Capture Stress Research Articles

Adjustment to War Captivity: The Role of Sociodemographic Background, Trauma Severity, and Immediate Responses, in the Long-Term Mental Health of Israeli Ex-Pows

This study assessed the role of sociodemographic features, pre-captivity combat exposure, captivity severity, emotional responses and coping during captivity, and social support at homecoming, to the short- and long-term mental health of 164 Israeli POWs of the 1973 Yom Kippur War. The major contributors to the POWs' mental health were psychological responses during captivity, followed first by their education and ethnic status, and then by severity of captivity. Both traumatic stress of captivity and the results of the study were discussed in the light of Conservation of Resources (COR) theory.

Evidence for a Hormonal Tactic Maximizing Green Turtle Reproduction in Response to a Pervasive Ecological Stressor

Mortality of breeding sea turtles due to excessive heat exposure after nesting activities is an unusual feature of the Raine Island green turtle rookery. Breeding turtles that fail to return to the ocean after oviposition can experience increasing body temperatures that exceed lethal limits (>39°C) as ambient temperatures rise after sunrise. We investigated how acute increases in body temperature influenced plasma corticosterone (B) concentrations of individual turtles. Furthermore, interactions between progesterone (P) and testosterone (T) and increasing body temperature and the glucocorticoid corticosterone were examined for negative correlations. Breeding green turtles exhibited a 16-fold mean increase in plasma corticosterone concentration as body temperature (cloacal) rose from 28.2 to 40.7°C in less than 6 h. However, the absolute increase in plasma B was small and much less than expected, despite the lethal stressor. Comparatively, the maximal B response to lethal heat stress was similar to plasma B concentrations obtained from breeding female turtles exposed to 8 h of capture stress. However, the maximal B response of breeding turtles exposed to heat and capture stressors was significantly less than the B response of nonbreeding adult female turtles subjected to an 8-h capture stressor. No negative correlations were observed between plasma T and plasma B, between plasma T and body temperature, between plasma P and plasma B, or between plasma P and body temperature. Our findings provide further evidence that reduced adrenocortical function operates in breeding green turtles in the presence of even the most pervasive of environmental stressors.

Behavioural and hormonal responses to capture stress in the male red-sided garter snake, Thamnophis sirtalis parietalis

We measured the behavioural and hormonal responses to capture stress in male red-sided garter snakes. Four hours of capture stress resulted in no suppression of mating behaviour relative to control individuals. In contrast, the same stress resulted in a significant increase in plasma levels of corticosterone and a significant decrease in plasma levels of testosterone. There was a significant negative correlation between plasma levels of corticosterone and testosterone in both control and capture-stress groups, suggesting that the increase in corticosterone directly drives the decrease in testosterone. While there was no relation between body size and initial plasma levels of the two steroids, longer individuals had a significantly greater increase in corticosterone following capture stress than did shorter individuals. Snakes display indeterminate growth, suggesting that older individuals have decreased sensitivity to negative feedback in the hypothalamic–pituitary–adrenal axis and thus hypersecrete glucocorticoids. These results suggest that male red-sided garter snakes have uncoupled their behavioural stress response from their hormonal stress response to maximize reproductive opportunities.

Seasonal Changes in Sex and Adrenal Steroid Hormones of Gopher Tortoises (Gopherus polyphemus)

We sampled a population of gopher tortoises (Gopherus polyphemus) from May to October 1997 to determine seasonal cycles of steroid hormones (testosterone, T; 17β-estradiol, E; and progesterone, P) and related them to observations of mating behavior. In males, plasma T levels peaked in July and August and remained elevated through October. This coincides with the reported time of peak mating and spermatogenesis, indicating that males display an associated pattern of reproduction. In females, E levels were high in September and October. Plasma T levels in females were elevated in May, decreased to basal levels in June and July, and rose again in August and September. Elevated E and T levels correspond to the reported time of peak vitellogenic activity, indicating that females also display an associated cycle. Plasma P in females remained basal throughout the active season, suggesting that ovulation occurs in late winter. We also determined levels of corticosterone (B) to assess the influence of capture stress on tortoises and correlated B levels with tortoise activity patterns and sex steroid levels. We found no seasonal variation in levels of B in males or females. Plasma B levels were not correlated with levels of T or E, but were positively correlated with female P levels. Further, we found no relationship between plasma B levels in males and mean distance moved, mean number of burrows used, or mean home range size. However, there was a significant negative correlation between plasma B levels and male body size. In females, there was no relationship between B levels and mean distance moved, but B levels were significantly negatively correlated with the number of burrows females occupied. Lastly, there was no relationship between levels of B and the number of minutes required to obtain blood from an animal. However, B levels increased with the length of time that a tortoise spent in a trap, suggesting that trapped tortoises do exhibit capture stress.

Problemas médico-veterinários de Lobo-guará (Chrysocyon brachyurus) em cativeiro

O lobo-guará, Chrysocyon brachyurus (Carnivora, Canidae), possui altíssimo valor biológico, em virtude de ser considerada espécie vulnerável à extinção, principalmente pela eliminação sistemática de seu habitat. Paralelamente, em cativeiro tem-se tido dificuldade na reprodução, manutenção, bem como na criação dos filhotes nascidos, devido a deficiências no manejo e problemas de doenças. O presente estudo retrospectivo de 30 anos, relaciona as principais alterações ocorridas com 100 animais (59,41, O) entre filhotes e jovens (20 animais) e adultos (80 animais) mantidos no Zoológico de São Paulo. Como resultado obtiveram-se lII processos: gastrointestinais, 62,0%; traumáticos, 13,6%; respiratório, 8,2%; urinários, 8,2%, circulatórios, 4,5%; além de casos isolados. Os sinais clínicos mais comumente observados referiram-se aos processos gastrentéricos representados por diarréia, vômito, anorexia, e prostração. Das principais enfermidades bacterianas prevaleceram a leptospirose, salmonelose e colibacilose. Decreve-se primeiro relato de surto de parvovirose no Brasil, que levou à morte 11 dos 17 animais atingidos. Dentre os parasitos prevaleceram Ancylostoma sp, Trichuris sp e coccídeos. Salientam-se 6 casos de parasitose renal por Dioctophyme renale. Os processos traumáticos foram representados, principalmente, por infantofagia cometida pelos pais. Para lobos-guarás em cativeiro deve-se ter especial cuidado com as enfermidades do aparelho gastrointestinal, em virtude de apresentarem alterações de etiologia variada como bacterianas, virais, verminóticas, por distúrbios alimentares e em decorrência do estresse em cativeiro. Recintos adequados e com tranqüilidade, aliados a programa efetivo de medicina preventiva, são fundamentais para reprodução e manutenção da espécie.

The Effects of an “El Niño” Southern Oscillation Event on Reproduction in Male and Female Blue-Footed Boobies,Sula nebouxii

This study attempted to determine endocrine correlates of reproductive success in relation to major deleterious environmental conditions. In 1992, an El Niño southern oscillation event resulted in complete reproductive failure in a colony of blue-footed boobies,Sula nebouxi,on Isla Isabel in the Pacific Ocean off San Blas, Nayarit, Mexico (21.5°N, 105.5°W). In 1993, the El Niño event had waned and reproductive success was high. The mean sea surface temperature in 1992 was 26.69°, the warmest year for 11 years of data (mean, 25.63°). In 1993, mean sea surface temperature was 25.75°. Plasma levels of testosterone were highest during the egg-laying period in 1993 and declined markedly during incubation. There were no differences between males and females. Comparisons of testosterone levels between 1992 and 1993 (egg-laying time point removed for 1993) showed no significant differences. Thus reproductive failure during an El Niño year was not related to testosterone levels. Baseline plasma levels of corticosterone did not change over the nesting cycle in either sex. There was a trend for plasma levels of corticosterone to be higher in males and females during the earlier stages of breeding in 1992 compared with 1993, and if all levels were combined within years then females showed significantly higher plasma levels of corticosterone in the El Niño year. Plasma levels of corticosterone showed marked increases following capture and handling in both sexes and at every stage of the breeding cycle in each year. There was no variation in the adrenocortical responses to stress with year or stage of nesting in males. However, in females, maximum corticosterone levels were greatest during the parental phase of 1992, the El Niño year, when all nests ultimately failed. Comparisons of the dynamics of corticosterone changes during the capture stress protocol revealed no correlations with body mass in 1992 or 1993. These data suggest that although massive reproductive failure in the El Niño year was not related to testosterone levels, baseline circulating concentrations of corticosterone may have a role in inhibiting onset of breeding. In contrast, after the nesting cycle has been initiated, increased adrenocortical sensitivity to acute stress may be involved in nest abandonment.

Exogenous Testosterone and the Adrenocortical Response in Dark-Eyed Juncos

Hormonal manipulations with implants allow examination of the costs and benefits of behaviors and physiologic states mediated by a given hormone. As a part of on- going research into the effects of the steroid hormone testosterone (T) in Dark-eyed Juncos (Junco hyemalis), we measured the corticosterone (B, a steroid hormone secreted by the ad- renal in response to stress ) response to the stress of capture and handling in males treated with T (T-males) and in control males (C-males). Although B may be essential for energy mobilization, chronic or repeated exposure to elevated levels of B can have many negative effects. Because T mediates many behaviors that may increase the likelihood that an indi- vidual will encounter stressors, we predicted that plasma B would rise more rapidly in T- males than in controls. In the first few minutes post-capture, the increase in B levels was significantly higher in T-males than in controls. B levels in samples collected 10, 30, and 60 min post-capture were consistently higher in T-males than in C-males; however, the differ- ence was not statistically significant. Because previous work has shown that T-males reduce their parental contribution, we compared females that were mated to T-males and C-males (hereafter T- and C-females). B levels of T-females increased sharply in the first few minutes post-capture, whereas in C-females they did not; however, the responses were not statisti- cally different. Males had higher initial levels and a greater B-response to stress than females when data were compared irrespective of treatment. Our results suggest that the behaviors or physiological changes induced by T are potentially costly and that such costs may in part be incurred through elevated B. Received 25 November 1997, accepted 5 May 1998. IN MOST NORTH-TEMPERATE BIRDS, circulating levels of testosterone (T) in males are elevated during the sexual phase of the breeding season

Impact of radio‐tracking on black grouse Tetrao tetrix reproductive success in the French Alps

From 1991 to 1995, we tested the effects of radio‐tracking, including trapping, handling and monitoring, on reproductive success of black grouse Tetrao tetrix hens in the southern French Alps. Reproductive success (total young/total hens with and without broods) was lower in hens marked with radio‐collars than in unmarked hens (0.77 vs 1.66 young/hen, P = 0.02). Brood size was similar in the two groups of hens, but the proportion of hens rearing a brood was lower among marked hens (23 vs 45%, P = 0.03). Reproductive success of hens marked at the beginning of laying, or just before, was lower than that of hens marked ≥6 months before laying (0.25 vs 1.20 young/hen, P = 0.058). The success of hens marked near the time of laying was also low compared with unmarked hens in all years but 1992 (the year*time of capture interaction was significant). In contrast, reproductive success of hens marked ≥6 months before laying was not statistically different from that of unmarked hens (1.20 vs 1.66 young/hen, P = 0.28). Higher predation rates on first clutches, and to a lesser extent lower ability to renest, were responsible for the lower reproductive success of hens marked at the beginning of or just before laying. Altogether, these results suggest that initial discomfort caused by the transmitter, stress of capture, handling and monitoring following capture may temporarily alter the behaviour of hens, thereby increasing detection of their nests by predators. After a period of adjustment, radio‐transmitters per se may have little or no adverse effect on reproduction. We conclude that to obtain reliable estimates of breeding parameters of black grouse in the French Alps using necklace type transmitters, hens must be equipped with these several months before laying, and nesting hens should not be approached closer than 20 m during radio‐tracking.

Changes in blood cortisol, glucose and lactate in carp retained in anglers’keepnets

Capture of carp Cyprinus carpio from holding tanks by dipnet, or from semi‐natural conditions by rod and line, elicits a physiological stress response characterized by elevation of plasma cortisol levels. The transfer of carp to keepnets subsequent to capture does not increase or reduce the magnitude or duration of this response and in both cases plasma cortisol levels have returned to pre‐stress levels within 24 h of the initial disturbance. The postcapture plasma cortisol elevation is accompanied by disturbances in plasma glucose and lactate levels but these are less consistent in severity and duration than the cortisol response. These data suggest that the retention of fish in keepnets following capture, does not represent a source of stress additional to that imposed by capture and has no effect on the rate of recovery of the fish from the initial capture stress.

Adrenocortical Responses to Stress in Breeding Pied Flycatchers Ficedula hypoleuca: Relation to Latitude, Sex and Mating Status

The adrenocortical response to acute stress, as measured by increases in plasma levels of corticosterone following capture and handling, has been shown to vary between individuals within a population as well as with season in a variety of species. However, the ecological bases for such endocrine phenomena remain unclear. One hypothesis predicts that populations of birds breeding under extreme conditions such as in sub-arctic habitats where the nesting season is short, decrease the amplitude of the adrenocortical response to acute stress so as to allow non-interrupted breeding under potentially severe conditions such as bad weather conditions and/or food shortage. To test this hypothesis we measured increases in circulating levels of corticosterone following capture and handling in populations of Pied Flycatchers Ficedula hypoleuca breeding in southern (G6teborg) and northern (Ammarndis) Sweden. We also sampled breeding females that did not have a male helping them to feed young (only in south Sweden). As predicted by the hypothesis we found male and female Flycatchers breeding in northern Sweden to be adapted to the short breeding season and harsh unpredictable sub-arctic climate by having a reduced adrenocortical response to stress, as indicated by the pattern of corticosterone levels in blood. Maximum corticosterone levels generated by the capture stress protocol were significantly higher in single females than all other groups. Unlike other passerines studied at high latitudes Pied Flycatchers showed no significant relationships between corticosterone levels and body mass or fat score.

Responsiveness of the interrenal tissue of yellow perch (Perca flavescens) from contaminated sites to an ACTH challenge test in vivo

The effects of chronic toxic stress on the hypothalamo-pituitary-interrenal (HPI) axis were investigated in yellow perch (Perca flavescens) captured at a reference site (Lake Memphremagog) and two sites contaminated with heavy metals and organic contaminants (Ile Perrot and Iles de la Paix, Lake St. Louis) in spring, summer, and fall. Cortisol secretion of the fish was stimulated in situ by an acute capture stress or by an i.p. injection of 4 IU/100 g body mass of porcine corticotropin (ACTH1-39). The response to both these challenges was lower in perch from the highly contaminated site than in perch from the reference site in the spring but not in summer. In fall, fish from the highly contaminated site had, as in spring, a lower response to ACTH than fish from the reference site. The reduced ability of perch to respond to capture stress or to ACTH indicates that the interrenal tissue in fish from contaminated sites is functionally impaired. Cortisol-impaired fish also had abnormal carbohydrate metabolism. The reduced ability of wild fish from contaminated sites to respond to a standardized ACTH challenge may be used as an early indicator of contamination-induced chronic stress.

Effect of capture, confinement and repeated sampling on plasma steroid concentrations and oocyte size in female striped trumpeter Latris lineata (Latrididae)

Wild female striped trumpeter were caught during the spawning season to examine the effect of capture, confinement and repeated handling on reproductive function. Blood and ovarian samples were obtained from 5 females within 10 minutes of capture and from a pool of female fish (n = 17), including the original 5, that were sampled regularly from Day 2 to Day 13 after capture. Plasma concentrations of cortisol, testosterone (T), 17β-oestradiol (E2) and 17,20β-dihydroxy-4-pregnen-3-one (17,20βP) were measured by radioimmunoassay. Four of the 17 fish ovulated and a small volume of eggs was obtained by hand stripping. Mean oocyte size did not change significantly, although there was a general trend toward decreasing oocyte diameters over time. Plasma concentrations of T and E2 decreased significantly after capture, and remained low thereafter. Concentrations of 17,20βP remained unchanged apart from a decrease on Day 13. Cortisol concentrations significantly increased after capture and remained elevated until Day 5, with subsequent elevations on Days 7 and 9. These results suggest that the stress of capture, confinement and repeated handling inhibits the ovarian production of T and E2 but not 17,20βP and arrests oocyte development at all but the most advanced stages.

Anesthesia of wild red howler monkeys (Alouatta seniculus) with medetomidine/ketamine and reversal by atipamezole.

Wild red howler monkeys (Alouatta seniculus) were translocated during the flooding of the forest at a hydroelectric dam site in French Guiana. For a variety of minor clinical procedures, 96 monkeys were anesthetized with various intramuscular injections of combinations of medetomidine and ketamine. The howler population was composed of healthy animals (42 males and 54 females) of various ages. Medetomidine (150 micrograms/kg) associated with ketamine (4 mg/kg) gave the best results and was used on 63 animals. The injection rapidly resulted in complete immobilization with good to excellent myorelaxation. The induction stage was quiet, with absence of both corneal and pedal withdrawal reflexes in 57 animals after 2.9 +/- 1.4 min. Six animals required an additional injection. Rectal temperature and respiratory and heart rates decreased during anesthesia, whereas relative oxyhemoglobin saturation increased. One death occurred during anesthesia. One abortion and one death also occurred the day following anesthesia but were more probably a result of capture stress. Atipamezole given i.m. at a dose of five times the medetomidine dose 38.4 +/- 8.0 min after the anesthetic injection led to standing recovery in 7.1 +/- 4.5 min. Spontaneous recovery occurred in 17 animals before the atipamezole injection after an average of 30.6 +/- 9.6 min. Total recovery time was shorter in young animals. Medetomidine/ketamine induced good myorelaxation and provided considerably shortened immobilization duration, which are two notable advantages for field studies. We recommend this association for short procedures including minor surgery in red howler monkeys.

Interrenal dysfunction in fish from contaminated sites: In vivo and in vitro assessment

AbstractCortisol, synthesized in the interrenal cells of teleost head kidney, has a major role in the physiologic response to physical and chemical stressors. Plasma levels of cortisol increase in physiologically competent fish acutely exposed to stressors such as cadmium or mercury. The effects of chronic low level exposures are less well understood. We have diagnosed an endocrine impairment characterized by a reduced capacity to elevate plasma cortisol levels in response to an acute standardized capture stress in yellow perch (Perca flavescens) and in northern pike (Esox lucius) sampled at sites contaminated by mixtures of pollutants (heavy metals, polycyclic aromatic hydrocarbons, and polychlorinated biphenyls), by heavy metals, or by bleached kraft mill effluent. Our studies with fish, as well as with amphibians at contaminated sites, demonstrated that low level chronic exposures impair secretion of corticosteroids. We have developed new tests for assessment of the functional integrity of teleost and amphibian interrenal tissue by using an adrenocorticotropic hormone (ACTH) challenge, in vivo and in vitro. The reduced ability to respond to ACTH indicates that the normal neuroendocrine response to stressors may be disrupted and that the ability to cope with biotic and abiotic stressors in the environment may be significantly reduced in the impaired animals.

Pathophysiological significance of hematochemical parameters of Capra ibex

Reference values for hcmatochemical parameters in wild animals are difficult to ob- tain. because of the effccts of capture stress or of the drugs used for chemical restraint. To establi- sh rcfcrcncc values for Capl-a ihex, we examined 30 females culled monthly from January to May 1991 in the Grisons (CH). The following serum variables were studied: cortisol, non esterified fatty acids (NEFA), glucose, triglycerides, cholesterol, total protein. calcium, inorganic phosphate. Va- lues were compared with those of animals culled in the same period of 1990. The only significant differences were in serum cortisol and triglycerides, which were higher in I99 1, when climatic con- ditions were less favourable. Serum NEFA were positively correlated with the animal's level of alertness. Most of the values of the serum parameters wcrc within the range of those of the domestic goat.

Stress of capture and captivity in kahawai Arripis trutta (Bloch and Schneider) (Perciformes: Arripidae)

Plasma cortisol in wild kahawai ( Arripis trutta), an active pelagic marine fish, immediately after capture by hook and line was 8 ± 5 ng/ml (capture time, 4.9 ± 0.8 min, range 1–11 min). Capture by angling was accompanied by high levels of lactate in the white muscle (46.6 ± 2.8 μmol/g) and moderate plasma lactate levels (8.4 ± 1.0 mmol/l). Peak plasma cortisol concentration in fish after transport to shore in live tanks aboard a boat (1–2 hr post-capture) was 161 ± 31 ng/ml. Cortisol levels in wild-caught kahawai had returned to basal values within 3 days of introduction to a shore-based holding pool. Kahawai reacted violently to confinement in still water in darkened enclosed boxes. This prompted the design and construction of a swim tunnel for holding individual kahawai. Confinement of chronically cannulated kahawai in the swim tunnel resulted in a progressive increase in plasma cortisol; 2 hr after cannulation and confinement in the swim tunnel, plasma cortisol concentration was 112 ± 31 ng/ml. This increased to 233 ± 55 ng/ml after 2 days of confinement. Thus, confinement and cannulation do not appear to be suitable approaches for studying the physiology of this species.

Impaired cortisol secretion in yellow perch (Perca flavescens) from lakes contaminated by heavy metals: in vivo and in vitro assessment

The characteristic elevation of plasma cortisol levels in response to an acute stress of capture was impaired in both male and female yellow perch (Perca flavescens) from lakes contaminated by heavy metals. The impairment of the cortisol stress response was observed in fish 4 + years and older whereas the capacity to elevate plasma cortisol levels of fish younger than 4 + was not significantly different at contaminated and reference sites. The responsiveness to ACTH of the interrenal tissue of 4 + yellow perch was evalutated in vitro to determine whether the impairment of the cortisol stress response is caused by a dysfunction of the interrenal tissue or if the dysfunction is located elsewhere in the hypothalamo-pituitary-interrenal axis controlling the secretion of cortisol. The amount of cortisol secreted by the interrenal tissue of yellow perch from a contaminated site in response to a 10-min stimulation with 10-7 M ACTH was significantly lower compared with fish from the reference site. These results indicate that the impairment of the cortisol stress response observed in fish from polluted sites is caused, at least in part, by a dysfunction of the interrenal tissue.

Seasonal Changes in Gonadal Activity and the Effects of Stress on Reproductive Hormones in the Common Snapping Turtle,Chelydra serpentina

The seasonal gonadal cycle (including gonadal histology, sex steroids, and gonadotropins) was studied in freshly captured common snapping turtles,Chelydra serpentina,from Wisconsin, and the effects of capture stress were evaluated. The ovarian and testicular cycles are shorter than those reported in other freshwater turtles; the cycles commence in mid-May and terminate in early September, immediately after the completion of gonadal growth and maturation. In the female, testosterone (T), 17β-estradiol (E2), and progesterone (Pro) were highly correlated with follicular growth and vitellogenesis. Ovulation in captivity and under natural conditions occurred after mid-May. In captivity, ovulation was a rapid process (24–48 hr); as the follicles descended into the uterine horns there was a significant increase in E2and Pro and eggs were retained in the uterine horns for about 2 weeks before oviposition. In the male, T was sig nificantly correlated with testicular growth and spermiation. Follicle-stimulating hormone (FSH) reached significantly higher levels (P<0.01) in males (8.99±0.38 ng/ml) than in females (2.66±0.22 ng/ml), but luteinizing hormone was undetectable in both sexes. FSH was not correlated with the steroids in either sex. Sex steroids and FSH began to rise before spermiation and vitellogenesis and remained elevated until completion of gonadal growth and maturation. Leydig cells, the main source of plasma androgen in this species, became active shortly after emergence from hibernation and remained steroidogenically active for the rest of the cycle. Sertoli cells became active only after spermatogenesis was under way but also stayed active for the rest of the summer. Courtship and mating behaviors were observed in spring, summer, and fall. The snapping turtle is strictly aquatic with no basking behavior and limited behavioral thermoregulation so there is little daily fluctuation in body temperature. Environmental correlates indicate that the snapping turtle is temperature dependent: recrudesence occurs with a slight increase in water temperature during spring and early summer, while a dramatic drop in gonadal activity accompanies a slight decrease in temperature in fall. Changes in temperature may underlie changes in gonadal activity in the face of relatively stable FSH. Male turtles subjected to captivity and periodic blood sampling show a significant decline in T. The hormonal levels continued to decline whether the turtles are exposed to optimum or extreme temperatures. However, there is more rapid decline in T values in animals with regressed testes (June) than in those with well-developed testes (July). Male and female turtles kept in captivity at different phases of the cycle exhibit different patterns and degrees of response to stress, possibly related to the hormonal levels and the condition of the gonads.

In vivo testing of the functional integrity of the corticosterone‐producing axis in mudpuppy (amphibia) exposed to chlorinated hydrocarbons in the wild

AbstractThe functional integrity of the hypothalamo–pituitary–interrenal (HPI) axis was tested in an aquatic salamander, the mudpuppy (Necturus maculosus), exposed in the wild to HPI axis disrupters. The response to stress challenges was compared in mudpuppies sampled at nine sites of the St. Lawrence and Ottawa rivers during winter. Polychlorinated biphenyls and organochlorine pesticides measured in gonads indicated that the exposure was highly variable among sites. Females subjected to a standardized capture and confinement stress, a treatment that induces a surge of circulating corticosterone, had significantly lower levels of corticosterone at a number of contaminated sites compared to animals from the reference areas. Among‐site differences could not be distinguished in males that had very low corticosterone levels overall. The reduced corticosterone response at contaminated sites was not associated with an atrophy of the interrenal corticosterone‐releasing cells. A corticotrophin (adrenocorticotrophic hormone, ACTH) challenge imposed in situ after a 24‐h postcapture recovery elicited a corticosterone surge significantly lower in contaminated females and males, pointing to disruptions along the HPI axis downstream of the pituitary ACTH‐secreting cells. Corticosterone levels measured after recovery were higher at the contaminated site, suggesting an increase in resting levels. Liver glycogen, whose replenishment is partly mediated by corticosterone, was significantly depleted in salamanders collected at most contaminated sites. Our results suggest xenobiotic‐induced disruptions within the HPI axis of an amphibian species, but the role of alternative factors is also discussed.

The adrenocortical responses to stress in breeding Willow Warblers Phylloscopus trochilus in Sweden: effects of latitude and gender

1. In the present study we tested the hypothesis that birds suppress their adrenocortical response to stress when breeding in a severe environment. 2. We measured increases in circulating levels of corticosterone following capture and handling in populations of Willow Warblers, Phylloscopus trochilus, breeding in a rich deciduous forest in southern Sweden and in Willow Warblers breeding in a subarctic environment in Swedish Lapland. Data from an 8‐year study on survival rates and nest predation in southern and northern Sweden are also included. 3. By comparing the changes in corticosterone levels immediately following capture, handling and restraint, and then up to 1‐h post‐capture across gender and latitude, we were able to assess possible ecological influences. 4. Willow Warblers had about the same survival rates in northern and southern Sweden (0·27 and 0·30, respectively). Depredated clutches were normally replaced in southern Sweden (72%), but not in northern Sweden (1%). 5. A reduced adrenocortical response to stress was found in Willow Warblers of both sexes breeding in northern Sweden where conditions were more severe and the nesting season shorter than in southern Sweden. At the southern site, males had a significantly more robust adrenocortical response to stress than females, whereas at the northern site changes in corticosterone following capture were identical in males and females. Maximum corticosterone levels generated by the capture stress protocol were significantly higher in males at the southern site than in all other groups. 6. There were marked individual variations in the patterns of corticosterone changes following capture in all groups, but there were no significant relationships of dynamics of corticosterone changes to body mass or fat score in males. However, in females at the southern site, the maximum corticosterone level and the rate of corticosterone increase during the capture stress protocol were positively correlated with body mass. In contrast, at the northern site females showed negative correlations of body mass with maximum corticosterone and rate of corticosterone increase. These differences may reflect different ecological bases for modulation of the adrenocortical response to stress with latitude, and with gender.