title: Two seconds is all it takes: European starlings (Sturnus vulgaris) increase levels of circulating glucocorticoids after witnessing a brief raptor attack.
abstract: Researchers typically study "acute" activation of the hypothalamic-pituitary-adrenal (HPA) axis by measuring levels of circulating glucocorticoids in animals that have been exposed to a predator or a cue from a predator (e.g., odor), or have experienced a standardized capture-and-restraint protocol, all of which are many minutes in duration. However, exposure to predators in the "wild", either as the subject of an attack or as a witness to an attack, is generally much shorter as most depredation attempts upon free-living animals last <5s. Yet, whether a stimulus lasting only seconds can activate the HPA axis is unknown. To determine if a stimulus of a few seconds triggers a glucocorticoid response, we measured levels of corticosterone (CORT; the primary avian glucocorticoid) in wild-caught European starlings (Sturnus vulgaris) after they witnessed a brief (<2-8s) raptor attack upon a conspecific, a human "attack" (i.e., a researcher handling a conspecific), and an undisturbed control. Witnesses of a raptor attack responded with CORT levels comparable to that induced by a standardized capture-and-restraint protocol. Glucocorticoid levels of individuals following the control treatment were similar to baseline levels, and those that witnessed a human "attack" had intermediate levels. Our results demonstrate that witnessing a predator attack of very brief duration triggers a profound adrenocortical stress response. Given the considerable evidence of a role for glucocorticoids in learning and memory, such a response may affect how individuals learn to recognize and appropriately react to predators.
authors.affiliation: Department of Biological Sciences, University of Memphis, Ellington Hall 239, 3700 Walker Ave, Memphis, TN 38152, USA. Electronic address: bcjones8@memphis.edu.
authors.forename: Blake C
authors.initials: BC
authors.lastname: Jones
authors.affiliation: Department of Natural Resources Science, University of Rhode Island, 105 Coastal Institute in Kingston, Kingston, RI 02881, USA.
authors.forename: Adam D
authors.initials: AD
authors.lastname: Smith
authors.affiliation: Department of Biological Sciences, University of Memphis, Ellington Hall 239, 3700 Walker Ave, Memphis, TN 38152, USA.
authors.forename: Sara E
authors.initials: SE
authors.lastname: Bebus
authors.affiliation: Department of Biological Sciences, University of Memphis, Ellington Hall 239, 3700 Walker Ave, Memphis, TN 38152, USA.
authors.forename: Stephan J
authors.initials: SJ
authors.lastname: Schoech
mesh_terms: D000818:Animals; D001522:Behavior, Animal; D003345:Corticosterone / Q000097:blood; D005938:Glucocorticoids / Q000097:blood*; D006801:Humans; D007030:Hypothalamo-Hypophyseal System / Q000502:physiology; D010775:Photic Stimulation; D010913:Pituitary-Adrenal System / Q000502:physiology; D011235:Predatory Behavior; D020304:Raptors; D012919:Social Behavior; D046749:Starlings / Q000097:blood / Q000502:physiology*; D013315:Stress, Psychological / Q000097:blood*; D013997:Time Factors; D015854:Up-Regulation
chemical_list: D005938:Glucocorticoids; D003345:Corticosterone
keywords: Avian; Corticosterone; Depredation; HPA axis; Stress response