations. We monitored the rectal temperature, as well as the non-evaporative (radiative and convective pathways) and evaporative heat exchanges of males and females. The mean rectal temperature of females and males was 37.58 ± 0.02 and 37.47 ± 0.02 °C, respectively. We identified thermal windows by infrared thermography. The surface temperatures and the long-wave radiation heat exchanges were higher in the periocular, preocular, pinnae and vibrissae regions, in that order. The surface temperature of the periocular and preocular regions correlated positively with rectal temperature. Convective heat exchange was insignificant for thermoregulation by G. spixii. Evaporative heat loss increased when the thermal environment inhibited the radiative pathway. Females showed higher evaporative thermolysis than males at times of greater thermal challenge, suggesting a lower tolerance to heat stress. Therefore, infrared thermography identified the thermal windows, which represented the first line of defense against overheating in G. spixii. The periocular and preocular surface temperatures could be used as predictors of the thermal state of G. spixii. 相似文献
17.
High environmental temperatures pose significant physiological challenges related to energy and water balance for small endotherms. Although there is a growing literature on the effect of high temperatures on birds, comparable data are scarcer for bats. Those data that do exist suggest that roost microsite may predict tolerance of high air temperatures. To examine this possibility further, we quantified the upper limits to heat tolerance and evaporative cooling capacity in three southern African bat species inhabiting the same hot environment but using different roost types (crevice, foliage or cave). We used flow-through respirometry and compared heat tolerance limits (highest air temperature (Ta) tolerated before the onset of severe hyperthermia), body temperature (Tb), evaporative water loss, metabolic rate, and maximum cooling capacity (i.e., evaporative heat loss/metabolic heat production). Heat tolerance limits for the two bats roosting in more exposed sites, Taphozous mauritianus (foliage-roosting) and Eptesicus hottentotus (crevice-roosting), were Ta = ~44 °C and those individuals defended maximum Tb between 41 °C and 43 °C. The heat tolerance limit for the bat roosting in a more buffered site, Rousettus aegyptiacus (cave-roosting), was Ta = ~38 °C with a corresponding Tb of ~38 °C. These interspecific differences, together with a similar trend for higher evaporative cooling efficiency in species occupying warmer roost microsites, add further support to the notion that ecological factors like roost choice may have profound influences on physiological traits related to thermoregulation. 相似文献
18.
Artificial selection,pre‐release diet,and gut symbiont inoculation effects on sterile male longevity for area‐wide fruit‐fly management
下载免费PDF全文
![点击此处可从《Entomologia Experimentalis et Applicata》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Juan Rull Rodrigo Lasa Christian Rodriguez Rafael Ortega Olinda Elisabeth Velazquez Martín Aluja 《Entomologia Experimentalis et Applicata》2015,157(3):325-333
Longevity is an important life‐history trait for successful and cost‐effective application of the sterile insect technique. Furthermore, it has been shown that females of some species – e.g., Anastrepha ludens (Loew) (Diptera: Tephritidae) – preferentially copulate with ‘old’, sexually experienced males, rather than younger and inexperienced males. Long‐lived sterile males may therefore have greater opportunity to find and mate with wild females than short‐lived males, and be more effective in inducing sterility into wild populations. We explored the feasibility of increasing sterile male lifespan through selection of long‐lived strains and provision of pre‐release diets with added protein, and inoculated with bacterial symbionts recovered from cultures of the gut of wild Anastrepha obliqua (Macquart). Artificial selection for long‐lived A. ludens resulted in a sharp drop of fecundity levels for F1 females. Nevertheless, the cross of long‐lived males with laboratory females produced a female F1 progeny with fecundity levels comparable to those of females in the established colony. However, the male progeny of long‐lived males*laboratory females did not survive in higher proportions than laboratory males. Provision of sugar to A. obliqua adults resulted in increased survival in comparison to adults provided only with water, whereas the addition of protein to sugar‐only diets had no additional effect on longevity. Non‐irradiated males lived longer than irradiated males, and supplying a generic probiotic diet produced no noticeable effect in restoring irradiated male longevity of A. obliqua. We discuss the need to evaluate the time to reach sexual maturity and survival under stress for long‐lived strains, and the inclusion of low amounts of protein and specific beneficial bacteria in pre‐release diets to increase sterile male performance and longevity in the field. 相似文献
19.
Animals typically respond to stressful stimuli such as handling by increasing core body temperature. However, small birds in cold environments have been found to decrease body temperature (Tb) when handled over longer periods, although there are no data extending beyond the actual handling event in such birds. We therefore measured both the initial Tb decrease during ringing and standardized Tb sampling, and subsequent recovery of Tb after this handling protocol in wild Great Tits Parus major roosting in nestboxes in winter. Birds reduced their Tb by 2.3 °C during c. 4 min of handling. When birds were returned to their nestboxes after handling, Tb decreased by a further 1.9 °C over c. 2 min, reaching a Tb of 34.6 °C before taking 20 min to rewarm to 2.5 °C above their initial Tb. The Tb reduction during handling could be a consequence of increased heat loss rate from disrupted plumage insulation, whereas Tb reduction after handling might reflect reduced heat production. These are important factors to consider when handling small birds in the cold. 相似文献
20.
Behavioral thermoregulation of New Zealand sea lions (Phocarctos hookeri) was studied at a male haul‐out ground at Papanui Beach, Otago Peninsula, New Zealand. The proportion of time spent by sea lions in each of five postures (prone, curled, oblique, ventral‐up, dorsal‐up) and also with the number of flippers exposed or tucked (hind and fore) at different black‐bulb temperature (Tbb°C) ranges was recorded. Use of prone and curled postures (0–1 flippers exposed) declined as Tbb increased, suggesting that these are adopted to conserve heat; oblique and dorsal‐up postures (3–4 flippers exposed) use increased with Tbb indicating a role in heat dissipation. The transition between heat conserving and heat dissipating postures occurred at about 14°–20°C (Tbb). Both foreflipper and hind flipper exposure increased with Tbb and the trends were similar, but overall hind flipper exposure was 89% of foreflipper exposure. The results show that surface area of flippers exposed to air is largely controlled by postural adjustment. The increase in flipper exposure with Tbb provides evidence of behavioral thermoregulation and that flippers are major sites for heat loss in the New Zealand sea lion, as observed for other otariid species. Nonpostural thermoregulatory behaviors such as flipper waving and sand flipping increased with Tbb, and may provide additional means of dissipating heat. Total body surface areas of six sea lions ranged from 1.72 to 3.39 m2 (curvilinear length range from 1.60 to 2.35 m), and total flipper surface area averaged 22.7% of total body surface area. As otariids do not employ their hind limbs for aquatic propulsion, their role in behavioral thermoregulation may provide an explanation for the relatively large size of the hind flippers of the New Zealand sea lion. 相似文献