Shaya Honarvar

Island biogeography reveals the deep history of SIV

Separation of the island of Bioko from West Africa about 10,000 years ago dates the origins of simian immunodeficiency virus. Simian immunodeficiency virus (SIV) lineages have been identified that are endemic to Bioko Island. The time the island formed offers a geological time scale calibration point for dating the most recent common ancestor of SIV. The Bioko viruses cover the whole range of SIV genetic diversity, and each Bioko SIV clade is most closely related to viruses circulating in hosts of the same genus on the African mainland rather than to SIVs of other Bioko species. Our phylogeographic approach establishes that SIV is ancient and at least 32,000 years old. Our conservative calibration point and analyses of gene sequence saturation and dating bias suggest it may be much older.

Density-dependent effects on hatching success of the olive ridley turtle, Lepidochelys olivacea

Historically, the olive ridley arribada at Playa Nancite, Costa Rica, was one of the largest olive ridley arribadas in the eastern Pacific with 70,000 nesting females in a year. Recently the Nancite arribada drastically declined. We hypothesized that the population decline at Playa Nancite could have been due to low hatching success as a result of the high density of nests on the beach, such that recruitment to the population was insufficient to balance losses. To test this hypothesis, we examined density-dependent effects on hatching success and their underlying mechanisms by experimentally manipulating nest densities in experimental plots on the nesting beach. We set up four nest-density treatments in five experimental blocks. We measured effects of density on hatching success, CO2 and O2 concentrations and temperature both within nests and in sand adjacent to nests frequently during incubation. Experimental nest densities affected hatching success with the highest density having the lowest hatching success. Higher nest density led to lower O2 levels and higher CO2 levels in the nest with greater changes in the latter part of the incubation. Highest temperatures occurred in high-density areas. Temperatures were lower in sand surrounding the nest than in the nest. Effects of density on temperature, CO2 and O2 were confirmed at a naturally high-density nesting beach, Playa La Flor, Nicaragua. Long-term failure in production of hatchlings due to historic high densities may have contributed to the decline of arribadas on Playa Nancite. Thus, density-dependent population control would have operated at the embryonic life stage in this population of olive ridley turtles.

Nonlethal amphibian skin swabbing of cutaneous natural products for HPLC fingerprinting

Small organic molecules found on the skin of amphibians may help impart resistance to pathogens, such as the lethal fungus Batrachochytrium dendrobatidis. The study of these compounds has traditionally required euthanasia of the amphibian, followed by chemical extraction of excised skin. As an alternative method, we report the development and assessment of a non-lethal technique using foam-tipped swabs and HPLC analysis to directly isolate and characterize small molecules found on the skin of amphibians. This protocol was field-tested on Bioko Island, Equatorial Guinea with forty-seven frogs (representing 14 native species). Multiple species (particularly Afrixalus paradorsalis and Didynamipus sjostedti) carried sets of species-specific compounds (i.e., a chromatographic fingerprint). A principal coordinate analysis (PCO) of the commonly occurring compounds detected across all species revealed a significant relationship between chromatographic profile and species for all swab samples.

Changes in Plasma Chemistry and Reproductive Output of Nesting Leatherbacks

Abstract Africas Gulf of Guinea, a major nesting ground for the critically endangered Leatherback Sea Turtle (Dermochelys coriacea), is experiencing rapid economic development. This study reports on the plasma biochemistry and packed cell volume (PCV) of turtles (55 samples collected from 23 individuals) nesting on Playa Moaba, Bioko Island, Equatorial Guinea. Because energy reserves and other resources in an individual are finite and turtles may not feed between nesting episodes, decreasing trends are expected in certain plasma biochemical concentrations and PCV values, as well as maternal investment in reproductive output (clutch size and egg mass). Calcium, potassium, sodium, phosphorous, plasma total protein, albumin, and globulin concentrations changed significantly with increasing number of nesting events, but remained within reported intervals in reptiles. Packed cell volume decreased significantly as the number of nesting events per individual increased. Although clutch size did not change, egg mass decreased significantly with increasing number of nesting events. The observed trends may be due to depletion of energy reserves and other resources during reproduction in a possible fasting state, and to the associated physiological stress.

Genetic signatures of a demographic collapse in a large-bodied forest dwelling primate (Mandrillus leucophaeus).

It is difficult to predict how current climate change will affect wildlife species adapted to a tropical rainforest environment. Understanding how population dynamics fluctuated in such species throughout periods of past climatic change can provide insight into this issue. The drill (Mandrillus leucophaeus) is a large-bodied rainforest adapted mammal found in West Central Africa. In the middle of this endangered monkeys geographic range is Lake Barombi Mbo, which has a well-documented palynological record of environmental change that dates to the Late Pleistocene. We used a Bayesian coalescent-based framework to analyze 2,076 base pairs of mitochondrial DNA across wild drill populations to infer past changes in female effective population size since the Late Pleistocene. Our results suggest that the drill underwent a nearly 15-fold demographic collapse in female effective population size that was most prominent during the Mid Holocene (approximately 3-5 Ka). This time period coincides with a period of increased dryness and seasonality across Africa and a dramatic reduction in forest coverage at Lake Barombi Mbo. We believe that these changes in climate and forest coverage were the driving forces behind the drill population decline. Furthermore, the warm temperatures and increased aridity of the Mid Holocene are potentially analogous to current and future conditions faced by many tropical rainforest communities. In order to prevent future declines in population size in rainforest-adapted species such as the drill, large tracts of forest should be protected to both preserve habitat and prevent forest loss through aridification.

Long-term urban market dynamics reveal increased bushmeat carcass volume despite economic growth and proactive environmental legislation on Bioko Island, Equatorial Guinea

Bushmeat hunting is extensive in west and central Africa as both a means for subsistence and for commercial gain. Commercial hunting represents one of the primary threats to wildlife in the region, and confounding factors have made it challenging to examine how external factors influence the commercial bushmeat trade. Bioko Island, Equatorial Guinea is a small island with large tracts of intact forest that support sizeable populations of commercially valuable vertebrates, especially endemic primates. The island also has a low human population and has experienced dramatic economic growth and rapid development since the mid-1990’s. From October 1997 – September 2010, we monitored the largest bushmeat market on Bioko in Malabo, recording over 197,000 carcasses for sale. We used these data to analyze the dynamics of the market in relation to political events, environmental legislation, and rapid economic growth. Our findings suggest that bushmeat hunting and availability increased in parallel with the growth of Equatorial Guinea’s GDP and disposable income of its citizens. During this 13-year study, the predominant mode of capture shifted from trapping to shotguns. Consequently, carcass volume and rates of taxa typically captured with shotguns increased significantly, most notably including intensified hunting of Biokos unique and endangered monkey fauna. Attempts to limit bushmeat sales, including a 2007 ban on primate hunting and trade, were only transiently effective. The hunting ban was not enforced, and was quickly followed by a marked increase in bushmeat hunting compared to hunting rates prior to the ban. Our results emphasize the negative impact that rapid development and unenforced legislation have had on Bioko’s wildlife, and demonstrate the need for strong governmental support if conservation strategies are to be successful at preventing extinctions of tropical wildlife.

From frugivore to folivore: Altitudinal variations in the diet and feeding ecology of the Bioko Island drill (Mandrillus leucophaeus poensis).

Variation in the quality and availability of food resources can greatly influence the ecology, behavior, and conservation of wild primates. We studied the influence of altitudinal differences in resource availability on diet in wild drill monkeys (Mandrillus leucophaeus poensis) on Bioko Island, Equatorial Guinea. We compared fecal samples (n = 234) collected across three consecutive dry seasons for drills living in lowland (0–300 m asl) forest with nearby (18 km distance) drills living in montane forest (500–1000 m asl) in the Gran Caldera Southern Highlands Scientific Reserve. Lowland forest drills had a frugivorous diet very similar to that reported from studies on nearby mainland drills (M. l. leucophaeus) and mandrills (M. sphinx), with fruits comprising 90% of their dried fecal samples. However drills living in montane forest had a more folivorous diet, with herbaceous pith, leaves and fungi comprising 74% of their dried fecal samples and fruit becoming a minor component (24%). Furthermore, a dietary preference index indicated that the differences in the proportion of fruit and fibrous vegetation in the diets of lowland compared to montane drills was not simply a result of relative availability. Montane drills were actively consuming a higher mass of the available fruits and fibrous vegetation, a condition reflected in the greater mass of their fresh feces. Our results demonstrate the unexpected flexibility and complexity of dietary choices of this endangered species in two adjacent habitat types, a comparison of considerable importance for many other limited‐range species faced with habitat loss and climate change. Am. J. Primatol. 77:1263–1275, 2015.

Challenges Confronting Sea Turtle Conservation on Bioko Island, Equatorial Guinea

Abstract Bioko Island, part of Equatorial Guinea, has been classified as a critically important nesting site for sea turtles in the Gulf of Guinea. However, construction of a road through a previously undeveloped scientific reserve is set to dramatically alter human interactions with nesting turtle populations. This article reports on the current status of sea turtle conservation and research on Bioko Island as well as recent economic considerations that affect local turtle conservation and use.

Assessment of Important Marine Turtle Nesting Populations on the Southern Coast of Bioko Island, Equatorial Guinea

Abstract Bioko Islands southern beaches are important nesting sites for marine turtles in the Gulf of Guinea region. In this study, we present data on the 4 species of sea turtles nesting on 5 nesting beaches (19 km) of Bioko Island, from 2000 to 2014. A total of 43,860 leatherback (Dermochelys coriacea), 16,778 green (Chelonia mydas), 1731 olive ridley (Lepidochelys olivacea), and 85 hawksbill turtle (Eretmochelys imbricata) encounters, defined as the number of tracks, were recorded on Biokos southern beaches. Since 2008, the estimated number of leatherback females ranged from 42 to 444, green turtles from 63 to 649, and olive ridley turtles from 22 to 53 annually. This study presents the first extensive tagging program on Bioko Island, where 790 leatherback turtles were tagged with Passive Integrated Transponder tags from 2008 to 2014. Only 6.1% of the tagged turtles returned to nest again with a remigration interval of 3–4 yrs. In addition, 279 green turtles were flipper-tagged in the 2013–2014 nesting season. Overall, the total number of leatherback turtle encounters decreased annually from 2000 to 2014. These declines may be attributed to adult turtle captures in commercial fisheries operating in the Gulf of Guinea and turtle take in local artisanal fisheries. On the other hand, olive ridley encounters increased from 2000 to 2014. The construction of a paved road from Luba, the second largest city on Bioko Island, directly to the nesting beaches is now set to dramatically alter human interaction with nesting turtles. These long-term data confirm the importance of Bioko Islands nesting beaches for the Southeast Atlantic and fill a critical need for sea turtle conservation in a data-deficient, yet globally significant, area.

Ecology of Olive Ridley Sea Turtles at Arribadas at Playa La Flor, Nicaragua

Abstract: Playa La Flor in Nicaragua is one of the few remaining beaches where Olive Ridley Sea Turtles (Lepidochelys olivacea) nest in arribadas. In this study, we present data on the status of the nesting population of L. olivacea on Playa La Flor from 1998 to 2006. Furthermore, in 2004 we established six plots (6 m × 6 m) on a 400-m section of the nesting beach to measure the levels of illegal egg take, clutch hatching success, and hatchling production. The total number of turtles nesting at Playa La Flor increased from 1998 to 2006 where arribadas ranged in size from 167 to 60,816 turtle encounters. In August 2004, 45% of the clutches laid during the arribada were taken illegally from the study plots, whereas these levels were lower during the arribadas occurring from September to November. In 2004, clutch hatching success and hatchling production were higher in plots located high on the beach compared with plots that were closer to or below the high-tide line. Clutch hatching success and hatchling production were higher in the September arribada than during other arribadas within the same year. The lower hatching success and hatchling production of nests laid during later arribadas might be explained by increased nest density, and overlapping clutches in the study plots could lead to an increase in microbial load, O2 demand, and CO2 production. If manipulating clutches is warranted on Playa La Flor, managers should target clutches that are at the highest risk of drowning, are in areas of high nest density, and are deposited during the larger arribadas that occur later in the nesting season. The location of clutches to be moved/removed might change between years, even on the same beach.