Sex differences in leadership during group movement in mantled howler monkeys (Alouatta palliata)

Benefits of group life depend in large part on whether animals remain cohesive, which often requires collective decisions about where and when to move. During a group movement, the leader may be considered as the individual occupying the vanguard position of the group progression, when its movement evokes following by other group members. In nondespotic societies, individuals with greater incentives to move frequently are leaders. During 15 months of observations (1,712 contact hours), we investigated two mantled howler monkey (Alouatta palliata) groups at La Flor de Catemaco (Los Tuxtlas, Mexico) to examine whether sex and female reproductive state influenced leadership likelihood in two contexts: movements toward feeding trees; movements associated with loud calls, a group-defense behavior used by males of this genus. Females led and occupied forward positions during group movements toward feeding trees more often than adult males. Adult females led these movements more frequently when they were gestating than when they were lactating or cycling. There were no differences between sexes in the leadership of group movements associated with loud calls. Leadership by gestating females is perhaps the result of their higher nutritional/energetic needs when compared with cycling females, and of their greater mobility when compared with lactating females carrying dependent offspring. Female leadership during movements toward feeding trees may be a mechanism to optimize access to food resources in mantled howler monkeys.     

Dual Color Neural Activation and Behavior Control with Chrimson and CoChR in Caenorhabditis elegans

By enabling a tight control of cell excitation, optogenetics is a powerful approach to study the function of neurons and neural circuits. With its transparent body, a fully mapped nervous system, easily quantifiable behaviors and many available genetic tools, Caenorhabditis elegans is an extremely well-suited model to decipher the functioning logic of the nervous system with optogenetics. Our goal was to establish an efficient dual color optogenetic system for the independent excitation of different neurons in C. elegans. We combined two recently discovered channelrhodopsins: the red-light sensitive Chrimson from Chlamydomonas noctigama and the blue-light sensitive CoChR from Chloromonas oogama. Codon-optimized versions of Chrimson and CoChR were designed for C. elegans and expressed in different mechanosensory neurons. Freely moving animals produced robust behavioral responses to light stimuli of specific wavelengths. Since CoChR was five times more sensitive to blue light than the commonly used ChR2, we were able to use low blue light intensities producing no cross-activation of Chrimson. Thanks to these optogenetics tools, we revealed asymmetric cross-habituation effects between the gentle and harsh touch sensory motor pathways. Collectively, our results establish the Chrimson/CoChR pair as a potent tool for bimodal neural excitation in C. elegans and equip this genetic model organism for the next generation of in vivo optogenetic analyses.     

Biochemical evidence accumulates across neurons to drive a network-level eruption

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Ants resort to majority concession to reach democratic consensus in the presence of a persistent minority

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FIM Imaging and FIMtrack: Two New Tools Allowing High-throughput and Cost Effective Locomotion Analysis

The analysis of neuronal network function requires a reliable measurement of behavioral traits. Since the behavior of freely moving animals is variable to a certain degree, many animals have to be analyzed, to obtain statistically significant data. This in turn requires a computer assisted automated quantification of locomotion patterns. To obtain high contrast images of almost translucent and small moving objects, a novel imaging technique based on frustrated total internal reflection called FIM was developed. In this setup, animals are only illuminated with infrared light at the very specific position of contact with the underlying crawling surface. This methodology results in very high contrast images. Subsequently, these high contrast images are processed using established contour tracking algorithms. Based on this, we developed the FIMTrack software, which serves to extract a number of features needed to quantitatively describe a large variety of locomotion characteristics. During the development of this software package, we focused our efforts on an open source architecture allowing the easy addition of further modules. The program operates platform independent and is accompanied by an intuitive GUI guiding the user through data analysis. All locomotion parameter values are given in form of csv files allowing further data analyses. In addition, a Results Viewer integrated into the tracking software provides the opportunity to interactively review and adjust the output, as might be needed during stimulus integration. The power of FIM and FIMTrack is demonstrated by studying the locomotion of Drosophila larvae.     

Play and Intentionality Among Today's Preschoolers

A comparison is made of data on the level of development of play activity and its influence on the volitional behavior of today's preschoolers and the preschoolers of the 1940s–1950s. The results of the comparison point to a substantial decrease in the level of narrative role-playing among children today. The study reproduces the widely known experiment of Z.V. Manuilenko (1948). The comparison of data on preschoolers of the mid-twentieth century and the beginning of the twenty-first shows a significant decrease in the level of volitional behavior in both play and nonplay situations. The results suggest that primitive, underdeveloped play cannot define a zone of proximal development and fulfill the status of primary activity.     

Effects of age and experience on the responses of territorial and floater male Red‐winged Blackbirds to models of receptive females

The ability of sexually mature non‐territorial floaters to sire offspring affects the success of floating as a breeding strategy. Red‐winged Blackbirds (Agelaius phoeniceus) have second‐year (SY) and after‐second‐year (ASY) floater males, and genetic studies suggest that floaters may gain paternity. Despite these studies, we still know little about the fitness costs and benefits of floating in this species. By presenting taxidermic models of females in soliciting, precopulatory postures in territories of experienced (previously attracted at least one mate in the study area) and inexperienced (did not previously defend a territory in the study area) males, I was able to examine the copulation behavior and success of floater male Red‐winged Blackbirds as well as the effect of experience for territorial males. Floaters trespassed during 66.1% of presentations and 85.4% of trespassers were SY males. Experienced territorial males (92.5%) and neighbors (87.5%) were most successful in attempts to copulate with models, inexperienced territorial males (62.5%) and ASY floaters (50.0%) had intermediate success, and SY floaters (6.9%) were least successful. Experienced territorial males were more likely to approach models than inexperienced males, and floaters were more likely to approach models in territories of experienced than inexperienced males. These results provide further evidence that floaters trespass frequently, suggest that floaters sire offspring, and demonstrate that prior breeding experience affects the behavior and reproductive success of territorial male Red‐winged Blackbirds. Floating appears to be a conditional strategy for ASY male Red‐winged Blackbirds, but, because it is still not known if SY floaters sire offspring, these males may be trespassing to gain information or experience.     

Peering into the Dynamics of Social Interactions: Measuring Play Fighting in Rats

Play fighting in the rat involves attack and defense of the nape of the neck, which if contacted, is gently nuzzled with the snout. Because the movements of one animal are countered by the actions of its partner, play fighting is a complex, dynamic interaction. This dynamic complexity raises methodological problems about what to score for experimental studies. We present a scoring schema that is sensitive to the correlated nature of the actions performed. The frequency of play fighting can be measured by counting the number of playful nape attacks occurring per unit time. However, playful defense, as it can only occur in response to attack, is necessarily a contingent measure that is best measured as a percentage (#attacks defended/total # attacks X 100%). How a particular attack is defended against can involve one of several tactics, and these are contingent on defense having taken place; consequently, the type of defense is also best expressed contingently as a percentage. Two experiments illustrate how these measurements can be used to detect the effect of brain damage on play fighting even when there is no effect on overall playfulness. That is, the schema presented here is designed to detect and evaluate changes in the content of play following an experimental treatment.     

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ABSTRACT

In most mammals, adults produce relatively low frequency vocalizations compared to those of juveniles. This rule is not maintained however at least in four species of ground squirrels, whose juveniles call at the adult's fundamental frequency. These findings have been obtained however with separate sets of juveniles and adults and no data is available concerning the ontogeny linked to these differences. Here we analyze the acoustic structure of alarm calls of the same Yellow Spermophilus fulvus and Speckled S. suslicus ground squirrel individuals, recorded as pups and as adults after hibernation. We found the fundamental frequencies of adults within the same frequency ranges as those of pups, in spite of the significant difference in body mass. In ground squirrels, severing the relationship between body size and call frequency removes some vocal cues to age. We discuss some functional hypotheses advanced to explain manipulations with fundamental frequencies in ground squirrels and other animals, and suggest the lack of data for discussing the mechanisms of such vocal tuning.     

Planarian fragments behave as whole animals

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