Methods of Optimal Foraging

AbstractMany animal populations include a diversity of personalities, and these personalities are often linked to foraging strategy. However, it is not always clear why populations should evolve to have this diversity. Indeed, optimal foraging theory typically seeks out a single optimal strategy for individuals in a population. So why do we, in fact, see a variety of strategies existing in a single population? Here, we aim to provide insight into this conundrum by modelling the particular case of foraging seabirds, that forage on patchy prey. These seabirds have only partial knowledge of their environment: they do not know exactly where the next patch will emerge, but they may have some understanding of which locations are more likely to lead to patch emergence than others. Many existing optimal foraging studies assume either complete knowledge (e.g. Marginal Value Theorem) or no knowledge (e.g. Lévy Flight Hypothesis), but here we construct a new modelling approach which incorporates partial knowledge. In our model, different foraging strategies are favoured by different birds along the bold-shy personality continuum, so we can assess the optimality of a personality type. We show that it is optimal to be shy (resp. bold) when living in a population of bold (resp. shy) birds. This observation gives a plausible mechanism behind the emergence of diverse personalities. We also show that environmental degradation is likely to favour shyer birds and cause a decrease in diversity of personality over time.

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He i‘a make ka ‘opihi: Optimal Foraging Theory, Food Choice, and the Fish of Death

Journal of Archaeological Method and Theory ◽

10.1007/s10816-021-09506-w ◽

2021 ◽

Author(s):

Ashleigh J. Rogers ◽

Marshall I. Weisler

Keyword(s):

Optimal Foraging ◽

Food Choice ◽

Optimal Foraging Theory ◽

Foraging Theory

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Changes in surface water drive the movements of Shoebills

Scientific Reports ◽

10.1038/s41598-021-95093-5 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Marta Acácio ◽

Ralf H. E. Mullers ◽

Aldina M. A. Franco ◽

Frank J. Willems ◽

Arjun Amar

Keyword(s):

Surface Water ◽

Optimal Foraging ◽

Animal Movement ◽

Bird Species ◽

Individual Variability ◽

Home Ranges ◽

Age Classes ◽

Water Index ◽

Normalized Difference Water Index ◽

Conservation Actions

AbstractAnimal movement is mainly determined by spatial and temporal changes in resource availability. For wetland specialists, the seasonal availability of surface water may be a major determinant of their movement patterns. This study is the first to examine the movements of Shoebills (Balaeniceps rex), an iconic and vulnerable bird species. Using GPS transmitters deployed on six immature and one adult Shoebills over a 5-year period, during which four immatures matured into adults, we analyse their home ranges and distances moved in the Bangweulu Wetlands, Zambia. We relate their movements at the start of the rainy season (October to December) to changes in Normalized Difference Water Index (NDWI), a proxy for surface water. We show that Shoebills stay in the Bangweulu Wetlands all year round, moving less than 3 km per day on 81% of days. However, average annual home ranges were large, with high individual variability, but were similar between age classes. Immature and adult Shoebills responded differently to changes in surface water; sites that adults abandoned became drier, while sites abandoned by immatures became wetter. However, there were no differences in NDWI of areas used by Shoebills before abandonment and newly selected sites, suggesting that Shoebills select areas with similar surface water. We hypothesise that the different responses to changes in surface water by immature and adult Shoebills are related to age-specific optimal foraging conditions and fishing techniques. Our study highlights the need to understand the movements of Shoebills throughout their life cycle to design successful conservation actions for this emblematic, yet poorly known, species.

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