Iguana 13.2 b&w text IGUANA • VOLUME 13, NUMBER 2 • JUNE 2006 163CONSERVATION RESEARCH REPORTS Dietary Shifts of Turtles in Pristine and Oil-polluted Habitats of the Niger Delta in Southern Nigeria LUISELLI ET AL. (2004. Herpetological Journal 14: 57–64) examined the diets of sympatric freshwater turtles at two study areas in the Niger Delta (southern Nigeria). One site was unpolluted and the other was polluted by an oil spill, but both areas were otherwise similar. Four species of turtle (Trionyx triunguis, Pelusios castaneus, Pelusios niger, and Pelomedusa subrufa) were captured in the unpolluted area, whereas only two species (Pelusios castaneus and Pelusios niger) were captured in the polluted area. In the unpolluted area, the taxonomic composition of the diets of Pelusios castaneus and Pelusios niger was similar, whereas the diets of Pelomedusa subrufa and Trionyx triunguis were very different from the other two species and one another. In the polluted area, the taxonomic composition of the diet of Pelusios castaneus was significantly different from that of conspecifics in the unpolluted area, and consisted mainly of plant matter, annelids (earthworms and leeches), and gastropods. The taxonomic composition of the diet of Pelusios niger was also significantly different from that of conspecifics at the unpolluted area, and consisted mainly of annelids and gas- tropods, and secondarily of plant matter. Amphibian prey (eggs, tadpoles, and adults), which were one of the main food types for all turtles in the unpolluted area, practically disappeared from the diet of turtles at the polluted area. The two species that survived the oil spill obviously shifted their dietary preferences. In both species, an obvious reduction in the breadth of the trophic niche was appar- ent. Such a reduction in trophic niche breadth may reflect the reduced availabil- ity of most food sources (particularly amphibians, fish, and environmentally- sensitive invertebrates) in the polluted area, despite over 10 years of restoration operations at the site. The reduction in trophic niche breadth also may reflect shifts in habitat use by the surviving tur- tles, which tended to concentrate into sin- gle habitat types in the polluted area, compared to the unpolluted area where they were more habitat generalists. Biology of Endangered Ploughshare Tortoises Successful conservation requires a good understanding of both the direct and indirect causes of any decline in popula- tion size. Harvests of wild populations often target the largest, oldest individuals that have the greatest economic value. If these individuals contribute dispropor- tionately more to recruitment than con- specifics, the harvest will cause a greater reduction in population viability than ini- tially anticipated. The Ploughshare Tortoise (Geochelone yniphora), endemic to Madagascar, has been reduced to <600 individuals due to exploitation and habi- tat loss. A trial release of captive-bred juveniles has been carried out but the rel- ative suitability of individuals for release, in terms of body size, was not considered. Using data from a long-term mark-recap- ture study of an unharvested wild popu- lation of ploughshare tortoises, O’BRIEN ET AL. (2005. Biological Conservation 126: 141–145) found that larger juveniles were significantly more likely to survive their first year of life than smaller tortoises. Juveniles that survived beyond their first year of life generally grew at the same rate, but had a significantly larger hatch size (mean = 41.7 mm), compared with juve- niles that did not survive (mean = 39.3 mm). The conservation implications of these results are that release of captive- bred Ploughshare Tortoises is likely to be more successful if larger individuals are released. Previous studies have reported larger female Ploughshare Tortoises laying larger eggs which hatch larger juveniles. This study shows individuals with a larger hatch size retain their size advantage over smaller conspecifics and are more likely to survive their first year of life. This suggests a harvest that targets the largest females in the Ploughshare Tortoises population could be highly detrimental to population viability. Herpetofaunal Diversity in Southeastern National Parks The southeastern United States supports about half of the nations species of amphibians and reptiles, of which about 20% are endemic to the region. Because few areas have been formally inventoried, C O N S E R V A T I O N R E S E A R C H R E P O R T S Pelomedusa subrufa was restricted to unpolluted areas in the Niger Delta (Nigeria). C H U C K S C H A FF ER The Ploughshare Tortoise (Geochelone yniphora), endemic to Madagascar, has been reduced to fewer than 600 individuals due to exploitation and habitat loss. LO R A S M IT H Iguana 13.2 b&w text.QX6 6/26/06 1:21 PM Page 163 164 IGUANA • VOLUME 13, NUMBER 2 • JUNE 2006 CONSERVATION RESEARCH REPORTS TURBERVILLE ET AL. (2005. Southeastern Naturalist 4:537–569) conducted biolog- ical inventories at 16 parks in the National Park Service’s Southeast Coast Network. Using a variety of standard field techniques and surveys of museum collec- tions, the authors documented the pres- ence of 123 native species of amphibians and reptiles in the 16 parks, with num- bers of species ranging from 6–64 per park. Increasing Leatherback Numbers Linked to Long-term Nest Protection The Leatherback Turtle (Dermochelys cori- acea) is considered to be at serious risk of global extinction, despite ongoing conser- vation efforts. Intensive long-term moni- toring of a Leatherback nesting popula- tion on Sandy Point (St. Croix, US Virgin Islands) offers a unique opportu- nity to quantify basic population param- eters and evaluate effectiveness of nesting beach conservation practices. DUTTON ET AL. (2005. Biological Conservation 126: 186–194) reported a significant increase in the number of females nesting annu- ally from ca. 18–30 in the 1980s to 186 in 2001, with a corresponding increase in annual hatchling production from ca. 2000 to over 49,000. They then analyzed resighting data from 1991 to 2001 with an open robust-design capture-mark- recapture model to estimate annual nester survival and adult abundance for this population. The expected annual survival probability was estimated at ca. 0.893 (95% CI: 0.87–0.92) and the population was estimated to be increasing ca. 13% pa since the early 1990s. Taken together with DNA fingerprinting that identify mother-daughter relations, their findings suggest that the increase in the size of the nesting population since 1991 was prob- ably due to an aggressive program of beach protection and egg relocation initi- ated more than 20 years ago. Beach pro- tection and egg relocation provide a sim- ple and effective conservation strategy for this Northern Caribbean nesting popula- tion as long as adult survival at sea remains relatively high. Impact of Deforestation on Lizards, Small Mammals, and Birds in Southern Madagascar Madagascar is a global biodiversity hotspot threatened by forest loss, degra- dation, and fragmentation, all of which are detrimental to the future survival of forest-dwelling organisms. For conserva- tion purposes, determining how species respond to habitat disturbance, specifi- cally deforestation, is essential. SCOTT ET AL. (2006. Biological Conservation 127: 72–87) investigated the impacts of defor- estation on three vertebrate communities, lizards, small mammals, and birds, in an area of spiny forest subjected to anthro- pogenic forest clearance. Spiny forest has high levels of endemism, but conservation in this unique ecosystem is hindered by the lack of research. The authors assessed species richness, species abundance, and community composition of lizards, small mammals, and birds in six areas of ‘forest’ and six ‘cleared’ areas. From surveys and opportunistic sightings, they recorded a total of 70 species of birds, 14 species of Leatherbacks (Dermochelys coriacea) are criti- cally endangered. Beach protection and egg relocation provide a simple and effective con- servation strategy for nesting populations as long as adult survival at sea remains relatively high. R O ZE N N L E SC A O Oustalet’s Chameleon (Furcifer oustaleti) is one of the world’s largest chameleons and is one of the many unique species of lizards that inhabit the spiny forests of Madagascar. M IC H IE L D E B O ER Alligator Snapping Turtles (Macroclemys tem- minckii) and American Alligators (Alligator mississippiensis) are but two of 123 native species of amphibians and reptiles found in 16 national parks in the southeastern United States. SU ZA N N E L. C O LL IN S, C N A H Where Gopher Tortoises (Gopherus polyphe- mus) are present, their burrows are used for shelter by many other animals. C H U C K S H A EF ER Iguana 13.2 b&w text.QX6 6/26/06 1:21 PM Page 164 mammals, and 38 species of reptiles and amphibians. They found forest clearing to have a negative effect on species richness and community structure of all groups and identified loss of canopy cover as a driving factor. However, the response and sensitivity to clearing varied between groups and species. Lizards (50%) and small mammals (40%) had the greatest decline in species richness in response to clearing as compared to birds (26%), although birds showed the greatest shift in community structure. The community in cleared areas contained more generalist and introduced species than species unique to the spiny forest. The first species to suffer from forest clearance were those of high conservation priority due to their restricted geographic range. Roads and Snake Movements Roads affect survivorship and behavior and can act as barriers to movement, which exacerbates habitat fragmentation and disrupts landscape permeability. ANDREWS AND GIBBONS (2005. Copeia 2005: 772–782) conducted field experi- ments that demonstrated interspecific dif- ferences in snakes of the southeastern United States that encountered roads. Smaller species exhibited higher levels of road avoidance, venomous species crossed more slowly than nonvenomous forms, and three species responded to traffic by becoming immobile, which prolonged crossing times and magnified susceptibil- ity to road mortality. All species crossed roads at perpendicular angles. Models using crossing speeds indicated that some species couldn’t successfully cross roads with high traffic densities. Conservation and Reptilian Diversity on the Guiana Shield The Guiana Shield region is a biologically rich area that includes much of northeast- ern South America. It is strictly defined by the underlying geological formation of the same name. Total area is approxi- mately 1,520,000 km2 and portions or all of five nations are included. In their intro- duction to the “Checklist of the terrestrial vertebrates of the Guiana Shield,” editors HOLLOWELL AND REYNOLDS (2005. Bulletin of the Biological Society of Washington (13): x + 98 pp.) addressed conservation: With the exception of a few populated localities, the environment of the Guiana Shield has benefited from limited access and low population densities, although this same isolation has hindered biodiver- sity research. Estimates vary, but much of the vegetation is still relatively undis- turbed by human activities. Recently, however, the pace of disturbance has greatly increased. Current threats include large-scale logging, large- and small-scale gold and diamond mining, oil prospect- ing, bauxite mining, hydroelectric dams, wildlife trade, and population-related pressures such as burning, grazing, agri- culture, and the expansion of Amerindian villages. Taken together, these impacts have begun to take their toll, with vast areas vulnerable to increasing disturbance. The status of conservation efforts varies by country. Throughout the Guiana Shield, many areas that are desig- nated as protected are often only “paper” parks, because a lack of infrastructure and funds fails to protect the areas. Over the last four decades, Venezuela has estab- lished seven national parks, 29 natural monuments, and two biosphere reserves covering about 142,280 km2, more than 30% of its share of the Guiana Shield. In Guyana, the progress of conservation efforts has been slower, with only one IGUANA • VOLUME 13, NUMBER 2 • JUNE 2006 165CONSERVATION RESEARCH REPORTS Larger individuals of Timber Rattlesnakes (Crotalus horridus) were more likely than smaller snakes to avoid roads. However, 50% of snakes on the road froze for up to a minute even before vehicles passed, prolonging cross- ing times and magnifying susceptibility to road mortality. R IC H A R D D A N IE L Number of reptilian species known to occur on the Guiana Shield: Total numbers of species listed by family, species with broadly endemic distributions within the area, and species with site- specific endemic distributions. Shield-wide Site-specific Family Species Endemics Endemics Colubridae 104 6 15 Gymnophthalmidae 45 7 18 Iguanidae (sensu lato) 32 2 9 Gekkonidae 16 4 1 Elapidae 13 4 1 Teiidae 12 1 1 Amphisbaenidae 10 3 5 Leptotyphlopidae 8 2 1 Boidae 8 1 - Viperidae 8 - 1 Chelidae 8 1 - Podocnemididae 6 1 - Crocodylidae 5 1 - Anomalepididae 4 - 1 Cheloniidae 4 - - Scincidae 3 1 - Typhlopidae 3 - - Testudinidae 2 - - Dermochelyidae 1 - - Kinosternidae 1 - - Bataguridae 1 - - Aniliidae 1 - - Iguana 13.2 b&w text.QX6 6/26/06 1:21 PM Page 165 national park of 627 km2, about 3% of the country’s area, although additional reserves are under consideration. Guyana’s 3,710 km2 Iwokrama Forest is dedicated to sustainable use. Surinam’s protected areas system includes one national park and a network of 11 reserves, totaling almost 20,000 km2, over 12% of its total area. This includes the recently created 16,000 km2 Central Surinam Nature Reserve, a UNESCO World Heritage Site that joined and expanded three exist- ing reserves. French Guiana has no offi- cially designated protected areas, but 18 proposed sites total 6,710 km2, about 7.5% of it area. The natural areas of Venezuela and Guyana are currently under the most anthropogenic pressure, while those of French Guiana are proba- bly less threatened. Cooperation among the nations with areas on the Guiana Shield is some- times hampered by border disputes and illegal cross-border transportation of gold and wildlife. The implementation of con- servation practices is further complicated by many issues concerning the indige- nous peoples of the region. All of these challenges will have to be overcome on the way to designing and maintaining a viable reserve system. ÁVILA PIRES (2005. Reptiles, pp. 24–40. In: Bulletin of the Biological Society of Washington (13): x + 98 pp.) listed 295 species of reptiles currently known from the Guiana Shield (see Table). When only species endemic to the region are consid- ered, the proportion of lizards and amphisbaenians increases, whereas the proportion of snakes decreases. These dif- ferences may be real or sampling artifacts. Amphisbaenians are difficult to sample and ranges of several species could be wider than presently known, decreasing the number of species considered to be Guiana Shield endemics. In contrast, ranges of widely distributed species of snakes are well-known and probably real, unless most currently recognized species turn out to be species complexes. Many new species remain to be discovered, especially in the highlands. Variability in Brachylophus Most iguanas are found in the Americas, but the genus Brachylophus occurs in Fiji and Tonga in the South Pacific. Effective conservation relies on understanding the relationships among the populations on various islands, which have previously been poorly understood. BURNS ET AL. (2006. Pacific Conservation Biology 12:64–77) analyzed DNA samples from 35 individuals from 10 islands. They identified three forms, of which the Tonga animals were the most genetically distinct. Fijian and Tongan populations have each evolved following their separa- tion at least 7 million years ago. The authors suggest a need to reassess conser- vation strategies to better reflect the greater degree of differentiation identified by this study. Most populations are small and vulnerable to introduced predators, especially cats and mongooses. Both on- site and zoo-based measures are urgently recommended. 166 IGUANA • VOLUME 13, NUMBER 2 • JUNE 2006 CONSERVATION RESEARCH REPORTS Fijian iguanas in the genus Brachylophus, like this B. vitiensis, may include more genetically dis- tinct entities than previously thought. JO E B U R G ES S Three species from the Guiana Shield: Phimophis guianensis (left) and Siphlophis compressus (center) are colubrid snakes, and Anolis (Norops) nitens nitens (right) is an iguanian lizard. © P H IL IP PE K O K , R O Y A L B EL G IA N IN ST IT U TE O F N A TU R A L SC IE N C ES Iguana 13.2 b&w text.QX6 6/26/06 1:21 PM Page 166