Fauna recorded
The fauna records are collated and summarised in Tables 1 and 2. Sixteen vertebrate and 170 invertebrate taxa, representing 12 and 99 families respectively, have been identified. An analysis of the recorded invertebrates by higher taxonomic group is given in Table 3.
Excluding accidentals, ectoparasites and those taxa for which ecological status could not be assessed, 11 vertebrate and 123 invertebrate cavernicoles (including guanophiles) were recorded in 8 and 72 families respectively. Sixty-five of these cavernicolous taxa (48%) are categorized as habitual trogloxenes, 44 (33%) as troglophiles, and 25 (19%) as guanophiles. No troglobites were identified.
Of the cavernicoles 112 (84%) are terrestrial animals, 22 (16%) aquatic. Of the 112 terrestrial cavernicoles 38 (34%) are categorized as parietal fauna. 19 (17%) of the terrestrial cavernicoles are almost certainly introduced non-indigenous species (all of them European in origin): the rest are Nearctic, circumpolar or cosmopolitan. All the non-indigenous species are invertebrates. Three further non-indigenous species which were collected are considered to occur only as accidentals in our caves.
In the case of aquatic invertebrate fauna, 20 cavernicolous taxa have been identified in the collections. Half of these are crustacea: Copepoda (5 species) or Ostracoda (5 species). Most of the rest are insect larvae: Odonata (3 species), Plecoptera (3 species), and Diptera (1 species). No introduced aquatic animals were found.
Cave environment
None of the accessible caves in the region have a constant temperature zone: all are subject throughout to surface environmental influences because of their small size, the presence of a stream, or through drafts due to multiple entrances. Radon gas concentrations in the inner areas of one of the largest caves, HC, (Morris, 1985) suggest almost stagnant air but even here the temperature changes seasonally, although the annual range is only ~2°C. This site may be considered “deep cave” in the sense of Howarth (1988). Annual temperature range in the dark zone of a more representative small Maritime Canadian cave is ~4°C (Fig. 3): many caves experience greater variation. During spring and early summer as the ambient temperature rises above that underground relatively cold air is retained inside caves, whilst warm air flows outwards in the autumn, thus skewing the annual curve (Fig. 3). In certain extreme special cases this effect results in so-called “ice caves” (see below). Maximum seasonal cave temperatures are recorded in September-October, minimum in January-February. Eastern Canada experiences a very rigorous winter climate. Cave entrances are subject to severe low temperature conditions throughout the winter and there is often a build up of ice and snow. They are subjected to repeated freeze-thaw cycles: the average annual number of cycles (-6°C to +2°C) at Dartmouth, Nova Scotia has been calculated as 30. As a result of this and ongoing dissolution of exposed rock, entrances are often almost filled in by blockfall and talus derived from within the threshold itself or from the cliff face outside (e.g. CB, HC, WIC, and FC). This physical barrier damps temperature fluctuations further inside resulting in fewer, perhaps only one, freeze-thaw cycle per annum in the deep threshold. The mean annual temperature inside caves in central Nova Scotia is ~5.7°C. However it is lower at a few sites. The aspect and physical shape of certain caves cause atypical temperature conditions with ice and snow persisting into mid- or even late summer. Snow and ice which accumulate during the winter in WIC for example have been observed to survive until early August. The minimum air temperature measured inside the cave on 29 July1997 was 2.5°C, and 0.4°C was recorded a few centimeters below the floor surface on 6 August 1999. Such sites were often used historically for cold storage or as a source of ice and are known locally as “ice caves”. However, none of the known local sites are true ice caves in the speleological sense of the term denoting a cave with permanent ice.
The temperature of standing water is usually within 0.5°C of the air in the immediate vicinity. There are several caves (e.g. CB, KC) with active stream sinks that modify the temperature. Temperature may also be affected by the presence of a spring. Some cave streams originate within the cave as eucrenal springs characterised by cold, clear sediment-free water with their temperature remaining within two degrees of the local annual mean. Examples are a small spring in MIC (4.3°C in September 1995) and the F2 cave stream (5.1°C in July 1997).
Cave waters in both limestone and gypsum caves are usually slightly alkaline: pH7.3-7.6. Acidic conditions may occur in stagnant or slowly flowing water where there are accumulations of porcupine dung or plant litter e.g. pH5.8 was measured in seeps with porcupine scat in WIC, pH6.5 in pools with plant flood debris in CB. Due to the high solubility of calcium sulphate (i.e. 2.438g.l-¹ in distilled water @10°C) and the presence of other dissolved solids such as calcium carbonate, gypsiferous waters have high conductivity. Analysis of water samples from ponds in HC (Morris, 1985) showed conductivity readings of 2220±10μS.cm-¹. Samples of water from FC were so high in calcium sulphate that microcrystals of selenite precipitated out on cooling in a domestic refrigerator.
Habitats
Although characteristically small, caves in the region contain a diversity of terrestrial and aquatic eutrophic (dung), mesotrophic and oligotrophic habitats. North American Porcupine (Fig. 2) dens are almost ubiquitous in caves and mines everywhere except Cape Breton Island. A den site is typically a small side passage, cavity or blind pocket within the deep threshold or dark zone occupied by a single animal. Cave dens always have an accumulation of faeces either as scattered pellets or more substantial accumulations (Fig. 4). In areas adjacent to the porcupine’s access routes sustained inputs of dung sometimes result in deposits tens of centimeters deep covering several square meters of cave floor. These dung piles can occur anywhere from the threshold through to the cave dark zone. Etiolated seedlings are commonly present on fresh dung growing from seeds which have passed through the gut of the porcupine (Calder & Bleakney, 1965) (Fig. 4). Decomposing dung fuels a varied community of bacteria, fungi, oligochaetes, insects, and other arthropods. The dung habitat is non-uniform, varying microclimatically and qualitatively with diet, stage of decomposition, and environmental factors including moisture content, ecological zone within the cave, and temperature profile at each site. Fresh dung is acidic (~pH5.1) but in wet areas, such as where there is seepage water or under roof drips, the acidity is neutralized by the buffering effect of cave waters. Also, as observed by Calder & Bleakney (1965), the decompositional sequence is accompanied by decreasing acidity, so that well decomposed and/or wet dung is slightly alkaline: ≤ pH7.3.
Because of the variability of pH and other empirically measurable factors, and because dung piles in the field often accumulate over many years, it was not possible to accurately determine the stage of decomposition of individual samples. However visual appearance is a useful approximate guide to the sequence. Fresh scat (Fig. 4) consists of scattered, ovoid, greenish-grey pellets with a mucoid surface. The mucoid material disappears rapidly (poorly decomposed). The pellets retain their shape and physical integrity for some time but turn darker brown in colour and the fibrous nature of their constituents becomes visible (moderately decomposed) (Fig. 5). In the later stages of decomposition they break down physically forming a material rather like dark well-weathered sawdust in appearance and consistency (well decomposed) (Fig. 6).
Invertebrate communities in porcupine dung piles are dominated by Acari, Collembola, dipteran larvae and enchytraeids (Figs. 7, 8). There are marked differences in the species composition and biomass of this community from site to site depending on microclimatic and qualitative factors. More than 35 terrestrial invertebrate taxa are recorded associated with dung in the Frenchman’s cave system (FC + F2), while the other extreme is represented by a remarkably simple ecosystem observed in GM where samples of well composted dung from the dark zone yielded only Protaphorura armata (Collembola) and enchytraeids. Qualitative observational evidence suggests that moisture content is the most important variable: both biomass and species diversity decrease in dry material. The abundance of Enchytraeidae in particular is affected by the moisture content and they are infrequent or absent in drier samples. Decompositional sequence is also a major factor. The general ecological succession reported by Calder & Bleakney (1965) with Acari numerically most abundant in “poorly decomposed” samples and Collembola becoming dominant later has been observed at other sites. It was very apparent in GM where mites were abundant in moderately decomposed material (which also contained isotomid Collembola as well as P. armata and Enchytraeidae) but, as mentioned above, were absent from samples of well composted dung. Acari are the most taxonomically diversified group in porcupine dung. Most have so far only been identified to genus or family. Parasitids (Parasitus, Eugamasus, Vulgarogasmus) are almost always abundant, and rhagidids (Rhagidia) are usually common. Other mites, some of which may be common to abundant at some sites, include Vegaidae (Vegaia), Zerconidae (Zerconopsis), Ascidae (Arctoseius), Ameroseidae (Epicriopsis), Eviphidae (Alliphis), Macrochelidae (Geolapsis), Pygmephoridae (Pygmephorus, Bakerdania), Tetranchidae (Bryobia), Acaridae (Acarus immobilis), Banksinomidae (Oribella) and various unidentified Uropodidae, Erynetidae and Histiostmatidae.
Collembolan populations are less diverse. They are almost always dominated by onychiurids (Protaphurura, Tullbergia) and isotomids (Folsomia, Isotoma). Neelids (Megalothorax minimus), podurids (Willemia scandinavia) and entomobryids (Pseudosinella alba, Tomoceros minor) are found more infrequently. The insect fauna of dung is dominated by nematoceran fly larvae. Larvae of Trichocera maculipennis and various sciarids are characteristically present and usually abundant (Figs, 7, 8). At least three different types of sciarid larvae are found, none of which have yet been matched with the adults recorded associated with dung in the caves. The latter include unidentified species of Bradysia, Lycoriella and Scatopsciara. Larvae of Limonia cinctipes, Chaoborus, Smittia, and Psychoda also occur in some samples, as do those of the brachyceran fly Leptocera. Adult Scatopsciara, Chaoborus and Leptocera have been observed attracted to fresh scat, presumably ovipositing. A few beetles are also found in this habitat. Larvae of Quedius s. spelaeus are often common in moderately decomposed dung, whilst the somewhat rarer adults are found under stones or running over the cave floor, almost always on or near dung (Moseley et al., 2006). The tiny guanophile Acrotrichis castanea is sometimes abundant, although it may be overlooked because of its size. Aphodius aleutus and Corticaria pubescens have been collected from dung: both occur in such habitats on the surface.
Other terrestrial invertebrates recorded associated with dung include Oniscus asellus (Isopoda), Lamyctes fulvicornis (Chilopoda), Proteroiulus fuscus, Ophyiulus pilosus, Polydesmus angustus (Diplopoda), and two linyphiid spiders Sisicottus montanus and Grammonota. Two earthworms (Dendrodrilus rubidus and Aporrectodea tuberculata) have also been collected, but as porcupine dung is almost unpalatable to earthworms it is at best a marginal habitat (McAlpine & Reynolds, 1977).
Most local caves are at shallow depth and in consequence detritus and plant debris seep in from the surface through crevices. Leaf and other plant litter also often accumulate particularly in cave and mine thresholds. Damp, often rotting, support timbers are found in disused mines. Beavers denning in caves (e.g. KC) store woods such as willow and alder as food. In stream sink caves such as CB, freshets and flooding resulting from the spring snowmelt carry in plant debris and organic sediment.
The varied invertebrate community of vegetation litter and detritus includes Dendrodrilus rubidus, Aporrectodea tuberculata, and Eisenia rosea (Oligochaeta); Hypogastrura pseudarmata, Neanura muscorum, Willemia scandinavica, Protaphorura pseudarmatus, Isotoma caeruleatra, Isotoma sp. nova? Pseudosinella collina, Sminthurides malmgreni, and Ptenothrix marmorata (Collembola); Quedius mesomelinus, Brathinus nitidus, and Gennadota canadensis (Coleoptera); various dipteran larvae; Parasitus, Eugamasus, Vegaia, Linopodes motatorius, Cocceupodes, Rhagidia, unidentified tetranchids, and Glycyphagus domesticus (Acari); and Discus catskillensis (Gastropoda). Flood debris is often rich in many otherwise unexpected aquatic stages of insects and other accidentals. Most are dipteran larvae e.g. Tipula, Erioptera pilipes, and Chrysops.
Many flies and other insects together with a few other arthropods and gastropods occur regularly on cave walls and ceilings. Several arthropods (Oniscus asellus [Isopoda], Polydesmus angustus [Diplopoda]) and gastropods (Arion, Deroceras laeve, and Trichia hispida) are commonly found within or near the threshold but almost never further inside. With the exception of these this assemblage tends to be richest both in number of species and in number of individuals in the deep threshold, but it extends into the dark zone. The species composition changes seasonally. Diptera predominate: there is an especially species rich fauna of mycetophilids (Boletina, Bolitophilia, Rhymosia, Exechia, and Exechiopsis) and helomyzids (Scoliocentra, Helomyza, Amoebaleria, and Tephrachlamys). By far the most numerically frequent Diptera in these caves are Trichocera maculipennis and various sciarids: adults of these flies are common in this assemblage. Culex females are abundant at many sites in winter. Other common flies are Limonia cinctipes, Chaoborus, Psychoda and Leptocera. Infrequent flies include Dolichopeza, Anopheles and Peromyia. As already mentioned the larvae of L. cinctipes, T. maculipennis, Chaoborus, several unidentified sciarids, Psychoda, and Leptocera live in porcupine dung. Other insects and arachnids found on cave walls include Ceuthophilus brevipes (Orthoptera); Scoliopteryx libatrix and Triphosa haesitata (Lepidoptera); Nelima elegans (Opiliones); Meta ovalis and Nesticus cellulanus (Aranea). One gastropod, Zonitoides arboreus, is found further inside than other gastropods.
Oligotrophic habitats are uncommon in caves in this region. They are more usual in limestone caves than in gypsum but can occur in the latter (e.g. F2) where they typically comprise areas of pebbles, gravel and/or sand adjacent to a fast-flowing stream or underground cold spring. Most terrestrial taxa recorded from such sites are Collembola: Heteromurus nitidus, Arrhopalites hirtus, and Arrhopalites nr. pygmaeus. Allajulus latestriatus (Diplopoda) and several unidentified Acari have also been collected.
The pool surface association comprises various Collembola (Protaphora cf. boedvarssoni, Folsomia candida, Isotoma sp. nova? Heteromurus nitidus, Pseudosinella alba and Arrahopalites hirtus), occasional Symphyla (Scutigerella), and a number of different unidentified Acari. A psocopteran (Liposcelis) was collected at one site.
Aquatic habitats comprise standing water, ranging from small pools on mud floors (e.g. CC) to lakes (e.g. HC); running water, ranging from tiny seeps and rivulets (e.g. WIC) to large streams (e.g. KC), and interstitial water. Cave streams may originate from the surface, or from an underground spring. In most gypsum caves there are substantial deposits of finegrained chocolate-brown sediment representing the insoluble residue of gypsum dissolution. These aquatic habitats support a diverse fauna dominated by copepods (Acanthocyclops spp., Eucyclops agilis, Diacyclops crassicaudis, Paracyclops poppei, and Macrocyclops albidus) ostracods (Pseudocandona albicans, Cypria, Cavernocypris, Cypridopsis, and Fabaeformiscandona wegelini), microdrile oligochaetes and aquatic insect larvae: particularly Odonata, Plecoptera and chironomid Diptera. Stonefly nymphs are common and display considerable taxonomic diversity: unidentified capnids, Amphinemura (Nemouridae), Taeniopteryx (Taeniopterygidae), Haploperla (Chloroperlidae) and unidentified perlids have all been collected, mostly from the threshold although Haploperla can live further inside in cold streams. Dragonfly nymphs (Aeshna, Macromia) are found frequently enough in cave thresholds to be considered habitual trogloxenes in that habitat. Planarians may also be present in pools in cave dark zones, and a water-beetle Agabus larsoni has been collected from dark zone pools and streams in both gypsum and limestone caves and may be habitual. Various other invertebrates may be present in cave pools near the entrance, sometimes straying well into the dark zone, but most of these are essentially part of the threshold fauna or accidentals. The leech Helobdella papillata and another waterbeetle A. semivittatus are examples of the latter.
Haploperla sp. nymphs (Plecoptera) and Simulium sp. larvae (Diptera) occur in the oligotrophic eucrenal streams arising from underground cold springs. There are occurrence records of three fish. Healthy looking Brook Trout (Salvelinus fontinalis) are sometimes seen in clear well-oxygenated streams well inside the dark zone in limestone caves. The Ninespine Stickleback (Pungitius pungitius) is at home in the thresholds of gypsum caves in large pools that have a connection with outside waters. It does not however stray far into the dark zone. A population of Northern Redbelly Dace (Phoxinus eos), was observed in HC for several years, but this fish has not been seen in any other cave.
Several different food inputs support animal communities in aquatic habitats. Dead insects are an important energy source. Insect corpses, especially Diptera, at times accumulate in large numbers on and in cave pools. A sample collected from a pool in F2 in October yielded Trichocera maculipennis, Leptocera, numerous sciarids and several Quedius s. spelaeus larvae and adults. These insects originate from the dung fauna and thus aquatic ecosystems are indirectly supported by porcupine dung. Dung may also be present as scattered droppings, or, sometimes (e.g. PT and GM) in substantial accumulations. Associated fauna includes planarians, aquatic microdriles, copepods (Acanthocyclops venustoides) and dipteran larvae. Bat droppings never form substantive accumulations: Scott & Grantham (1985) observed cyclopoid copepods associated with droppings in ponds in HC and Moseley (unpublished) made the same observation in MC.
Plant flood debris and other detritus carried in by sinking streams is also an important source of food in some caves. This input tends to be seasonal, with most material being brought in by spates during the spring snowmelt. The aquatic invertebrate fauna found associated with such material is more diverse than where this food supply is not available, but it is difficult to distinguish resident cavernicoles from the many accidentals carried in along with the plant debris.
Beaver living quarters with stored willow and alder were found well inside the dark zone of KC (McAlpine, 1977). The site had been abandoned when it was examined in 2005.
Sites that meet appropriate microclimatic and morphological conditions and are relatively undisturbed by human traffic are used by four species of insectivorous vespertilionid bats as winter hibernacula. Three gregarious non-migratory species (Myotis lucifugus, M. septentrionalis and Pipistrellus subflavus) commonly use caves and mines as winter hibernacula, entering in late September/early October and leaving in early summer. Another non-migratory bat Eptesicus fuscus preferentially hibernates in buildings but may occasionally use underground sites (Scott & Hebda, 2004). Hibernating P. subflavus are solitary and only the two Myotis spp. form hibernating colonies. The known colonies are not large: the population (>95% Myotis spp.) in the largest known hibernaculum is estimated to be
Other mammals, amphibians and fishes occasionally reported from caves and mines are listed in Table 2. Wright (1979) reported two species of ectoparasitic Acari and one siphonapteran collected ex-Myotis from non-cave sites.
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