Ground-Dwelling Arthropod Community Response to Livestock Grazing: Implications for Avian Conservation.

Hayes B Goosey,Joseph T Smith,David E Naugle,Kevin M O’Neill

doi:10.1093/ee/nvz074

Hayes B Goosey, Joseph T Smith + Show 2 more

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https://doi.org/10.1093/ee/nvz074

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Abstract

Terrestrial arthropods are a critical component of rangeland ecosystems that convert primary production into resources for higher trophic levels. During spring and summer, select arthropod taxa are the primary food of breeding prairie birds, of which many are imperiled in North America. Livestock grazing is globally the most widespread rangeland use and can affect arthropod communities directly or indirectly through herbivory. To examine effects of management on arthropod community structure and avian food availability, we studied ground-dwelling arthropods on grazed and ungrazed sagebrush rangelands of central Montana. From 2012 to 2015, samples were taken from lands managed as part of a rest-rotation grazing program and from idle lands where livestock grazing has been absent for over a decade. Bird-food arthropods were twice as prevalent in managed pastures despite the doubling of overall activity-density of arthropods in idle pastures. Activity-density on idled lands was largely driven by a tripling of detritivores and a doubling in predators. Predator community structure was simplified on idled lands, where Lycosid spiders increased by fivefold. In contrast, managed lands supported a more diverse assemblage of ground-dwelling arthropods, which may be particularly beneficial for birds in these landscapes if, for example, diversity promotes temporal stability in this critical food resource. Our results suggest that periodic disturbance may enhance arthropod diversity, and that birds may benefit from livestock grazing with periodic rest or deferment.

Highlights

Terrestrial arthropods are a critical component of rangeland ecosystems that convert primary production into resources for higher trophic levels
More recent work has linked survival of young sage-grouse chicks to abundance of Lepidopteran larvae (Gregg and Crawford 2009), and a recent diet study using DNA barcoding revealed the importance of Lepidopterans to lesser prairie chickens (Sullins et al 2018)
Total arthropod activity-density was greatest on idle land, this pattern masked important variation in responses of arthropod taxa to long-term absence of grazing

Summary

Introduction

Terrestrial arthropods are a critical component of rangeland ecosystems that convert primary production into resources for higher trophic levels. Diets of nestling grassland-obligate passerines in Saskatchewan were dominated by Lepidopteran larvae, and members of Lepidoptera, Orthoptera, and Coleoptera were preferentially selected (Maher 1979) The importance of these three orders to passerine nestling diets is consistent across a range of North American grassland and shrubland ecosystems (Wiens and Rotenberry 1979). Lesser prairie chickens feed primarily on Orthoptera and Coleoptera, though Hemiptera were frequently consumed in some areas (Doerr and Guthery 1983) These early studies, which employed microhistological analysis of crop contents or feces, likely underestimated intake of soft-bodied arthropods such as Lepidopteran larvae, because these food items are. Avian dietary studies in grassland and shrubland systems indicate a few orders make up the bulk of arthropod food items important for survival

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