Herpetofaunal Species Abundance, Richness, and Diversity in a Dry Tropical Forest and Agricultural Matrix at the Sakaerat Biosphere Reserve, Thailand
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Herpetological Conservation and Biology 13(3):586–597. Submitted: 9 November 2016; Accepted: 21 October 2018; Published: 16 December 2018. HERPETOFAUNAL SPECIES ABUNDANCE, RICHNESS, AND DIVERSITY IN A DRY TROPICAL FOREST AND AGRICULTURAL MATRIX AT THE SAKAERAT BIOSPHERE RESERVE, THAILAND MATT S. CRANE1, COLIN T. STRINE1, TYLER K. KNIERIM1, TAKSIN ARTCHAWAKOM2, AND PONGTHEP SUWANWAREE1,3 1School of Biology, Institute of Science, Suranaree University of Technology, 111 University Avenue, Muang, Nakhon Ratchasima, Thailand 30000 2Sakaerat Environmental Research Station, 1 Moo 9 Udom Sab Subdistrict, Wang Nam Khiao District, Nakhon Ratchasima, Thailand 30370 3Corresponding author, email: [email protected] Abstract.—With ongoing rapid anthropogenic deforestation and habitat degradation, it is critical that we understand the role of human-disturbed areas in conserving the biodiversity of the world. Despite intensive deforestation in Southeast Asia, there are few studies investigating faunal communities in human-modified landscapes there. We assessed herpetofauna in dry dipterocarp forest, disturbed forest, and Eucalyptus plantations in the Sakaerat Biosphere Reserve of Thailand. In May and June of 2015, we conducted surveys using 12 passive trapping arrays with funnel and pitfall traps. We captured 436 individuals representing 38 species, with 266 amphibians (13 species) and 170 reptiles (25 species). The Eucalyptus plantations and highly disturbed forest sites hosted higher amphibian abundance and richness than protected areas of dry dipterocarp forest. Reptile species richness did not differ between habitat types, but capture rates in the Eucalyptus plantations were significantly higher than in the dry dipterocarp forest. Funnel traps yielded significantly higher reptile capture rates than pitfall traps. For reptiles, the results support other studies, which have concluded that reptiles are less sensitive than amphibians to disturbance and possibly positively affected by human disturbance in some cases. The terrestrial amphibian abundance and species richness documented here indicate that disturbed habitats may provide suitable areas for these species. Key Words.—degraded forest; dipterocarp forest; herpetofaunal survey; human disturbance; passive trapping; Southeast Asia INTRODUCTION Stibig et al. 2014). Replacing forests with other land use types is detrimental for many taxa (Kwok and Corlett Loss of species in species-rich tropical regions is 2000; Sodhi et al. 2004). Conservationists, however, one of the greatest threats to global biodiversity loss are only beginning to understand the underlying as these areas undergo extensive deforestation, losing mechanisms for this in a few well-studied taxa, such large swaths of forested land each year (Brooks et al. as birds (Hsu et al. 2010), mammals, and invertebrates 2002; Bradshaw et al. 2009). Human-dominated land (Trimble and van Aarde 2012). Herpetofauna are in use types, such as plantation forests and agricultural need of intensive conservation effort as these taxa developments, are rapidly replacing natural forests are facing global declines resulting from a variety of (Rudel et al. 2005; Wright 2005). The conversion of factors, such as habitat loss, spread of invasive species, forests to agrarian lands has left mosaics of small forest overcollection of naïve fauna (Gibbons et al. 2000), patches surrounded by a mixture of anthropogenic climate change (Reading et al. 2010; Araújo et al. land uses (Saunders et al. 1991). These changes are 2006), and pandemic disease (Alford 2011; Lips et al. important because land use composition significantly 2005). Despite the severity of threats faced by many influences the structure of tropical species assemblages herpetofaunal taxa, Böhm et al. (2013) described one in found within disturbed habitat patches (Urbina-Cardona five reptilian species as Data Deficient using IUCN Red et al. 2006). List categories, with tropical species being among the Southeast Asia has among the least remaining forest most deficient. cover of all of the historically forested tropical regions Research on the impacts of replacing forests with (Achard et al. 2002; Laurance 2007) yet continues to plantations or other land uses is plentiful for temperate experience high rates of deforestation (Sodhi et al. 2004; regions (Trimble and van Aarde 2012). The studies Copyright © 2018. Matt S. Crane 586 All Rights Reserved. Crane et al.—Herpetofaunal community at the Sakaerat Biosphere Reserve, Thailand. FIGURE 1. Map of Thailand with the location of the Sakaerat Biosphere Reserve (left) and the land use provided by the Thai Land Development Department (2004) for the study area with sampling sites (right). (Map created by Mathew S. Crane) have produced varied results. While some studies argue diversity from disturbance (Kaensa et al. 2014) and that there are detrimental impacts upon herpetofaunal another finding higher amphibian abundances in highly diversity (Faria et al. 2007; Gardner et al. 2007; disturbed agricultural habitats (Phochayavanich et al. Wanger et al. 2010; Kurz et al. 2014), others suggest 2008). We aimed to further elucidate the impacts of that plantations are capable of housing herpetofaunal forest degradation in Thailand by comparing reptile communities similar in composition to those in and amphibian assemblages between protected and primary forests (Germano et al. 2003; Fredericksen degraded forest habitats in the northeastern part of and Fredericksen 2004; Folt and Reider 2013). Others the country. We also aimed to further address the suggest that these changes may have a positive influence knowledge gap concerning the diverse reptile and on amphibian diversity by maintaining forest cover amphibian communities in Thailand using standardized through the conversion to plantation forests (Vonesh passive trapping techniques across both protected 2001; Fredericksen and Fredericksen 2002). and degraded habitats. We hypothesized that forest The lack of consensus in the literature highlights the degradation affects species diversity and we predict that need for more studies to help determine the causes for more degraded forest habitats would have relatively the wide range of herpetofaunal community responses to lower amphibian abundance and species richness with land use change. There have been relatively few studies little to marginal influence of the habitat degradation on in Southeast Asia concerning herpetofaunal community reptiles compared to non-degraded forests. composition and land use changes (Wanger et al. 2010; Sung et al. 2012). It is critical to assess the conservation MATERIALS AND METHODS value of plantation and remnant forests for herpetofaunal communities in Southeast Asia to construct a broad set Study site.—We conducted the study within the of policy guidelines targeting land use management. Sakaerat Biosphere Reserve (SBR) located in Nakhon In Thailand, several studies have investigated Ratchasima Province, Thailand (14.44–14.55°N, herpetofaunal diversity along elevation (Kongjaroen 101.88–101.95°E). The reserve has an 80 km2 protected and Nabhitabhata 2007; Phochayavanich et al. 2010) Core Area, surrounded by a 360 km2 belt, comprised of and disturbance gradients (Konlek and Lauhachinda the Buffer and Transitional Zones (Fig. 1). The forested 2008; Kaensa et al. 2014), as well as between habitats areas occur predominately in the Core and Buffer Zones, (Inger and Colwell 1977; Suttanon and Lauhachinda which consist of primary-growth dry evergreen forest, 2008). The studies showed contrasting results with dry dipterocarp forest and secondary reforestation one study showing a negative impact on amphibian (Trisurat 2010). The Transition Zone comprises nearly 587 Herpetological Conservation and Biology double funnel traps measuring 2 × 0.5 × 0.3 m at the end of each fence line in the array. We placed a 40 L pitfall trap, extending 36 cm deep into the soil from the surface at the midpoint of each line for a total of three pitfalls per array. Additionally, we attached six double- chambered funnel traps to the center of each array for a total of 12 funnel traps and three pitfall traps (Fig. 2). To avoid flooding during rains, we drilled holes into the base of each pitfall trap. We fitted pitfall bases with a sheet of screen wire to prevent blockages and animals from escaping through the drainage holes. To reduce capture mortalities from exposure, we constructed shade covers over the traps from plastic mesh tarps affixed to bamboo stakes. We placed sponges in the second compartment of each funnel trap and in the pitfall traps to avoid desiccation for sensitive taxa. During sampling periods, we checked traps early in the morning to reduce the exposure of a captive to extreme temperatures. We sampled in May and June of 2015 to assess FIGURE 2. Passive trapping array showing the line (A), wings (B), herpetofauna. May had slightly higher average and traps (C and D). (Photographed by Mathew S. Crane) temperatures (26.3° C) and less rain (8.55 mm) compared 82% of the Reserves total area and is characterized by to June (25.6° C; 79.25 mm). Each month, we opened isolated forest fragments in a patchwork of agricultural a group of six plots (two from each habitat type) for 3 d fields, small plantation forests, and human settlements. before switching to the second set of six plots for a total of 6 d/mo. However, one of the PLE sites was destroyed Site selection and herpetofaunal sampling.— after the first sampling period in May, which created an We assessed