Influence of season, habitat, temperature, and invertebrate availability on nocturnal activity of the New Zealand long‐tailed bat (Chalinolobus tuberculatus)

Abstract

Nocturnal patterns of activity by the New Zealand long-tailed bat (Chalinolobus tuberculatus) varied significantly in relation to habitat, season, time of night, temperature, and invertebrate activity. Automatic bat detection units recorded 12072 bat passes containing 593 feeding buzzes during 580 nights of sampling. Overall, 46.3% of passes were along roads within forest, 42.7% along forest edges, 8.1% in open grassland and 2.9% within forest. Pass rates averaged 30.8/night (95% confidence interval (CI) = 23.3-38.4) during spring, 31.7 (CI = 21.3-42.1) during summer, 6.7 (CI = 4.4-9.0) during autumn and 1.6 (CI = 0.2-3.0) during winter. Bats were active throughout the night in all habitats, but the patterns of their activity were different in each. During spring and summer a significantly higher proportion of bat passes in edge and open habitats were recorded in the first 2 h after sunset, and activity then declined steadily towards dawn. In road habitats activity peaked in the second hour but was more consistent during the remaining hours of the night. Activity in forest did not vary through the night. Patterns were similar, though less pronounced, in autumn but in winter there was little activity during the first three hours after sunset or in the 5 h before dawn. Analysis of deviance models indicated that habitat, season, minimum overnight temperature, and invertebrate activity contributed to explaining the activities of bats. Overnight temperature was more important than invertebrate activity in explaining total bat activity in a night. Invertebrate activity was more significant than minimum temperature in the model explaining the amount of foraging activity per night, inferring that minimum temperature determines whether bats fly at night, while invertebrate activity determines how long bats feed. Techniques for indexing bat activity that are designed to survey distribution or monitor population trends should control for temporal variation and temperature to enable valid comparisons between counts.

Habitat use and nocturnal activity of lesser short‐tailed bats(Mystacina tuberculata)in comparison with long‐tailed bats(Chalinolobus tuberculatus)in temperate rainforest

“…They are typical aerial insectivores that primarily forage along forest edges and along roads within forest after leaving their roosts at dusk. They feed throughout the night, but the extent of their foraging activity is influenced by such factors as season, temperature, and availability of flying insects (Griffiths 1996;Sedgeley & O'Donnell 1999a,b;O'Donnell 2000bO'Donnell , 2005Alexander 2001;Moore 2001). In contrast, little is known about lesser short-tailed bats' habitat requirements or temporal patterns of activity beyond the general observation that they are usually associated with large expanses of mature indigenous forest (Daniel 1976(Daniel ,1979Daniel & Williams 1984;Arkins et al 1999;Lloyd 2005).…”

“…Long-tailed bats have been studied in the same area since 1993, and their temporal patterns of activity have been reported elsewhere (O'Donnell 2000b).…”

The importance of exotic plantation forest for the New Zealand long-tailed bat (Chalinolobus tuberculatus)

“…Other research into long-tailed bats in Kinleith Forest found they were detected more commonly along roads among P. radiata which were near harvest age, and that bat activity along a road in one area of P. radiata exceeded that along the same road where it passed through a nearby indigenous remnant (Moore 2001). Nevertheless, rates of detection of bats in Kinleith Forest were far lower than in comparable bat detector-based research in the native Nothofagus forest of Fiordland's Eglinton Valley (O'Donnell 2000a;Borkin & Parsons 2009), and whilst no direct relationship has yet been established between detection rates and actual numbers of bats present (Parsons 2001), we presume that this indicates a smaller population in Kinleith Forest.…”

“…Torpor is especially important in cold weather (Webb 1999;O'Donnell 2000a) because it reduces the energy expenditure required to maintain life (Speakman & Thomas 2003), but it may be used during the day even in summer (Turbill et al 2003). The metabolic state of torpid bats is reduced, and correspondingly also their ability to breathe, move (Speakman & Thomas 2003) and escape when their roost tree is felled.…”

“…This increase in value of exotic plantations as they age certainly appears to be the case for bat species, because rates of detection often increase and are more consistent in older forest stands (Thomas 1988;Erickson & West 1996;Parker et al 1996), although this varies amongst species (Loeb & O'Keefe 2006). Detection rates are highest along roads in the oldest stands (Moore 2001), probably because more roosts are available in older trees (Swystun et al 2007), and because well-established forests create warmer and more stable local climates, allowing longer periods of profitable foraging throughout the night (Alma 1975;Chen et al 1995;O'Donnell 2000a;Turbill 2008).…”