SALIVARY CORTISOL RESPONSE TO FLIES BY MOOSE CALVES

Young animals are particularly vulnerable to environmental stressors that can impair growth and compromise survival. We used salivary cortisol, a glucocorticosteroid hormone, to measure possible stress response of moose calves in Alaska to the abundance of biting and non-biting flies relative to calf age, time of day, and ambient air temperature. We measured salivary cortisol in 5 captive calves up to 4 times daily on 25 days in June-August with corresponding on-host fly collections. We simultaneously collected 2,618 flies, of which 68% were moose flies (Haematobosca alcis), 13% coprophagous flies, 9% mosquitoes (Culicidae), 5% horse and deer flies (Tabanidae), and 2% black flies (Simuliidae). The proportion of moose flies increased steadily, representing nearly all flies by study end. Salivary cortisol levels were minimal and similar (