McCartney et al.—Feeding behaviour of short-tailed bats 227New Zealand Journal of Zoology, 2007, Vol. 34: 227–2380301–4223/07/3403–0227 © The Royal Society of New Zealand 2007

Feeding activity in captive New Zealand lesser short-tailed bats (Mystacina tuberculata)

J. McCaRTNey1

I. a. N. STRINgeR2

M. a. PoTTeR1

1ecology group, Institute of Natural ResourcesMassey UniversityPrivate Bag 11222Palmerston North 4442, New ZealandJ.McCartney@massey.ac.nz

2Department of ConservationPo Box 10420Wellington 6143, New Zealand

Abstract Lesser short-tailed bats (Mystacina tu-berculata) have been reported as commonly feeding on the ground, but few direct observations of the diet and foraging behaviour of these rare and secretive bats have been published. Here, we describe the feeding behaviour of six captive M. tuberculata at Wellington Zoological gardens, in order to experi-mentally clarify and validate some of the feeding behaviours previously reported from anecdotal ob-servations. In particular, we focused on food type choice and dependence on nectar. The bats emerged every night 80 ± 30 (mean ± Se) min after sunset, irrespective of the weather, and spent most of their time foraging in leaf litter on the ground (when available) and on the branches of trees. Larvae of meal worms (Tenebrio molitor) and cerambycid beetles (Prionoplus reticularis) were favoured in the diet, followed in diminishing order by adult meal worms, tree weta (Hemideina crassidens) and crick-ets (Teleogryllus commodus), some nectars, sugar solutions, and finally water. Nectar from Eucalyptus sp. was preferred, followed by nectar of pohutukawa (Metrosideros excelsa), wood rose (Dactylanthus taylorii), and kakabeak (Clianthus puniceus). Nectar of Acacia sp., Hebe sp., and synthetic Dactylanthus nectar were not taken. The bats visited 50 and 25%

sugar solutions significantly more frequently (91% of visits) than 12.5 and 0% sugar solutions. Various meats (carrion) and fruit were not eaten. Faecal con-tent fairly represented the invertebrates consumed the previous night, but the volumes of invertebrates consumed could not be reliably estimated from fae-cal analysis.

Keywords bats; captivity; conservation; feeding behaviour; Mystacinidae; Mystacina tuberculata

INTRODUCTION

The lesser short-tailed bat (Mystacina tuberculata, gray 1843) is the sole survivor of the endemic fam-ily Mystacinidae (Hill & Daniel 1985; Pierson et al. 1986; Lloyd 2005). The long-tailed bat (Chalinolo-bus tuberculatus, Forster 1844), New Zealand’s only other extant species of bat, feeds by hawking insects in the air, whereas M. tuberculata is thought to be much more terrestrial and frequently feeds on the ground (Dwyer 1960a, 1962a; Daniel 1979; Lloyd 2005; o’Donnell 2005). Three subspecies of Mystacina tuberculata have been described (Hill & Daniel 1985) and these are genetically distinct (Winnington 1999; Lloyd 2003). one other species, Mystacina robusta, was last seen in 1967 and may now be extinct (Lloyd 2005). Most of the physiological and behavioural dif-ferences between M. tuberculata and other bats (Microchiroptera) relate to its habit of feeding on terrestrial surfaces rather than in flight (Daniel 1976, 1979; Riskin et al. 2006). Morphological peculiari-ties include comparatively robust hind legs (Daniel & Baker 1986; Daniel 1990); special basal talons on the toe and thumb claws (Dobson 1876; Dwyer 1962a; Daniel 1979; Daniel & Baker 1986); short, smooth, velvet-like body hair (Myers 1921; Dwyer 1962a); basal wing folds that protect the folded wings from damage when on the ground (Dwyer 1960a, 1962a); and peculiar dentition (Dwyer 1962b). Most of these features facilitate dextrous climbing or burrowing through leaf-litter, and allow the bats to exploit a

Z07033; Online publication date 8 August 2007 Received 12 July 2007; accepted 17 July 2007

New Zealand Journal of Zoology, 2007, Vol. 34228

remarkably wide variety of foods (Daniel 1976, 1979, 1990; Dwyer 1960a,b, 1962a,b; McCartney 1994; Ecroyd 1995; Arkins et al. 1999; Lloyd 2005; McCartney & Lloyd unpubl. data). Mystacina tuber-culata is also the only temperate microchiropteran bat reported to consume plant matter such as fruit, pollen and nectar, which they collect with the aid of enlarged tongue papillae (Knox 1872; Koopman 1970; Daniel 1976; McNab 1982). The secretive nature of M. tuberculata, and the often remote and rugged nature of its habitat, make it difficult to study in its natural environment, and nearly impossible to manipulate experimentally, so little research has been conducted on its diet since this species was described over 160 years ago (gray 1843). Thus, there are large gaps in our basic knowl-edge of the feeding behaviour of this bat, which inevitably impedes progress towards conservation of this species. The general aims of this study were to investigate feeding behaviours not previously studied, and to clarify and validate some known feeding behav-iours. Specifically, we aimed to: (1) investigate M. tuberculata’s food preferences using random choice experiments; (2) investigate what concentrations of sugar-water these bats prefer, to help determine whether they might select nectars based on their sugar concentration; and (3) determine the extent to which faecal content reflects their diet, in order to ex-plore how well this non-invasive but indirect method of determining diet might apply in the field. as part of aim (1), we exposed the bats to a range of meat, fat and carrion, because carrion has often been considered a natural part of Mystacina’s diet (e.g., Stead 1936; Dwyer 1962a,b; Daniel 1976, 1979). We also tested their response to a range of exotic and native flowers and nectar—including Dactylanthus taylorii (a root parasite from which M. tuberculata has been reported taking nectar: Ecroyd 1995) and the Three Kings vine Tecoman-the speciosa (a native species that may potentially be pollinated by Mystacina: Cranwell 1962; Lloyd 1985).

MATERIALS AND METHODS

Study animalsObservations were conducted each night between 9 May and 3 June 1994 on two male and four female southern lesser short-tailed bats (M. t. tuberculata) of unknown age held at Wellington Zoological

Gardens. These bats were captured on Codfish Island approximately 2 years previously, and were nor-mally fed each evening with approximately 120 live mealworms (c. 15 g), 50 g exotic fruit (banana, ap-ple, orange, feijoa) and 50 ml honey-water (c. 60% honey). During this study the weights of all six bats stayed within ±1 g of their initial weight (c. 16 g for the males and 17 g for the females).

Study locationThe bats were observed in their enclosure, which measured 8 × 3.5 × 3 m and was covered in 10 mm wire mesh (Fig. 1). The enclosure included a flight area with some native shrubs and trees, a thin layer of leaf litter on the ground, and a covered shelter, half of which contained an observation room with a glass door, a window, and a trapdoor that all opened into the shelter. The trapdoor provided access to a removable rectangular feeding tray situated 0.5 m up the wall of the shelter. The bats roosted in a box hung near the ceiling in the shelter.

Experimental constraintsDuring our experiments, the bats’ diet was not changed markedly from their usual diet for more than 1 night, except on one occasion when the bats were given only meat and honey water for 2 nights. This was to ensure that their health was not adversely affected. Thus, for example, the choice experiments (experiments 1 and 2, described below) mostly in-cluded their usual food items together with the new food being assessed.

EquipmentDirect observation of bats was aided by using a night scope (Noctron V) with an infrared spotlight. Remote observations were made of the bats at the feeding tray using two low-light sensitive video cameras (Panasonic WV-BP504) with an array of infrared light-emitting diodes above it and an in-frared spotlight directed towards it from about 2 m away for illumination. Video recordings were taken from 1700 h (dusk) to 0700 h each night on a long-playing video-recorder. Vocalisation was detected using a Mini-2 Bat Detector (Ultrasound advice, Birmingham).

Experimental design

Experiment 1: Food choiceobservations were made over 21 nights between 10 and 31 May. a range of food (Tables 1, 2) was provided each evening, and the number of visits bats

McCartney et al.—Feeding behaviour of short-tailed bats 229

Fig. 1 Study site (bat enclosure) at Wellington Zoo Trust (not drawn to scale).

made to each item or the number of items eaten was recorded with infra-red video equipment. Food was placed on the feeding tray, except when live insects were added to leaf litter on the floor of the shelter. Nectar or flowers from a range of native plants (Table 1) and a gum tree (Eucalyptus sp.) were also provided. Samples of nectar were frozen and their sugar concentrations determined later using a refractometer. Favoured foods were identified by the number of visits to each food item per night, where each visit was an approach to and stop on or next to the food item. Visits were used as the response variable because it was impracticable (and sometimes impos-sible) to measure the quantities consumed by bats, as they often spilt liquid, knocked solid food off the eating tray, or took insects to another location.

In some cases it was also not possible to quantify the amount of food offered or eaten, such as the amount of nectar taken from flowers. Therefore, it was not possible to compare quantities consumed statistically.

Experiment 2: Sugar-water concentrationWe used a randomised block design in a choice test with four different sugar concentrations (0, 12.5, 25 and 50% sugar solutions (weight for weight)). The four solutions were the only food provided to the bats on the 4 nights of this trial (23, 25, 27 and 29 May), and each trial night was followed with a night when the bats were provided with their normal diet. The four solutions (each 30 ml) were presented in separate petri dishes on the feeding tray, and the numbers of visits to each solution were counted from

 

8 m

3.5 m

Door

Aviary(Flight area)

Trees

Covered shelter(feeding room)

Observation area

Camera

Feeding tray

Door

windowsDoor

Branches Roosting box

Camera (trained on feeding tray)

 

New Zealand Journal of Zoology, 2007, Vol. 34230

Table 1 Food eaten by short-tailed bats in captivity over 10 nights. Mean numbers of visits per night are given. (? = not sure if food was visited, see text).

FoodMean no.

visits per nightNo. nights observed

Meat Chicken, beef, beef mince, dead baby chickens, “Chef” canned dog food, ox heart, beef blood

0 1–4

Fruit apple, banana, feijoa, orange, tomato, Coprosma sp. berries

0 1–7

Nectar Acacia sp. 0 1Coprosma sp. 0 1gum (Eucalyptus sp.) 76 1Hebe stricta 0 2Kakabeak (Clianthus puniceus) 3.7 3Kohekohe (Dysoxylum spectabile) 0 1Mistletoe (Peraxilla colensoi) 0 2Pohutukawa (Metrosideros excelsa) 27 1Synthetic Dactylanthus 0 2Three Kings vine Tecomanthe speciosa 0 1Wood rose (Dactylanthus taylorii) 7.7 3

Invertebrates Crickets (Teleogryllus commodus) 15 1Darkling beetle (Tenebrio molitor) 8 1Diptera larvae ? 1earthworm (Lumbricus terestrius) ? 1Huhu grub (Prionoplus reticularis) 2 2Meal worms (Tenebrio molitor) 134 9Moths (Lepidoptera sp.) ? 2Snails (Cantareus asperses) ? 1Weta (Hemidiena crassidens) ≅ 56 1

Honey water/sugar water (during preference experiment)

100% water 2 612.5% sugar/water 4 625% sugar/water 27.5 650% sugar/water 28.5 6

other Chicken eggs 0 1“Tararua” mild cheese 0 1

video tape recordings. The Kruskal-Wallis test was used to test for significant differences between the numbers of visits to each solution.

Experiment 3: Faecal analysisFaeces were collected on a white polythene sheet spread under the roost box. The faeces were sepa-rated by prising apart with forceps after soaking in water, and then all recognisable pieces of food were extracted and identified under a dissection micro-scope. The percentages of different food items in the faeces were then compared with the amount of each food item provided the previous night. Faecal samples from different days were coded, and then examined in randomised order to ensure that the analyses were not affected by knowledge of what food had been fed the preceding night.

RESULTS

General observationsThe bats always emerged from their roost each night during the 4 weeks of observations, regardless of the temperature (range = 6–13°C) or the presence of rain and lightning. emergence was delayed if a human was moving about in the enclosure. over a series of 11 nights, when left undisturbed, the bats consistently began flying 80 ± 30 min (mean ± Se) after sunset. after emergence, the bats spent much of their time flying around the enclosure, and stopped only occasionally to take something from the feeding tray. However, when a thick layer of leaf litter and branches (pohutukawa, Metrosideros excelsa and Eucalyptus sp.) were provided on the floor of the

McCartney et al.—Feeding behaviour of short-tailed bats 231

Table 2 Comparison of the faecal content with the food from the previous meal over 10 nights between 10 and 30 May 1994.

Night Food provided Food eatenPercentage of recognisable

material in faeces1 120 mealworms (100 g)

60 ml honey water200 g ox heart100 g beef mince

120 mealworms60 ml honey water – –

100% mealworm – – –

2 2 × 6 g weta120 mealworms (100 g)200 g beef mince150 g exotic fruit60 ml honey water

4 weta legs120 mealworms – –60 ml honey water

100% mealworm – – – –

3 and 4 100 g beef mince100 g of exotic fruit120 mealworms5 adult mealworms120 ml honey water

– –120 mealworms1 adult mealworms120 ml honey water

– –80% mealworm10% adult mealworm 10% unknown

5 30 ml, water30 ml, 12.5% sugar water30 ml, 25% sugar water30 ml, 50% sugar water

– –15 ml, 25% sugar water10 ml, 50% sugar water

40% mealworm60% unknown – –

6 200 mealworms in freshly gathered leaf-litter5 huhu grub larvae (20 g) on feeding tray

Many mealworms taken –

90% mealworm5% unknown5% spider legs 1 mite (probably contamination)

7 120 mealworms 10 crickets20 moths10 adult mealwormsRotten beef with fly eggs (all in leaf-litter)10 ml of pure Dactylanthus (in a petri dish)

Not observed (all except nectar was scattered in freshly gathered leaf-litter)

–

–

65% mealworm35% adult mealworm – – –

8 30 ml, water30 ml, 12.5% sugar water30 ml, 25% sugar water30 ml, 50% sugar water

Not measured

50% mealworm10% adult mealworm40% crickets

9 120 mealworms200 g exotic fruit

Not observed 50% mealworm5% adult mealworm45% cricket

10 260 mealworms60 ml honey water200 g exotic fruit

260 mealworms60 ml honey water –

100% mealworm –

shelter (3 nights), the bats spent approximately 40% of their time on the ground, 30% gleaning in trees and 30% flying. Usually they disappeared entirely under the litter for considerable periods and only sporadically appeared at the surface to make sniffing movements. No vocalisations were detected from the bats while they were in leaf litter.

Food choiceSoft-bodied mealworms (Tenebrio molitor L.) were preferred to more sclerotised adult beetles (T. molitor; note that the latter excrete toxic qui-nones, and so are subsequently not normally fed to bats (Barnard 1995)), weta (Hemideina crassidens, Blanchard) and crickets (Teleogryllus commodus,

New Zealand Journal of Zoology, 2007, Vol. 34232

Table 3 Concentrations of sugar (Brix) in native flowers presented to short-tailed bats. Concentrations for mistletoes are from Ladley (1994).

Species of flower Sugar concentration (Brix) (%)Synthetic Dactylanthus 9.7Wood rose (Dactylanthus taylorii) 13.0Kakabeak (Clianthus puniceus) 22.0gum (Eucalyptus sp.) 11.0Three Kings vine (Tecomanthe speciosa) 19.0Mistletoe (Peraxilla colensoi) 14.3Mistletoe (Paraxilla tetrapatala) 12.2

Fig. 2 Mean number of visits made per night by six captive lesser short-tailed bats to different invertebrates (±Se, n = number of nights offered).

Fig. 3 Mean number of visits made per night by six captive lesser short-tailed bats to flowers and synthetic Dactylanthus nectar (±Se, n = number of observed nights).

n=1

n=1

n=3n=3

n=2 n=2 n=2 n=1 n=1 n=2 n=10

10

20

30

40

50

60

70

80

90

Num

ber o

f vis

its

Eucaly

ptus s

p.

Hebe s

tricta

Acacia

sp.

Copros

ma sp.

Kaka b

eak

McCartney et al.—Feeding behaviour of short-tailed bats 233

Walker) (Fig. 2). Fruit, meat, eggs, cheese, snails (Cantareus asperses, Müller) and some types of nectar were never visited (Table 1). No meat, fat, carrion, or chicken carcasses were consumed even when the only alternative food provided on 2 suc-cessive nights was honey dissolved in water. Live earthworms and snails (Table 1) were offered on one occasion, and all were missing the following morn-ing, but it was possible they had escaped. on one occasion 360 mealworms (c. 50 g) were provided and all seem to have been eaten, or at least taken from the feeding dish.

Nectar choicesThe bats visited certain types of nectar more fre-quently than others (Fig. 3). However, the most frequently visited dishes were not necessarily those with the highest sugar concentrations (Table 3). on average, each individual made 76 visits per night to a branch of flowering gum tree (Eucalyptus sp.) com-pared to nightly averages of 27 visits to small blooms of pohutukawa, 7.6 visits to Dactylanthus taylorii and 5.5 visits to kakabeak (Clianthus puniceus). The bats approached flowers of Three Kings vine, Acacia sp., Hebe stricta, and synthetic Dactylanthus nectar, but were never observed to lick or drink from them. Flowers of kohekohe (Dysoxylum spectabile), mistletoe (Peraxilla colensoi) and Coprosma sp. were never visited.

Sugar-water concentration preferencesWhen provided only with sugar and water solutions, 91% of visits were to 25 and 50% sugar solutions, whereas 9% were to water or 12.5% sugar solution. This difference between visits to high and low sugar concentrations was significant (H = 9.18, d.f. = 3, P < 0.05: Kruskal-Wallis test).

Faecal analysisPredictably, highly sclerotised insects were well represented in faeces whereas insects with little sclerotisation were poorly represented (Table 2). The quantity of food consumed the previous night could not be determined accurately by faecal analysis, but the proportions of parts of different arthropod taxa represented in the faeces were similar to the propor-tions of these taxa provided as food the preceding night (e.g., nights 1, 2, 3 and 4; see Table 2). The presence of mealworm parts in faeces from night 5, when no mealworms were provided, shows that they can remain in the digestive system for more than 24 h.

DISCUSSION

Food choiceour results corroborate previous reports for many of the food types eaten by M. tuberculata, but we found no evidence that they would eat the fruit or any meat, fat, carrion, or carcasses we provided. The seeds of native fruits have been found in the stomachs of short-tailed bats (Daniel 1976, 1979) making this the only known temperate bat to con-sume plant material. Our study confirms previous reports that this bat drinks nectar, and adds to the list of species visited. In addition, we confirmed that M. tuberculata will eat huhu grubs (Prionoplus reticularis larvae; Co-leoptera: Cerambycidae). While these wood-boring larvae may not normally be available to them, Daniel (1979) reported that adults are rejected. Evidently, tests of food acceptability may not hold for every M. tuberculata in every situation, because Daniel (1979) found that they did not eat tree weta (orthoptera: anostostomatidae), whereas ours did. Furthermore, these bats will also eat tree weta in the field, as evi-denced by a M. tuberculata that was recently caught in a mist-net on Little Barrier Island with a tree weta (Hemidiena thoracica) in its mouth (yvan Richard pers. comm.). The consumption of insects that are almost as large as the bat itself is unusual because small bats, in general, eat only small prey (aldridge & Rautenbach 1987). Such differences in food acceptance may be due to a range of factors, such as neophoby or pre-vious familiarity with a particular food. Mystacina tuberculata is, however, an aggressive bat that cer-tainly possesses suitable dentition for consuming large invertebrates (Dwyer 1962b). one of the more unusual foods reported for M. tuberculata is carrion (Stead 1936; Dwyer 1960b, 1962a). If this bat does eat the flesh of dead verte-brates, then it is one of only two bats worldwide that are known to do so (Fenton et al. 1981). References to consumption of carrion by M. tuberculata seem to originate from a single report by Stead (1936), who stated that he had fed them skinned diving petrels (Pelecanoides urinatrix), although he did not observe them actually eating them. He also speculated that these bats may have eaten the flesh from the backs of dead bellbird chicks (Anthornis melanura). In addition, Dwyer (1960b) later stated that “strong transverse ridges on the tongue of this bat are suitable for scraping flesh from animal car-casses” and that “Mystacina has at times caused

New Zealand Journal of Zoology, 2007, Vol. 34234

considerable damage to the bodies of mutton birds (Puffinus griseus), when these were hung to dry”. Dwyer (1960b) does not provide references for his sources or give any details of observations he may have made himself, but he later (Dwyer 1962a) cites Stead (1937) as the source of this information. Stead, however, did not publish a paper in 1937. on the other hand, the page numbers and journal given by Dwyer (1962a) are the same as those for Stead (1936), suggesting that the date of 1937 was given in error. Stead (1936) does not mention that M. tuberculata eat the flesh of dead mutton-birds, so the source of this information remains unsubstanti-ated, even though several authors have cited Dw-yer (1962a) as the source for this bat’s carnivorous habits (for example, Dwyer 1962b; Daniel 1976, 1979). It is therefore quite likely that this bat does not eat vertebrate flesh, and we found no evidence that they eat fresh or rotten meat or flesh from chick carcasses. During our study, M. tuberculata certainly took mealworms that had strayed onto minced beef, but there was no evidence that any of this meat was eaten. Bird feathers have been found inside the faeces of M. tuberculata collected from Codfish Island, suggesting that they may have been consumed with carrion. These faeces were collected from a roost that was close to a dead kaka (Nestor meridionalis) that was full of maggots, so it is also possible that the feathers were consumed unintentionally when the maggots were eaten, rather than when the bats ate the bird (McCartney & Lloyd unpubl. data). Mystacina tuberculata are reported to eat the fruit of some native plants (Daniel 1976, 1990; Arkins et al. 1999) but we were able to test only the berries of puriri (Vitex lucens) and Coprosma species, and neither was eaten. The bats did not eat the commer-cially available fruit provided during our study, but staff at the Wellington Zoological gardens found that they would occasionally eat a range of fruit including banana, apple, peach, feijoa, and plum (Blanchard 1992); a juvenile held in captivity for 15 months readily ate pear, grapes, melon and avocado, but not citrus fruit, banana or apple (Shirley McQueen pers. comm.). However, our results indicate that, given the opportunity, M. tuberculata may choose mealworms and other soft-bodied arthropods over fruit, either commercially available or from the two native plants tested. our results for food preferences are only in-dicative, for three reasons. (1) We used a relative measure—the number of visits made to a food item,

rather than the absolute volume of food consumed; (2) it was not practicable in the time available to experimentally test all combinations of food in order to show definitive preferences between them; (3) the bat’s food choices may already have been changed by the foods given to them in captivity over the pre-vious 2 years. our aim was to determine what foods these bats would eat when they were presented with a selection while they were relatively well fed (the tests with sugar solutions were an exception), and it is quite possible that these bats may eat some of the foods they normally avoid in different circum-stances, such as if they are sufficiently hungry. This is apparent in their differing responses to tree weta and fruit as mentioned above. We therefore did not attempt to control for all of the confounding behav-ioural factors that may affect choice testing over a large array of foods. Such factors may include, for example, hunger, neophobia, and the degree of previ-ous familiarity with a food, as mentioned above, as well as what foods were offered previously or the order of presentation, what food options are avail-able during a meal, and individual preferences. Barclay (1991) remarks that all bats survive in extremis, and this must certainly hold true for M. tu-berculata, which is active throughout winter (Sedge-ley 2001). other temperate bats eat only insects, and hibernate when their food becomes seasonally sparse. This suggests that the wide range of foods eaten by M. tuberculata may facilitate this bat’s abil-ity to remain active during the winter months. Their habit of foraging in leaf litter may also help them stay active during winter because some of the larger invertebrates, such as ground weta (anostostomati-dae), remain active in leaf-litter even when covered with snow (Cary 1983; Sedgeley 2001; Christie & Simpson 2006).

Flower choice and sugar-water concentrationPollen grains from a range of plant species have been found adhering to M. tuberculata bats, and pollen from rewarewa (Knightia excelsa), rata and pohutukawa (Metrosideros spp.), kanuka (Kunzea ericoides), kahakaha (Collospermum hastatum), and tree ferns (Cyathea spp.) have been found in their guano (Daniel 1976, 1979; Holloway 1976; Arkins et al. 1999). However, it is not clear whether the bats ate the pollen or whether they acquired it by eating invertebrates coated in pollen or while drinking nectar. The latter certainly seems likely because the pollens most commonly found on these bats were associated with flowers that produce abundant nectar

McCartney et al.—Feeding behaviour of short-tailed bats 235

such as kiekie (Freycinetia baueriana), kahakaha, rewarewa, pohutukawa and rata. Mystacina tuberculata are now known to be more important pollinators than was initially thought. Daniel (1976, 1979) confirmed that they pollinate kiekie and take the nectar, pollen and fruit bracts of this plant. Blanchard (1992) reported that the flowers of a range of other plants were “torn apart” by bats in captivity, but it is not clear if the bats consumed anything. Ecroyd (1995) and Ecroyd et al. (1995) found that they regularly visit the flowers of Dac-tylanthus taylorii and drink its nectar. The flowers of this plant have the chiropterophilous characteristics of a pungent odour, they open at night, and they produce large quantities of nectar (Higham 1992). Finally, Arkins et al. (1999) and Winnington (1999) reported that it is likely that they take the nectar from Metrosideros spp., which our observations in captivity confirmed. We have added to this list the nectars of Eucalyptus sp., and kakabeak, but the nectars of Hebe stricta, Acacia sp., kohekohe, mis-tletoe and Coprosma sp. were ignored, as also was a synthetic Dactylanthus nectar. Interestingly, our M. tuberculata also ignored the Three Kings vine, even though it has large white petals and abundant nectar with a high sugar concentration, two characteristics of chiropterophilous plants (Cranwell 1962; Lloyd 1985). No bats have been reported from the Three Kings Islands. one common factor with all of the species of flowers visited by M. tuberculata is that they pro-duce abundant nectar. our results suggest that the concentration of sugar in nectar alone was not suf-ficient in itself to explain why certain flower species were visited more than others. although the bats consumed sugar water with higher concentrations in the randomised block experiment, they visited wild flowers with variable sugar levels. It is pos-sible that the bats preferred higher concentrations of sugar water because they had previously been fed for about 2 years on a solution of 60% honey and water. other factors also clearly affect whether M. tuberculata visit flowers, because we found that the flowers of D. taylorii and Eucalyptus sp. were the most frequently visited flowers tested and yet they contained some of the lowest concentrations of sugar in their nectar of all the plants we tested. There is possibly a trade-off between the volume of nectar supplied and sugar concentration, as both play an important role in flower preference for bats overseas (e.g., Baker et al. 1998; Sanmartin-Gajardo & Sazima 2005).

Faecal analysisFaecal analysis is often considered superior to other methods of diet analysis (such as stomach content analysis) because the fragments are more concen-trated than in the stomach (Black 1972) and because it does not involve killing or manipulating endan-gered animals (Belwood & Fenton 1976; Dickman & Huang 1988). Studies on both insectivorous bats (Fenton et al. 1981; Kunz & Whitaker 1983; Bel-wood & Fullard 1984) and frugivorous bats (Wilson 1971) indicate that faecal analysis does provide a reliable indicator of their diets. Faecal analysis has also been used to estimate both percent frequency of food species consumed and percentage of volume eaten together with error estimates (Whitaker 1972; Kunz 1974; Kunz & Whitaker 1983; Belwood & Fullard 1984). Our results corroborate overseas findings that faecal analysis is a reliable indicator of diet, and that it is likely to be especially useful with M. tuberculata because of its protected status (New Zealand Wildlife Act 1953). Belwood & Fenton (1976) showed that faecal analysis fails to detect whether soft-bodied insects and fruit have been eaten, and this is certainly relevant to the analysis of M. tuberculata faeces. However, spores, pollen and seeds are nearly always consumed when nectar and fruit are eaten, and these pass through the gut and can easily be identified (Daniel 1976).

Nightly emergence from the roostThe time of first emergence from the roost is likely to have been affected by the relative safety of a captive environment, so it is perhaps not surpris-ing that they emerged every night (irrespective of weather) given the constancy of the feeding regime they were exposed to for the 2 years before our observations. Their emergence time corresponds with anecdotal evidence that they emerge well after dusk (Stead 1936; Dwyer 1960b, 1962a), and is consistent with studies of wild M. tuberculata that emerged on average 42 min after sunset (range = 20–80 min) over summer in Fiordland (Christie 2006). By contrast, the New Zealand long-tailed bat leaves the roost much earlier, on average at about sunset, while it is still light in the forest (o’Donnell 2000, 2005). In the wild, one might presume that M. tuberculata should emerge soon after the day-flying predators cease hunting and close to the onset of night. However, the behaviour of these partly ground- and tree-branch-hunting bats might be more strongly influenced by avian predators. The New Zealand falcon (Falco novaeseelandiae) is reported

New Zealand Journal of Zoology, 2007, Vol. 34236

to prey on them, together with morepork owls (Ninox novae seelandiae) and the now extinct laughing owl (Sceloglaux albifacies) (Stead 1936; Worthy & Holdaway 1995, 1996; Worthy et al. 1996).

CONCLUSIONS

our research supports other published observations by confirming that M. tuberculata consume a wide range of foods. We found no evidence that they eat meat, and note that previous references to this habit appear unsubstantiated. We also found that faecal analysis is a good qualitative indicator of their diet, but that it is probably a poor quantitative indicator. Clearly, M. tuberculata is remarkable in the range of foods it will consume, but further research is required to document fully what these bats will eat and the factors that affect their choice of foods.

ACKNOWLEDGMENTS

We thank Kim Carter and Chris Devine for helping with data collection; the staff at the Wellington Zoological gardens, especially Ron goudswaard and the bird staff, for invaluable logistic support. We are indebted to Colin o’Donnell and two referees for helping to improve the manuscript and Mary Rossiter, alastair Robertson, Jill Rapson and Ian Henderson for commenting on earlier drafts. We thank Chris ecroyd for supplying us with natural and synthetic Dactylanthus nectar and Brian Lloyd (Department of Conservation) for the use of observation equipment.

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