Singing in the suburbs: point count surveys efficiently reveal habitat associations for nocturnal Orthoptera across an urban-to-rural gradient

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 conservation Ultimately, 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.

Ecology and abundance of a relict population of the bush cricket Saga pedo in the Northern Apennines, Italy

“…However, this sampling method is not applicable to S. pedo due to the absence of males and song production. However, the detection probability estimated with such methods for other orthopterans ranged from 43% to 98% (McNeil & Grozinger, 2020 ), significantly higher than that for S. pedo . The low detectability of S. pedo should be interpreted in light of the species' ecological characteristics.…”

Biodiversity changes in abandoned military training areas: relationships to different management approaches in multiple taxa

“…In each of both periods, every point was visited once between the mid-July and the end of August at the time of the highest grasshopper diurnal activity (between 10: 00 and 17:00) under suitable weather conditions (warm sunny days with no wind). Surveys combined two methods widely used for grasshopper monitoring, i.e., sweeping (e.g., Racz et al, 2013) and acoustic detections (e.g., McNeil and Grozinger, 2020). Specifically, at each point, the observer made exactly 20 sweeps with a sweep net followed by a 2-min long acoustic detection of stridulating individuals.…”

The role of community science in orthopteran research

“…Because many male orthopterans sing to attract mates, community science studies quantifying species richness, abundance, and emergence times in Orthoptera are relatively simple. Species can be identified by their acoustic profiles, and acoustic survey data can be recorded from trails and roadsides (Fischer et al 1997, Riede 1998, Penone et al 2013, Jeliazkov et al 2016, McNeil and Grozinger 2020, Paiero et al 2020, Kaláb et al 2021. This is particularly useful in fragile habitats or for threatened species, where scientists must balance effective monitoring with reducing disruption in conservation spaces (Moran et al 2014, McNeil andGrozinger 2020).…”

“…Species can be identified by their acoustic profiles, and acoustic survey data can be recorded from trails and roadsides (Fischer et al 1997, Riede 1998, Penone et al 2013, Jeliazkov et al 2016, McNeil and Grozinger 2020, Paiero et al 2020, Kaláb et al 2021. This is particularly useful in fragile habitats or for threatened species, where scientists must balance effective monitoring with reducing disruption in conservation spaces (Moran et al 2014, McNeil andGrozinger 2020). New technologies in acoustic monitoring allow for large-scale monitoring of singing insects, which provides an easier, less time-consuming means of estimating metrics such as species abundance and richness.…”