Ecology and conservation of insectivorous bats in fragmented areas of macadamia production in eastern Australia

Abstract

Microbats perform important ecological services in agro-ecosystems, but several species are globally threatened by loss of roosting and breeding habitats. The successful conservation of bats in agricultural land requires adequate knowledge of their ecology. Using ultrasonic recorders, we studied the activity of insectivorous bats in areas of macadamia production in eastern Australia at two spatial scales: across woodland-orchard transects at the local scale and across three levels of fragmentation at the landscape scale. At the local scale, activity patterns of 'clutter' and 'edge' specialists were consistently higher in woodland patches, gradually decreasing towards isolated orchards, where only a few 'open' specialists were active. At the landscape scale, bat community activity was affected by the level of fragmentation, partly because three of the most recorded taxa (Austronomus australis, Saccolaimus flaviventris and Miniopterus australis) had their highest activity in less-fragmented areas. A distance-based model explained 24% of the bat community activity based on a combination of six environmental variables. Canonical correspondence analysis showed that a number of bat taxa were associated with open areas of macadamia, whereas other taxa were associated with increasing values of landscape composition, and arthropod and water availability. In addition, total bat activity was highly correlated with foraging rate. These results suggest that most bat taxa were influenced by proximity to woodland and the degree of fragmentation, and only few taxa were able to exploit isolated orchards. Environmental factors that promote bat activity could be exploited to strengthen conservation efforts. Preserving remnant woodland and promoting habitat heterogeneity will benefit several bat species. In particular, the foraging activity of 'edge' specialists could be fostered by increasing landscape connectivity and maintaining unobstructed water bodies near macadamia orchards. Considering that bats forage as they navigate these areas, conservation efforts could also bring benefits to farmers through pest-reduction services.

The use of bat houses as day roosts in macadamia orchards, South Africa

“…The distance to water, the altitude above sea level and the height of bat houses did not significantly influence bat house occupancy in our study. While water availability is known to influence bat activity (Crisol-Martínez et al, 2016; Grindal, Morissette & Brigham, 1999; Rainho & Palmeirim, 2011) the bat houses in this study were erected within a range of two to 680 m from the closest water source, all within the known home range of even small plain-faced bats (Monadjem et al, 2010b). We suggest that the distance to water might be more significant in arid regions compared to our high rainfall subtropical study area.…”

Peer Review #3 of "The use of bat houses as day roosts in macadamia orchards, South Africa (v0.2)"

“…The distance to water, the altitude above sea level and the height of bat houses did not significantly influence bat house occupancy in our study. While water availability is known to influence bat activity (Crisol-Martínez et al, 2016;Grindal et al, 1999;Rainho & Palmeirim, 2011) the bat houses in this study were erected within a range of two to 680 meters from the closest water source, all within the known home range of even small plain-faced bats (Monadjem et al, 2010b). We suggest that the distance to water might be more significant in arid regions compared to our high rainfall subtropical study area.…”

Bioacoustics Reveal Species-Rich Avian Communities Exposed to Organophosphate Insecticides in Macadamia Orchards

“…Additionally, 10 min point counts found 47 out of the 62 species recorded with acoustic recorders, which indicates that acoustic recorders can be more efficient as they require a lower survey effort and detect birds that may be hidden by branches or foliage in the structurally complex macadamia orchards [24,25]. Besides birds and arthropods, the mixed forest-orchard landscapes in Bundaberg maintain rich insectivorous bat communities, which are also highly active in macadamia stands [29]. A study of macadamia in South Africa has also indicated the importance of macadamia landscapes as habitat for birds, as well as bats and monkeys [48].…”

“…Additionally, during this period the macadamia phenology was between the peak of flowering and early nut development phases. At this time, the numbers of insect herbivores normally increase on the crop [29], so insecticide treatments are generally conducted in the orchards.…”

“…), a native Australian nut producing tree, is one of the main crops produced in the region with a current cropping area of approximately 24,000 ha [27]. In the region, macadamia orchards are frequently located adjacent to forested natural habitats, and previous studies have shown that both the forests and the orchards play a key role in sustaining bird and bat communities [28,29]. Bird communities in macadamia orchards can be diverse, particularly those close to woodlands.…”