Using Markov Chain Analysis to assess stereotyped scent marking behaviour in wild brown bears

Members of the order Carnivora employ a wide range of postures and stereotyped patterns to mark their scent onto objects, and therein communicate with conspecifics. Despite much anecdotal evidence on the marking behaviour of Ursids, empirical data examining marking patterns displayed by wild populations is lacking. Situated on the west coast of British Columbia (2009-2011), we used trail cameras stationed at marking trees to investigate scent marking and investigatory behaviour by wild brown bears Ursus arctos. Transitions between postures were assessed using Markov Chain Analysis. Results showed that scent marking patterns varied by age and sex; adult males exhibited a cyclic pattern of marking behaviour which included ‘core’ and ‘secondary’ postures, whereas adult females failed to exhibit any subset postures. The behaviour of subadults (sexes combined) was a variation and simplification of the patterns displayed by adult males and females. The wider variety of marking postures selected by adult males may convey a more complex signal, relating to the function of scent marking in the species. Females with young were classified separately to assess potential similarities/differences in the behaviour of all members of the family group. Using a simplified ethogram, we found the behaviour of cubs to be dependent on their age and the behaviour of their mother. Younger cubs were more likely to conduct the same behaviour as their mother, whereas older cubs exhibited behaviours independently. This study presents the first detailed description of the development of scent marking behaviour by cubs in the Ursidae

Assessing the scent marking behaviour of wild brown bears: an exploration of time and energy investment, motor patterns and age-related development

Members of the order Carnivora employ a wide range of postures and stereotyped patterns to mark their scent onto objects and thereby communicate with conspecifics. Despite much anecdotal evidence on the marking behaviour of ursids, empirical evidence of scent marking motor patterns displayed by wild populations is lacking. Analysing the time bears spend at marking trees and the behaviours involved, could provide further insight into the function of marking and highlight time and energy investment. Over a three year period, camera traps stationed at marking trees were used to investigate scent marking and investigatory behaviour by wild brown bears Ursus arctos in coastal British Columbia. This work follows on from data presented at the 18th, 19th & 20th IBA conferences

Food availability affects the scent marking frequencies of wild brown bears

For many species, chemical signalling is used to signal the competitive ability of individuals and therefore plays an important role in the breeding system. As breeding generally promotes intrasexual competition, the potential fitness costs associated with competitive behaviour may be mitigated if individuals are able to assess their own ability, and the competitive ability of others, prior to agonistic encounters. Due to their hierarchical social structure and large home-range size, bears (Ursidae) are thought to rely highly on olfactory methods of communication. Through camera traps orientated towards bear ‘rub trees’ over a three-year period, we have begun to establish the function of strategic tree selectivity and the social function of marking behaviour for brown bears Ursus arctos in the Glendale drainage, British Columbia. We hypothesised that marking trees function to signal competitive ability between individuals, with dominant individuals signalling their high competitive ability and receivers detecting these cues and modifying their behaviour accordingly. Here, we provide evidence to further these hypotheses by demonstrating how scent marking frequencies vary in relation to food availability

A two-dimensional finite element model of front surface current flow in cells under non-uniform, concentrated illumination

A two-dimensional finite element model of current flow in the front surface of a PV cell is presented. In order to validate this model we perform an experimental test. Later, particular attention is paid to the effects of non-uniform illumination in the finger direction which is typical in a linear concentrator system. Fill factor, open circuit voltage and efficiency are shown to decrease with increasing degree of non-uniform illumination. It is shown that these detrimental effects can be mitigated significantly by reoptimization of the number of front surface metallization fingers to suit the degree of non-uniformity. The behavior of current flow in the front surface of a cell operating at open circuit voltage under non-uniform illumination is discussed in detail

pi/K -> e nu branching ratios to O(e^2 p^4) in Chiral Perturbation Theory

We calculate the ratios R_{e/mu}^{(P)} = Gamma(P -> e nu)/Gamma (P -> mu nu) (P=pi,K) in Chiral Perturbation Theory to order e^2 p^4. We complement the one- and two-loop effective theory results with a matching calculation of the local counterterm, performed within the large-$N_C$ expansion. We find R_{e/mu}^{(\pi)} = (1.2352 \pm 0.0001)*10^{-4} and R_{e/mu}^{(K)} = (2.477 \pm 0.001)*10^{-5}, with uncertainty induced by the matching procedure and chiral power counting. Given the sensitivity of upcoming new measurements, our results provide a clean baseline to detect or constrain effects from weak-scale new physics in these rare decays. As a by-product, we also update the theoretical analysis of the individual pi/K -> \ell nu modes.Comment: 40 pages, 4 figures, 3 table

Enhancing adult hippocampal neurogenesis with lysophosphatidic acid: a proposal for erasing cocaine contextual memory

Stimulating adult hippocampal neurogenesis (AHN) has been uncovered as a promising approach in the manipulation of retrograde memories. This work aims to study whether increasing AHN with lysophosphatidic acid (LPA, an endogenous lysophospholipid with proneurogenic actions) promotes the forgetting of previously established cocaine-contextual associations. C57BL/6J mice previously trained in a cocaine-induced conditioned place preference (CPP) paradigm were submitted to 23 days of withdrawal, during which they received repeated intracerebroventricular infusions of LPA, ki16425 (a selective LPA1/3 receptors antagonist), or vehicle solution. Then, CPP maintenance was assessed, and the causal role of AHN in this process was evaluated using a mediation analysis. In a complementary experiment, wild-type and LPA1-null mice were acutely infused with LPA or ki16425 to determine the involvement of the LPA1 receptor in the in vivo proneurogenic actions of LPA. The chronic LPA treatment significantly weakened the long-term retention of a previously acquired cocaine-CPP memory, an effect clearly mediated by a LPA-induced increase in the number of adult-born dentate granule cells. In contrast, the ki16425-treated mice displayed aberrant responses of initially decreased CPP retention that progressively increased CPP across the extinction sessions, in absence of effects on AHN. The histological studies suggested that the proneurogenic actions of LPA were related to the enhancement of cell proliferation and critically depended on the LPA1 receptor function. Our results suggest that the LPA/LPA1-pathway acts as a potent in vivo modulator of AHN, and highlight the usefulness of a post-learning increase of adult-born hippocampal neurons as a strategy to promote the forgetting of cocaine-context associations.Plan Propio de Investigación y Transferencia. Campus de Excelencia Internacional Andalucía Tech. Spanish Ministry of Economy and Competitiveness (Agencia Estatal de Investigación), co‐funded by the European Research Development Fund (AEI/FEDER, UE) (PSI2013‐44901‐P and PSI2017‐82604‐R to L.J.S. and PSI2015‐73156‐JIN to E.C.O.); by the National System of Health‐Instituto de Salud Carlos III, which is co‐funded by AEI/FEDER, UE (Red de Trastornos Adictivos; RD16/0017/0001 to F.R.d.F.); and by the Andalusian R&D&I Programme, Regional Ministry of Economy and Knowledge (PAIDI CTS643 to G.E.T.). D.L.G.M. hold a FPU grant from the Spanish Ministry of Education, Culture and Sports (FPU13/04819 ). F.R.d.F. and G.E.T. are supported by Nicolas Monardes Programme, from the Andalusian Regional Ministry of Health. E.C.O. holds a ‘Jóvenes Investigadores’ grant (code: PSI2015‐73156‐JIN) from the Spanish Ministry of Economy and Competitiveness (Agencia Estatal de Investigación), which is co‐funded by the AEI/FEDER, UE

Inter-sexual and inter-seasonal differences in the chemical signalling strategies of brown bears

The brown bear (Ursus arctos) is a species which, due to its solitary, dominance hierarchy social system and large home range, is thought to rely heavily on chemical signals as a means of communication. Through camera traps orientated towards bear ‘rub trees’ over a two-year period, we assessed the proportional contribution of scent marking in different seasons by different age sex classes, and gained insights into the role of chemical signalling in maintaining social structure. We found, during the breeding season (June-July), that both adult males (n=38 P1 year (n=11 P=0.003) scent marked trees significantly more often than expected, whereas lone adult females (n=7) and subadults (n=3) marked less than expected. Outside of the breeding season (August-October), adult males (n=70) marked in an expected proportion, females with cubs (all ages) marked significantly more than expected (n=71 P<0.001), and lone adult females (n=11) and subadults (n=15) marked less than expected. During both the breeding season (n=7 P=0.026) and the fall (n=11 P<0.001), adult females marked trees significantly less than their occurrence on bear trails would expect, as did subadults during the breeding season (n=3 P=0.026) but not during the fall (n=15). Adult males marked at significantly high frequencies both during and outside of the breeding season, potentially to communicate dominance between males. Supported by the low frequency of scent marking by subadults. We observed a total avoidance of bear trails containing active rub trees by females with cubs <1 year during the breeding season, a possible counterstrategy to sexually selected infanticide due to the strong male bias in scent marking during the breeding season. We hypothesize that scent marking in brown bears is taught by the mother, beginning with cubs <1 year outside of the breeding season at a relatively ‘safe’ time of year

Magnetite-supported palladium single-atoms do not catalyse the hydrogenation of alkenes but small clusters do

The activity of supported noble metal catalysts strongly depends on the particle size. The ultimate small-size limit is the single-atom catalyst (SAC), which maximizes the catalytic efficiency in the majority of the examples. Here, we investigate the catalytic behavior of Pd SACs supported on magnetite nanoparticles and we unambiguously demonstrate that Pd SACs are absolutely inactive in the hydrogenation of various alkene substrates. Instead, Pd clusters of low atomicity exhibit outstanding catalytic performance.Postprint (author's final draft

Thin Sea Ice, Thick Snow, and Widespread Negative Freeboard Observed During N-ICE2015 North of Svalbard

In recent years, sea-ice conditions in the Arctic Ocean changed substantially toward a younger and thinner sea-ice cover. To capture the scope of these changes and identify the differences between individual regions, in situ observations from expeditions are a valuable data source. We present a continuous time series of in situ measurements from the N-ICE2015 expedition from January to June 2015 in the Arctic Basin north of Svalbard, comprising snow buoy and ice mass balance buoy data and local and regional data gained from electromagnetic induction (EM) surveys and snow probe measurements from four distinct drifts. The observed mean snow depth of 0.53 m for April to early June is 73% above the average value of 0.30 m from historical and recent observations in this region, covering the years 1955–2017. The modal total ice and snow thicknesses, of 1.6 and 1.7 m measured with ground-based EM and airborne EM measurements in April, May, and June 2015, respectively, lie below the values ranging from 1.8 to 2.7 m, reported in historical observations from the same region and time of year. The thick snow cover slows thermodynamic growth of the underlying sea ice. In combination with a thin sea-ice cover this leads to an imbalance between snow and ice thickness, which causes widespread negative freeboard with subsequent flooding and a potential for snow-ice formation. With certainty, 29% of randomly located drill holes on level ice had negative freeboard