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Non-invasive Methods of Stress Monitoring in Animals under Human Care

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A special issue of Animals (ISSN 2076-2615). This special issue belongs to the section "Wildlife".

Deadline for manuscript submissions: closed (1 June 2023) | Viewed by 30553

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Special Issue Editors

Dr. Rachel Santymire

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Guest Editor

Biology Department, Georgia State University, Atlanta, GA 30302, USA
Interests: stress physiology; reproductive physiology; conservation biology; endangered species

Dr. Linda M. Penfold

E-Mail Website
Co-Guest Editor

South-East Zoo Alliance for Reproduction and Conservation, Yulee, FL 32097, USA
Interests: reproduction; elasmobranchs; ungulates; spermatozoa; cryopreservation; endocrinology; zoo; wildlife

Special Issue Information

Dear Colleagues,

Understanding the stress physiology of animals under human care is vital to their management and the designing of informative research. As humans continue to negatively impact the planet, wildlife species are increasingly under threat due habitat loss and degradation. Ex situ populations are now under more pressure to be successful, but unfortunately, that is not typically case. To better understand how the human-managed environment is impacting wildlife, it is imperative to develop non-invasive techniques that will allow sampling without influencing the individual’s stress physiology. By conducting observational research along with non-invasive sampling to evaluate physiology, we can better understand and modify our management of wildlife. This will lead to their population success and provide a haven for imperilled wildlife.

Original manuscripts that address non-invasive tools to evaluate wildlife stress physiology are invited for this Special Issue. Topics of special interest include innovative techniques for evaluating wildlife stress physiology, integrated behavioural and endocrinological research on wildlife under human care, and developing methods to evaluate not just stress hormones, but stress responses, to better understand the role of captive management on wildlife success.

Dr. Rachel Santymire
Dr. Linda M Penfold
Guest Editors

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Keywords

glucocorticoids
wildlife
stress
hormones
stress responses
under human care, ex situ

Published Papers (13 papers)

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Research

14 pages, 1827 KiB

Open AccessArticle

Analytical Validation and Assessment of Baseline Fecal Glucocorticoid Metabolites in Northern Sea Otters (Enhydra lutris kenyoni) in Human Care

by Amy Y. Olsen, Angela Smith, Caroline Hempstead and Shawn E. Larson

Animals 2023, 13(13), 2175; https://doi.org/10.3390/ani13132175 - 2 Jul 2023

Viewed by 1292

Abstract

Fecal glucocorticoid metabolites (FGMs) have been used as a non-invasive and indirect measurement of the complex stress response in a variety of species. Animals in facilities under managed care allow for the longitudinal study of FGMs in a controlled environment. Animal histories often include environmental, husbandry, and medical notes that can be matched to FGM concentrations to aid in the physiological validation of adrenal stimulation and response. The goal of this study was to demonstrate analytical validations using two enzyme-linked immunosorbent assays (EIA) to measure FGMs from northern sea otters (Enhydra lutris kenyoni) under human care (Seattle Aquarium, Seattle, WA, USA) and to determine baseline and stress response spike levels for individual sea otters. Individual variation was found among the four subjects in the study with fecal baseline levels ranging from 20.2 to 83.7 ng/g for cortisol-immunoreactive metabolites and 52.3 to 102 ng/g for corticosterone-immunoreactive metabolites. As a retrospective study, 39 percent of hormone peaks were associated with notes and most FGM spikes were associated with veterinary procedures or days in which enrichment items were provided and produced an excitatory response. Monitoring baseline FGMs levels and events associated with hormone peak values may provide insight into effective husbandry management to improve the overall welfare of sea otters and other marine mammals. Full article

(This article belongs to the Special Issue Non-invasive Methods of Stress Monitoring in Animals under Human Care)

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14 pages, 1562 KiB

Open AccessArticle

Integrating Measures of Fecal Glucocorticoid Metabolites and Giving-Up Densities to Assess Adrenocortical Activity and Well-Being in Zoo-Housed Three-Banded Armadillos (Tolypeutes matacus)

by Jennifer Howell-Stephens, Emily J. Potratz, Joel S. Brown, Dave Bernier and Rachel M. Santymire

Animals 2023, 13(12), 1975; https://doi.org/10.3390/ani13121975 - 13 Jun 2023

Viewed by 1084

Abstract

To monitor adrenocortical activity in zoo-housed species, we propose using physiological and behavioral indicators that are non-invasive and practical to implement. We explore this model in the southern three-banded armadillo (Tolypeutes matacus; armadillo), which is a near-threatened species commonly found in zoos. We aimed to (1) deploy food patches to quantify foraging behavior (via giving-up densities, GUDs); (2) determine the effects of food patch and environmental modifications on individuals’ GUDs and adrenocortical activity (via fecal glucocorticoid metabolites, FGMs); and (3) examine the relationship between GUDs and FGMs. Three males and four females received food patches under varying experimental conditions at the Lincoln Park Zoo (Chicago, IL, USA). Fecal samples were collected before, during, and after foraging experiments to examine FGMs. Armadillos did not respond to patch modifications but did forage more when given increased cover. Individual mean FGMs and GUDs were highly variable, and individuals had consistent FGM and GUD ranks across experiments. FGMs and GUDs did not vary across the experiments nor did they relate to each other. Armadillos and species with a limited behavioral repertoire (i.e., constant movement) can benefit from this multi-trait model to determine the effect of environmental modifications on individuals and provide meaningful information about adrenocortical activity. Full article

(This article belongs to the Special Issue Non-invasive Methods of Stress Monitoring in Animals under Human Care)

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16 pages, 2229 KiB

Open AccessArticle

Skin Cortisol and Acoustic Activity: Potential Tools to Evaluate Stress and Welfare in Captive Cetaceans

by Chung-Hei Wong, Ming-An Tsai, Fung-Chi Ko, Jiann-Hsiung Wang, Yi-Jing Xue and Wei-Cheng Yang

Animals 2023, 13(9), 1521; https://doi.org/10.3390/ani13091521 - 1 May 2023

Cited by 1 | Viewed by 2240

Abstract

As people’s focus broadens from animals on farms to zoos and aquaria, the field of welfare science and the public’s concern for animal welfare continue to grow. In captive animals, stress and its causes are topics of interest in welfare issues, and the identification of an objective method that can be used to assess animals’ stress as a physiological state is essential. Both behavioral and physiological parameters can be used as indicators in order to assess animal stress quantitatively. To validate this approach, acoustic activity and the sloughed scrape skin cortisol concentration were used to evaluate the animal welfare of captive beluga whales (Delphinapterus leucas). The acoustic activity (5 min at 10:00 am) of three captive D. leucas was routinely recorded by a transducer and analyzed using audio editing software. The calls were separated into three main categories: whistles, pulses, and combo calls. The sloughed scrape skin samples were collected non-invasively once a week from all three animals’ fluke and/or flipper. Cortisol was extracted using a modified skin steroid extraction technique, and detected via commercially available enzyme immunoassays. The results showed that the cortisol concentration increased by varying levels when the whales encountered the same event. In addition, the number and distribution of the calls changed along with the events. This indicated that the changes in the cortisol concentration and acoustic behavior may have reflected the fluctuations in the environment and body condition. Therefore, the scrape cortisol measurement and acoustic recordings could be used to monitor stress levels in captive beluga whales. We recommend that aquaria consider incorporating skin scrape cortisol and acoustic activity monitoring into their standards for animal welfare. Full article

(This article belongs to the Special Issue Non-invasive Methods of Stress Monitoring in Animals under Human Care)

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16 pages, 2040 KiB

Open AccessArticle

Validation of Enzyme Immunoassays via an Adrenocorticotrophic Stimulation Test for the Non-Invasive Quantification of Stress-Related Hormone Metabolites in Naked Mole-Rats

by Tshepiso Lesedi Majelantle, Nigel Charles Bennett, Stefanie Birgit Ganswindt, Daniel William Hart and Andre Ganswindt

Animals 2023, 13(8), 1424; https://doi.org/10.3390/ani13081424 - 21 Apr 2023

Cited by 1 | Viewed by 1507

Abstract

Small size in mammals usually restricts long-term, frequent monitoring of endocrine function using plasma as a matrix. Thus, the non-invasive monitoring of hormone metabolite concentrations in excreta may provide an invaluable approach. The aim of the current study was to examine the suitability of enzyme immunoassays (EIAs) for monitoring responses to stressors in the naked mole-rat (Heterocephalus glaber, NMR) using urine and feces as hormone matrices. A saline control administration, and a high- and low-dose adrenocorticotropic hormone (ACTH) challenge were performed on six male and six female disperser morph NMRs. The results revealed that a 5α-pregnane-3β,11β,21-triol-20-one EIA detecting glucocorticoid metabolites (GCMs) with a 5α-3β-11β-diol structure is the most suitable assay for measuring concentrations in male urine samples, whereas an 11-oxoaetiocholanolone EIA detecting GCMs with a 5β-3α-ol-11-one structure appears the most suitable EIA for quantifying GCMs in female urine. An 11-oxoaetiocholanolone EIA detecting 11,17 dioxoandrostanes was the most suitable EIA for quantifying GCMs in the feces of both sexes. There were sex-related differences in response to the high- and low-dose ACTH challenge. We recommend using feces as a more suitable matrix for non-invasive GCM monitoring for NMRs which can be valuable when investigating housing conditions and other welfare aspects. Full article

(This article belongs to the Special Issue Non-invasive Methods of Stress Monitoring in Animals under Human Care)

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14 pages, 2242 KiB

Open AccessArticle

Longitudinal Analysis of Variability in Fecal Glucocorticoid Metabolite Concentrations in Three Orangutans (Pongo pygmaeus pygmaeus and Pongo pygmaeus abelii) before, during, and after Transition from a Regular Habitat Environment to Temporary Housing in Indoor Holding Facilities

by Laurel B. Fink, Asaba Mukobi, Lindsey Gruber, Colleen Reed, Jason DeLibero, Scott Jackson, Sierra Neill, Julia Walz, Cydney Sines, Becca VanBeek, Candace D. Scarlata and Nadja Wielebnowski

Animals 2022, 12(23), 3303; https://doi.org/10.3390/ani12233303 - 26 Nov 2022

Cited by 2 | Viewed by 1473

Abstract

Considerable research has been conducted on the effects of inter-institutional transfers, but far less consideration has been given to intra-institutional transfers and extended housing in off-habitat holding. On 15 May 2018, The Oregon Zoo’s orangutans (n = 3) were moved from the Red Ape Reserve (RAR) to the Veterinary Medical Center (VMC) indoor holding areas and remained there until 22 December 2020, resulting in over two years of housing in a facility not specifically designed for orangutans. This study aimed to quantify potential changes in fecal glucocorticoid metabolites (fGM) typically associated with increased adrenal activity as a result of transfers, as well as potential differences in fGM concentrations associated with housing in the two different types of locations. We collected fecal samples from all orangutans during three time periods: the initial housing at RAR (RAR1), the time spent at VMC holding (VMC), and the return to RAR (RAR2). Samples were analyzed using enzyme-immunoassay (EIA) analyses and compared using two-way ANOVA tests with Games–Howell post-hoc evaluations. The results of our analyses showed the following: (1) significant differences in fGM concentrations based on location in two orangutans, with the highest fGM concentration occurring in fecal samples collected at the VMC; and (2) a lack of significant fGM peaks following multiple intra-institutional transfers for all three orangutans. Though requiring further corroboration through future studies, we speculated that pre-transfer behavior training and intensive, continued care by familiar animal care staff may have helped to mitigate the stress responses commonly associated with transfers and major changes in housing. Furthermore, this study highlights the individualistic nature of the stress response, as illustrated by the substantial variation in fGM concentrations across different housing regimens in the three orangutans. Full article

(This article belongs to the Special Issue Non-invasive Methods of Stress Monitoring in Animals under Human Care)

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11 pages, 1015 KiB

Open AccessArticle

Preliminary Investigation into Developing the Use of Swabs for Skin Cortisol Analysis for the Ocean Sunfish (Mola mola)

by Rachel M. Santymire, Marissa Young, Erin Lenihan and Michael J. Murray

Animals 2022, 12(20), 2868; https://doi.org/10.3390/ani12202868 - 21 Oct 2022

Cited by 1 | Viewed by 1377

Abstract

The ocean sunfish (mola; Mola mola) is the heaviest bony fish in the world. This slow-moving fish often is injured by fishing boats that use drift gillnets attributing to its listing as Vulnerable by the IUCN. The Monterey Bay Aquarium (Monterey, CA, USA) has a program that brings in smaller molas from the ocean and acclimates them for an exhibit. When they grow too large for the million-gallon Open Seas exhibit, they are returned to Monterey Bay through a “reverse” acclimatization. Our overall goal was to use skin swabs to evaluate mola stress physiology to better understand the effects of this program. Our objectives were to validate this non-invasive method by taking opportunistic swabs throughout acclimatization and during stressful events. We swabbed each individual (n = 12) in three different body locations. Swabs were analyzed using a cortisol enzyme immunoassay. We averaged the three swabs and examined the absolute change of cortisol from the first taken upon handling to during treatments and the different acclimation stages. We considered elevated cortisol concentrations to be ≥1.5-fold higher than the first sample. Overall, mean (±SEM) cortisol varied among individuals (564.2 ± 191.5 pg/mL swab (range, 18.3–7012.0 pg/mL swab). The majority (four of six) of molas swabbed within the first week or month had elevated skin cortisol compared to their first sample. All seven molas that were being treated for an injury or illness had elevated skin cortisol (range, 1.7- to 127.6-fold higher) compared to their post-acclimation sample. This is the first step in validating the use of non-invasive skin swabs for glucocorticoid analysis in the mola. Further biochemical analysis is needed to determine the specific steroids that are being measured. Full article

(This article belongs to the Special Issue Non-invasive Methods of Stress Monitoring in Animals under Human Care)

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14 pages, 1183 KiB

Open AccessArticle

Application of Felid Hair for Non-Invasive Tracking of Animal Reproductive Status and Adrenal Activity

by Sergey V. Naidenko, Galina S. Alekseeva, Polina S. Klyuchnikova and Mariya N. Erofeeva

Animals 2022, 12(20), 2792; https://doi.org/10.3390/ani12202792 - 16 Oct 2022

Cited by 5 | Viewed by 2357

Abstract

Hair can be a useful matrix to examine the hormonal status of an animal, although it is difficult to correlate the results to a specific time point. The aim of this study was to evaluate seasonal changes in cortisol and testosterone levels in the hair of four feline species (lynx, Lynx lynx, n = 8; Amur wildcat, Prionailurus bengalensis euptilurus, n = 8; caracal, Caracal caracal, n = 6 and domestic cat, Felis catus, n = 17) with different breeding strategies. Animals of both sexes were sampled over the year, once per season (every three months), and the concentrations of hair testosterone and cortisol were measured by EIA. Both hormones showed annual dynamic changes, which coincided with the reproductive seasonality of the studied species. Sexual differences in testosterone level were found only during the mating season (spring for lynx and Amur wildcats, spring–summer for domestic cats), when testosterone levels were higher in males than in females. Cortisol levels were higher in males than in females in domestic cats and Amur wildcat, but also only during the mating season. Seasonal increases in testosterone were observed in three seasonal breeders (lynx, Amur wildcat and domestic cat) but not in caracal, which had high testosterone levels over the whole year. In lynx and Amur wildcat, it decreased sharply in the summer. Cortisol levels increased during the mating period in domestic cat males and lynx of both sexes; in caracal, an increase in cortisol was related to the transfer of animals to smaller winter cages. Measurements of steroids in hair can provide a reliable method for evaluating the reproductive status and the activity of the hypothalamus–pituitary–adrenal axis in several felid species. Full article

(This article belongs to the Special Issue Non-invasive Methods of Stress Monitoring in Animals under Human Care)

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19 pages, 1932 KiB

Open AccessArticle

Validation of an Enzyme Immunoassay to Measure Faecal Glucocorticoid Metabolites in Common Brushtail Possums (Trichosurus vulpecula) to Evaluate Responses to Rehabilitation

by Holly R. Cope, Tamara Keeley, Joy Keong, Daniel Smith, Fabiola R. O. Silva, Clare McArthur, Koa N. Webster, Valentina S. A. Mella and Catherine A. Herbert

Animals 2022, 12(13), 1627; https://doi.org/10.3390/ani12131627 - 24 Jun 2022

Cited by 5 | Viewed by 2144

Abstract

Volunteer wildlife rehabilitators rescue and rehabilitate thousands of native animals every year in Australia. However, there is little known about how exposure to novel stimuli during rehabilitation could affect the physiology of wildlife. We investigated this question in a species that commonly enters rehabilitation, the common brushtail possum (Trichosurus vulpecula). We evaluated five enzyme immunoassays (EIA) to determine the most suitable for measuring faecal glucocorticoid metabolites (FGM) as a proxy for evaluating the response of brushtail possums to potential stressors during rehabilitation. An adrenocorticotrophin hormone (ACTH) challenge was conducted on wild-caught possums to determine the best-performing EIA based on the successful detection of FGM peaks in at least two of three possums. While a number of assays met these criteria, the 11-oxoaetiocholanolone (abbreviation: 72a) EIA was selected as it had the largest amplitude of change in response to the ACTH challenge. This assay was then used to measure FGM concentrations in 20 possums during rehabilitation. There was high variation in baseline FGM concentrations and response to captivity between possums. Significant changes in FGM levels were detected in most possums during captivity, but were not reliably associated with potentially stressful events that were identified by rehabilitators. The probability of an FGM peak occurring within five days of a potentially stressful event was about 50%, regardless of the type of event. Our study has demonstrated that injured and orphaned possums show changes in FGMs during captivity and rehabilitation and has identified events that can induce a physiological response in some individuals. We recommend that research now focus on the relationship between these responses during rehabilitation and pre- and post-release survival. Full article

(This article belongs to the Special Issue Non-invasive Methods of Stress Monitoring in Animals under Human Care)

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18 pages, 2600 KiB

Open AccessArticle

The Adrenal Cortisol Response to Increasing Ambient Temperature in Polar Bears (Ursus maritimus)

by Emily M. Leishman, Maria Franke, Jill Marvin, Dylan McCart, Carol Bradford, Zoltan S. Gyimesi, Anne Nichols, Marie-Pierre Lessard, David Page, C-Jae Breiter and Laura H. Graham

Animals 2022, 12(6), 672; https://doi.org/10.3390/ani12060672 - 8 Mar 2022

Cited by 5 | Viewed by 4568

Abstract

Our objective was to identify the upper ambient temperature threshold that triggers an increase in cortisol in response to increased thermoregulatory demands in polar bears. The results reported here include endocrine data collected over two years from 25 polar bears housed in 11 accredited zoological institutions across North America. The effects of ambient temperature, sex, age group (juvenile, adult, elderly), breeding season and humidity on fecal cortisol metabolite (FCM) concentrations (N = 8439 samples) were evaluated using linear mixed models. Ambient temperatures were placed into five different categories: <5 °C, 6–10 °C, 11–15 °C, 16–20 °C, and >20 °C. Ambient temperature and humidity had a significant (p < 0.05) effect on FCM concentrations with significant (p < 0.05) interactions of sex, age and breeding season. Once biotic factors were accounted for, there was a significant (p < 0.05) increase in FCM concentrations associated with ambient temperatures above 20 °C in adult polar bears. The implications of these findings for the management of both zoo and wild polar bears are discussed. Full article

(This article belongs to the Special Issue Non-invasive Methods of Stress Monitoring in Animals under Human Care)

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16 pages, 721 KiB

Open AccessArticle

Salivary Cortisol Reaction Norms in Zoo-Housed Great Apes: Diurnal Slopes and Intercepts as Indicators of Stress Response Quality

by Verena Behringer, Jeroen M. G. Stevens and Ruth Sonnweber

Animals 2022, 12(4), 522; https://doi.org/10.3390/ani12040522 - 21 Feb 2022

Cited by 4 | Viewed by 2926

Abstract

Monitoring changes in cortisol levels is a widespread tool for measuring individuals’ stress responses. However, an acute increase in cortisol levels does not necessarily denote an individual in distress, as increases in cortisol can be elicited by all factors that signal the need to mobilize energy. Nor are low levels of cortisol indicative for a relaxed, healthy individual. Therefore, a more fine-grained description of cortisol patterns is warranted in order to distinguish between cortisol fluctuations associated with different stress response qualities. In most species, cortisol shows a distinct diurnal pattern. Using a reaction norm approach, cortisol levels across the day can be described by the two regression coefficients: the intercept and the slope of the curve. We measured immunoreactive salivary cortisol in three zoo-housed ape species under three conditions (routine days, enrichment days, and after the move to a new house). We examined salivary cortisol intercepts (SCI) and salivary cortisol slopes (SCS) of the diurnal curves. SCI and SCS were independent from each other. SCI was highest on enrichment days and lowest on routine days. SCS was steep on routine days and blunted after the move. Only SCI was species-specific. Our study provides evidence that combining SCI and SCS measures allows us to differentiate between types of stress responses, thereby constituting a useful tool for welfare assessment. Full article

(This article belongs to the Special Issue Non-invasive Methods of Stress Monitoring in Animals under Human Care)

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12 pages, 741 KiB

Open AccessArticle

Corticosterone Metabolite Concentration Is Not Related to Problem Solving in the Fawn-Footed Mosaic-Tailed Rat Melomys Cervinipes

by Misha K. Rowell, Rachel M. Santymire and Tasmin L. Rymer

Animals 2022, 12(1), 82; https://doi.org/10.3390/ani12010082 - 30 Dec 2021

Cited by 4 | Viewed by 1811

Abstract

Animals can respond physiologically, such as by adjusting glucocorticoid hormone concentrations, to sudden environmental challenges. These physiological changes can then affect behavioural and cognitive responses. While the relationships between adrenocortical activity and behaviour and cognition are well documented, results are equivocal, suggesting species-specific responses. We investigated whether adrenocortical activity, measured using corticosterone metabolite concentration, was related to problem solving in an Australian rodent, the fawn-footed mosaic-tailed rat (Melomys cervinipes). Mosaic-tailed rats live in complex environments that are prone to disturbance, suggesting a potential need to solve novel problems, and have been found to show relationships between physiology and other behaviours. We measured problem solving using five food-baited puzzles (matchbox and cylinder in the home cage, and activity board with pillars to push, tiles to slide and levers to lift in an open field), and an escape-motivated obstruction task in a light/dark box. Faecal samples were collected from individuals during routine cage cleaning. Adrenocortical activity was evaluated non-invasively by measuring faecal corticosterone metabolites using an enzyme immunoassay, which was biochemically and biologically validated. Despite varying over time, adrenocortical activity was not significantly related to problem solving success or time spent interacting for any task. However, as adrenocortical activity is reflective of multiple physiological processes, including stress and metabolism, future studies should consider how other measures of physiology are also linked to problem solving. Full article

(This article belongs to the Special Issue Non-invasive Methods of Stress Monitoring in Animals under Human Care)

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22 pages, 2180 KiB

Open AccessArticle

Non-Invasive Assessment of the Seasonal Stress Response to Veterinary Procedures and Transportation of Zoo-Housed Lesser Anteater (Tamandua tetradactyla)

by Gabina V. Eguizábal, Mariella Superina, Rupert Palme, Camila J. Asencio, Daniel P. Villarreal, Luciana Borrelli and Juan M. Busso

Animals 2022, 12(1), 75; https://doi.org/10.3390/ani12010075 - 30 Dec 2021

Cited by 4 | Viewed by 2249

Abstract

Management procedures affect behavioural and physiological stress responses of wild mammals under human care. According to the Reactive Scope Model, normal values are presumed to exist within predictive and reactive ranges. First, stress parameters of zoo-housed adult Tamandua tetradactyla were evaluated in winter and summer (29 days each), determining the level of behaviour and/or physiological parameters needed to respond to predictable environmental changes. Secondly, the effects of veterinary procedures and transportation were studied in both seasons. Non-invasive methods were applied, assessing behaviour through videos and adrenocortical activity by faecal glucocorticoid metabolites (FGMs). Lesser anteaters exhibited seasonality (summer > winter) in some behavioural parameters, such as nocturnal activities, as well as in the activity cycle (e.g., acrophase) and FGMs. A veterinary check elicited an increase in total activity (TA), natural behaviours and repetitive locomotion and affected the activity cycle, particularly in summer. Transport produced changes in TA, nocturnal and natural activity and some variables of the activity cycle, mostly during summer. Although the effects of routine management procedures were different from each other and presumably stressful, they elicited changes only at the behavioural level, which was greater during summer. The differences observed according to non-invasive methodologies highlight the importance of a multidisciplinary approach in this context and suggest that it is unlikely that individual welfare was affected. Full article

(This article belongs to the Special Issue Non-invasive Methods of Stress Monitoring in Animals under Human Care)

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24 pages, 2056 KiB

Open AccessArticle

Effects of Positive Reinforcement Training and Novel Object Exposure on Salivary Cortisol Levels under Consideration of Individual Variation in Captive African Elephants (Loxodonta africana)

by Susan Hambrecht, Ann-Kathrin Oerke, Michael Heistermann, Johannes Hartig and Paul W. Dierkes

Animals 2021, 11(12), 3525; https://doi.org/10.3390/ani11123525 - 10 Dec 2021

Cited by 2 | Viewed by 3478

Abstract

Dealing with potential stress in species that have high husbandry requirements, such as elephants, is a challenge for zoos. The objective of the present study was to determine whether positive reinforcement training (PRT) and exposure to a novel object (NOV) for enrichment induced a salivary cortisol response indicative of activation of the hypothalamic–pituitary–adrenal (HPA) axis and which factors determine individual variation in this regard in captive African elephants. We repeatedly sampled the saliva of ten animals (three zoos) for the analysis of cortisol (SACort) before and up to 60 min (in 10–15 min intervals) after the onset of PRT (three repeats) or NOV (nine repeats), which lasted 10 min. There was considerable individual variation in SACort in response to PRT or NOV. Using mixed models, we were able to control these and to reveal that PRT was associated with high SACort before and relatively low SACort after PRT, while NOV induced a moderate SACort increase. The individual differences in SACort were related to age and sex (NOV), while the effects of zoo, handling method (free vs. protected contact) and reproductive and social status were variable. We conclude that positive affective states, such as anticipation or arousal, should be taken into account when interpreting the differences in the SACort responses between PRT and NOV. In addition, understanding the individuality of stress will support management decisions aimed at promoting captive elephant welfare. Full article

(This article belongs to the Special Issue Non-invasive Methods of Stress Monitoring in Animals under Human Care)

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