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The evolution of food hoarding: from environmental pressures to brain mechanisms

Periodic Reporting for period 1 - HOARDEVOL (The evolution of food hoarding: from environmental pressures to brain mechanisms)

Reporting period: 2016-07-01 to 2018-06-30

Some species have evolved to store rather than consume food while availability is high, for consumption when food is scarce. The mechanisms that allow animals to retrieve widely scattered food stores has been explored, but comparatively little is known about the mechanisms that underpin the motivation to hoard food. This project experimentally addressed this knowledge gap this using two closely related bird species that live in social groups during winter when hoarding motivation is high: the food hoarding coal tit, Periparus ater, and the non-hoarding great tit, Parus major. To understand the evolution of hoarding motivation, we have to not only understand the environmental factors that control it (and hence the survival problem it evolved to solve), but we also need to understand how these environmental factors are translated into neural signals. Therefore, this project addresses the fundamental question of how novel behaviors evolve. Understanding the mechanisms that control hoarding motivation will provide insights into the evolution of this behaviour and test the hypothesis that it has evolved by building on the existing, widely-conserved appetite regulation system.
We captured free-living coal tits and great tits in autumn and transported them to aviaries at Newcastle University. Birds were held under winter conditions; short day length, low temperature, and unpredictable food supply. After birds had been held under winter conditions they behaviour in response to short-term food removal was recorded. Both great tits and coal tis increased feeding after food deprivation, and coal tis also increased food hoarding, relative to ad libitum food. Following this, half the birds from each species where given either ad libitum access to food or food was removed for 1.5 hours. Birds were then humanly sacrificed for collection of neural tissue. Brains were sectioned to identify the distribution and intensity of appetite regulating neuropeptides in the hypothalamus using in situ hybridization. In situ hybridization is yet to be completed, but we predict that AgRP/NPY will be elevated, and CART/POMC will be decreased in the hypothalamus of food deprived birds related to fed birds. Furthermore, we predict that the distribution pattern of these neuropeptide may differ within the brain between a food-hoarding and non-hoarding species.
This project will be the first to identify the neural mechanisms that regulate motivation to consume and hoard food in birds.