Assessment of adrenocortical activity and behavior of the collared anteater (Tamandua tetradactyla) in response to food-based environmental enrichment

Abstract

One of the current standard approaches to the study of animal welfare is measuring hypothalamic-pituitary-adrenal activity, frequently in association with behavioral assessment. We studied the effects of food-based environmental enrichment on adrenocortical activity and behavior in zoo-housed collared anteaters (Tamandua tetradactyla; n=5). We successfully validated measurements of fecal cortisol metabolites (FCMs) using an 11-oxoetiocholanolone enzyme immunoassay by stimulating (ACTH injection) and suppressing (dexamethasone administration) adrenocortical activity. Three months later, we subjected animals to an ABA-type experiment (three 6-week periods): pre-enrichment (routine diet: A), enrichment (modified diet: B), and post-enrichment (routine diet: A) periods. We assessed adrenocortical activity by collecting individual feces three times a week (total number of samples: 228), and evaluated behavior by performing 3 days of behavioral observations per period (with a total of 3,600 behavioral data points for the individuals studied). Statistical analysis revealed changes in FCM concentrations (μg/g) over the periods (3.04±0.68, 2.98±0.66, and 4.04±0.90, respectively). Additionally, it showed that the number of FCM peaks was highly reduced during enrichment; meanwhile active natural behaviors were significantly increased. We consider that these changes in response to food-based environmental enrichment improved the welfare of individual zoo-housed collared anteaters. This research might contribute to in situ and ex situ studies on the physiology and behavior of this endemic South American species.