Abstract
As evidence for global insect population declines continues to amass, several studies have indicated that Orthoptera (grasshoppers, crickets, and katydids) are among the most threatened insect groups. Understanding Orthoptera populations across large spatial extents requires efficient survey protocols, however, many previously established methods are expensive and/or labor-intensive. One survey method widely employed in wildlife biology, the aural point count, may work well for crickets and katydids (suborder: Ensifera) because males produce conspicuous, species-specific mating calls. We conducted repeated point count surveys across an urban-to-rural gradient in central Pennsylvania. Occupancy analyses of ten focal species indicated that, although detection probability rates varied by species from 0.43 to 0.98, detection rates compounded over five visits such that all focal species achieved cumulative > 0.90. Factors associated with site occupancy varied among species with some positively associated with urbanization (e.g., Greater Anglewing, Microcentrum rhombifolium), some negatively associated with urbanization (e.g., Sword-bearing Conehead, Neoconocephalus ensiger), and others exhibiting constant occupancy across a habitat gradient (e.g., Common True Katydid, Pterophylla camellifolia). Our community-level analysis revealed that different species’ habitat associations interacted such that intermediate levels of urbanization (i.e., suburbs) hosted the highest number of species.Implications for insect conservationUltimately, our analyses clearly support the concept that aural point counts paired with static occupancy modeling can serve as an important tool for monitoring night-singing Orthoptera populations. Applications of point count surveys by both researchers and citizen scientists may improve our understanding Ensifera populations and help in the global conservation of these threatened insects.
Highlights
As evidence for global insect population declines continues to amass (Thomas 2016; Hallmann et al 2017; Leather 2017; van Klink et al 2020), ecologists are tasked with the increasingly urgent need to establish robust monitoring regimes for sensitive insect taxa (Thomas 2005; Montgomery et al 2020)
Our study provides the first empirical demonstration that aural point counts conducted by field biologists may serve as an important survey method to study cricket/katydid populations because they are efficient, accurate, and nondestructive
Efficiency was accomplished by coupling high rates of species detection probability (Fig. 4) with a brief survey duration while requiring essentially no special equipment
Summary
As evidence for global insect population declines continues to amass (Thomas 2016; Hallmann et al 2017; Leather 2017; van Klink et al 2020), ecologists are tasked with the increasingly urgent need to establish robust monitoring regimes for sensitive insect taxa (Thomas 2005; Montgomery et al 2020). Central to the establishment of insect population monitoring programs is the availability of cost-effective survey protocols that yield effective assessments of focal taxa presence across large geographic extents (Yoccoz et al 2001; Potts et al 2011). Effective monitoring is useful for identifying habitat needs for sensitive species, an important requisite to the development of species conservation plans (Menz et al 2013).
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