Wall-following behavior is the movement along a wall exhibited by various animals. It is a conserved behavior among taxa, from unicellular organisms to humans, prone to selection pressure, and it is energetically cheap since it provides a homogenous trail and can help animals to follow the shortest distance between two points. There are three sets of explanations for this behavior. The first is that it is a defensive behavior meant to lead the animal to shelter or reduce predation risk, and which, at least in vertebrates, is a proxy of anxiety. The second explanation suggests it is an exploratory behavior, helping an animal either to exit an enclosed space or to orient in a novel (unfamiliar) environment, especially when vision is limited. As novel environments often induce stress, these two explanations are not mutually exclusive. Finally, the wall itself may offer some desired biotic or abiotic conditions, such as a higher prey availability moving along it or favorable microclimate conditions. Wall following is a variable behavior, easily affected by the test conditions, such as the test arena size (e.g., more in smaller arenas), shape, and illumination level. Standardization of its measurement is required to facilitate comparison among studies and species. The timing of examination plays a role too: Wall following often changes along development and with aging. Generally, females follow walls more often than do males. Furthermore, certain conditions experienced at a young age affect wall-following later, so the behavioral changes may be long-lasting. Wall following is correlated with a few other behaviors, such as a negative correlation with phototaxis and activity. We end our review by presenting some future research directions, such as examining wall-following behavior in predator-prey systems, examining whether and when wall-following is adaptive, and studying it in the context of urban ecology. Finally, there is a need to examine how common this behavior is in the wild as most studies have been conducted in the lab.
Several factors, such as the susceptibility of different host species to the attacks and particular nutritional requirements of the parasitoids, may influence the patterns of host specificity in host-parasitoid interactions. These patterns are relevant in determining the geographic range of parasitoid species and the impacts on their hosts' population dynamics. In this review, we systematically compile the information available on the use of spider hosts by a group of koinobiont parasitoid wasps, the polysphinctines (Ichneumonidae). These wasps are known by the capacity of their larvae to induce behavioral changes in their hosts, obtaining web structures suitable for the attachment and permanence of the cocoons. We present a host-parasitoid network including data on 173 interactions between 143 spider species and 89 wasp species, discussing the factors involved in the determination of host specificity patterns, such as phylogenetic constraints, host defenses, and the variation in the attack behaviors of wasps during host immobilization. We also investigated the longitudinal and latitudinal patterns of distribution of host-parasitoid interactions within the group. Although some polysphinctines establish associations with numerous hosts, there seems to be a high level of specialization, which becomes evident when we consider the connectivity levels in their interaction network and the limited number of spider families they target. Although traits such as the structural pattern of webs and host size do not appear to be critical factors determining specificity, the identification of stereotyped and specific behaviors adjusted for attacking particular hosts reinforces the hypothesis that specificity within this group of koinobiont manipulative parasitoids is influenced by host's defensive strategies. Our analysis demonstrated that the number of hosts and host diversity per polysphinctine species were not influenced by latitudinal variation, which suggests that these parasitoids have limited tolerance for a wide range of abiotic conditions. Finally, a broad longitudinal distribution of the preferential host species may increase the chances for some of these parasitoids to be in contact with other potential suitable hosts, favoring the use of multiple hosts.
The flexible execution of highly repeated, discrete, and easily recorded tasks makes orb web construction an attractive model for a new generation of general questions concerning complex, flexible behavior by small, apparently simple animals. Accumulated data make it profitable to focus attention on one type of decision that is repeated over and over in each orb: where to attach the sticky spiral to each radius that it crosses. Spiders use at least ten cues to make this decision. Combining this progress with new neurobiological techniques and concepts makes it possible to address new questions concerning higher levels of behavioral organization, including behavioral imprecision (errors), attention and lack of attention, mental maps, open-ended versus rigidly flexible behavioral rules, and the effects of psychoactive drugs. I discuss these and other promising lines for future research. Some data suggest that at least rudimentary higher- level analytical processes occur in orb weavers.
Over 20 years ago, an adaptive, silent male morph called 'flatwing' was discovered in a population of Hawaiian crickets (Teleogryllus oceanicus). Silence protects males against lethal, eavesdropping parasitoid flies (Ormia ochracea). Since then, numerous independent, protective morphs have been discovered, including parallel 'flatwing' mutations, 'small-wing', 'curly-wing', 'rattling-wing', and 'defiled-wing', all of which disrupt structures that generate sound when males rub their wings together. Some crickets also produce a protective, attenuated signal called 'purring'. This cricket-fly arms race is a microcosm of behavioral and evolutionary biology. Here we provide a user's guide to the system. Our research efforts have revealed an important role for behavioral flexibility (i.e., plasticity) in accommodating and accelerating genetic adaptation by enabling both sexes to cope with a changing social environment caused by adaptive signal loss. We describe a unique mode by which behavioral flexibility and novel adaptations are bound together in this system: as each one affects the fitness of the other in a way that facilitates rapid responses to selection, the two co-evolve over time. We advocate for viewing behavior's role in evolution as dynamic rather than static. Our research supports the idea that behavior can change dynamically depending on genetic architecture, demography, and other factors. In addition, the widespread reduction of singing through morphological rather than behavioral change in T. oceanicus pinpoints wing morphology as a hotspot of evolution, and we describe ongoing behavioral and genomic research characterizing this underappreciated mode of adaptation—adaptive breakage—which disrupts previously canalized form-function relationships.
Inbreeding and inbreeding depression are important topics in evolutionary biology and conservation but relatively peripheral to the field of animal behavior. Here, we make a case for why the field of animal behavior should take a greater interest in inbreeding and inbreeding depression. Social interactions, including cooperation, competition, and communication, can have important consequences for our understanding of inbreeding and inbreeding depression. We review studies that examine inbreeding in a social context. This work shows that social interactions can moderate the severity of inbreeding depression by either exacerbating or buffering against the fitness costs of being inbred. Furthermore, social interactions can mediate indirect genetic effects associated with inbreeding—even passing the costs of inbreeding onto outbred individuals. We discuss how a social perspective on inbreeding can advance both our understanding of inbreeding and inbreeding depression and provide an experimental tool to address fundamental problems in the study of animal behavior.
