Summary: Milinkovitch et al. (2013)

Many amniotes (an animal possessing an amnion - sac enclosing the developing embryo) show keratinization of various skin appendages, such as hair, feathers and scales. These different appendages differentiate during embryonic development. The differentiation is genetically controlled by developmental units and reaction-diffusion mechanisms (RDMs) pattern the spatial organisation of these units. Milinkovitch et al. (2013) demonstrate that the face and jaw scales of crocodiles do not form under the influence of these genetically controlled elements. Rather, they are random polygonal domains of highly keratinized skin that form by cracking of the skin in a stress field (a physical self-organizing stochastic process). They suggest that this occurs because the embryonic facial and jaw skeleton undergoes rapid growth and is highly keratinized, which generates the mechanical stress that induces cracking.

Summary: Benedict et al. (2012)

Animals often signal at low frequency or with harsh sounds to indicate aggression. For some species, larger body size is correlated with lower frequency sound production and can potentially indicate fighting ability. Low frequency and harsh sounds may also indicate motivation to be aggressive and to attack. Benedict et al. (2012) investigated whether canyon wrens Catherpes mexicanus alter vocal behaviour (facultative adjustment) in the low frequency range, and whether they utter more harsh calls, in response to territorial intrusions (playback simulations). They found that territory holders altered their song type usage, lowered their frequency and increased song production rate in response to simulated intrusions. Territory holders were also more likely to attach harsh notes to the ends of songs. Benedict et al. (2012) indicate that these results support the motivation-structural hypothesis.

Summary: Mainwaring & Hartley (2013)

Individuals vary in behaviour. While the evolutionary and ecological consequences of this variation have been relatively well studied, the causes remain unknown. One of the primary influences of offspring behavioural development are the parents, which exert the majority of influence during the pre- and early post-natal periods. Female zebra finches Taeniopygia guttata, as for many other bird species, will hatch asynchronous clutches when females initiate incubation prior to completing laying. This drives differences in phenotypic expression between early and late-hatched young. Mainwaring & Hartley (2013) manipulated the hatching patterns of zebra finches and found that late-hatched birds from asynchronous clutches were bolder, exploring a novel environment more, than their earlier hatched or synchronous hatched siblings. They also noted sex differences in exploration of a novel object, with females being bolder than males, regardless of hatching regime. Mainwaring & Hartley's (2013) study provide support that variations in an offspring's early environment can have a significant influence on the expression of its behaviour and provides an insight into how parental investment plays a role in maintaining and generating behavioural variation.

Summary: Padmanabhan et al. (2012)

Transcriptional feedback loops drive the functioning of eukaryotic circadian clocks. Two important mammalian proteins involved in this process are Period (PER) and Cryptochrome (CRY). These proteins aggregate and form large nuclear complexes (PER complex), suppressing their own transcription. Padmanabhan et al. (2012) found the RNA helicases DDX5 and DHX9 are included in the PER complexes of mice. In addition, other molecules, such as RNA polymerase II large subunit, were also located here, promoting the termination of transcription. They found that RNA polymerase II accumulates, during circadian negative feedback, near termination sites on Per and Cry genes, but it does not control these genes. They conclude that this negative feedback mechanism includes direct control of the termination of protein transcription.

Summary: Stamatakis & Stuber (2012)

Negative reward-related information is carried to the ventral portion of the middle brain (including the rostromedial tegmental nucleus) via projections of the lateral habenula. Stamatakis & Stuber (2012) studied the behavioural complications of selective activation of this particular pathway in the brain in mice. They found that aversive stimuli increased the excitatory drive of the lateral habenula, which resulted in conditioned, passive and active behavioural avoidance of the aversive stimulus. The activity of these projections to the midbrain is thus aversive, and functions to negatively reinforce behavioural response.

Summary: Markham et al. (2012)

Social species benefit from group living, however, social groups must also compete for resources with other groups. Competition can be a major driver influencing a group's movements and space use and has the potential to shape the evolution of sociality. Markham et al. (2012) investigated the ecological factors influencing baboon Papio cynocephalus group dominance, with a specific focus on what spatial features influence dominance and what occurs when a group is defeated. They found that the number of adult males in a group predicted which group would win a direct conflict, but they also found that a group's intensity of use of areas associated with the encounter location also predicted a win, over a longer time period (9-12 months). Losing groups  used the area surrounding the encounter location less, possibly incurring short-term costs associated with reduced access to resources. Markham et al.'s (2012) study highlights the importance of inter-group competition on social group space use.

Summary: Kronfeld-Schor et al. (2013)

The circadian "clock" is the body's internal mechanism for keeping track of time. This "clock" is driven by an individual's physiology and it influences an animal's behaviour on a daily basis. Alterations to environmental light conditions results in the natural time-keeping rhythms to become entrained to particular light-dark (day-night) cycles. The circadian system consists of molecular, cellular, tissue and organismal levels, and how these levels contribute to an individuals behaviour is quite well understood. The shortcomings of these studies relate to the species studied, typically those that are standard laboratory species that have been maintained in captivity (so called "model" organisms). Kronfeld-Schor et al. (2013) suggest that to understand the evolutionary significance of the circadian clock, we need to study a variety of species from multiple taxonomic groups that display a diversity in activity patterns (e.g. diurnal, nocturnal, cathemeral, crepuscular). In a special feature of the Proceedings of the Royal Society of London B, Kronfeld-Schor et al. (2013) highlight seven papers that attempt to explore the adaptive significance of the circadian clock, with the reviews including the influence of moonlight, latitude, evolutionary history, sociality, temporal niche specialization, annual variation and post-transcriptional mechanisms. These seven papers demonstrate the complexity, as well as the diversity, of the circadian system.