OWEN-ASHLEY, N. T.; HAYS, Q.; BENTLEY, G. E.; WINGFIELD, J. C.; Univ. of Washington, Seattle; Univ. of Montana, Missoula; Univ. of Washington, Seattle; Univ. of Washington, Seattle: Testosterone reduces sickness behavior in songbirds

At the onset of parasitic and viral infections, animals display a suite of behavioral patterns that are collectively known as sickness behaviors. These include anorexia, lethargy and a reduction in social contact. Activation of sickness behavior is thought to be adaptive as energy normally used in daily activities is conserved to combat infection. However, expression of sickness may be costly to male songbirds if it interferes with territory defense, mate attraction and production of offspring. As testosterone (T) is elevated in male songbirds during this life-history stage, and because of the extensive literature on T and immune function, we hypothesized that T is involved in the regulation of sickness behavior. Captive male white-crowned sparrows (Zonotrichia leucophrys gambelii) were gonadectomized (GDX), photostimulated on long days (20L:4D), and implanted with T or control (empty) silastic implants. A third group of birds was sham-GDX and given a control (C) implant. Subjects were injected with either bacterial lipopolysaccharide (LPS) to induce expression of sickness behavior or vehicle, and changes in food intake, mass, and behavior were assessed. GDX + T birds were more active and experienced higher food intake rates and lost less weight after an LPS challenge compared to GDX + C and sham-GDX controls. These results demonstrate a hormonal mechanism for potentially masking symptoms of parasitic infection in the wild.