Memoirs of the Museum of Victoria 56(2):649-653 (1997) 28 February 1997 https://doi.org/10.24199/j.mmv.1997.56.65 INVERTEBRATE AND CONSERVATION IN TASMANIAN CAVES

N. E. Doran, S. M. Eberhard', A. M. M. Richardson, and R. Swain

Zoology Department, University of , GPO Box 252C, Hobart, Tas. 7001, 'NSW National Parks and Wildlife Service, PO Box 733, Queanbeyan. NSW 2620, Australia

Abstract

Doran, N.E., Eberhard, S.M., Richardson, A.M.M. and Swain, R., 1 997. Invertebrate biod- iversity and conservation in Tasmanian caves. Memoirs of the Museum of Victoria 56(2) 649-653. Tasmanian caves support a diverse invertebrate fauna, representing the richest known assemblages of cave obligate species in temperate Australia. Current studies have yielded much valuable and unusual information regarding , amphipod and cricket species in particular, while highlighting their sensitivity to environmental disturbance.

Introduction limited. In Tasmania, the barren appearance of caves is increased by the absence of any major Cave ecosystems offer unique opportunities to vertebrate usage; roosting bats and birds are not evolutionary biologists because of their often present (most probably due to the low tempera- highly adapted fauna combined with their well- ture of Tasmanian caves), nor are any cave fish defined abiotic environmental parameters. known. The only visiting vertebrates are Despite its barren appearance and slow rate of humans and the occasional rodent, macropod, change, the cave environment can be remark- or snake seeking shelter. In spite of this, ably speciose, and Tasmanian caves have Tasmanian invertebrate cave assemblages are recently been identified as hosting the richest amongst the richest known in temperate zone assemblages of cave obligate invertebrates in Australia. temperate Australia (Eberhard et al., 1991). This Cave , or cavernicoles, are essentially a high biodiversity combined with Tasmania's heterogeneous assemblage occupying different location at a climatic and geographic extreme, regions of caves, and their classification is based and its relative abundance of undisturbed sites, around their relationship to particular cave the region extremely valuable for the makes zones. While there are many systems for such study of the evolutionary history of Australian classification, the simplest (Vandel, 1965; with cave biota. expansion by Howarth, 1983) divides animals In Tasmania as elsewhere, however, land into four groups as follows. land degradation problems management and Troglobites are obligate cave species, strictly significant danger to caves and their pose a adapted to subterranean habitats and unable to studies of the life cycles of certain fauna. Current survive outside them. These animals often dis- animals have highlighted their sus- cave play a large suite of distinctive morphological, environmental disturbance ceptibility to physiological, and behavioural adaptations, (Richardson et al., in press, and our unpublished many quite bizarre, and their domain is that of time indicating both the data), while at the same the deep cave. further study may pro- practical benefits that Troglophiles are facultative cavernicoles that scientific and conservation vide, and the high commonly live and reproduce in caves, but are delicate ecosystems. values of these not totally confined to them; they may be found in similar sheltered, cool, dark and humid background General epigean microhabitats. Trogloxenes are occasional cavernicoles that The deceptive first impression that caves are regularly inhabit caves, usually near the depauperate is based on a combination of the refuge and a favourable microcli- small size of many cave organisms, their fre- entrance, for quently sparse distributions, and their cryptic mate, but must periodically return to the surface at night. Such animals often nature^ since animals more frequently occur in to feed, usually direct access to both the epigean and the smaller cracks, crevices, and folds of cave require environments in order to survive. formations to which human access is severely hypogean

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Accidentals are surface animals which wan- ensured the 's survival during the rapidly der, fall, or are washed into caves, but cannot fluctuating conditions of the Pleistocene survive there. (Goede, 1967). Examples of the first three of these groups are In contrast, very little has yet been discovered presented in the following section. about the troglobitic amaurobiids (Family Amaurobiidae), which inhabit deeper parts of Components of the Tasmanian cave fauna the cave not prone to external seasonal influ- ence. These do not spin webs, but wan- The cavernicolous fauna of Tasmania consists of der widely, although they may display some five major phyla, Platyhelminthes, Nemertini, degree of territoriality (our unpublished data). Aschelminthes, Annelida, and Arthropoda, with The amaurobiids are often locally abundant, the , crustaceans, and insects being and the juveniles at least are depigmented and particularly well represented (Eberhard et al., display some degree of eye reduction (M. Gray, 1991). Ninety percent of the recorded Tasman- pers comm.). ian cave genera are , and most of the cave obligate species belong to this phylum. In A mph ipods (Malacostraca) the course of numerous cave studies and surveys Several genera and species of troglobitic carried out by the authors, the following groups amphipods in the Superfamily Crangonyctoidea have received particular attention. inhabit streams and pools in Tasmanian caves. The stream dwelling Antipodeus sp. (Family Spiders (Araneae) Paramelitidae), the generic placement of which Tasmanian caves support an interesting and is currently under review (W.D. Williams, pers diverse spider fauna, including Hickmania trog- comm.), is a stygobiont: an obligate groundwater lodytes (the Tasmanian Cave Spider) which is a dweller, or aquatic troglobite. It is found at sev- troglophile, and an un-named amaurobiid eral sites in northern Tasmania, including Little spider, which is a troglobite. Trimmer Cave at Mole Creek (see follow ing sec- Hickmania troglodytes (Family Austrochili- tion). In contrast to terrestrial troglobites, this dae) is the largest spider in Tasmania, with a Species displays distinct seasonal tendencies, leg-span of up to 18 cm when fully grown, and and its lifecycle appears to be almost directly constructs a web of up to 1 20 by 60 cm. Endemic dependent upon the yearly changes in stream to Tasmania, and the only known species in the flow. Mating occurs from late-winter to spring, , /-/. troglodytes is of high systematic and and over the summer months the amphipods zoogeographic interest. Its closest relatives live may display protective burrowing behaviour in Chile and Argentina, and it is of considerable prior to stream drying (our unpublished data). evolutionary significance as it possesses major This burrowing allows the amphipods to survive physical traits of both the primitive (liphistio- seasonal dry spells, and appears to be triggered morph and mygalomorph) and advanced (ara- (perhaps by increasing calcium concentrations neomorph) spider groups. While the species is in the water) before the pools dry. These amphi- no longer considered a direct evolutionary link pods generally feed on detritus that is carried in between these groups, it is considered one of the by the stream, although different size classes closest araneomorphs to the ancestral spider appear to have their own preferences amongst type from which thev all diverged (Marples, the selection that this material offers. 1968). Hickmania troglodytes builds large pear Crickets (Orthoptera) shaped egg sacs which hang from the roof and Cave crickets (Family Rhaphidophoridae) are sides of the cave. The young take approximately easily the most common trogloxenes in Tas- nine months to emerge from these sacs, a period mania, the two main genera being Micropathus significantly longer than the one to two months and Parvotettix. While species from both genera typical of epigean spiders, and their lifespan may may inhabit the same cave, species from the cover decades (Doran, unpublished data). The same genus appear not to coexist (Eberhard et egg sacs themselves are of intricate internal al., 1991). Micropathus species are most com- design and are highly resistant to fungal growth, mon in the moister western and southern parts which can over-run other organic materials in of Tasmania, where they are established in large caves in a matter of days or even hours. A very colonies, and the distribution and derivation of ancient member of the Tasmanian fauna, //. the species-complexes may have been influ- troglodytes' stronghold is the twilight and tran- enced by Pleistocene glaciation (Richards, sition (early) zones of caves, which may have 1971a). Cave crickets are generally omnivorous, BIODIVERSITY AND CONSERVATION IN TASMANIAN CAVES 651 and leave the cave at night to feed on forest floor yielded over 55 taxa (Houshold and Clarke invertebrates and materials (Barr, 1968), 1988). although they may also prey on juvenile spiders within the cave (our unpublished data). To adult Comparisons with temperate mainland spiders, beetles and other animals, the crickets Australia provide a major source of food input to the cave, Few data have been published for caves in tem- either directly as prey, or through their drop- perate mainland Australia, but the literature pings and eggs. The latter are buried in silt banks includes over 6 troglobites from the Nullabor of the deep cave, and possibly provide the sole Plain (e.g., Richards, 1971b; Knott, 1983), at food source for troglobitic beetles specially least 6 more from five cave areas in Victoria adapted to retrieve them. (Davey and White, 1986), 2 troglobites and 5 troglophiles from Wombeyan Caves (Smith,

Major sites and regions examined 1 982) and 2 species of troglophile from Bun- gonia Caves in New South Wales (Wellings, In the Mole Creek region of northern Tasmania, 1977), and 25 species of aquatic cavernicole 71 invertebrate taxa have been recorded from from a cave at Yanchep in Western Australia Kubla Khan and Genghis Khan caves (although the number of stygobiontic species is (Eberhard, 1990b), including 3 species each of not given; Jasinska and Knott, 1991). Against flatworms and springtails, 5 species each of these figures, it would appear that Tasmania is annelids, myriapods and molluscs, 6 species of comparatively rich in troglobitic diversity. crustaceans, 21 arachnids and 23 insects.

1 of these species were acciden- Although about 9 Conclusions tals, at least 1 1 , and possibly more, are troglo- bitic. The diversity of species recorded here is by While data currently show that Tasmanian caves far the highest for any single Tasmanian cave support substantially higher biodiversity than (Eberhard et al. 1991). caves in temperate mainland Australia, such Precipitous BlufF, far southern Tasmania, comparisons will remain rather crude until sam- supports the richest assemblage of cave obligate pling strategies and sampling intensities can be species presently known in temperate zone Aus- in some way standardised, and until all karst surveyed. However, Tasmania tralia, with at least 1 5 troglobitic or stygobiontic areas have been species recorded among a total cave fauna of is likely to remain an extremely rich source of some 32 (+ +) species (Eberhard et al., 1991). cave fauna, whose age and diversity is related to This area has the most highly cave adapted rep- the geology and geomorphic history of the karst resentatives in several animal groups, including systems in which it is found. outside amphipods, beetles, molluscs, and harvestmen, As caves are entirely dependent on while the hydrobiid mollusc and opilionid (har- sources for their energy input, and as their vestmen) faunas are particularly notable for the environments are slow to change and/or predict- vulnerable to diversity of species represented. able, these ecosystems are highly at some Ida Bay, far southern Tasmania, has 31 external events, which may even occur recorded cavernicolous species including 5 tro- distance from the caves themselves. Two major cricket guano and water globites (21% of the fauna) from one survey sources of food input, risk from land use practices (Richards and Oilier, 1976), and 30 species carriage, are at high (Eber- that affect surrounding forest and water quality. including 1 1 troglobites (36%) in another disruption of How levels into the cave, hard, 1990a). These figures exclude accidental Even the an increase or decrease, can have or surface fauna, and cover such groups as the whether by effects on the cave fauna. While opilionids, pseudoscorpions, aranaeids, crus- devastating levels fluctuate enormously during taceans, collembolans, hemipterans, and coleop- water may normal yearly cycle, this is generally predict- terans amongst others (Eberhard et al., 1991). the Mount Anne (southern Tasmania) and Mount able, and exceptionally severe conditions during are not as potentially cata- Ronald Cross (central to western Tasmania) the normal season species strophic as relatively minor floods occurring at support at least 5 and 3 troglobitic unusual times, or even the absence of floods at respectively (Eberhard, 1987, 1989), while at the expected time (Howarth, 1983). Bubs Hill (western Tasmania) at least 6 definite More direct effects arc also important. Caves troglobites and 6 other taxa of uncertain status heavily affected by quarrying, rubbish have been recorded (Clarke 1989). Including may be has dumping, the in-filling of entrances or clearance accidentals, one cave in the Bubs Hill karst 652 N.E. DORAN

minimal. of surrounding land. Visitors are also a signifi- and release, the impact on the fauna is party cant potential source of disturbance, and some Records are also kept of the date, duration, cave inhabitants and habitats are particularly number, and course taken through the cave for the cave vulnerable to them (Richardson et al., in press). each visit, so that the impact on Indirect disturbance alone, such as light or environment of even these few visits can be movement, can disturb cave spiders and disrupt assessed. courtship and mating. Spiders may desert their The benefits of this monitoring strategy have found egg sacs if disturbed frequently, which probably been many. Little Trimmer Cave has been accounts for the rarity of these animals in tourist to contain a rich invertebrate fauna in keeping caves. Seepage pools supporting rare syncarid with that observed in other areas of the state, shrimps (Family Psammaspididae) can be and this diversity is due, at least in part, to the destroyed by a single careless footstep, as can silt wide variety of substrates and consequently banks which support many of the small terres- habitat types within the cave. Through the mini- trial invertebrates deep in caves. The cave mal impact nature of our program, these animals environment is a very special, fragile habitat, and habitat types have been able to be studied in into which even scientific visits should be care- an essentially undisturbed state, and this fully regulated to reduce potential, and very real, approach has yielded much valuable infor- impacts. mation. The species presented as examples in this paper are present in large numbers in Little Trimmer, and much of the new information Future directions: the Little Trimmer Cave reported has come about as a direct result of the Biological Monitoring Program — a model Little Trimmer program. The slow rate of cave study biological processes means that long-term, A faunal study designed to be of low impact was intensive studies are essential for comprehend- specifically formulated for Little Trimmer Cave ing the ecology of cave organisms, and the nine

at Mole Creek, Tasmania, in 1 990. This program month incubation period and apparent lon- was established at the cave at the beginning of gevity of the Tasmanian Cave Spider in particu- 1991 and is still ongoing today. lar demonstrate how ideal an opportunity the Little Trimmer Cave is a well decorated, Little Trimmer program presents. stream bearing cave of reasonable length (the In view of the success of the Little Trimmer major passage is approx. 200 m). Situated in study, we fully endorse the 'sampling with

State forest, it has been gated by the Tasmania replacement' recommendations of Slaney and Forestry for several years, so that access is lim- Weinstein (at this conference), and believe that ited to facilitate scientific studies in an undis- such low impact, non-collection studies are the turbed hypogean environment. Visits are regular way forward in biospeleological research. We and infrequent (ranging from monthly to believe that the Little Trimmer program is an bimonthly), visitor numbers are restricted, and excellent example of how data collection can be studies are designed around conservation of the optimised yet at the same time balanced against cave environment and its fauna. Movement the needs of faunal conservation. through the cave is kept smooth and quiet to minimise disturbance due to noise and sudden Acknowledgements vibration, and in all but the most carefully con- sidered cases the introduction of any foreign Parts of the work reported here were supported matter, particularly organic, volatile, or odor- by grants from both the Australian Research iferous substances which may attract or repel Council and the National Estate Grants cavernicoles, is avoided. Pathways are marked Program. Thanks are also given to the Forest by string to reduce the area exposed to disrup- Practices Unit of Forestry Tasmania, for kindly tion by researchers traversing the cave, and the offering and allowing us continued access to the greatest care is taken to avoid even the smallest closed environment of Little Trimmer Cave. animals and cave formations on and above these paths. Substrate Protection Zones are estab- lished thoughout the cave to preserve the more References types, fragile habitats and subcommunity and Barr, T.C.. 1968. Cave ecology and the evolution of study of the fauna is conducted by census, mark- troglobites. Evolutionary Biology 2: 35-102. strict ing, and careful observation. With a Clarke. A.. 1 989. Faunafrom the cases and karsts ofthe regime of capture, measurement, description Bubs Hill area. Western Tasmania. From a report .

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