Leatherback turtles satellite-tagged in European waters

The North Atlantic is considered a stronghold for the critically endangered leatherback sea turtle. However, limited information exists regarding the movements of individuals to and from the seas off Europe's northwesterly fringe, an area where featherbacks have been historically sighted for the past 200 yr. Here, we used satellite telemetry to record the movements and behaviour of 2 individuals bycaught in fisheries off the southwest coast of Ireland. The turtle T1 (tagged 1 September 2005; female; tracked 375 d) immediately travelled south via Madeira and the Canaries, before residing in West African waters for 3 mo. In spring, T1 migrated north towards Newfoundland where transmissions ceased. T2 (29 June 2006; male; 233 d) travelled south for a short period before spending 66 d west of the Bay of Biscay, an area previously asserted as a high-use area for leatherbacks. This prolonged high latitude summer residence corresponded with a mesoscale feature evident from satellite imagery, with the implication that this turtle had found a rich feeding site. A marked change in dive behaviour was apparent as the turtle exited this feature and provided useful insights on leatherback diving behaviour. T2 headed south in October 2006, and performed the deepest-ever dive recorded by a reptile (1280 m) southwest of Cape Verde. Unlike T1, T2 swam southwest towards Brazil before approaching the major nesting beaches of French Guiana and Surinam. Importantly, these tracks document the movement of leatherbacks from one of the remotest foraging grounds in the North Atlantic. © Inter-Research 2008.

Predicting forest attributes In southeast Alaska using artificial neural networks

Artificial neural network (ANN) methods are used to predict forest characteristics. The data source is the Southeast Alaska (SEAK) Grid Inventory, a ground survey compiled by the USDA Forest Service at several thousand sites. The main objective of this article is to predict characteristics at unsurveyed locations between grid sites. A secondary objective is to evaluate the relative performance of different ANNs. Data from the grid sites are used to train six ANNs: multilayer perceptron, fuzzy ARTMAP, probabilistic, generalized regression, radial basis function, and learning vector quantization. A classification and regression tree method is used for comparison. Topographic variables are used to construct models: latitude and longitude coordinates, elevation, slope, and aspect. The models classify three forest characteristics: crown closure, species land cover, and tree size/structure. Models are constructed using n-fold cross-validation. Predictive accuracy is calculated using a method that accounts for the influence of misclassification as well as measuring correct classifications. The probabilistic and generalized regression networks are found to be the most accurate. The predictions of the ANN models are compared with a classification of the Tongass national forest in southeast Alaska based on the interpretation of satellite imagery and are found to be of similar accuracy.

Tracking leatherback turtles (Dermochelys coriacea) during consecutive inter-nesting intervals: Further support for direct transmitter attachment

Over recent years there have been substantial efforts to record and interpret the post-nesting movements of leatherback turtles (Dermochelys coriacea) breeding in tropical regions. Less well documented are the movements undertaken by individual turtles during the breeding season itself, or more specifically between sequential nesting events. Such movements are of interest for two reasons: (1) gravid female leatherbacks may range extensively into the territorial waters and nesting beaches of neighbouring countries, raising questions for conservationists and population ecologists; and (2) the magnitude of movements themselves help elucidate underlying reproductive strategies (e.g. whether to rest near to the nesting or forage extensively). Here, satellite relay data loggers are used (SRDLs) to detail the movements and behaviour of two female leatherback turtles throughout three consecutive inter-nesting intervals in the Commonwealth of Dominica, West Indies. Both near-shore residence and extensive inter-nesting movements were recorded, contrasting previous studies, with movements away from the nesting beach increasing towards the end of the nesting season. Using this behavioural study as a backdrop, the suitability of attaching satellite transmitters directly to the carapace was additionally explored as an alternative approach to conventional harness deployments. Specifically, the principal aims were to (1) gather empirical data on speed of travel and (2) assess dive performance (aerobic dive limit) to enable comparisons with turtles previously fitted with harnesses elsewhere in the Caribbean (n = 6 turtles; Grenada, WI). This produced mixed results with animals bearing directly attached transmitters travelling significantly faster (55.21 km day(-1): SD 6.68) than harnessed individuals (39.80 km day(-1); SD 6.19); whilst no discernable difference in dive performance could be found between the two groups of study animals. (C) 2009 Elsevier B.V. All rights reserved.

The role of infrequent and extraordinary deep dives in leatherback turtles (Dermochelys coriacea)

Infrequent and exceptional behaviours can provide insight into the ecology and physiology of a particular species. Here we examined extraordinarily deep (300-1250 m) and protracted (>1h) dives made by critically endangered leatherback turtles (Dermochelys coriacea) in the context of three previously suggested hypotheses: predator evasion, thermoregulation and exploration for gelatinous prey. Data were obtained via satellite relay data loggers attached to adult turtles at nesting beaches (N=11) and temperate foraging grounds (N=2), constituting a combined tracking period of 9.6 years (N=26,146 dives) and spanning the entire North Atlantic Ocean. Of the dives, 99.6% (N=26,051) were to depths <300 m with only 0.4% (N=95) extending to greater depths (subsequently termed 'deep dives'). Analysis suggested that deep dives: (1) were normally distributed around midday; (2) may exceed the inferred aerobic dive limit for the species; (3) displayed slow vertical descent rates and protracted durations; (4) were much deeper than the thermocline; and (5) occurred predominantly during transit, yet ceased once seasonal residence on foraging grounds began. These findings support the hypothesis that deep dives are periodically employed to survey the water column for diurnally descending gelatinous prey. If a suitable patch is encountered then the turtle may cease transit and remain within that area, waiting for prey to approach the surface at night. If unsuccessful, then migration may continue until a more suitable site is encountered. Additional studies using a meta-analytical approach are nonetheless recommended to further resolve this matter.

First records of oceanic dive profiles for leatherback turtles, Dermochelys coriacea, indicate behavioural plasticity associated with long-distance migration

We used Satellite Relay Data Loggers to obtain the first dive profiles for critically endangered leatherback turtles outside the nesting season. As individuals moved from the Caribbean out into the Atlantic, key aspects of their diving behaviour changed markedly, in line with theoretical predictions for how dive duration should vary with foraging success. In particular, in the Atlantic, where foraging success is expected to be higher, dives became much longer than in the Caribbean. The deepest-ever dive profile recorded for a reptile was obtained in the oceanic Atlantic, with a 54-min dive to 626 m on 26 August 2002. However, dives were typically much shallower (generally

Rapid glacial retreat on the Kamchatka Peninsula during the early 21st Century

Monitoring glacier fluctuations provides insights into changing glacial environments and recent climate change. The availability of satellite imagery offers the opportunity to view these changes for remote and inaccessible regions. Gaining an understanding of the ongoing changes in such regions is vital if a complete picture of glacial fluctuations globally is to be established. Here, satellite imagery (Landsat 7, 8 and ASTER) is used to conduct a multi-annual remote sensing survey of glacier fluctuations on the Kamchatka Peninsula (eastern Russia) over the 2000–2014 period. Glacier margins were digitised manually and reveal that, in 2000, the peninsula was occupied by 673 glaciers, with a total glacier surface area of 775.7 ± 27.9 km2 . By 2014, the number of glaciers had increased to 738 (reflecting the fragmentation of larger glaciers), but their surface area had decreased to 592.9 ± 20.4 km2 . This represents a ∼ 24 % decline in total glacier surface area between 2000 and 2014 and a notable acceleration in the rate of area loss since the late 20th century. Analysis of possible controls indicates that these glacier fluctuations were likely governed by variations in climate (particularly rising summer temperatures), though the response of individual glaciers was modulated by other (non-climatic) factors, principally glacier size, local shading and debris cover.