Does Environmental Enrichment Reduce Stress? An Integrated Measure of Corticosterone from Feathers Provides a Novel Perspective

Enrichment is widely used as tool for managing fearfulness, undesirable behaviors, and stress in captive animals, and for studying exploration and personality. Inconsistencies in previous studies of physiological and behavioral responses to enrichment led us to hypothesize that enrichment and its removal are stressful environmental changes to which the hormone corticosterone and fearfulness, activity, and exploration behaviors ought to be sensitive. We conducted two experiments with a captive population of wild-caught Clark's nutcrackers (Nucifraga columbiana) to assess responses to short- (10-d) and long-term (3-mo) enrichment, their removal, and the influence of novelty, within the same animal. Variation in an integrated measure of corticosterone from feathers, combined with video recordings of behaviors, suggests that how individuals perceive enrichment and its removal depends on the duration of exposure. Short- and long-term enrichment elicited different physiological responses, with the former acting as a stressor and birds exhibiting acclimation to the latter. Non-novel enrichment evoked the strongest corticosterone responses of all the treatments, suggesting that the second exposure to the same objects acted as a physiological cue, and that acclimation was overridden by negative past experience. Birds showed weak behavioral responses that were not related to corticosterone. By demonstrating that an integrated measure of glucocorticoid physiology varies significantly with changes to enrichment in the absence of agonistic interactions, our study sheds light on potential mechanisms driving physiological and behavioral responses to environmental change

Simplified method to measure glucocorticoid metabolites in faeces of horses

Glucocorticoids or their metabolites can be measured in several body fluids or excreta, including plasma, saliva, urine and faeces. In recent years the measurement of glucocorticoid metabolites (GCMs) in faeces has gained increasing attention, because of its suitability for wild populations. In horses, however, the group-specific enzyme immunoassay described so far has a limited practicability due to its complex extraction procedure. Therefore, we tested the applicability of other enzyme immunoassays for glucocorticoid metabolites. The present study clearly proved that an enzyme immunoassay (EIA) for 11-oxoaetiocholanolone using 11-oxoaetiocholanolone-17-CMO: BSA (3alpha,11-oxo-A EIA) as antigen showed high amounts of immunoreactive substances. Therefore it was possible to use just a small amount of the supernatant of a methanolic suspension of faeces. The results correlated well with the already described method for measuring GCMs in horse faeces, i.e. analysing the samples with an EIA after a two step clean up procedure of the samples (Merl et al. 2000). In addition, the 3alpha,11-oxo-A EIA has the advantage of providing a bigger difference between baseline values and peak values after ACTH stimulation. The new assay increased the accuracy of the test, lowered the expenses per sample, and storing samples at room temperature after collection was less critical than with other assays investigated in our study. This is a big advantage both in the field of wildlife management of equids and in the field of equestrian sports and it shows the importance of choosing an assay which is in good accordance with the metabolites excreted in a given species

Evaluating camera traps as an alternative to live trapping for estimating the density of snowshoe hares (Lepus americanus) and red squirrels (Tamiasciurus hudsonicus)

Live trapping is one of the methods typically used to estimate population densities of small mammals, but this is labor-intensive and can be stressful to individuals. We assess the use of camera trap hit (detection) rates as a noninvasive alternative to live trapping for estimating population densities of snowshoe hares (Lepus americanus (Erxleben, 1777)) and red squirrels (Tamiasciurus hudsonicus (Erxleben, 1777))—two common small (≤1.5 kg) mammal species in the boreal forests of northern North America. We compared hit rates from camera trapping to live trapping mark-recapture density estimates and asked if the hit window—the length of time used to group consecutive videos together as single detections or “hits”—has an effect on the correlation between hit rates and live trapping density estimates. The relationship between hit rate and population density was sensitive to hit window duration for red squirrels with R2 values ranging from 0.41 to 0.68, and a 5-min hit window generated the highest value. R2 values for snowshoe hares ranged from 0.70 to 0.90, and a 10-min hit window generated the highest value, but hares were live trapped and filmed only at very low densities. Our results indicate that camera trapping is a robust means for estimating the density of red squirrels, but the appropriate hit window duration must be determined empirically if camera trapping data are to be used to monitor populations of this species. Additional live trapping and filming of snowshoe hares is required to better assess camera trapping of this species.</p