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Phillips K.P.,University of East Anglia | Phillips K.P.,University of Sheffield | Mortimer J.A.,Island Conservation Society | Mortimer J.A.,rros Research Center | And 5 more authors.
Journal of Experimental Marine Biology and Ecology | Year: 2014

The concept of 'effective population size' (Ne), which quantifies how quickly a population will lose genetic variability, is one of the most important contributions of theoretical evolutionary biology to practical conservation management. Ne is often much lower than actual population size: how much so depends on key life history and demographic parameters, such as mating systems and population connectivity, that often remain unknown for species of conservation concern. Molecular techniques allow the indirect study of these parameters, as well as the estimation of current and historical Ne. Here, we use genotyping to assess the genetic health of an important population of the critically endangered hawksbill turtle (Eretmochelys imbricata), a slow-to-mature, difficult-to-observe species with a long history of severe overhunting. Our results were surprisingly positive: we found that the study population, located in the Republic of Seychelles, Indian Ocean, has a relatively large Ne, estimated to exceed 1000, and showed no evidence of a recent reduction in Ne (i.e. no genetic bottleneck). Furthermore, molecular inferences suggest the species' mating system is conducive to maintaining a large Ne, with a relatively large and widely distributed male population promoting considerable gene flow amongst nesting sites across the Seychelles area. This may also be reinforced by the movement of females between nesting sites. Our study underlines how molecular techniques can help to inform conservation biology. In this case our results suggest that this important hawksbill population is starting from a relatively strong position as it faces new challenges, such as global climate change. © 2014 Elsevier B.V. Source


von Brandis R.G.,rros Research Center
Ocean and Coastal Management | Year: 2012

Abandoned coconut plantations occur on tropical islands worldwide. Despite their adverse effect on local biodiversity, there is a paucity of information concerning rehabilitation methods and their respective outcomes. Previous accounts of coconut forest rehabilitation programs exclusively advocate clearcutting followed by planting of native saplings. Having experienced considerable practical and ecological complications from clearcutting on D'Arros Island, Republic of Seychelles, an alternative protocol was developed in which the upper coconut canopy was temporarily preserved so that the resultant shady environment on the forest floor might accelerate natural forest succession. Activities and progress were monitored in three experimental plots and compared to previously clearcut sites. Results suggest that the proposed method allows rehabilitation of abandoned coconut forests to be achieved sooner and at a lesser cost than clearcutting. © 2012 Elsevier Ltd. Source


Mortimer J.A.,Seychelles Islands Foundation | Mortimer J.A.,University of Florida | Von Brandis R.G.,Seychelles Islands Foundation | Von Brandis R.G.,rros Research Center
Chelonian Conservation and Biology | Year: 2013

Adult mortality at the nesting site is an important demographic parameter for green turtles (Chelonia mydas) at Aldabra Atoll, Seychelles, where, between 1995 and 2008, records were kept of adult green turtles found dead (n=158) or so trapped or incapacitated in the vicinity of the nesting beaches as to be unable to return to the sea without human assistance (n=50). The main cause of death (n=121) was entrapment and/or incapacitation on beach rock (62.0%), and adjusted rates of mortality were twice as high on the windward south coast as on the north coast and 3 times that on the west coast. Annual natural mortality, conservatively reported at 16-30 females per year, claims an estimated 0.3%-1.0% of the annual adult female nesting population at Aldabra, which is otherwise healthy, increasing, and free of terrestrial predation. © 2013 Chelonian Research Foundation. Source


Von Brandis R.G.,Tshwane University of Technology | Von Brandis R.G.,rros Research Center | Mortimer J.A.,University of Florida | Mortimer J.A.,rros Research Center | Reilly B.K.,Tshwane University of Technology
Chelonian Conservation and Biology | Year: 2010

The diving behavior of immature hawksbill turtles (Eretmochelys imbricata) was recorded by means of direct in-water observations during a period of 8 months over 4 years on a coral reef at D'Arros Island in the Seychelles. For 4 turtles that had become habituated, detailed behavioral observations were recorded and quantified during 148 contact hours during which 187 turtle dives were documented. Mean dive depth and duration were 8.2 m and 27.4 minutes, respectively. Surfacing intervals lasted on average 81.5 seconds and the mean number of breaths was 6.6 per surface interval. Dive duration was positively correlated with dive depth. On average, larger turtles conducted longer dives than smaller turtles and spent more time at the surface. Immature hawksbills at D'Arros averaged longer surface intervals and took more breaths than did those reported at other sites. We attribute this, at least in part, to the increased energy demands required to excavate cryptic food items at D'Arros. Although average foraging dives in this and other studies tended to be shallow (<15 m) and short (<30 minutes), the turtles are capable of significantly deeper and longer dives. We propose that immature hawksbills forage well below their physiological dive limits and do not strive to maximize their bottom times. © 2010 Chelonian Research Foundation. Source


Mortimer J.A.,University of Florida | Mortimer J.A.,rros Research Center | Camille J.-C.,rros Research Center | Boniface N.,rros Research Center
Chelonian Conservation and Biology | Year: 2011

We report on data collected during the first long-term turtle monitoring and conservation program conducted in the Amirantes Islands Group of Seychelles. Green turtle (Chelonia mydas) and hawksbill (Eretmochelys imbricata) nesting activity was recorded on a daily basis, year-round, over a period of 62 months between November 2004 and December 2009 at D'Arros Island, in the context of a community-based turtle monitoring and conservation program coordinated by the D'Arros Research Centre (DRC). Green turtle nesting occurred year-round with a distinct peak in late March but also evidence of a bimodal pattern with a dominant peak during February to April and a secondary peak in July and August. For hawksbills, nesting peaked in early December, with 94.0% of nesting emergences during the four-month interval from 1 October to 31 January. Along the 5-km nesting beach, the estimated average number of clutches laid annually was 95 for green turtles (range 65-120) and 300 (range 277-318) for hawksbills. Assuming an average of 5 clutches annually for green turtles and 4-5 for hawksbills, this would represent some 20 green turtles and 60-75 hawksbill females nesting annually. This indicates an increase in nesting activity - but not necessarily in numbers of nesting females - from that reported in the early 1970s, early 1980s, and mid-1990s when exploitation was intense. During the 5 years that the DRC turtle conservation and monitoring program was underway, turtle poaching has virtually ceased at D'Arros Island and adjacent St. Joseph atoll. © 2011 Chelonian Research Foundation. Source

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