Deterministic modelling of seed dispersal based on observed behaviours of an endemic primate in Brazil

Plant species models are among the available tools to predict the future of ecosystems threatened by climate change, habitat loss, and degradation. However, they suffer from low to no inclusion of plant dispersal, which is necessary to predict ecosystem evolution. A variety of seed dispersal models have been conceived for anemochorous and zoochorous plant species, but the coupling between vegetation models and seed dispersal processes remains rare. The main challenge in modelling zoochoric dispersal is simulating animal movements in their complex habitat. Recent developments allow straightforward applications of hidden Markov modelling (HMM) to animal movements, which could ease generalizations when modelling zoochoric seed dispersal. We tested the use of HMM to model seed dispersal by an endangered primate in the Brazilian Atlantic forest, to demonstrate its potential simplicity to simulate seed dispersal processes. We also discuss how to adapt it to other species. We collected information on movement, fruit consumption, deposition, and habitat use of Leontopithecus chrysomelas. We analysed daily trajectories using HMM and built a deterministic Model Of Seed Transfer (MOST), which replicated, with good approximation, the primate's movement and seed deposition patterns as observed in the field. Our results suggest that the dispersal behaviour and short daily-trajectories of L. chrysomelas restrict the species' role in large-scale forest regeneration, but contribute to the prevalence of resource tree species locally, and potentially maintaining tree diversity by preventing local extinction. However, it may be possible to accurately simulate dispersal in an area, without necessarily quantifying variables that influence movement, if the movement can be broken down to step-length and turning angles, and parametrised along with the distribution of gut-transit times. For future objectives, coupling MOST with a DVM could be used to test hypotheses on tree species survival in various scenarios, simulating regeneration and growth at regional scales by including data on main dispersal agents over the area of interest, distribution of tree species, and land use data. The principal advantage of the MOST model is its functionality with data available from the literature as the variables are easy to parametrise. We suggest using the coupled model to perform experiments using only available information, but varying the numbers and species of seed dispersers, or modifying land cover or configuration to test for possible thresholds preventing the extinction of selected tree species.

Nest boxes do not cause a shift in bat community composition in an urbanised landscape

Nest boxes are often used to provide supplementary roosts for cavity-dependent wildlife, but little is known about if they influence faunal community composition. Long-term monitoring of bat boxes in south-eastern Australia indicated that their use was dominated by one generalist species (Chalinolobus gouldii), causing concern that installing bat boxes could cause a shift toward less diverse bat communities. To test this, we conducted a large-scale before-after control-impact experiment at 18 sites, over five years. Sites were either: (1) those with existing bat boxes, (2) those where boxes were added during the study, or (3) controls without boxes. We used echolocation call data from 9035 bat detector nights to compare community composition, diversity, and species' relative activity between the sites. Chalinolobus gouldii continued to dominate the use of existing boxes, but we found little difference in community composition between sites based on the presence, absence, or addition of boxes. Our study is the first to explore the influence installing artificial hollows has on localized faunal assemblages over spatio-temporal scales relevant to management. We conclude that there is cause for optimism that bat boxes might not have perverse outcomes on local community composition in the short- to medium-term, as we had feared.

Summer and autumn activity patterns of the eastern bent-wing bat (Miniopterus orianae oceanensis) at a large maternity site in southern New South Wales

The eastern bent-wing bat (Miniopterus orianae oceanensis) is a small (11–20 g, mean 14 g) insectivorous bat with a distribution that extends along the eastern seaboard of mainland Australia. It is primarily a cave-dwelling species, particularly for breeding females who form large maternity colonies at just a few locations throughout its range. Seasonal population changes at one of the three large New South Wales maternity colonies (Church Cave) were studied from December to March every year for 12 years when adult females were resident at a maternity site. Five key periods were identified: (1) adult arrival, (2) adult peak, (3) juvenile independence, (4) adult–juvenile peak, and (5) autumn migration. The average duration of the adult peak period was 38 days and usually commenced around late December or early January. This is the critical period in which to estimate the female adult population. All other periods lasted ~14 days. Understanding the timing of these different periods is important in estimating various population parameters. The timing of migration is also important with respect to windfarm construction and impact assessments of turbine strike to migrating bats. Four separate variables were investigated to describe the timing of autumn migration from Church Cave; moon illumination, minimum nightly temperatures, barometric pressure, and timing of adult arrival. The timing of adult arrival was the only model that was significant in explaining the onset of migration. This generally occurs 83–87 nights after the commencement of arrival of female adult bent-wing bats at Church Cave in early to mid December.

Activity patterns of insectivorous bats during a seasonal transition period from hibernation to reproduction

Bat activity is influenced by fluctuating environmental variables. It may also be influenced by energetic pressures related to pregnancy, lactation, and emergence following winter inactivity. We evaluated nightly changes in relative bat activity at Royal National Park in response to Julian date, ambient temperature, precipitation, wind speed and moon phase on a nightly scale for six weeks during spring, as insectivorous bats move out of hibernation or frequent, prolonged torpor, and into the maternal season. Interestingly, later Julian date (reflecting seasonal transition) was the sole variable that best predicted total nightly activity. In addition, we opportunistically assessed bat activity in response to a severe storm, considered a Category 1 cyclone, resulting in 96.4mm of rain in one night and wind speeds up to 94km h–1. Only one species of bat, Chalinolobus gouldii, was active during the storm, with activity restricted to the latter part of the evening when precipitation had reduced, indicating rapid resumption of activity following severe weather. The results of this research can be used as an indicator of emergence from winter inactivity and highlight activity patterns of bat species in relation to environmental variables to inform timing of monitoring programs, bat surveys, and targeted research.

Roosting behaviour and the tree-hollow requirements of bats: insights from the lesser long-eared bat (Nyctophilus geoffroyi) and Gould’s wattled bat (Chalinolobus gouldii) in south-eastern Australia

Access to suitable roosts is critical for the conservation of tree-hollow roosting bats worldwide. Availability of roost sites is influenced by human land-use, but also by the roosting requirements and behaviour of species. We investigated roosting behaviour of the lesser long-eared bat (Nyctophilus geoffroyi) and Gould’s wattled bat (Chalinolobus gouldii) in a rural landscape in south-eastern Australia. Forty-five N. geoffroyi and 27 C. gouldii were fitted with radio-transmitters, resulting in the location of 139 and 89 roosts, respectively. Most (88%) roosts occupied by male N. geoffroyi contained only a single individual. During the breeding season female colonies were larger, with maternity roosts containing 18.3 ± 5.7 (s.e.) individuals. Mean colony sizes for C. gouldii were 8.7 ± 1.4 individuals. Both species shifted roosts frequently: on average, individual N. geoffroyi moved every 2.2 ± 0.23 days and C. gouldii every 2.2 ± 0.14 days. Notably, lactating female N. geoffroyi shifted roosts more frequently than non-breeding females. Individuals of both species roosted within a discrete area, with roosts typically <300 m apart; and consistently returned there from foraging up to 12 km distant. This roosting behaviour highlights three important requirements: (1) a relatively large overall number of hollows to support a population; (2) discrete roost areas with a high density of suitable hollows in close proximity; and (3) a range of hollow types to provide the specialised roosts required, particularly for breeding.

Long-term effects of grating derelict mines on bat emergence activity, abundance and behaviour

In Australia, there are at least 50 000 derelict mines, many of which provide habitat for cave-roosting bats. Grating of derelict mines, be it horizontal (adits) or vertical (shafts) drives, is commonly undertaken to prevent human access, though longer-term responses of bats are largely unknown. We assessed the long-term (2–20 years) effects of grating on bats by documenting trends in emergence activity and bat abundance at grated and ungrated derelict mines and quantified behavioural responses of bats in autumn and winter. Emergence activity was dominated by the eastern horseshoe bat (Rhinolophus megaphyllus) with limited activity of other less manoeuvrable species. Both emergence activity and minimum colony size at horizontal adits were 8–9 times greater than at vertical shafts, with bats observed emerging from only 2 of 13 shafts. Emergence activity and minimum colony size were 7–10 times greater at adits with ‘bat friendly’ grating (horizontal bars with spacing >125 mm) than at other treatments (ungrated adits and adits with standard grating). In winter, there were 4–11 times more aborted exit attempts per bat at adits with ‘bat friendly’ grating compared with other treatments, which corresponded to greater emergence activity. Emergence activity and minimum colony size were not related to spacing between bars or time since grating, indicating rapid habituation by R. megaphyllus. However, circling at grates continued for many years and bentwing bats (Miniopterus spp.) made little use of these sites. Bat-friendly grates appear to be an effective management option for R. megaphyllus, but alternatives need to be trialled for other species.

Seasonal occupancy of abandoned mines by cave-dwelling bats in the western Blue Mountains, New South Wales

Cave-dwelling microbats are known to occupy abandoned mines, which can be important habitat for threatened species. Surveys and monitoring between 2012 and 2014 in Mugii Murum-ban State Conservation Area identified use of three adits from historic mine workings by three species: Chalinolobus dwyeri, Miniopterus orianae oceanensis and Rhinolophus megaphyllus. One of the adits is a potential small maternity roost for the threatened M. o. oceanensis, as indicated by captures of pregnant females in December 2014, as well as increased emergence counts and call activity in spring compared with autumn. While there were some signs of reproducing R. megaphyllus at the adits (a single pregnant female in late October, and postlactating females and juveniles in February) the complete absence of females during December trapping indicated otherwise. Use of the three adits was typical for roost and access preferences of the species, with only R. megaphyllus occupying a doored adit and all species recorded at a large unobstructed adit, and a shallow adit likely only used as a night roost by all species.