Reproductive synchrony in a recovering bottlenecked sea turtle population

1. The assessment of species extinction risk has been well established for some time now. Assessing the potential for recovery in endangered species is however much more challenging, because complementary approaches are required to detect reliable signals of positive trends. 2. This study combines genetics, demography and behavioural data at three different time-scales to assess historical and recent population changes and evidence of reproductive synchrony in a small population of olive ridley sea turtle Lepidochelys olivacea. Lepidochelys is considered as the most extraordinary example of reproductive synchrony in reptiles, yet to date, it has only been reported in large populations. 3. Using Bayesian coalescent-based models on microsatellite nuclear DNA variability, we demonstrate that effective population size in olive ridleys nesting in French Guiana has dramatically declined by 99% over the last 20 centuries. This low current population size is further illustrated by the absence of genetic mitochondrial DNA diversity in the present nesting population. Yet, monitoring of nesting sites in French Guiana suggests a possible recovery of the population over the last decade. 4. Satellite telemetry shows that over the first 14 days of their 28-days inter-nesting interval, i.e. when eggs maturation is likely to occur, gravid females disperse over the continental shelf. They then gather together with a striking spatiotemporal consistency close to the nesting site, where they later emerge for their second nesting event. 5. Our results therefore suggest that reproductive synchrony also occurs in small populations. Olive ridleys may ensure this synchrony by adjusting the duration of the second half of their inter-nesting interval prior to landing, possibly through social mediation. 6. Such reproductive synchrony may be related to the maintenance of some species-specific strategy despite former collapse and may contribute to the present population recovery. The gregarious behaviour of reproductive individuals close to shore where human-induced perturbations occur is however a cause for conservation concern for this still poorly known species.     

Immobilization of free-ranging nine-banded and great long-nosed armadillos with three anesthetic combinations

Nine-banded (n = 47) and great (n = 31) long-nosed armadillos (Dasypus novemcinctus and Dasypus kappleri) were immobilized for clinical examination and collection of biological samples as part of a wildlife rescue during the filling of a hydroelectric dam (Petit Saut, French Guiana) from May 1994 to April 1995. Three intramuscular (i.m.) anesthetic combinations were evaluated: (1) tiletamine/zolazepam (T/Z) at a dose of 8.5 mg/kg in 12 nine-banded long-nosed armadillos (NBA) and 10 great long-nosed armadillos (GLA), (2) ketamine at 40 mg/kg combined with xylazine at 1.0 mg/kg (K/X) in 18 NBA and nine GLA, and (3) ketamine at 7.5 mg/kg combined with medetomidine at 75 microng/kg (K/M) in 17 NBA and 12 GLA, antagonized by 375 microg/kg atipamezole. Induction was smooth, ranged from mean +/- SD = 2.8+/-0.6 to 4.3+/-1.8 min, and did not differ significantly between protocols, species, or sex. In NBA, immobilization time ranged from 43.8+/-27.8 to 66.5+/-40.0 min and did not differ between protocols or sex. Muscle relaxation was judged to be better with K/X and K/M versus T/Z. In GLA, the response to the anesthetic protocols was more variable and immobilization time ranged from 30.4+/-6.2 to 98.4+/-33.7 min. The main difference was observed in GLA females receiving the T/Z combination, in which immobilization time was significantly longer versus males, but also versus GLA K/M group, and versus NBA T/Z group. Effects on body temperature, heart rate and respiratory rate were limited. Thirty six to 50% of the individuals showed hypoxemia (SpO2 < 85%) throughout anesthesia and values <80% also were recorded but the hypoxemia was not associated with clinical signs. With T/Z and K/X, recovery was irregular and prolonged up to 2 to 3 hr in some individuals. In K/M groups, first standing was observed 1.0 to 16.4 min after i.m. atipamezole injection without adverse effects. Finally, the three anesthetic combinations used in this study were effective and safe agents for 30 to 40 min immobilizations including minor surgery procedures. The ability to antagonize the medetomidine-induced sedation with atipamezole significantly reduces the recovery time, making the K/M combination preferable, especially in field conditions.     

Predators,Prey and Habitat Structure: Can Key Conservation Areas and Early Signs of Population Collapse Be Detected in Neotropical Forests?

Tropical forests with a low human population and absence of large-scale deforestation provide unique opportunities to study successful conservation strategies, which should be based on adequate monitoring tools. This study explored the conservation status of a large predator, the jaguar, considered an indicator of the maintenance of how well ecological processes are maintained. We implemented an original integrative approach, exploring successive ecosystem status proxies, from habitats and responses to threats of predators and their prey, to canopy structure and forest biomass. Niche modeling allowed identification of more suitable habitats, significantly related to canopy height and forest biomass. Capture/recapture methods showed that jaguar density was higher in habitats identified as more suitable by the niche model. Surveys of ungulates, large rodents and birds also showed higher density where jaguars were more abundant. Although jaguar density does not allow early detection of overall vertebrate community collapse, a decrease in the abundance of large terrestrial birds was noted as good first evidence of disturbance. The most promising tool comes from easily acquired LiDAR data and radar images: a decrease in canopy roughness was closely associated with the disturbance of forests and associated decreasing vertebrate biomass. This mixed approach, focusing on an apex predator, ecological modeling and remote-sensing information, not only helps detect early population declines in large mammals, but is also useful to discuss the relevance of large predators as indicators and the efficiency of conservation measures. It can also be easily extrapolated and adapted in a timely manner, since important open-source data are increasingly available and relevant for large-scale and real-time monitoring of biodiversity.     

Recent Demographic History and Present Fine-Scale Structure in the Northwest Atlantic Leatherback (Dermochelys coriacea) Turtle Population

The leatherback turtle Dermochelys coriacea is the most widely distributed sea turtle species in the world. It exhibits complex life traits: female homing and migration, migrations of juveniles and males that remain poorly known, and a strong climatic influence on resources, breeding success and sex-ratio. It is consequently challenging to understand population dynamics. Leatherbacks are critically endangered, yet the group from the Northwest Atlantic is currently considered to be under lower risk than other populations while hosting some of the largest rookeries. Here, we investigated the genetic diversity and the demographic history of contrasted rookeries from this group, namely two large nesting populations in French Guiana, and a smaller one in the French West Indies. We used 10 microsatellite loci, of which four are newly isolated, and mitochondrial DNA sequences of the control region and cytochrome b. Both mitochondrial and nuclear markers revealed that the Northwest Atlantic stock of leatherbacks derives from a single ancestral origin, but show current genetic structuration at the scale of nesting sites, with the maintenance of migrants amongst rookeries. Low nuclear genetic diversities are related to founder effects that followed consequent bottlenecks during the late Pleistocene/Holocene. Most probably in response to climatic oscillations, with a possible influence of early human hunting, female effective population sizes collapsed from 2 million to 200. Evidence of founder effects and high numbers of migrants make it possible to reconsider the population dynamics of the species, formerly considered as a metapopulation model: we propose a more relaxed island model, which we expect to be a key element in the currently observed recovering of populations. Although these Northwest Atlantic rookeries should be considered as a single evolutionary unit, we stress that local conservation efforts remain necessary since each nesting site hosts part of the genetic diversity and species history.