When can we measure stress noninvasively? Postdeposition effects on a fecal stress metric confound a multiregional assessment

Measurement of stress hormone metabolites in fecal samples has become a common method to assess physiological stress in wildlife populations. Glucocorticoid metabolite (GCM) measurements can be collected noninvasively, and studies relating this stress metric to anthropogenic disturbance are increasing. However, environmental characteristics (e.g., temperature) can alter measured GCM concentration when fecal samples cannot be collected immediately after defecation. This effect can confound efforts to separate environmental factors causing predeposition physiological stress in an individual from those acting on a fecal sample postdeposition. We used fecal samples from American pikas (Ochotona princeps) to examine the influence of environmental conditions on GCM concentration by (1) comparing GCM concentration measured in freshly collected control samples to those placed in natural habitats for timed exposure, and (2) relating GCM concentration in samples collected noninvasively throughout the western United States to local environmental characteristics measured before and after deposition. Our timed‐exposure trials clarified the spatial scale at which exposure to environmental factors postdeposition influences GCM concentration in pika feces. Also, fecal samples collected from occupied pika habitats throughout the species' range revealed significant relationships between GCM and metrics of climate during the postdeposition period (maximum temperature, minimum temperature, and precipitation during the month of sample collection). Conversely, we found no such relationships between GCM and metrics of climate during the predeposition period (prior to the month of sample collection). Together, these results indicate that noninvasive measurement of physiological stress in pikas across the western US may be confounded by climatic conditions in the postdeposition environment when samples cannot be collected immediately after defecation. Our results reiterate the importance of considering postdeposition environmental influences on this stress metric, especially in multiregional comparisons. However, measurements of fecal GCM concentration should prove useful for population monitoring within an eco‐region or when postdeposition exposure can be minimized.     

Comparison of different enzyme-immunoassays for assessment of adrenocortical activity in primates based on fecal analysis

Most studies published to date that used fecal glucocorticoid measurements to assess adrenocortical activity in primate (and many nonprimate) species applied a specific cortisol or corticosterone assay. However, since these native glucocorticoids are virtually absent in the feces of most vertebrates, including primates, the validity of this approach has recently been questioned. Therefore, the overall aim of the present study was to assess the validity of four enzyme-immunoassays (EIAs) using antibodies raised against cortisol, corticosterone, and reduced cortisol metabolites (two group-specific antibodies) for assessing adrenocortical activity using fecal glucocorticoid metabolite (GCM) measurements in selected primate species (marmoset, long-tailed macaque, Barbary macaque, chimpanzee, and gorilla). Using physiological stimulation of the hypothalamo-pituitary-adrenocortical (HPA) axis by administering exogenous ACTH or anesthesia, we demonstrated that at least two assays detected the predicted increase in fecal GCM levels in response to treatment in each species. However, the magnitude of response varied between assays and species, and no one assay was applicable to all species. While the corticosterone assay generally was of only limited suitability for assessing glucocorticoid output, the specific cortisol assay was valuable for those species that (according to high-performance liquid chromatography (HPLC) analysis data) excreted clearly detectable amounts of authentic cortisol into the feces. In contrast, in species in which cortisol was virtually absent in the feces, group-specific assays provided a much stronger signal, and these assays also performed well in the other primate species tested (except the marmoset). Collectively, the data suggest that the reliability of a given fecal glucocorticoid assay in reflecting activity of the HPA axis in primates clearly depends on the species in question. Although to date there is no single assay system that can be used successfully across species, our data suggest that group-specific assays have a high potential for cross-species application. Nevertheless, regardless of which GC antibody is chosen, our study clearly reinforces the necessity of appropriately validating the respective assay system before it is used.     

Fecal corticosterone reflects serum corticosterone in Florida sandhill cranes

Florida sandhill cranes (Grus canadensis pratensis) were conditioned to confinement 6 hr/day for 7 days. On day 8, each bird's jugular vein was catheterized, blood samples were drawn, and each crane was confined for 6 hr. Using a randomized, restricted cross-over design, cranes were injected intravenously with either 0.9% NaCl solution or ACTH (cosyntropin; Cortrosyn; 0.25 mg). During the 6 hr of confinement, fecal samples (feces and urine) were collected from each of five cranes immediately after defecation. Individual fecal samples were collected approximately at hourly intervals and assayed for corticosterone. We showed previously that serum corticosterone did not vary significantly following saline injection, but peaked significantly 60 min after ACTH injection. Maximal fecal corticosterone concentrations (ng/g) were greater (P < 0.10; median 1087 ng/g) following ACTH stimulation compared to maximal fecal corticosterone concentrations at the end of acclimation (day 7; median 176) and following saline treatment (median 541). In cranes under controlled conditions, fecal corticosterone concentration reflects serum corticosterone levels, fecal corticosterone, Grus canadensis pratensis, sandhill cranes, serum corticosterone levels.     

Foraging Behaviour of the Brown Hyaena (Hyaena brunnea Thunberg, 1820) in the Southern Kalahari

Observations on six free ranging adult brown hyaenas (Hyaena brunnea) fitted with radio collars and beta lights were supplemented by observations on three untagged large cubs and by tracking spoor. Brown hyaenas are predominantly nocturnal and cover large distances alone each night searching for vertebrate remains and other food. Carrion is mainly located by olfactory sense, although auditory cues are also used. Excess food is often stored for short periods. Wild fruits and birds' eggs are eaten and hunting behaviour is directed towards small vertebrates and insects. Some adaptations of the brown hyaena to its environment are discussed.     

Comparison of fecal preservation and extraction methods for steroid hormone metabolite analysis in wild crested macaques

Since the non-invasive field endocrinology techniques were developed, several fecal preservation and extraction methods have been established for a variety of species. However, direct adaptation of methods from previous studies for use in crested macaques should be taken with caution. We conducted an experiment to assess the accuracy and stability of fecal estrogen metabolite (E1C) and glucocorticoid metabolite (GCM) concentrations in response to several preservation parameters: (1) time lag between sample collection and fecal preservation; (2) long-term storage of fecal samples in 80% methanol (MeOH) at ambient temperature; (3) different degrees of feces drying temperature using a conventional oven; and (4) different fecal preservation techniques (i.e., freeze-drying, oven-drying, and field-friendly extraction method) and extraction solvents (methanol, ethanol, and commercial alcohol). The study used fecal samples collected from crested macaques (Macaca nigra) living in the Tangkoko Reserve, North Sulawesi, Indonesia. Samples were assayed using validated E1C and GCM enzyme immunoassays. Concentrations of E1C and GCM in unprocessed feces stored at ambient temperature remained stable for up to 8 h of storage after which concentrations of both E1C and GCM changed significantly compared to controls extracted at time 0. Long-term storage in 80% MeOH at ambient temperature affected hormone concentrations significantly with concentrations of both E1C and GCM increasing after 6 and 4 months of storage, respectively. Drying fecal samples using a conventional oven at 50, 70, and 90 °C did not affect the E1C concentrations, but led to a significant decline for GCM concentrations in samples dried at 90 °C. Different fecal preservation techniques and extraction solvents provided similar results for both E1C and GCM concentrations. Our results confirm previous studies that prior to application of fecal hormone analysis in a new species, several preservation parameters should be evaluated for their effects on hormone metabolite stability. The results also provide several options for fecal preservation, extraction, and storage methods that can be selected depending on the condition of the field site and laboratory.     

Heterogeneity in the density of spotted hyaenas in Hluhluwe-iMfolozi Park,South Africa

Animal population sizes and trends, as well as their distributions, are essential information to the understanding and conservation of ecosystems. During this study in Hluhluwe-iMfolozi Park, South Africa, a spotted hyaena Crocuta crocuta Erxleben, 1777 (Hyaenidae) population was surveyed by attracting individuals with pre-recorded sounds. The hyaena population (excluding cubs) is substantially larger (321 individuals) than the previous estimate of 200 and this population is the second largest protected population in South Africa. Average hyaena density, at 0.357 individuals/km², was relatively high compared to other southern African conservation areas, and range from 0 to 1.25 individuals/km² across sampling stations. For short periods, spatial heterogeneity in density was marked at small and large spatial scales, but decreased when averaged over a longer period. This heterogeneity may be important in promoting the coexistence of other large and mobile carnivores in Hluhluwe-iMfolozi Park by creating potential dynamic competition refugia in space and time. Furthermore, heterogeneity of hyaena density at smaller scales should influence studies investigating the avoidance of hyaenas by competitively inferior carnivores.     

Socioecology of a high-density brown hyaena population within an enclosed reserve

Understanding the spatial ecology of wildlife is an essential prerequisite for making informed management decisions and is of particular importance for those species residing in enclosed reserves where space use may be influenced by restricted dispersal and high population densities. As the brown hyaena Parahyaena brunnea is a species likely to increasingly rely on enclosed protected areas for its long-term persistence, due to the intense persecution experienced outside of protected areas, we examined the spatial ecology of 10 brown hyaenas from a high-density population, within a small (200 km2) enclosed reserve in north-central Namibia. Spatial data, in combination with camera trap data from communal den sites, suggested six clans and at least one nomadic individual in the reserve. A mean home range size of 37 km2 (± 21 km2, range 16–97 km2) was recorded, with 92% of the reserve utilized as brown hyaena home range. Whilst these home range sizes are some of the lowest recorded for brown hyaena, the degree of overlap between neighbouring clans was similar to that recorded for open systems. Given that the majority of the reserve is utilized as brown hyaena home range, options for dispersing subadults may be limited and these individuals may represent ideal candidates for translocation into other enclosed reserves as part of metapopulation management schemes.     

Anthropogenic influences on spotted hyaena diet in the Kruger National Park,South Africa

Rapid urban expansion has led to an increase in carnivores that live close to human dominated environments. Some carnivore species have successfully adapted to these novel conditions and taken advantage of opportunities associated with human habitation. Whilst many studies have compared carnivores living in protected areas to those in an urban setting, few have looked at the relationships between carnivores and human habitation within protected areas. In this study, we examined the effects of human habitation on the diet of spotted hyaenas (Crocuta crocuta) in the Kruger National Park (KNP), South Africa. Our results suggested a limited effect of anthropogenic resources on spotted hyaena diet in the KNP. We found neither temporal nor spatial variation in the amount of, nor types of, anthropogenic material in spotted hyaena scats, despite observations of more road side litter close to large anthropogenic sites. We therefore suggest that anthropogenic resources may not have been utilised completely according to abundance. We encourage further research evaluating potential secondary effects of human activity and infrastructure on spotted hyaena diet and also stable isotope approaches that may provide further insights into the importance of anthropogenic food for spotted hyaenas inside the KNP.     

SPOTTED HYAENA WHOOPS: FREQUENT INCIDENCE OF VOCAL INSTABILITIES IN A MAMMALIAN LOUD CALL

ABSTRACT

Spotted hyaena Crocuta crocuta whoops are loud calls normally produced in a sequence termed a bout. Whoops are produced by hyaenas irrespective of age or sex to display identity and convey information about the location of the caller. The majority (91%, n=460) of whoops produced by spotted hyaenas, from two geographically separate populations in southern Africa and one population in eastern Africa, showed pronounced nonlinear phenomena, predominantly subharmonics. Whoops produced by males and females had a similarly high probability of sub- harmonics, and 91.5% of the 78 bouts examined contained calls with subharmonics. These results provide evidence that nonlinear vocal phenomena are a common feature of hyaena whoops. The presence of subharmonics in whoops may be enhanced by vocal tract resonances when the fundamental frequency and first formant in the calls are close or coincide. Vocal membranes may also play a role. The high incidence of subharmonics in whoops may enhance individual recognition by adding structural complexity to calls. As 33 of 34 individually known spotted hyaenas examined in this study produced whoops containing subharmonics, it is unlikely that the production of subharmonics is confined to calls from individuals of a particular social status, sex, size, or level of developmental asymmetry, as proposed for nonlinear phenomena in the calls of other mammalian species, although variation in structural features of subharmonics may convey information about these characteristics.     

Validation of a Fecal Glucocorticoid Metabolite Assay to Assess Stress in the Budgerigar (Melopsittacus undulatus)

The budgerigar (Melopsittacus undulatus) is a small parrot native to Australia that is commonly held in zoos, laboratories, and private homes. Assessment of budgerigar stress levels would aid welfare monitoring and improve our understanding of their biology. Analyzing fecal glucocorticoid metabolites provides a noninvasive method to measure stress levels in birds. For this method to be reliable, the antibody to be used in an immunoassay must be carefully selected for each species, and validation must be performed. A common limitation in many existing assays is the inability to accurately detect variable fecal glucocorticoid metabolites in minute quantities of feces, requiring small samples to be combined. We have developed a double antibody radioimmunoassay protocol based on a commercially available ¹²⁵I‐corticosterone radioimmunoassay kit for use in detecting fecal glucocorticoid metabolites in small quantities (<20 mg) of budgerigar droppings. The assay was validated pharmacologically with an adrenocorticotropic hormone challenge and with oral administration of corticosterone. Our validation has demonstrated our assay is both sensitive and a reliable approach to noninvasive monitoring of stress in budgerigars. Zoo Biol. 32:112‐116, 2013. © 2012 Wiley Periodicals, Inc.     

Noninvasive monitoring of fecal cortisol metabolites in the eastern chipmunk (Tamias striatus): validation and comparison of two enzyme immunoassays

Monitoring fecal glucocorticoid metabolites in wild animals, using enzyme immunoassays, enables the study of endocrinological patterns relevant to ecology and evolution. While some researchers use antibodies against the parent hormone (which is typically absent from fecal samples), others advocate the use of antibodies designed to detect glucocorticoid metabolites. We validated two assays to monitor fecal cortisol metabolites in the eastern chipmunk (Tamias striatus). We compared an antibody produced against cortisol and one produced against 5α-pregnane-3β, 11β, 21-triol-20-one using a radiometabolism study and an injection with adrenocorticotropic hormone (ACTH). Most cortisol metabolites were excreted in the urine (～83%). Peak excretion in the feces occurred 8 h after injection. Both assays detected an increase in fecal cortisol metabolite levels after injection of ACTH. Males, but not females, exhibited a circadian variation in metabolite levels. The sexes did not exhibit any difference over the time course and route of excretion or the relative increase in fecal cortisol metabolite levels after ACTH injection. The cortisol assay displayed higher reactivity to ACTH injection relative to baseline than did the metabolite assay. While both antibodies gave comparable results, the cortisol antibody was more sensitive to changes in plasma cortisol levels in eastern chipmunks.     

Factors associated with fecal glucocorticoids in Alaskan brown bears (Ursus arctos horribilis)

The aims of this study were to validate a radioimmunoassay (RIA) for quantifying glucocorticoid metabolite concentrations in the feces of Alaskan brown bears (Ursus arctos horribilis) and to investigate whether any of the following factors are associated with those concentrations: the presence of humans or other bears, fishing difficulty, sex-age class, diet, and season. We tested an established corticosterone RIA for assay sensitivity, similarity, precision, and sample matrix effects of brown bear feces, and it proved satisfactory. We collected fecal samples from brown bears along salmon-spawning streams and assessed fecal glucocorticoid (FG) concentrations. We observed that the factors explaining the most variation in measured concentrations were date and diet type and that there was a significant interaction between the two. We did not observe a significant effect of human and bear activities or sex-age class on FG concentrations. This study demonstrates that although FG concentrations may be assessed in brown bears, complex dietary patterns and seasonal variations must be taken into consideration in the study design in order to make inferences regarding stress.     

Excretion and metabolic fate of radiolabeled estradiol and testosterone in the cockatiel (Nymphicus hollandicus)

The metabolism and time courses for clearance of radiolabeled estradiol and testosterone were studied in the female cockatiel (Nymphicus hollandicus) using a simple technique of solubilizing dried fecal/urine matter in an aqueous solution. Carbon ¹⁴ radiolabeled estradiol and testosterone were injected intramuscularly and the urine and fecal matter collected for the pursuant 168 hr. The predominant radiolabel peak was found associated with the aqueous residue of the ether extracted aliquot for both hormones. High-performance liquid chromatographic (HPLC) separation of solubilized fecal/urine material collected during the first sampling interval (0–4 hr after injection) demonstrated that the majority of the excreted radiolabel was in the form of conjugated steroid metabolites in both the estradiol and testosterone injected birds. Subsequent hydrolysis of the aqueous residue of the ether extracted aliquots and HPLC characterized the estrogen and testosterone metabolites as being estrone/estradiol and a variety of androgen based moieties, respectively. By 24 hr postinjection, 79.4 and 79.1% of the original radiolabel was recovered in birds injected with estradiol and testosterone, respectively. These findings demonstrate that steroid hormone excretion in the cockatiel is a rapid and efficient process that is 79% complete by 24 hr and that the primary excretion products are conjugated metabolites. This study also supports the concept that fecal/urine collection is a practical and efficient method of monitoring sex steroid excretion and provides additional evidence that simple solubilization of fecal matter is a sufficient and efficient method for processing feces for subsequent metabolite measurements. Zoo Biol 16:505–518, 1997. © 1997 Wiley-Liss, Inc.     

Non‐invasive fecal hormone analysis and behavioral observations for monitoring stress responses in captive western lowland gorillas (Gorilla gorilla gorilla)

Non‐invasive techniques for monitoring the stress response in captive western lowland gorillas (Gorilla gorilla gorilla) were investigated. Fecal samples for cortisol measurement and concurrent behavioral data were collected from six individuals in a socially housed gorilla group (one adult male, three adult females and their three offspring) over a 7‐month period. Despite inter‐individual variation in the dynamics of fecal cortisol concentrations over time, several major secretory peaks coincided across individuals. High cortisol concentrations in feces were correlated with induced stressors or behavioral observations indicating high social tension, with a 1–2 day lag period. Entry progression order of the gorillas into a den complex and a supplant‐based dominance index were suitable indicators of overall dominance hierarchies, and fluctuations over time reflected periods of instability. Diurnal variation in fecal cortisol was not apparent when comparing afternoon and morning samples, however the sample collection interval was relatively short (3–5 hr). These results demonstrate the feasibility of monitoring stress responses based on the dynamics of both fecal cortisol excretion and behavior. This non‐invasive approach may be used for gauging responses to changes in husbandry, environment and group structure of captive gorillas. Zoo Biol 0:1–15, 2005. © 2005 Wiley‐Liss, Inc.     

How much does a spotted hyaena eat? Perspective from the Namib Desert

The amount of food consumed by a clan of spotted hyaenas in the Namib desert was determined gravimetrically for 19 nights and the amount consumed by each individual was calculated according to its feeding time budget. At large, fleshy ungulate carcasses, each adult clan member ate about 8.7kg nightly, except for the bottom-ranking male, who obtained only half that amount per night. Skin and bone remains were consumed at a slower rate of 2kg/hyaena/night. Medium-sized ungulates were devoured rapidly so that each hyaena obtained more during such feeding nights than at large carcasses. Over a 29 day period, a hyaena clan consumed five cacasses at a rate of 4.0kg/hyaena/day, which compared well with previous estimates of average daily consumption in large social carnivores studied elsewhere. Annually, sixteen Namib hyaenas ate some 4.8% of the ungulate bio-mass, removing, in terms of numbers 14.3% of the gemsbok and 2.2% of the mountain zebra. This depletion did not appear to limit these populations.     

Hair cortisol: a parameter of chronic stress? Insights from a radiometabolism study in guinea pigs

Measurement of hair cortisol has become popular in the evaluation of chronic stress in various species. However, a sound validation is still missing. Therefore, deposition of radioactivity in hair and excretion into feces and urine after repeated injection of (3)H-cortisol was studied in guinea pigs (n?=?8). Each animal was given intraperitoneally 243.6?kBq (3)H-cortisol/day on 3 successive days. After the first injection, all voided excreta were collected for 3?days. After the second injection, hair was shaved off the animals' back and newly grown hair was obtained on day 7. Following methanol extraction, radiolabeled and unlabeled glucocorticoid metabolites (GCM) in fecal and hair samples were characterized by high-performance liquid chromatography (HPLC) and enzyme immunoassays (EIA). In feces, maximum radioactivity was reached 8?h (median) post each injection, whereas maxima in urine were detected in the first samples (median 2.5?h). Metabolites excreted into feces (13.3?%?±?3.7) or urine (86.7?%) returned nearly to background levels. HPLC of fecal extracts showed minor variation between individuals and sexes. In hair, small amounts of radioactivity were present. However, two EIAs detected large amounts of unlabeled GCM, including high levels at the position of the cortisol standard; radioactivity was absent in this fraction, demonstrating that (3)H-cortisol was metabolized. Furthermore, large amounts of immunoreactivity coinciding with a radioactive peak at the elution position of cortisone were found. These results show for the first time that only small amounts of systemically administered radioactive glucocorticoids are deposited in hair of guinea pigs, while measurement of large amounts of unlabeled GCM strongly suggests local production of glucocorticoids in hair follicles.     

Assessment of reproductive status and ovulation in female brown kiwi (Apteryx mantelli) using fecal steroids and ovarian follicle size

Despite being listed as endangered on the IUCN (World Conservation Union) red list [BirdLife International 2005], and intense conservation efforts on its behalf, little is known about the reproductive physiology of the brown kiwi (Apteryx mantelli). This study therefore was undertaken to describe ovarian function in brown kiwi using noninvasive methods that can be utilized in the field. This study describes a simple method for extraction and detection of steroid metabolites in brown kiwi feces by enzyme‐linked immunosorbent assay (ELISA). Average fecal steroid hormone metabolite concentrations were derived from 10 egg‐lay cycles in 2 hens. Testosterone began to increase between 23 and 18 days before oviposition (?23d to ?18d) and remained elevated until just before oviposition. Estradiol rose from ?28d to ?13d and remained elevated until 12 days after oviposition. Progesterone exhibited an increase of short duration from ?8d to +7d with a peak at ?3d. Ovarian follicle growth rate was determined by serial ultrasound measurements of follicles in three habituated female kiwi. Follicle growth rate was described by the formula y=132.54e^0.0569x (y=follicle diameter, x=days before oviposition). Follicles ranged in size from 10 to 76 mm. Day of ovulation was estimated using egg yolk size, follicle growth curve, and day of oviposition. This yielded an ovulation‐oviposition cycle length of 7–10 days, significantly shorter than the only other estimate of 16–17 days derived using body weights of a single kiwi hen. The correlation of fecal steroid hormone concentrations with follicle growth provides new insight into the reproductive physiology of the female brown kiwi. Zoo Biol 0:1–10, 2005. © 2005 Wiley‐Liss, Inc.     

Evaluation of adrenocortical function in Florida manatees (Trichechus manatus latirostris)

The study objectives were to determine the predominant manatee glucocorticoid; validate assays to measure this glucocorticoid and adrenocorticotropic hormone (ACTH); determine diagnostic thresholds to distinguish physiological vs. pathological concentrations; identify differences associated with sex, age class, female reproductive status, capture time, and lactate; and determine the best methods for manatee biologists and clinicians to diagnose stress. Cortisol is the predominant manatee glucocorticoid. IMMULITE 1000 assays for cortisol and ACTH were validated. Precision yielded intra‐ and inter‐assay coefficients of variation for serum cortisol: ≤23.5 and ≤16.7%; and ACTH: ≤6.9 and ≤8.5%. Accuracy resulted in a mean adjusted R²≥0.87 for serum cortisol and ≥0.96 for ACTH. Assay analytical sensitivities for cortisol (0.1 µg/dl) and ACTH (10.0 pg/ml) were verified. Methods were highly correlated with another IMMULITE 1000 for serum cortisol (r=0.97) and ACTH (r=0.98). There was no significant variation in cortisol or ACTH with sex or age class and no correlation with female progesterone concentrations. Cortisol concentrations were highest in unhealthy manatees, chronically stressed by disease or injury. ACTH was greatest in healthy free‐ranging or short‐term rehabilitating individuals, peracutely stressed by capture and handling. Cortisol concentrations ≥1.0 µg/dl were diagnostic of chronic stress; ACTH concentrations ≥87.5 pg/ml were diagnostic of peracute stress. In healthy long‐term captive manatees, cortisol (0.4±0.2 µg/dl) and ACTH (47.7±15.9 pg/ml) concentrations were lower than healthy free‐ranging, short‐term rehabilitated or unhealthy manatees. Capture time was not significantly correlated with cortisol; ACTH correlation was borderline significant. Cortisol and ACTH were positively correlated with lactate. Zoo Biol 30:17–31, 2011. © 2010 Wiley‐Liss, Inc.     

Cortisol metabolism in the domestic cat and implications for non-invasive monitoring of adrenocortical function in endangered felids

Three domestic cats were given i.m. injections of ³H-cortisol to determine the time course and relative proportion of excreted ³H-cortisol metabolites into urine and feces. Most urinary radioactivity was detected in the first sample collected at 3.9 ± 2.5 hr postinjection and accounted for 13.9 ± 2.1% of the total radioactivity recovered. High performance liquid chromatography (HPLC) detected four urinary metabolites, one of which (13.7% urinary radioactivity) eluted with the ³H-cortisol reference tracer and was quantifiable using a commercial cortisol radioimmunoassay (RIA). The majority of cortisol metabolites in feces (85.9 ± 2.1%) was excreted at 22.3 ± 6.2 hr. HPLC analysis detected several fecal metabolites consisting primarily of nonhydolyzable water-soluble forms, none of which eluted with ³H-cortisol or ³H-corticosterone reference tracers. No immunoreactivity was detected in HPLC-separated fecal eluates using the cortisol RIA; however, two of the more polar metabolites were quantifiable using a commerical cortisosterone RIA. The physiological relevance of the immunoreactive fecal metabolites was determined in four domestic cats given an adrenocorticotropin (ACTH) challenge. Increased serum cortisol concentrations were detected within 30 min of ACTH injection, which was maintained for at least 6 hr. A corresponding increase in fecal cortisol metabolite concentrations (ranging from 238% to 826% over individual baseline values) was observed 24–48 hr later. These data indicate that adrenocortical activity can be monitored nonivasively in the cat by measuring cortisol metabolites excreted in feces. This procedure is a potentially valuable tool for endangered felid management to help evaluate responses to physiological and psychological stressors associated with environmental conditions and husbandry practices. (This article is a US Government work and, as such, is in the public domain in the United States of America.) © 1996 Wiley-Liss, Inc.     

Evidence for prey selection by spotted hyaena in the Eastern Cape,South Africa

We tested the widely accepted hypothesis that spotted hyaenas (Crocuta crocuta) are non-selective in their diet. The prey preference of spotted hyaena was studied in the Addo Elephant National Park (AENP), South Africa. Diet (frequency of occurrence of prey items in the diet) was quantified through the analysis of 55 scats, and compared with available prey. A combination of large- and medium-sized mammals (buffalo (Syncerus caffer), red hartebeest (Alcelaphus buselaphus) and common duiker (Sylvicapra grimmia) were the most preferred prey items. The most abundant species, warthog (Phacochoerus africanus) and kudu (Tragelaphus strepsiceros), were ignored and avoided, respectively. These results show that the assumption that hyaena prey on the most abundant available prey species may be overly simplistic. Predation patterns, such as the ones observed in AENP, may have important ramifications for less common species that are selected by hyaena in small enclosed reserves.