Geometric Graph Properties of the Spatial Preferred Attachment model

The spatial preferred attachment (SPA) model is a model for networked information spaces such as domains of the World Wide Web, citation graphs, and on-line social networks. It uses a metric space to model the hidden attributes of the vertices. Thus, vertices are elements of a metric space, and link formation depends on the metric distance between vertices. We show, through theoretical analysis and simulation, that for graphs formed according to the SPA model it is possible to infer the metric distance between vertices from the link structure of the graph. Precisely, the estimate is based on the number of common neighbours of a pair of vertices, a measure known as {\sl co-citation}. To be able to calculate this estimate, we derive a precise relation between the number of common neighbours and metric distance. We also analyze the distribution of {\sl edge lengths}, where the length of an edge is the metric distance between its end points. We show that this distribution has three different regimes, and that the tail of this distribution follows a power law

A novel approach to seabird posture estimation: finding roll and yaw angles of dynamic soaring albatrosses using tri-axial magnetometers

With advances in bio-logging technology, the posture of animals is now commonly described by inertial measurement units, which include tri-axial accelerometers to estimate pitch and roll angles. Many large seabirds use dynamic soaring flight to travel long distances, but this low-cost flight mode results in high centripetal acceleration, which obscures posture derived from accelerometers. Tri-axial magnetometers are not influenced by acceleration and might provide a way to estimate the posture of animals that experience high centripetal acceleration. We propose a new method to estimate the posture of dynamic soaring seabirds using tri-axial magnetometer data, with the assumption that they do not have large pitch angles during routine flight. This method was field-tested by deploying a combination of bio-logging devices on three albatross species breeding on Marion Island, using bird-borne video loggers to validate the roll angles. Validated data showed that the method worked well in most instances, but accuracy decreased when the heading was close to magnetic north or south. Accurate, fine-scale posture estimates may provide insight into dynamic soaring flight and allow estimates of fine-scale tracks using dead-reckoning, not only for seabirds, but potentially for other species where centripetal acceleration limits the use of accelerometers to estimate posture

Low resting metabolic rate and increased hunger due to β-MSH and β-endorphin deletion in a canine model

Mutations that perturb leptin-melanocortin signaling are known to cause hyperphagia and obesity, but energy expenditure has not been well studied outside rodents. We report on a common canine mutation in pro-opiomelanocortin (POMC), which prevents production of β–melanocyte-stimulating hormone (β-MSH) and β-endorphin but not α-MSH; humans, similar to dogs, produce α-MSH and β-MSH from the POMC propeptide, but rodents produce only α-MSH. We show that energy expenditure is markedly lower in affected dogs, which also have increased motivational salience in response to a food cue, indicating increased wanting or hunger. There was no difference in satiety at a modified ad libitum meal or in their hedonic response to food, nor disruption of adrenocorticotropic hormone (ACTH) or thyroid axes. In vitro, we show that β-MSH signals comparably to α-MSH at melanocortin receptors. These data implicate β-MSH and β-endorphin as important in determining hunger and moderating energy expenditure and suggest that this role is independent of the presence of α-MSH

Impact of test, vaccinate or remove protocol on home ranges and nightly movements of badgers a medium density population

In the British Isles, the European badger (Meles meles) is thought to be the primary wildlife reservoir of bovine tuberculosis (bTB), an endemic disease in cattle. Test, vaccinate or remove (‘TVR’) of bTB test-positive badgers, has been suggested to be a potentially useful protocol to reduce bTB incidence in cattle. However, the practice of removing or culling badgers is controversial both for ethical reasons and because there is no consistent observed effect on bTB levels in cattle. While removing badgers reduces population density, it may also result in disruption of their social behaviour, increase their ranging, and lead to greater intra- and inter-species bTB transmission. This effect has been recorded in high badger density areas, such as in southwest England. However, little is known about how TVR affects the behaviour and movement of badgers within a medium density population, such as those that occur in Northern Ireland (NI), which the current study aimed to examine. During 2014–2017, badger ranging behaviours were examined prior to and during a TVR protocol in NI. Nightly distances travelled by 38 individuals were determined using Global Positioning System (GPS) measurements of animal tracks and GPS-enhanced dead-reckoned tracks. The latter was calculated using GPS, tri-axial accelerometer and tri-axial magnetometer data loggers attached to animals. Home range and core home range size were measured using 95% and 50% autocorrelated kernel density estimates, respectively, based on location fixes. TVR was not associated with measured increases in either distances travelled per night (mean = 3.31 ± 2.64 km) or home range size (95% mean = 1.56 ± 0.62 km2, 50% mean = 0.39 ± 0.62 km2) over the four years of study. However, following trapping, mean distances travelled per night increased by up to 44% eight days post capture. Findings differ from those observed in higher density badger populations in England, in which badger ranging increased following culling. Whilst we did not assess behaviours of individual badgers, possible reasons why no differences in home range size were observed include higher inherent ‘social fluidity’ in Irish populations whereby movements are less restricted by habitat saturation and/or that the numbers removed did not reach a threshold that might induce increases in ranging behaviour. Nevertheless, short-term behavioural disruption from trapping was observed, which led to significant increases in the movements of individual animals within their home range. Whether or not TVR may alter badger behaviours remains to be seen, but it would be better to utilise solutions such as oral vaccination of badgers and/or cattle as well as increased biosecurity to limit bTB transmission, which may be less likely to cause interference and thereby reduce the likelihood of bTB transmission

Movements in Adelie penguins foraging for chicks at Ardley Island, Antarctica; circles within spirals, wheels within wheels

Eighteen Adelie penguins Pygoscelis adeliae tending chicks at Ardley Island (62°13\u27S, 58°55\u27W), Antarctica during December 1991 and January 1992 were equipped with multiple channel data loggers recording swim heading, speed and dive depth. These parameters were then equated together using vectors to calculate the foraging tracks of the birds at sea as well as depth utilisation. The deepest dive recorded was 97m although most dives terminated within 70m. In accordance with previous studies, descent and ascent speed of diving birds increased with maximum dive depth and absolute time spent for the descent and ascent increased with maximum dive depth. The distance moved to the farthest point from the island was 35km although 70% of all time at sea was spent within 10km of the island (all birds considered together). Consideration of the fine scale features of bird movement indicated that three major patterns were apparent; (i) virtual straight line movement, (ii) a circular or spiralling movement where circles had diameters ranging between 20 and 200m and (iii) extensive movement without any substantial displacement. A travel index (total distance travelled during a specified time divided by the straight line distance covered during this time) showed that the three behaviours had very different values. The frequency of occurrence of particular travel index values followed a logarithmic decay with straight line travel (with indices around 1) accounting for ca. 35% of all movement at sea with greater deviations from a straight line course occurring less often. It is supposed that straight line travel serves displacement, highly localised movement reflects prey pursuit and that the circular or spiralling movement arises from birds seeking out prey using detection systems other than vision

Beyond rings on birds for determination of movements: Wither the archival tag?

Two methods for determining the movement of birds are discussed; Global Location Sensing (determination of position by consideration of day length and local timing of mid-day) and dead reckoning (calculation of routes by vectors). These are examined for their utility over a number of scales. Work conducted on penguins demonstrates that, although global location sensing is not subject to drift errors, its temporal and spatial resolution makes the system only applicable for large scale movements over at least tens of km. Dead reckoning, however, can be used over scales ranging from tens of kilometres to centimetres. Positions derived from dead reckoning are relatively more accurate the closer they are in time and distance to each other although drift over time can be problematic. The high temporal and spatial resolution of dead reckoning means that animal decisions leading to their movements can be determined and this is examined for penguins over a scales ranging from tens of kilometres to metres. Future work is likely to concentrate on small scale movements in 3 dimensions which, to date, cannot be resolved with other system

Reconstructing the past using futuristic developments: Trends and perspectives using logger technology on penguins

Over the last two decades there has been remarkable progress in the development of sensory systems coupled with loggers that have been attached to free-living marine animals. Increases in sensor resolution, sensor diversity and memory size have been coupled with decreases in unit size. Thus, the periods over which animals have been monitored have increased from hours to months while the sampling frequency has decreased from minutes or seconds to fractions of a second. Four main interrelated trends can be identified. Determination of; (1) animal position in three dimensions, (2) the characteristics of the environment in which the animals operate, (3) animal behaviour and (4) energy management. The elucidation of these trends in penguins is discussed and perspectives given with regard to what is expected in the future