Habitat Use and Abundance of a Low-Altitude Chameleon Assemblage in Eastern Madagascar
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HERPETOLOGICAL JOURNAL 17: 247–254, 2007 Habitat use and abundance of a low-altitude chameleon assemblage in eastern Madagascar Jeanneney Rabearivony1, Lee D. Brady2, Richard K.B. Jenkins3,4 & Olga R. Ravoahangimalala1 1Département de Biologie Animale, Université d’Antananarivo, Madagascar 2Durrell Institute of Conservation and Ecology, University of Kent, Canterbury, UK 3School of Biological Sciences, University of Aberdeen, UK 4Madagasikara Voakajy, Antananarivo, Madagascar We studied the density and abundance of chameleons in a lowland Malagasy rainforest during the austral summer and winter. Nocturnal searches for chameleons were conducted along transects within relatively intact forest and vegetation on abandoned agricultural land adjacent to the forest. Four chameleon species were encountered during the study, Brookesia superciliaris, Calumma parsonii parsonii, Calumma nasutum and Furcifer pardalis. Brookesia superciliaris was most common inside relatively intact forest and the few individuals located in the regenerating forest on abandoned agricultural land were found in tiny, isolated patches of degraded rainforest next to rivers. Calumma p. parsonii was only encountered on three occasions in relatively intact forest and was a rare member of the community. The abundance of C. nasutum was highest in relatively intact forest but this species also occurred in vegetation on abandoned agricultural land. Furcifer pardalis was only found on the abandoned agricultural land, where it was observed laying eggs in sandy soil in August. The abundance of all species in habitats alongside rivers was higher in January than July–August, with the exception of C. p. parsonii, which was not detected during the former period. Additional investigations into habitat preference of chameleons and surveys in other forests in region are needed to establish whether the low abundance of C. p. parsonii and the absence of the Brookesia minima group at this site are related to 1) abiotic factors associated with altitude, 2) physical barriers that have prevented dispersal, or 3) the selective logging that occurred at the site until 1993. Key words: Brookesia, Calumma, deforestation, Furcifer, seasonality INTRODUCTION Chameleons from the genus Calumma Gray 1865 are chiefly restricted to the eastern and northern part of the he remaining humid forests of eastern Madagascar island and are usually associated with intact humid forest Tare of international conservation importance as the (Andreone et al., 2005). Calumma are found across a wide last refuges for many forest-dependent vertebrates. altitudinal range, from around sea level to 2800 m above These forests have high herpetofaunal diversity and sea level (Raxworthy & Nussbaum, 1996). Brookesia Gray many threatened species have restricted ranges within 1865 occupies a broadly similar distribution to Calumma, the remaining intact vegetation (Raxworthy, 2003). New although some species are also found in the deciduous species continue to be discovered in these forests and dry forests in the west, at sites where no Calumma occur the amphibian fauna has received particular attention (Raselimanana & Rakotomalala, 2003). Like Calumma, from herpetologists (e.g. Glaw & Vences, 2002; Vences & Brookesia are usually associated with intact forest Glaw, 2004; Vences et al., 2005). (Raxworthy, 1991; Raxworthy & Nussbaum, 1995; Jenkins Interest in the taxonomy and evolution of Malagasy et al., 2003), but some species have been recorded from reptiles (e.g. Raxworthy & Nussbaum, 1995; Raxworthy et degraded habitats (Glaw et al., 1999). Furcifer Fitzinger, al., 2002, 2003) has yet to be complemented by similar ad- 1834 chameleons mainly occur in dry areas and in the east vances in ecology, and basic information on habitat are restricted to open habitats, whilst in the west they are preferences, natural history and population structure re- found inside deciduous forest (Jesu et al., 1999; mains poorly documented for many forest reptiles. Whilst Andreone et al., 2005). some forest reptile groups are notoriously difficult to Lowland (<800 m) humid dense forest is one of the study in the field (e.g. Andreone & Randrianirina, 2000), most threatened habitat types in Madagascar and its ex- conservation-relevant ecological information is compara- tent has been dramatically reduced by agricultural tively straightforward to obtain for chameleons (e.g. expansion in recent decades (e.g. Green & Sussman, 1990; Jenkins et al., 1999; Andreone et al., 2005; Metcalf et al., McConnell et al., 2004). In this study we investigated the 2005; Randrianantoandro et al., 2007). chameleon community in a lowland humid forest to deter- There are 66 species of chameleon in Madagascar and mine which chameleons utilize secondary growth on all are endemic (Raselimanana & Rakotomalala, 2003). abandoned agricultural land adjacent to relatively intact Correspondence: Richard K.B. Jenkins, School of Biological Sciences, University of Aberdeen, Aberdeen, AB24 2TZ. E-mail: [email protected] and [email protected] 247 J. Rabearivony et al. Fig. 1. Map of Ambodiriana forest showing major habitat types, rivers and extent of the private reserve. forest. We also investigated the impact of seasonality on Logging was mainly for commercial purposes to supply chameleon abundance in forests alongside rivers. the local demand for timber products for the construction of pirogues and houses, and mature individuals of the MATERIALS AND METHODS preferred tree species, such as Calophyllum spp., Ocotea The Réserve Privée (R.P.) d’Ambodiriana (16º40'S, spp., Dalbergia spp. and Sideroxylon spp., are now rela- 49º42'E) is within the forest of Ambodiriana, approxi- tively rare in the reserve. Uapaca spp. are infrequently mately 6 km north-west of the Rural Commune of used by people and are now the most common canopy- Manompana (16º41'S, 49º45'E) and 40 km north of the forming tree. The area at the edge of and outside the town of Soanierana-Ivongo, in the province of reserve is subject to chronic degradation and humid for- Toamasina. It is flanked by the Antsahamangarana River est is removed, using the slash and burn technique (tavy to the south and by the Antsalovana River to the east; in Malagasy), and replaced with agriculture for three to altitude varies from 45 to 230 m a.s.l. and the total area is 67 ha. It is divided into two sections by the river Manompana (Fig. 1). Table 1. ANOVA results on vegetation characteristics Field work was conducted in two seasons, the first dur- of relatively intact forest and tavy, winter 2001. Values ing the austral winter (24 July – 25 August 2001) and the are means ± SE. second during the austral summer (5–27 January 2002). Habitat type The climate in R.P. d’Ambodiriana is tropical and humid Relatively Forest on with rain in every month; during the surveys, a total of 116 intact regenerating mm of rain occurred over 29 days in winter, and 115 mm Vegetation forest agricultural over 23 days in summer. Average daily temperature is characteristics (n=20) land (n=20) P around 25 °C in the summer and 20 °C during the winter. Average daily precipitation is approximately 5 mm per day Trees (>1.0 m dbh) 1.5±0.29 0.0±0.00 <0.001 during the summer and 4 mm per day in the winter. Trees (<1.0 m dbh) 15.3±2.01 0.2±0.11 <0.0001 We selected two main types of habitat within the re- Small trees (0.5–2 m) 31.4±3.25 2.0±0.56 <0.0001 serve. The first was relatively intact humid forest (Dufils, % vegetation ground 2003), which had been selectively logged before 1993. cover (<0.5 m) 62.9±4.88 91.7±3.27 <0.0001 248 Low-altitude chameleons in Madagascar Table 2. Abundance (mean±SE) and density (individuals per ha, coefficient of variation in parentheses) of four chameleon species from R.P. d’Ambodiriana, eastern Madagascar during the austral winter. Density calculations were only performed for species with $10 individuals. Sample effort was 32 transects (4.6 km) in the relatively intact forest and 26 (4.1 km) in the forest on regenerating agricultural land. ANOVAs performed on log-transformed abundance counts. Species Habitat type n Density ha-1 Abundance One-way (CV) ANOVA (habitat comparison) Brookesia superciliaris Relatively intact forest 19 7.0 (23.5) 0.42±0.11 F1,56=6.2 Forest on regenerating agricultural land 2 n/a 0.05±0.05 P=0.02 Calumma p. parsonii Relatively intact forest 3 n/a 0.06±0.04 n/a Forest on regenerating agricultural land 0 n/a 0 Calumma nasutum Relatively intact forest 17 4.2 (38.6) 0.37±0.15 F1,56=0.9 Forest on regenerating agricultural land 5 n/a 0.13±0.05 P=0.76 Furcifer pardalis Relatively intact forest 0 n/a 0 F1,56=3.4 Forest on regenerating agricultural land 10 2.0 (63.1) 0.26±0.16 P=0.07 five years before being abandoned. After abandonment, other to the right, taking care to look backwards and to the land cover is replaced by a thick herb layer and a few locate chameleons concealed by foliage from the front. small trees and low shrubs, mainly Lantana camara to a The perpendicular distance between the transect line and height of 1.5 m. We therefore compared the chameleon the chameleon was measured with a 5 m or 10 m tape meas- community in the relatively intact forest inside the reserve ure to the nearest 0.5 cm. Species name and age class with that from the secondary growth in abandoned (1–3 (adult, juvenile, hatchling) were also recorded. Vegetation years ago) agricultural land adjacent to, or just inside, the characteristics in the transect zone were taken the day reserve boundary. following the surveys. No voucher specimens were col- A total of 32 and 26 transects were installed in rela- lected during the study. tively intact forest and regenerating agricultural land To assess vegetation structure in the study site, a sin- respectively during the winter.