Meeting Abstract
The hormonal control of feeding and hoarding behaviour in mammals is reasonably well characterized. Contrary to mammalian studies, the hormones that regulate appetite and consumption, ghrelin and leptin, both cause a reduction in consumption in birds. To date, the role of these hormones in the regulation of hoarding behaviour in birds has not been examined. To investigate this we injected wild caught coal tits (Periparus ater) with high-dose ghrelin (0.25 nmol), low-dose ghrelin (0.05 nmol), leptin (10 μg) and a saline control in the laboratory. We then measured hoarding activity and mass gain, as a proxy of food consumption, every 20 mins for two hours post injection. We found that both the ghrelin-high and leptin injection significantly reduced hoarding behavior and mass gain compared to controls. But the ghrelin-low injection did not differ from controls for hoarding or mass gain. The results are consistent with previous findings from birds that show both leptin and ghrelin cause a reduction in consumption and mass gain. Unlike hoarding mammal species, where ghrelin promotes hoarding and leptin reduces hoarding; our results provide the first evidence that hoarding behaviour is reduced by both leptin and ghrelin in a passerine bird. These findings add to evidence that the hormonal control of consumption and hoarding in avian species differs from that in mammals. Furthermore, food hoarding and consumptive behaviours consistently show the same response to leptin and ghrelin, which suggests that the hormonal regulation of hoarding behaviour has evolved from the consumption regulatory system.
