Fine-scale food hoarding decisions in New Zealand Robins ( Petroica australis ): is inter-sexual competition important? |
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Authors: | K C Burns |
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Institution: | (1) School of Biological Sciences, Victoria University of Wellington, P.O. Box 600, Wellington, New Zealand |
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Abstract: | Competition for cache retrieval is hypothesised to influence food hoarding intensity. Previous work has tested this hypothesis
by evaluating food hoarding rates during foraging bouts when animals are exposed to different levels of competition for cache
retrieval. Little is known about how competition might influence fine-scale food hoarding decisions within foraging bouts.
I evaluated fine-scale food hoarding decisions of New Zealand Robins (Petroica australis) by offering mealworms to competitively dominant males and subordinate females, both when they were alone and when they foraged
together. I then compared food hoarding rates of sequentially handled prey between sexes and social conditions by assessing
how the total number of prey cached increased with the total number of prey handled. Relationships for solitary females, solitary
males and paired males were non-linear, indicating that they were more likely to consume initially handled prey, and increasingly
likely to cache subsequently handled prey items. Non-linear rates of food hoarding may result from declines in the energetic
value of prey that are consumed and stored internally as birds become satiated. Somewhat differently, the relationship for
paired females was linear, indicating that paired females make a single food hoarding decision based on bout-level foraging
conditions, which results in constant fine-scale food hoarding rates. Constant food hoarding rates in paired females, which
experience the strongest competitive effects of any treatment, suggest that food consumption is consistently more advantageous
than food hoarding under these conditions, regardless of satiation level. Overall results from this study indicate that New
Zealand Robins continuously update food hoarding decisions according to their competitive environment and satiation levels,
resulting in scale-dependent patterns in food hoarding intensity. |
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Keywords: | Cache Competition Experiment Foraging Scale |
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