Abstract: High-latitude environments show extreme seasonal variation in physical and biological variables. The classic paradigm of Arctic marine ecosystems holds that most biological processes slow down or cease during the polar night. One key process that is generally assumed to cease during winter is diel vertical migration (DVM) of zooplankton. DVM constitutes the largest synchronized movement of biomass on the planet, and is of paramount importance for marine ecosystem function and carbon cycling. Here we present acoustic data that demonstrate a synchronized DVM behaviour of zooplankton that continues throughout the Arctic winter, in both open and ice-covered waters. We argue that even during the polar night, DVM is regulated by diel variations in solar and lunar illumination, which are at intensities far below the threshold of human perception. We also demonstrate that winter DVM is stronger in open waters compared with ice-covered waters. This suggests that the biologically mediated vertical flux of carbon will increase if there is a continued retreat of the Arctic winter sea ice cover.

Abstract: Abstract Facial flushing, a colour change caused by variation of blood flow through highly vascularized skin, has been observed in taxonomically diverse bird species but the function of the behaviour has not been assessed. Lappet-faced vultures, Aegypius tracheliotos, have unfeathered heads that can rapidly flush from pink to dark red, and this has been hypothesized to indicate contest ability in vulture gatherings. We show that adults with flushed heads won most interactions against those with pale heads. A previously unnoticed colour variation of the throat, visible only when the head is flushed, was also related to the outcome of interactions: blue-throated adults participated in, and won, more interactions than red-throated adults. We suggest that the non-fixed groups of which lappet-faced vulture populations consist promote the evolution of signals of dominance that can be adjusted extremely rapidly.

Abstract: Although horses are social animals they are often housed individually with limited social contact to other horses and this may compromise their welfare. The present study included eight young female horses and investigated the strength of motivation for access to full social contact, head contact and muzzle contact, respectively, to a familiar companion horse. Horses were housed individually next to their companion horse and separations between pens prevented physical contact. During daily test sessions horses were brought to a test area where they could access an arena allowing social contact. Arena access during 3 min was given after completion of a predetermined number of responses on a panel. Fixed ratios (FR) of 8, 16, 24, 32 and 40 responses per arena access were applied in a random order, one per daily test session, within each test week (Monday to Friday), and the number of rewards per daily test session was recorded. All horses could access all three types of social contact in a cross-over design, and an empty arena was used as control. Motivational strength was assessed using elasticity of demand functions, which were estimated based on the number of rewards earned and FR. Elasticities of demand for the three types of social contact were low (-0.20), and not significantly different, although increasing FR still resulted in a decrease in rewards obtained for all three types of social contact (P < 0.001). Across FR-levels horses earned more rewards for social contact than for an empty arena, as shown by much higher intercept values (2.51 vs. 0.99; P < 0.001). However, the elasticity of demand for infrequent access to an empty arena (-0.08) was lower than for social contact (P < 0.01) and not significantly different from zero (P = 0.07). Horses performed more social behaviour the lesser the restriction on social contact (full > head > muzzle). However, the finding that horses showed a similar and high motivation for all three types of social contact suggests that they are valued equally highly in a situation where the alternative is no social contact.

Abstract: Intelligence quotient (IQ) is a standardized measure of human intellectual capacity that takes into account a wide range of cognitive skills1. IQ is generally considered to be stable across the lifespan, with scores at one time point used to predict educational achievement and employment prospects in later years1. Neuroimaging allows us to test whether unexpected longitudinal fluctuations in measured IQ are related to brain development. Here we show that verbal and non-verbal IQ can rise or fall in the teenage years, with these changes in performance validated by their close correlation with changes in local brain structure. A combination of structural and functional imaging showed that verbal IQ changed with grey matter in a region that was activated by speech, whereas non-verbal IQ changed with grey matter in a region that was activated by finger movements. By using longitudinal assessments of the same individuals, we obviated the many sources of variation in brain structure that confound cross-sectional studies. This allowed us to dissociate neural markers for the two types of IQ and to show that general verbal and non-verbal abilities are closely linked to the sensorimotor skills involved in learning. More generally, our results emphasize the possibility that an individual’s intellectual capacity relative to their peers can decrease or increase in the teenage years. This would be encouraging to those whose intellectual potential may improve, and would be a warning that early achievers may not maintain their potential.