Herpetofauna of Nusa Penida (Asad, 2012)

In 'The Herpetofauna of Nusa Penida, Indonesia', various expert authors report their findings on the amphibians and reptiles on Nusa Penida, published in 2012, revised and published online in 2014, by Sami Asad (1), J. Lindley McKay (2,4) and Agus Pradana Putra (3), refer to sources below. Additional observations by Godi Dijkman in square brackets.

Abstract

The Nusa Penida group, three islands lying offshore of Bali, Indonesia, were systematically surveyed for the first time on behalf of the Friends of the National Parks Foundation, using timed searches in representative habitats. Ten species were newly recorded for the islands. In combination with previous data we record a total of 3 anurans, 11 lizards and 14 snakes. The herpetofauna is very strongly related to that of Bali, sharing only one species exclusively with Lombok and islands further east, the fossorial lizard Dibamus taylori. Richest habitats from a herpetological standpoint are remnant tropical rainforest and semi-deciduous forest, and these are priorities for conservation efforts.

Table 1. Location and habitat details of the sites surveyed on Nusa Penida in 2011

Site nr. Site name Altitude (m) dpl Habitat type Vegetation composition Vegetation diversity Anthropogenic disturbances Soil quality
1 Penangkidan 203 scrub Acacias, palms, grasses moderate moderate low - moderate
2 Penida 19 wetland predominantly aquatic vegetation, lilies, mangrove trees, palms high low high
3 Sebunibus 147 tropical semi-deciduous forest/scrub deciduous trees, vines, ferns, palms, Acacias moderate - high moderate moderate
4 Toyapakeh 13 plantation palms low high low
5 Ped 7 plantation/scrub Acacias, palms moderate moderate moderate
6 Pilah 182 plantation/tropical semi-deciduous forest deciduous trees, palms, Acacias moderate moderate moderate
7 Batumulapan 6 plantation palms low high low
8 Karangsari 35 tropical semi-deciduous forest deciduous/evergreen trees, Acacias, ferns, vines high low high
9 Sumaya 8 scrub/plantation Acacias, palms, grasses moderate moderate poor
10 Pejukutan 245 tropical semi-deciduous forest deciduous/evergreen trees, Acacias, vines, ferns high low high
11 Tanglad 442 savannah predominantly grasses, Acacias, palms low moderate low
12 Sekartaji 234 scrub/plantation Acacias, palms, grasses moderate - high high moderate
13 Sebuluh 195 scrub/ tropical semi-deciduous forest deciduous/evergreen trees, ferns, vines, Acacias high low high
14 Tembeling 259 tropical rain forest predominantly evergreen trees, deciduous trees, ferns, vines, palms, Acacias high low high
15 Mundi 530 tropical semi-deciduous forest deciduous/evergreen trees, ferns, vines, Acacias high low high
16 Pangalan 288 plantation/ tropical semi-deciduous forest deciduous trees, palms, Acacias moderate - high moderate moderate
17 Soyo 444 savannah predominantly grasses, Acacias, palms low high low

[NB. above table in current publication omits 'Location']

Introduction

(p.2) The Nusa Penida group lie at –8.7389°, 115.5402°, 14km SE of Bali, Indonesia, and are administered as a branch of Bali's Klungkung regency. The largest of the group is Nusa Penida island, around 207 sq km, comprised mostly of rolling hills, with a highest point of Gunung Mundi at 529 m asl, a narrow northern low coastal strip and cliffs to the south. Nusa Ceningan and Nusa Lembongan, nestled against their sibling's northeast corner, are a fraction of the size and have a similar geography on a smaller scale. Despite their proximity to volcanic Bali, the group are coralline islands. Their calcareous geology, coupled with comparatively low annual rainfall, make the soils very dry and the habitats relatively barren (Giambelli 1999), and the semi- deciduous forests which once covered most of the islands (Whitten et al 1996) have largely been cleared for agriculture. Tree-felling began 4oo+ years ago, by exiled convicts supplying timber to the mainland (Giambelli 1999). Surviving mature forest is confined to valleys and ravines which have proved too difficult or costly to exploit (McKay 2006a).

The known flora and fauna are Wallacean transitional assemblages with the majority of taxa being of the South East Asian Assemblage and secondarily species of Lesser Sundanese affinity. Bali and neighboring Lombok represent the eastern range limit of many Asian species and the western limit of a number of Lesser Sundanese organisms (Jonsson. et.al. 2008). Smaller size and limited mature habitat suggests Nusa Penida harbours a small subset of the Bali-Lombok taxa. To date the wildlife of Nusa Penida has been poorly documented and there is no definitive species database, an essential tool for future studies and the implementation of conservation programs. Previous herpetological research (McKay 2006a) provides some information on species presence in a handful of areas. With the assistance of the Friends of National Parks Foundation, a conservation NGO recently lauded for success in re-establishing a wild population of the Bali Starling, Leucopsar rothschildi, and establishing an island-wide protected bird sanctuary under traditional law on Nusa Penida island, we aimed to conduct a more comprehensive assessment of the herpetofauna richness and habitat associations on Nusa Penida, the overall objective being to not only create a herpetofauna database, but provide a better understanding of the islands' biodiversity.

Methods

17 vehicle-accessible sites were established across Nusa Penida island, each comprising a transect of approximately 500m. Coordinates and elevation were logged with a Garmin Etrex GPS 12 Channel unit. Sites were distributed across six major habitats: scrubland, with a high diversity of Acacia spp, other shrubs and small deciduous trees; savannah, characterized by large quantities of grasses with little other vegetation except some Acacias and palms, and no 3+m trees; plantation, areas of active agricultural activity with crops including bananas, palms, cassavas, corn and chillies, most often in monocultures; tropical semi-deciduous forest, comprising mostly deciduous trees, some intermittent evergreens and thick fern and shrub ground layers; tropical rainf orest, diverse communities of primarily evergreen trees, deciduous trees, shrubs, ferns and epiphytes; and wetland, a freshwater spring with diverse aquatic plants.

At each of these sites (p.3) anthropogenic disturbance was scored in three categories: further than 150m from an anthropogenically disturbed area – Low; within 150m of anthropogenically disturbed area – Moderate; site positioned within anthropogenically disturbed area– High. Soil quality was also scored in three classes: less than 3cm/little or no organic matter – Low; 3-5cm / intermittent organic matter – Moderate; >5cm/predominantly organic matter – High. During Aug-Sep 2011 each site was visited three times (morning/afternoon/night), and walked for a duration of approx. 2 hrs, followed by searches of specific micro-habitats, recording any herpetofauna encountered. This method may not discriminate smaller or more agile species glimpsed momentarily by the observer who may not be experienced in differentiating between sibling species, in such case genus/species group was recorded.

The data was combined with records collected by JLM in 2002, 2007 and 2010, the results of opportunistic day/night searching on foot and vehicle, mostly in preparation for subsequent field guides (McKay 2006a, 2006b). We then comment on species richness in comparison to the known Balinese-Lombok fauna, and draw inferences for the significance of Nusa Penida's herpetofauna and remaining habitat to conservation efforts on the islands.

Results

The visual transects yielded 3 amphibian and 22 reptile species. 10 species are newly recorded for the Nusa Penida group (2 frogs, 1 lizard and 7 snakes). The maximum number of taxa recorded in a site was 10, from site 14, a relatively undisturbed tropical rainforest gully. Tropical semi-deciduous forests, and tropical semi-deciduous forest associated with scrub, yielded the next highest richness of taxa, between 9 and and 7 taxa per site. Other habitats yielded a moderate number of species; the lowest diversity was from the savannah and wetland sites with zero or a single species. As could be expected, sites with greatest species richness had correspondingly high organic soil content and low anthropogenic disturbance.

Of the amphibia, Duttaphrynus melanostictus was by far the most prevalent, not only detected in the study areas but also observed throughout the island between sites. Polypedates leucomystax was found at only two sites, in tropical semi-deciduous forest/scrub, and tropical rainforest. Fejervarya cancrivora occurred only in the wetland.

With the exception of Varanus salvator bivittatus, all the lizards on Nusa Penida are small insectivores, with four Gekkonidae, three Scincidae species and one Dibamid. The three most widespread and abundant are Gecko gecko, Cyrtodactylus fumosus and Eutropis multifasciata, which all inhabited a wide range of habitats throughout the island. Cyrtodactylus fumosus appeared to be the most abundant of these, and was highly detectable as a result of its active terrestrial lifestyle. Hemidactylus frenatus and H. platyurus were found predominately around human habitation, hunting invertebrates around artificial lights. Lygosoma bowringii and Eutropis rugifera were found at various sites throughout the island where deep leaf litter was accumulated. Dibamus taylori was found at only two sites (both tropical semi-deciduous forest) in subterranean (p.4) microhabitats. Dibamus taylori presents an interesting case as it was the only specimen found during the study which is not a part of the south-east Asian assemblage. Dibamid taylori is a lesser Sundanese species, inhabiting the seasonally dryer areas of eastern Indonesia and New Guinea (Hallerman 1998). Our D. taylori specimens conformed with anatomical characteristics of other populations in their range.

Thirteen species within four families of snake were recorded. Despite this high diversity, few species were recorded regularly, with the majority of observations made of single individuals. Three species measuring over a metre were found during the study, Naja sputatrix, Pytas korros and a large unidentified colubrid. Snake records came almost entirely within tropical semi- deciduous and rain forests and their adjacent habitats. The most abundant and widespread species were Dendrelaphis pictus, Ramphotyphlops braminus, Lycodon aulicus capucinus and Lycodon subcinctus. These, with the exception of Ramphotyphlops braminus, are active foragers, which no doubt increases their detectability. Ramphotyphlops braminus is the most ecologically distinct of NUSA PENIDA's snakes, its ecology and morphology more closely resemble that of Dibamus taylori than any of the other snake species. Specimens of this fossorial nocturnal snake were only found via microhabitat searches.

Table 2. Herpetofauna recorded at the 17 sites surveyed on Nusa Penida in 2011 (data collected on behalf of the Friends of the National Park Foundation).

Order: Sub order Family Species Site                  
      1 2 3 4 5 6 7 8 9 10
Anura Bufonidae Duttaphrynus melanostictus x x x x - - - - - -
  Dicroglossidae Fejervarya cancrivora - x - - - - - - - -
  Rhacophoridae Polypedates leucomystax - - x - - - - - - -
Squamata: Lacertilla Dibamidae Dibamus taylori - - - - - - - x - -
  Gekkonidae Crytodactylus fumosus x x x x - x x x x x
    Gekko gecko x x x x x x x x x x
    Hemidactylus frenatus x - x - - - x - x -
    Hemidactylus platyurus - - - x x - - - - -
  Scincidae Eutropis multifasciata x - x - x x - x x x
    Eutropis rugifera - - - - x - x - - -
    Lygosoma bowringii - - - - - - - - - x
  Varanidae Varanus salvator x x - - - - - - - -
  Colubridae Ahaetulla prasina - x - - - - - - - -
    Boiga multomaculata - - - - - - - x - -
    Coelognathus radiatus - - - - x - - - - -
    Dendrelaphis pictus - - x - x - - x - -
    Lycodon aulicus capucinus - - - - - - - x - -
    Lycodon subcinctus - - - - - - - x - x
    Pareas carinatus - - - - - - - - - x
    Psammodynastes pulverulentus - - - - - - - - - -
    Pytas korros - - x - - - - - - -
    Rhabdophis chrysargos - - - - - x - - - -
  Crotalidae Cryptelytrops insularis - - - - -   - - - x
  Elapidae Naja sputatrix - - x - - - - - - -
  Typhlopidae Ramphotyphlops braminus - - - - x - x - x x
Total     6 6 9 4 7 4 5 8 5 8

Discussion

The results of this study form the most definitive herpetofauna list for the Nusa Penida group. Our recent fieldwork increases the known number of species present by 55%, and to date 4 anurans, 11 lizards and 14 snakes are known from Nusa Penida. Indonesian herpetofauna in general is very poorly known and even the most intensively studied areas, such as Bali, are still underestimated in terms of diversity (McKay & Lilley 2012). We expect future work to uncover the presence of more taxa on Nusa Penida, and the use of traps and surveys in varying seasons would likely be fruitful.

From our data we infer the composition of Nusa Penida's herpetofauna to essentially be frogs adapted to xeric habitats, and close-canopy forest squamates. None of the taxa associated with relictual drier open woodland are recorded, such as Python molurus or Psammophis condanarus. This fits with our understanding of modern pre-agricultural Nusa Penida as receiving low and highly seasonal rainfall, and being covered with tropical semi-deciduous and evergreen forest.

In comparison with its close and grander neighbour Bali, Nusa Penida is predictably a smaller subset of (with one exception) the same fauna. Approximately half of Bali's squamates are known from Nusa Penida (11 vs 21 lizards, 14 vs 32 snakes); and only a third of Bali's frogs (4 vs 13 species). Amphibian diversity on Nusa Penida is likely to have been historically depauperate, as the island receives significantly lower rainfall than mainland Bali, coupled with calcareous soil of little to no water holding ability, meaning streams run only for a short period after heavy rainfall (McTaggart 1989).

Penida was the only wetland habitat found on (p.7) the island, with other bodies of water being significantly smaller and of lesser quality. As such, the habitat is also unsuitable for freshwater turtles and none of three turtles known from Bali are recorded on Nusa Penida. We observe that many large forest snakes are noteably absent on Nusa Penida, species such as Ptyas mucosa, Gonyosoma oxycephalum and Bungarus candidus, and postulate that the size of Nusa Penida is not great enough to support a richer assemblage of high-ranked predators. Scrutinising the fauna of Lombok absent from Nusa Penida we find that taxa associated with the Lesser Sundas, including Lamprolepis smaragdina, Cyrtodactylus darmandvillei, Ramphotyphlops polygrammicus and Coelognathus subradiatus (de Lang 2011, Mertens 1930) have not colonised Nusa Penida.

The only exception is Dibamus taylori, known from Lombok and further east, but not Bali. Biogeographic barriers in the faunal transition zone termed Wallacea have been much discussed (eg How et al 1996b, Kitchener & Suyanto 1996), and the effects of changes in sea level, sea beds, and land masses in the Sundas is complex and far from precisely known (see Auffenberg 1980). That some taxa, including large mammals such as pygmy stegodonts, dispersed eastwards into the Lesser Sundas, yet reptiles of Lesser Sunda affiliation have almost entirely failed to disperse west beyond Lombok suggests climatic factors are more important and/or these taxa have evolved in recent times, when the Lombok Strait has been an effective barrier (eg How et al 1996a). The presence of Dibamus taylori on Nusa Penida is yet another demonstration of the region's complexity of biogeographic evolution.

Evidently the majority of areas on Nusa Penida have been altered by past and present anthropogenic activity. Most habitats are secondary growth, few if any support primary vegetation. This lack of forest is attributed to felling activity initiated by convicts exiled to the island by the king of Bali more than four centuries ago, after which regrowth has been severely hindered by further felling, agricultural activity and the islanders "slash and burn" farming practices (Giambelli 1999). The result has been fragmentation of the island's former forests, with remaining areas serving as biodiversity "islands" for Nusa Penida's wildlife and housing the greatest remaining reptile and amphibian species richness. It is likely that they also harbour the richest caches of mammals and other vertebrate families.

Therefore these reservoirs of diversity, in particular the sites at Karangsari, Tembling, Pejukutan and Mundi, are of high value for conservation. However, quantifying species richness is only one way of calculating biodiversity, for example Schmidt et al (2000) found Nusa Penida populations of Eutropis multifasciata to be the most genetically divergent within the Lesser Sundas. Generalist species occupying a wide range of habitats, such as Eutropis multifasciata, Gecko gekko and Crytodactylus fumosus, are a notable biomass and their management should not be ignored, as can be seen in the recent many-fold increase in Gecko gekko harvest for the medicine trade, a trend which easily results in local extinction (Caillabet 2011).

Acknowledgments

Many thanks to the FNPF (friends of the national park foundation). In particular CEO and founder Dr. Gede Nyoman Bayu Wirayudha and FNPF's Nusa Penida base manager Mike Appleton, who have (p.8) not only made this research possible but have also provided constant support and advice throughout the project. Thanks also to Ben Phillips, Stuart Young, Olya Milenkaya, Andrew Smith and Phillip Pugh for their valuable aid with the manuscript.

1) 28 Forshaws lane, Burtonwood, Warrington WA5 4ES, England; 2) 1/4 O'Connor St, Blackrock 3193, Australia; 3) Jalan Keboiwa, Br.Pagutan, Gapura: 1 No. 1, Denpasar barat, Indonesia; 4) corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

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