Predator Escape Research Articles

The effects of background risk on behavioural lateralization in a coral reef fish

Summary Behavioural lateralization – the preferential use of one side of the body or either of the bilateral organs or limbs – has been well documented in many species, in a number of contexts. While the benefits reported are numerous, existing latent variability in the degree of lateralization within and across populations, species and taxa indicates that existing costs may modulate its expression. Few studies have reported changes in the degree of lateralization at the individual level, in response to long‐term changes in environmental conditions, but not in response to short‐term changes in environmental conditions. Predation is highly variable both temporally and spatially and hence is a good candidate for testing lateralization effects based on short‐term changes in environmental conditions. Here, we tested the hypothesis that the degree of behavioural lateralization changes following short‐term exposure to different levels of risk. We tested whether wild‐caught juvenile damselfish exposed to a high or low background level of risk for 4 days would subsequently differ in their turning bias, a trait that has been linked to predator escape behaviour in fishes. We found that 4 days is enough to induce a difference in the absolute lateralization scores of the fish, with high‐risk fish being more strongly lateralized than low‐risk fish. Practically, this difference stemmed from decreasing lateralization scores for newly recruiting coral reef fishes that were kept in low‐risk environments, with the concurrent maintenance of higher lateralization scores for fish maintained under high‐risk conditions. Fish from the high‐risk background had higher survival than those from the low‐risk background upon release into mesocosms containing reef predators. Our study highlights how early exposure to differential predation risk affects the degree of behavioural lateralization. Given the profound effects of lateralization on many aspects of an animal's life from its ability to discriminate conspecifics to how it forages and interacts during agonistic interactions, predation risk may be a key driver of animal development.

The effects of substratum on locomotor performance in lacertid lizards

Locomotion is important to animals because it has direct implications for fitness through its role in predator escape, prey capture, and territory defence. Despite significant advances in our understanding of animal locomotion, studies exploring how substrate properties affect locomotor performance remain scant. In the present study, we explore how variation in substrate (sand, slate, cork) affects locomotor performance in lacertid lizards that differ in morphology. Moreover, we explore whether substrate effects are the same for different types of locomotor performance (speed, acceleration, and stamina). Our results show that the substrate affected most types of locomotor performance studied but not always in the same way. Although substrate effects were species-dependent for the maximal speed over 50 cm and the distance run to exhaustion, this was not the case for acceleration capacity. These results suggest that substrate texture differentially affects burst performance versus longer duration measures of locomotor performance. Finally, straightforward relationships between habitat use and the substrate on which performance was maximized were not observed. This suggests that the evolution of locomotor capacity is complex and that animals may show compromise phenotypes allowing them to deal with a variety of substrates in their natural environment. © 2015 The Linnean Society of London, Biological Journal of the Linnean Society, 2015, ●●, ●●–●●.

Beetles (Coleoptera) of Peru: A Survey of the Families. Elateridae Leach, 1815

Diversity in Peru: 8 subfamilies, 43 genera, 164 species. Recognition: The beetles of this family are immediately recognized by their generally elongate and narrow body, a disproportionately large and loosely attached prothorax that rapidly articulates with the mesothorax to “snap” the body for predator escape and self-righting; serrate to pectinate antennae; large prosternum; large subtriangular hypomeron; large subquadrate metaventrite; and slender legs with long pentamerous tarsus, usually with ventral setal brushes or membranous pads. Habitat: Elaterids are found primarily in forests, savannas, thorn-forests, and scrublands, with different taxa between wet and dry vegetation types. Some are specialized by larval adaptions to arboreal and terrestrial bromeliads, epiphyte mats on large tree limbs, sandy riparian soils, grassland soils, or various stages of internal decay of dead and dying trees. Adult activity is short-lived and mostly crepuscular and nocturnal, especially in warm to hot environments. Mid and upper elevation species are often diurnal. They feed at high-carbohydrate sources such as plant wounds and weeps, floral and extra-floral nectaries, decaying fruits, plant glandular exudates, but also predate on small plant-feeding arthropods. Larvae are mostly predators under loose bark, within decaying wood, among roots and rhizomes of epiphytes, leaf axils of bromeliads, and in soil. Some species are rhizophages in soil. Notes: The checklist of Elateridae is based on Gemminger and Harold (1869),

Predator-induced phenotypic plasticity of laterality

Lateralized brain function, or partitioning of tasks to separate hemispheres of the brain, directly impacts behaviour and fitness. Highly lateralized individuals tend to outperform nonlateralized individuals in many survival-related behaviours, such as the ability to learn, escape predators and multitask. Despite these benefits to lateralization, there is a great deal of observed variation in this trait within and between populations that is likely determined by the balance between costs and benefits of laterality in a given environment. Laterality appears to be heritable, but it can also vary with the environment experienced during development. We investigated the role of evolutionary history and developmental plasticity in determining the degree of laterality in the Trinidadian guppy, Poecilia reticulata, a freshwater fish that experiences variable predation pressure in its native range. We compared pairs of closely related populations that experience either high or low levels of predation in the wild, and manipulated the perceived predation risk in the rearing environment using a common garden split-brood design. We assayed laterality in mature male guppies using a detour test. Fish reared with exposure to chemical predator cues were more lateralized than their brothers reared without predator cues. This plastic response is in the direction we would predict if lateralization is favoured in environments with high predation risk. However, unlike findings in related species, we did not detect repeatable differences in degree of laterality associated with historical predation regime, suggesting that predation risk experienced over evolutionary history does not shape laterality patterns in guppies. Thus, although it is currently underemphasized in the literature, plasticity is likely an important contributor to variation in laterality.

Conditions favouring hard seededness as a dispersal and predator escape strategy.

Summery The water-impermeable seed coat of ‘hard’ seeds is commonly considered a dormancy trait. Seed smell is, however, strongly correlated with seed water content, and hard seeds are therefore olfactionally cryptic to foraging rodents. This is the rationale for the crypsis hypothesis, which proposes that the primary functions of hard seeds are to reduce seed predation and promote rodent seed dispersal. We use a mechanistic model to describe seed survival success of plants with different dimorphic soft and hard seed strategies. The model is based on established empirical–ecological relationships of moisture requirements for germination and benefits of seed dispersal, and on experimentally demonstrated relationships between seed volatile emission, predation and predator escape. We find that water-impermeable seed coats can reduce seed predation under a wide range of natural humidity conditions. Plants with rodent dispersed seeds benefit from producing dimorphic soft and hard seeds at ratios where the anti-predator advantages of hard seeds are balanced by the dispersal benefits gained by producing some soft seeds. The seed pathway predicted from the model is similar to those of experimental seed-tracking studies. This validates the relevance and realism of the ecological mechanisms and relationships incorporated in the model. Synthesis. Rodent seed predators are often also important seed dispersers and have the potential to exert strong selective pressures on seeds to evolve methods of avoiding detection, and hard seeds seem to do just that. This work suggests that water-impermeable hard seeds may evolve in the absence of a dormancy function and that optimal seed survival in many environments with rodent seed predators is obtained by plants having a dimorphic soft and hard seed strategy.

Identifying non-point sources of endocrine active compounds and their biological impacts in freshwater lakes.

Contaminants of emerging concern, particularly endocrine active compounds (EACs), have been identified as a threat to aquatic wildlife. However, little is known about the impact of EACs on lakes through groundwater from onsite wastewater treatment systems (OWTS). This study aims to identify specific contributions of OWTS to Sullivan Lake, Minnesota, USA. Lake hydrology, water chemistry, caged bluegill sunfish (Lepomis macrochirus), and larval fathead minnow (Pimephales promelas) exposures were used to assess whether EACs entered the lake through OWTS inflow and the resultant biological impact on fish. Study areas included two OWTS-influenced near-shore sites with native bluegill spawning habitats and two in-lake control sites without nearby EAC sources. Caged bluegill sunfish were analyzed for plasma vitellogenin concentrations, organosomatic indices, and histological pathologies. Surface and porewater was collected from each site and analyzed for EACs. Porewater was also collected for laboratory exposure of larval fathead minnow, before analysis of predator escape performance and gene expression profiles. Chemical analysis showed EACs present at low concentrations at each study site, whereas discrete variations were reported between sites and between summer and fall samplings. Body condition index and liver vacuolization of sunfish were found to differ among study sites as did gene expression in exposed larval fathead minnows. Interestingly, biological exposure data and water chemistry did not match. Therefore, although results highlight the potential impacts of seepage from OWTS, further investigation of mixture effects and life history factor as well as chemical fate is warranted.

Does variation in morphology correspond with variation in habitat use in freshwater gastropods?

We tested if variations (i.e., breadth) in morphology and habitat use vary predictably among six aquatic gastropod species that were collected across Indiana and Illinois, USA. We predicted that interspecific morphological variation would positively covary with variation in habitat use among species. We used geometric morphometrics (Procrustes technique and relative warp analysis) to quantify morphology and multivariate analyses (PCA) to quantify habitat. Increased morphological breadth did not vary predictably with increased habitat breadth. However, we found that life history traits correspond with patterns in morphological and habitat breadth for these six aquatic gastropods. Pulmonate gastropods (use lungs for respiration) that lack an operculum cover exhibited decreased morphological breadth compared to coenogastropods (use gills for respiration). This pattern may ultimately be a function of behavioral adaptations in freshwater gastropods. Gastropods that are capable of breathing air or using other behavioral modifications such as burrowing to escape predators may not require high morphological breadth. Conversely, selection may favor higher morphological breadth in gastropods with gills that also do not move out of the water column to escape predators.

Effects of predator and prey hunting and escape strategies on ecosystem dynamics

Understanding of an ecosystem’s resilience and stability requires an understanding of predatorprey dynamics because ecosystems consist of dynamical interacting subsystems that include predator-prey relationships. These relationships are closely related to the hunting-escaping strategies employed by the predator and prey. Therefore, understanding the effects of hunting and escaping strategies on ecosystems will lead to a better understanding of those systems. To this end, we constructed a spatially explicit lattice model to simulate integrative predator-prey-plant relationships. When an individual simultaneously encounters its predator and prey, either hunting or escaping should take priority. Hunting priority is referred to as a hunting preferred strategy (HPS), while escape priority is referred to as an escape preferred strategy (EPS). These strategies are associated with some degree of willingness to either hunt (H) or escape (E). In our model, the willingness of an individual to hunt or escape increased with increasing value of H or E, respectively we investigated changes in the predicted population densities for predator, prey, and plant species with changes in the values of H and E. Simulation results indicated that HPS positively contributed to ecosystem stability because those individuals that employed HPS had a greater chance of reproduction than those that employed EPS. In addition, we briefly discuss the development of our model as a tool for understanding behavioral strategies in specific predator-prey interactions.

Vibratory noise in anthropogenic habitats and its effect on prey detection in a web-building spider

In nature, animals must contend with the presence of noise, which may limit their ability to detect prey, attract mates and escape predators. Sources of noise vary and may originate from natural (e.g. animal sounds, water) or anthropogenic (e.g. traffic, construction) sources. The vibratory sensory modality has long been overlooked in the study of anthropogenic effects on wildlife. Human-induced environmental changes may introduce noise sources as well as artificial substrates that alter vibratory noise profiles, leading to maladaptive behavioural responses. We conducted field measurements of vibratory noise on various substrate types (natural and artificial) used by animals in human-developed habitats. Next, we conducted laboratory experiments on how vibratory noise affects the prey detection ability of the European garden spider, Araneus diadematus. We tested whether changes in vibratory noise profiles consistent with anthropogenic alterations of vibratory habitats are sufficient to alter the spider's sensitivity to prey cues. We found that overall noise amplitude on artificial substrates was lower and less variable across contexts compared with natural substrates. In experiments with different noise levels, we observed that garden spiders showed noise-dependent changes in sensitivity to prey-mimicking cues, with response thresholds lowest at intermediate noise levels. Experimental levels of intermediate noise consistent with field measurements on natural substrates suggest that spiders' predatory performance is higher when webs are constructed on natural substrates. This suggests that human-introduced substrates may interfere with spiders' predatory performance. As human activities and habitat alteration are widespread, our findings highlight the need to consider the vibratory sensory channel in assessing anthropogenic impacts on wildlife.

Diel vertical distribution and life history characteristics of Tropodiaptomus simplex and its importance in the diet of Stolothrissa tanganicae, Kigoma, Tanzania

Tropocyclops simplex abundance, diel distribution and the impact of the planktivore fish Stolothrissa tanganicae on the T. simplex population were studied at a deep-water site in Kigoma Bay, Lake Tanganyika during the wet period (October 2008–February 2009). The top 40 m were examined using discrete depth samples, filtered through a 40-μm mesh. Ovigerous and copepodids of Tropodiaptomus simplex exhibited a very clear diel vertical migration. Ovigerous females of Tropodiaptomus were negligibly low in the 0–30 m depth during the day, while at night they stayed above 20 m. Tropodiaptomus nauplii did not show any clear diel vertical migration. The contribution of adults, copepodite and nauplii stages to the total numbers of Tropodiaptomus simplex was 8.2, 8.6 and 83.2%, respectively. Stolothrissa tanganicae stomachs were analysed to quantify the contribution of zooplankton in their diets, which revealed a dominance of Tropodiaptomus females and the electivity indices proved that T. simplex females (with or without eggs) were highly selected by S. tanganicae, which could probably be explained by size-selective feeding. Life table analysis indicated that approximately 60% of T. simplex nauplii did not develop into copepodites, a loss which could not be explained by the results of the present study. 68% of the fish gut contents were contributed by female Tropodiaptomus individuals and the contribution of shrimps and Cyclopidae increased substantially to almost 20%. S. tanganicae consumed largely ovigerous Tropodiaptomus females. However, eggs found in the guts were significantly smaller than those found in the zooplankton discrete samples, suggesting that digestion had started. The calculated electivity indices underline that ovigerous and non ovigerous females of T. simplex are being positively selected in the feeding process. It infers existence of selective predation in L. Tanganyika by S. tanganicae on females of T. simplex (with or without eggs) and as a result distinct vertical migration as a predation escape mechanism is performed.

Sound Modulation in Singing Katydids Using Ionic Polymer-Metal Composites (IPMCs)

Many insect families have evolved to produce and detect complex singing patterns for the purposes of mating, display of dominance, predator escape, and other needs. While the mechanisms of sound production by insects have been thoroughly studied, man-machine exploitation of such mechanisms has remained unreported. We therefore describe a method to modulate the frequency spectrum in the chirp call of a singing insect, Gampsocleis gratiosa (Orthoptera: Tettigoniidae), a large katydid indigenous to China and commonly known as Guo Guo or Chinese Bush Cricket. The chirp modulation was achieved through the contact of a ribbon of Ionic Polymer-Metal Composite (IPMC) against wing of the insect. The IPMC effectively served as an actuator when a small DC voltage was applied to the ribbon's faces. By applying a sequential on/off voltage waveform to the IPMC ribbon, the katydid's chirp was modulated in a corresponding manner. This configuration can be used as part of a broader application of using singing insects to harness their acoustic power to produce and propagate machine-induced messages into the acoustic environment.

Using acoustic technology to reduce bark beetle reproduction

Acoustic signals play a critical role in mate choice, species recognition, communication, territoriality, predator escape and prey selection. Bark beetles, which are significant disturbance agents of forests, produce a variety of acoustic signals. A bioacoustic approach to reducing bark beetle reproduction within wood tissues was explored. Playback of modified biological sounds reduced beetle reproductive output, tunneling distance and adult survival. The targeted use of biologically relevant sounds disrupts insect behaviors and could be a species-specific, environmentally friendly method of insect management.

Effects of water discharge on fledging time, growth, and survival of piping plovers on the Missouri River

AbstractRiver flow management and modification is a global issue, and its effects on river‐dependent organisms are pervasive. Flow modification can directly affect avian species through mortality or habitat loss, but less is known about indirect and sublethal effects of flow modification on reproductive output in these species. Young birds are more vulnerable to predation between hatching and fledging than after flight is achieved, but tradeoffs must be made to balance growth and survival. Predation pressure appears to be a significant factor affecting the time to fledging in altricial birds, but less is known about this threat for precocial birds. Birds reaching fledging earlier should have greater rates of survival to migration because their predator escape repertoire includes flight at an earlier age. We evaluated the effect of varying outflows from the Gavins Point Dam on the growth, age at fledging, and survival of piping plover (Charadrius melodus) chicks on the Missouri River (2006–2009). The study was characterized by 2 relatively high flow years (2006 and 2009) and 2 relatively low flow years (2007 and 2008). We used success rate in recapturing chicks in capture–mark–recapture models as an index for fledging. We attempted to recapture all chicks (n = 1,099) by hand every 3–4 days throughout the season to acquire morphological measurements. Models indicated that as flows from the dam increased, age at fledging increased. We also found that increasing flows were associated with decreasing daily survival rates (βflow = −2.401, 95% CI: −4.351 to −0.452). Flow was also negatively related to chick mass gain, but we found less evidence for an effect on wing‐chord length. Increased flows covered wet‐substrate foraging habitat, and likely affected plover reproductive output directly through chick survival and indirectly through decreased growth and increased fledging times. © The Wildlife Society, 2013

The Vertebral Column, Ribs, and Sternum of the African Giant Rat (Cricetomys gambianusWaterhouse)

Examined bones were obtained from eight adult African giant rats, Cricetomys gambianus Waterhouse. Animals used had an average body mass of 730.00 ± 41.91 gm and body length of 67.20 ± 0.05 cm. The vertebral formula was found to be C7, T13, L6, S4, Ca31–36. The lowest and highest points of the cervicothoracic curvature were at C5 and T2, respectively. The spinous process of the axis was the largest in the cervical group while others were sharp and pointed. The greatest diameter of the vertebral canal was at the atlas (0.8 cm) and the lowest at the caudal sacral bones (2 mm). The diameter of the vertebral foramen was the largest at C1 and the smallest at the S4; the foramina were negligibly indistinct caudal to the sacral vertebrae. There were 13 pairs of ribs. The first seven pairs were sternal, and six pairs were asternal of which the last 2-3 pairs were floating ribs. The sternum was composed of deltoid-shaped manubrium sterni, four sternebrae, and a slender processus xiphoideus. No sex-related differences were observed. The vertebral column is adapted for strong muscular attachment and actions helping the rodent suited for speed, agility, dexterity, and strength which might enable it to overpower prey and escape predation.

Tail loss reduces locomotor ability but not metabolic rate in a viviparous skink, Sphenomorphus indicus

Tail autotomy is an efficient predator escape form, but imposes locomotor costs in many lizard species. It has been hypothesized that locomotor impairment following tail autotomy results from the altered running dynamics or loss of energy available for locomotion, but there is a paucity of data available to demonstrate such effects. We evaluated the locomotor costs of tail loss in a viviparous skink, Sphenomorphus indicus, and examined whether locomotor costs were related to changes in gait characteristics and metabolic rate. Of 24 field-captured adult males with original intact tails, 12 individuals were used as experimental animals, and the remaining 12 as controls. Locomotor performance and CO2 production were measured for the experimental skinks before and after tail removal; the same parameters were measured at the same time for the control skinks. Compared with tailed skinks, the mean locomotor speed and stamina of tailless skinks was reduced by approximately 26% and 17%, respectively. At any given speed, tailless skinks had a shorter stride length for hindlimbs (but not for forelimbs) and a greater stride frequency than did tailed skinks. In S. indicus, locomotor impairment may be a result of the reduced stride length, and energetic constraints on stride frequency. We found no significant change in standard metabolic rate after the skinks underwent tail removal, which may reflect a minor effect on energy expenditure for maintenance. Although the reduction in metabolically active tissue might cause a lower metabolic rate, tail regeneration counteracted such an effect because it was energetically expensive.

Effects of predation pressure and resource use on morphological divergence in omnivorous prey fish

BackgroundBody shape is one of the most variable traits of organisms and responds to a broad array of local selective forces. In freshwater fish, divergent body shapes within single species have been repeatedly observed along the littoral-pelagic axes of lakes, where the structural complexity of near shore habitats provides a more diverse set of resources compared to the open-water zones. It remains poorly understood whether similar resource-driven polymorphism occurs among lakes that vary in structural complexity and predation pressure, and whether this variation is heritable. Here, we analyzed body shape in four populations of omnivorous roach (Rutilus rutilus) inhabiting shallow lakes. We tested the relationship between body shape, gradients of resources, predation pressure, and, in a subset of two lakes, diet composition. We used genome scans of 331 polymorphic AFLP markers to test whether there was a heritable component to the observed morphological diversification.ResultsBody shape differed among lakes and was significantly correlated to differences in predation pressure. Roach from the lake with highest predation pressure were most divergent from the average body shape of all populations, characterized by a more streamlined body and caudally inserted dorsal fins; features that facilitate predator escape. Surprisingly, diet composition was not associated with morphology. AFLP analysis revealed weak genetic differentiation among lakes and no isolation by distance (IBD). Outlier analysis detected three loci under positive selection with differing frequencies in the four populations. General linear models did not support an association of lake-specific genotypes with morphological variation.ConclusionBody shape was divergent among lakes, suggesting that processes previously reported from within single lakes may also be operating at the scale of whole lakes. We found no evidence for body shape being heritable, although sample size was small in these natural populations. Rather than habitat structure and diet, we conclude that predation had a stronger effect on the prevalence of local morphotypes. A variable morphotype facilitating the efficient uptake of a variety of spatially and temporarily scattered resources seems to be favored in these small aquatic systems.

Ocean acidification induces budding in larval sea urchins

Ocean acidification (OA), the reduction of ocean pH due to hydration of atmospheric CO2, is known to affect growth and survival of marine invertebrate larvae. Survival and transport of vulnerable planktonic larval stages play important roles in determining population dynamics and community structures in coastal ecosystems. Here, we show that larvae of the purple urchin, Strongylocentrotus purpuratus, underwent high-frequency budding (release of blastula-like particles) when exposed to elevated pCO2 level (>700 μatm). Budding was observed in >50 % of the population and was synchronized over short periods of time (~24 h), suggesting this phenomenon may be previously overlooked. Although budding can be a mechanism through which larval echinoids asexually reproduce, here, the released buds did not develop into viable clones. OA-induced budding and the associated reduction in larval size suggest new hypotheses regarding physiological and ecological tradeoffs between short-term benefits (e.g. metabolic savings and predation escape) and long-term costs (e.g. tissue loss and delayed development) in the face of climate change.

Reply to Dorrington: Oxygen concentration and predator escape abilities are important controls on insect size

Dorrington (1) argues that oxygen is not an important control on insect size and that selective pressure for maneuverability and predator escape is not inversely related to body size. Because these claims are contradicted by many experimental studies, we stand by our hypothesis (2) that controls on maximum insect size shifted from environmental (primarily oxygen concentration) to biotic (primarily predation) following the evolution of flying predators like birds.

Overcoming obstacles: the effect of obstacles on locomotor performance and behaviour

Sprinting and jumping ability are key performance measures that have been widely studied in vertebrates. The vast majority of these studies, however, use methodologies that lack an ecological context by failing to consider the complex habitats in which many animals live. Because successfully navigating obstacles within complex habitats is critical for predator escape, running, climbing, and/or jumping performance are each likely to be exposed to selection. In the present study, we quantify how behavioural strategies and locomotor performance change with increasing obstacle height. Obstacle size had a significant influence on behaviour (e.g. obstacle crossing strategy, intermittent locomotion) and performance (e.g. sprint speed, jump distance). Jump frequency and distance increased with obstacle size, suggesting that it likely evolved because it is more efficient (i.e. it reduces the time and distance required to reach a target position). Jump angle, jump velocity, and approach velocity accounted for 58% of the variation in jump distance on the large obstacle, and 33% on the small obstacle. Although these variables have been shown to significantly influence jump distance in static jumps, they do not appear to be influential in running (dynamic) jumps onto a small obstacle. Because selection operates in simple and complex habitats, future studies should consider quantifying additional measures such as jumping or climbing with respect to the evolution of locomotion performance.

A fecundity cost of (walking) mobility in an insect

Evolutionary theory predicts trade-offs between fecundity and mobility, but there is substantial lack of empirical evidence if and how basic mobility relates to fitness costs. In a field experiment, we investigated fecundity costs of mobility in a non-migratory, wing-monomorphic grasshopper, Stenobothrus lineatus, and at the same time tested for possible effects of reproductive state (egg-load) on the mobility. For 10 days, body weight and activity radius of 60 females were recorded daily and oviposition events were inferred from abrupt weight losses. We found a strong and significant relationship between the individual mobility and the time between egg pods laid (interpod period). Individual egg-laying was reduced by a rate of 0.36 eggs per day with each meter increase in mean daily activity radius. The trade-off was not biased by the size of the females, that is, constitution did not positively influence both offspring number and mobility. Egg-load had no significant influence on the individual distances travelled. We could demonstrate that mobility – as induced and selected for by foraging, thermoregulation, predator escape, shelter seeking, and reproduction – can be directly paid off by fecundity. This direct consequence of mobility on individual fitness was detected for the first time in a walking insect.