Impact of weather conditions, seasonality and moonlight on the use of artificial canopy bridges by nocturnal arboreal mammals

Abstract

Natural and artificial canopy bridges can be used to mitigate the effects of habitat fragmentation. Understanding the ecological factors that influence bridge use is imperative to the effective design and placement of this potential conservation intervention. Moonlight, seasonality and weather may influence the cost and risk of using bridges, potentially reducing their effectiveness. We installed five artificial waterline bridges and, between 2017 and 2019, monitored via camera trapping their use by Javan palm civets Paradoxurus musanga javanicus and Javan slow lorises Nycticebus javanicus. We used a weather station to record microclimate data (temperature and relative humidity) and calculated the illumination percentage of the moon. We tested the influence of moon luminosity, relative humidity, seasonality (Julian day) and temperature on the frequency of bridge use via Generalised Additive Models. Camera traps captured 938 instances of bridge use by civets, which was significantly lower than the reference value at moon luminosity >90%, temperatures >20°C, humidity >90%, and during the drier period (May-July). Camera traps captured 1036 instances of bridge use by lorises, which was significantly lower than the reference value during the drier period and higher than the reference value at temperatures >20°C. Lorises showed peaks in bridge use close to sunset and sunrise whereas civets showed peaks around 2 h after sunset and 2 h before sunrise. Our study illustrates the utility of simple-to-construct bridges by two sympatric nocturnal mammals facing severe habitat loss, with bridge use differing between those species according to abiotic factors. In particular, less use by both taxa during the drier season could suggest modifying placement of bridges or providing another intervention during that time. Camera traps were an excellent mechanism to record these differences and to validate the importance of the bridges, including during inclement weather and dark nights, when observations would be more difficult for human observers. By understanding the influence that abiotic factors have on the use of artificial bridges, we can improve bridge placement and construction to encourage use by a variety of species, particularly those threatened by habitat fragmentation.

Assessment of Ecological Bridges at Wildlife Crossings in Türkiye: A Case Study of Wild Boar Crossings on the Izmir-Çeşme Motorway

“…The initiation of their activity is closely linked to sunset [ 70 ]. This behavior aligns with existing literature when considering the use of ecological bridges by wild boars, where both wild and herd crossings exhibit similar patterns [ 71 , 72 ].…”

Influence of Moon Luminosity, Seasonality, Sex and Weather Conditions on the Activity Levels of the Nocturnal Javan Slow Loris

“…The predictions on seasonality were only partially met as we found two high peaks, one between December and February (as predicted) and one between June and August (not predicted). The peak during the dry period was not predicted as resources are scarce and Javan slow loris is expected to reduce energy expenditures [40]. Additionally, the activity patterns should follow photoperiodic variations, thus in periods when day length is shorter (i.e., austral winter), activity levels are also expected to be reduced [37].…”

“…Behavioral observations indicate that females tend to have a higher consumption of crude proteins, fruits, gum, and flowers during gestation and lactation than males [41], and they tend to have higher feeding time than males [58]. This would indicate that they would increase their energy intake instead of saving energy during periods of low food availability, but males have usually larger home ranges than females [40,45]. The activity levels might have thus been shaped by sex differences in the feeding and spatial ecology of the species, although these topics need further research.…”

“…Seasonality is also expected to influence the activity levels of Javan slow lorises, with a potential reduction of activity during dry periods (i.e., May-October) when resources are scarce, and they need to save energy. Javan slow lorises, in fact, were also found to reduce the number of crossings of wildlife bridges during the dry period to save energy [40]. The consumption of flowers, however, is higher during the dry period [41], and this might entail higher activity levels as the consumption of flowers needs longer feeding time to satisfy the energetic needs compared to other food items [42].…”

Analysis of Accelerometer Data Using Random Forest Models to Classify the Behavior of a Wild Nocturnal Primate: Javan Slow Loris (Nycticebus javanicus)

“…Direct observations by human researchers have provided detail about behaviour of slow lorises in particular in the wild, but for significant portions of time animals are out of view [47]. Despite the challenge of following these nocturnal primates, they have been shown to eat gum, nectar, and insects; their activity patterns are influenced by weather and moon phase; they go into torpor often in dense foliage where this behavior may be missed; and are frequently social, a behavior said to be rare for nocturnal primates [47][48][49][50]. Although all slow loris species are arboreal and prefer tree connectivity, several slow loris species occur in agroforests with reduced canopy connectivity that may disrupt loris activities or impact their energetics [51][52][53][54].…”