Abstract

For generalist predators, a mixed diet can be advantageous as it allows individuals to exploit a potentially broad range of profitable food types. Despite this, some generalist predators show preferences for certain types of food and may forage selectively in places or at times when these foods are available. One such species is the lesser hairy-footed dunnart (Sminthopsis youngsoni). Usually considered to be a generalist insectivore, in the Simpson Desert, Australia, this small marsupial predator has been found to selectively consume wolf spiders (Family Lycosidae), for reasons yet unknown. Here, we tested whether lycosids have relatively high energy or nutrient contents compared to other invertebrates, and hence whether these aspects of food quality can explain selective predation of lycosids by S. youngsoni. Energy, lipid and protein composition of representatives of 9 arthropod families that are eaten by S. youngsoni in the Simpson Desert were ascertained using microbomb calorimetry, chloroform-methanol extraction and Dumas combustion, respectively. Although lycosids contained a high proportion of energy and nutrients, they were not found to yield statistically greater amounts of these food components than many other available arthropod prey that are not selected by S. youngsoni. Our results therefore suggest that alternative factors may be more influential in shaping dietary selection in this marsupial predator, such as high rates of encounter between lycosids and S. youngsoni.

Highlights

  • When animals forage, a trade-off exists between maximizing net energy and nutritional gain, and minimizing costs such as predation, time and energy expenditure [1,2,3]

  • This study explores the composition of different types of prey in the diet of an Australian desert-dwelling insectivore, the lesser hairy-footed dunnart (Sminthopsis youngsoni)

  • S. youngsoni is nocturnal, diurnal arthropods were sampled because they are hunted by dunnarts at night while they are at rest or under cover [27]

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Summary

Introduction

When animals forage, a trade-off exists between maximizing net energy and nutritional gain, and minimizing costs such as predation, time and energy expenditure [1,2,3]. According to optimal foraging theory, predators should prefer foods that deliver the greatest value per unit of effort or time expended acquiring them [4,5,6]. When the most profitable food type is constant, some predators develop morphological or physiological specialisations that constrain them to that prey Strategy and Education Infrastructure Fund - Super Science Initiative through the Department of Industry, Innovation, Science, Research and Tertiary Education.

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