Reptile assessment for the Sedibeng sewer pipeline construction

Transcription

1 Reptile assessment for the Sedibeng sewer pipeline construction 09 June 2010 INTRODUCTION AND METHODS A reptile assessment with specific reference to the striped harlequin snake (Homoroselaps dorsalis) was requested for the construction of the Sedibeng sewer pipeline (Figure 1). A general scoping assessment was performed by investigating habitat suitability, connectivity and conservation value. All reptiles species encountered are reported as well as all possible reptile species expected to occur on the site. Harlequin snakes are frequently found in abandoned termitaria where they hunt their subterranean prey (Branch 1998; pers. obs.). Consequently, in order to find these snakes it is fruitful to excavate suitable termitaria (destructive sampling) although care must be taken to prevent the destruction of too many as they often represent a limited refuge resource in the grassland veldt type as shelter is scarce. Only two suitable termitaria were therefore excavated which were situated directly on the proposed pipeline (Figure 1) as it was assumed that these could eventually be excavated by machinery. Sampling these termitaria would provide useful knowledge of the herpetofauna community and any captured individuals could be relocated safely away from the proposed pipeline. All available books providing information on distribution ranges and/or conservation status of South African herpetofauna were utilized to make predictions of occurrence in the area (see reference list). The South African red data book Reptiles and amphibians (Branch, 1988) is outdated. The Southern African Reptile Conservation Assessment (SARCA) is currently taking action to generate a new Red data book but at this time it is still in preparation. Nevertheless, the SARCA website ( makes all species occurrence information available to the public at the quarter degree cell level and this resource was utilized as the most current distribution authority for reptiles (snakes, lizards and tortoises). All records were however cross-checked with behavioural and habitat requirement information from Branch (1998) and Marais (2004) as well as the authors understanding of each species habitat requirements. All reptile records acquired during this study will be submitted to SARCA. The IUCN website ( was utilized to provide the most current account of the conservation status of herpetofauna. RESULTS & DISCUSSION Striped harlequin snakes are listed as near-threatened by the IUCN ( and are not listed in the South African red data book or by NEMBA (2004). These snakes are very secretive and feed exclusively on thread snakes (Leptotyphlops). SARCA does not have any records of occurrence of this species on the quarter degree grid cell 2627DA (through which the proposed pipeline extends) although a record exists for the adjacent quarter degree grid cell 2627DB (Figure 2). Two snake species namely, rhombic skaapsteker (Psammophylax rhombeatus) and Cape centipede eater (Aparallactus capensis) were encountered during the scoping (Figures 3 & 4). These snakes were found during excavation of the termitaria, which represent a significant refuge source for snakes in the grassland habitat. For example 5 snakes (4 A. capensis and 1 P. rhombeatus) were encountered in termitaria 2 (Figure 1). This concentration of individuals strongly suggests that few suitable refuge resources are available in the vicinity.

2 Although striped harlequin snakes have not been recorded for quarter degree grid cell 2627DA (Figure 2) it does not necessarily exclude the possibility that they do occur here. For example, the rhombic skaapsteker captured on site has also not been recorded for this grid cell before (Figure 3). This is clearly a sampling artifact as these snakes are expected to be common in this area. Because the grassland habitat type is extensive it is suggested that the species list from quarter degree grid cell 2627DA and all 8 adjacent quarter degree grid cells represents a more accurate list of expected reptile species to be found on the site. The abundance of snakes found in only 2 termitaria suggests that this habitat is of sufficient quality to support a healthy reptile community despite the fragmented nature of the portion of semi-natural grassland which was surveyed (Figure 1). It is perhaps the lack of available habitat due to intensive agriculture and the presence of roads that has forced all herpetofauna into relatively high densities in the remaining fragmented semi-natural areas. Impacts Direct impacts of pipelines are likely to be limited to disturbance and displacement of herpetofauna during the construction phase. During construction the direct impacts expected are from habitat destruction/alteration from clearance of vegetation and soil excavations for the pipeline and the creation of pipeline servitude roads as well as disturbance and possible mortality from these activities. With appropriate mitigation measures (see below), these unavoidable impacts are unlikely to adversely affect the herpetofauna community in the long term. Indirect impacts are expected to be caused by the presence of a servitude road (if any). This negative indirect impact is of medium- to long-term concern. Once the direct impact from the construction of a servitude has taken place the vehicle traffic on the servitude represents a potential threat to the herpetofauna community since many herpetofauna species are killed by vehicles while crossing roads. Servitude roads may also impair dispersal and increase habitat fragmentation for example, compacted roads may represent a dispersion barrier for strictly fossorial (ground-living) species. Mitigation During the construction phase trained personnel should be present that are capable of removing and relocating unearthed or disturbed herpetofauna. Construction during the night should be avoided. Where possible the pipeline should be kept as close to the road verge as possible as this area is regularly disturbed by mowing and the presence of cars and people and is of little conservation value (Figure 5). Direct impact can be further mitigated by avoiding the unnecessary destruction of termitaria during the construction phase. Any termitaria situated directly on the pipeline route should be excavated in an intact manner (e.g. using a deep bucket back actor) and relocated nearby. The negative indirect impact of servitudes can be mitigated to a large degree. Firstly, all vehicles traveling on the servitudes must do so at very slow speed to allow herpetofauna species to move off the road. Slow speed may be enforced by the construction of speed humps in the road if necessary. Secondly, vehicles must stick to the roads and not drive through the semi-natural vegetation. Finally, since the construction of a new road poses a much greater impact than the upgrading of an existing road the servitude should make use of existing roads wherever possible so that the construction of new roads is kept to a minimum. CONCLUSION & RECOMMENDATIONS Although it is unlikely, striped harlequin snakes may occur on the site. However, if proper mitigation measures are followed as outlined above, both direct and indirect impacts are unlikely to significantly affect the herpetofauna community in the long-term as most species have the capacity to adapt to

3 such changes and will likely only experience short-term disruption. The very small portion of seminatural grassland that the pipeline will extend through on the western side of the highway (Figure 1C) is the most sensitive and every precaution that is reasonably possible (outlined above) should be taken to ensure that this suitable reptile habitat remains suitable during and after construction has taken place. Luke Verburgt (M.Sc. Zoology) REFERENCES Branch, W.R. ed. (1988). South African red data book Reptiles and amphibians. NMB Printers, Port Elizabeth. Branch, W.R. (1998). Field guide to snakes and other reptiles of southern Africa. Struik, Cape Town. International Union for Conservation of Nature. (2010). The IUCN red data list website. Marais, J. (2004). A complete guide to the snakes of Southern Africa. National Environmental Management: Biodiversity Act. (2004). Act 10 of 2004: Publication of lists of critically endangered, endangered, vulnerable and protected species. South African Reptile Conservation Assessment (SARCA). (2010).

4 Table 1. Herpetofauna species list recorded for quarter degree grid cell 2627DA only and 2627DA and all 8 adjacent quarter degree grid cells (SARCA). Species highlighted in bold were directly observed during the scoping survey. 2627DA only Agama aculeata distanti Agama atra Aparallactus capensis Cordylus vittifer Crotaphopeltis hotamboeia Dasypeltis scabra Hemachatus haemachatus Lamprophis capensis Lycophidion capense capense Pachydactylus capensis Panaspis walbergii Prosymna sundevallii Psammophis crucifer Rhinotyphlops lalandei Trachylepis capensis Trachylepis punctatissima Trachylepis varia Varanus niloticus 2627DA & 8 adjacent QDGC's Acontias gracilicauda gracilicauda Afrotyphlops bibronii Agama aculeata distanti Agama atra Aparallactus capensis Atractaspis bibronii Bitis arietans arietans Causus rhombeatus Chamaeleo dilepis Chamaesaura aenea Cordylus vittifer Crotaphopeltis hotamboeia Dasypeltis scabra Elapsoidea sundevallii media Gerrhosaurus flavigularis Hemachatus haemachatus Homoroselaps dorsalis Kinixys lobatsiana Lamprophis aurora Lamprophis capensis Leptotyphlops scutifrons conjunctus Leptotyphlops scutifrons scutifrons Lycodonomorphus rufulus Lycophidion capense capense Lygodactylus capensis capensis Nucras holubi Nucras ornata Pachydactylus affinis Pachydactylus capensis Panaspis walbergii Pedioplanis lineoocellata Pelomedusa subrufa Prosymna sundevallii Psammophis angolensis Psammophis brevirostris Psammophis crucifer Psammophis trinasalis Psammophylax rhombeatus Pseudaspis cana Rhinotyphlops lalandei Stigmochelys pardalis Telescopus semiannulatus semiannulatus Trachylepis capensis Trachylepis punctatissima Trachylepis varia Varanus niloticus

5 Figure 1. Remote sensing image (courtesy Google Corporation) showing the proposed sewer pipeline (Blue). The red track shows the area inspected during the scoping visit of 8 June 2010 and the camera icons indicate positions from which photographs were taken. The yellow markers show where the two termitaria were excavated. A) Overall impression of area surveyed. B) & C) Zoomed in sections of pipeline separated by the highway. Please note position of North marker in each image. A

6 B

7 C

8 Figure 2. Species distribution records for the striped harlequin snake (Homoroselaps dorsalis) (SARCA) showing the absence of records for the quarter degree grid cell 2627DA (blue arrow).

9 Figure 3. A. Photographic evidence of the rhombic skaapsteker Psammophylax rhombeatus found on site. B. Species distribution records for Psammophylax rhombeatus (SARCA) showing the absence of records for the quarter degree grid cell 2627DA (blue arrow). A B

10 Figure 4. Photographic evidence of A) and adult and B) a juvenile Cape centipede eater (Aparallactus capensis) found on site at termitaria 1 and 2 respectively (see Figure 1). A B

11 Figure 5. Mowed road verge where the sewer pipeline should be confined to if possible.