The survival of ectotherms worldwide is threatened by climate change. Whether increasing temperatures increase the vulnerability of ectotherms inhabiting temperate plateau areas remains unclear. To understand altitudinal variation in the vulnerability of plateau ectotherms to climate warming, Qinghai toad-headed lizards (Phrynocephalus vlangalii) were subjected to semi-natural enclosure experiments with simulated warming at high (2,600 m) and superhigh (3,600 m) elevations of the Dangjin Mountain, China. Our results revealed that the thermoregulatory effectiveness and warming tolerance (WT) of the toad-headed lizards were significantly affected by climate warming at both elevations, but their thermal sensitivity remained unchanged. After warming, the thermoregulatory effectiveness of lizards at superhigh elevations decreased because of the improved environmental thermal quality, whereas that of lizards at high-elevation conditions increased. Although the body temperature selected by high-elevation lizards was also significantly increased, the proportion of their active body temperature falling within the set-point temperature range decreased. This indicates that it is difficult for high-elevation lizards to adjust their body temperatures within a comfortable range under climate warming. Variations in the WT and thermal safety margin (TSM) under climate warming revealed that lizards at the superhigh elevation benefited from improved environmental thermal quality, whereas those at the high elevation originally on the edge of the TSM faced more severe threats and became more vulnerable. Our study highlights the importance of thermal biological traits in evaluating the vulnerability of ectotherms in temperate plateau regions.
Sexual selection is thought to play a major role in the evolution of color due to the correlation between a signaler's physiological state and the displayed color. As such, researchers often investigate how color correlates to the quality of the signaler. However, research on the relationship between color and individual quality is often taxonomically limited and researchers typically investigate how color phenotypes relate to one index of quality, such as a linear measure of body size. Here, we investigated the relationship among body size, claw size, claw muscle mass, lipid content, and the color of the claw in male fiddler crabs (Leptuca uruguayensis) which wield an exaggerated claw that varies in color from brown to red. We hypothesized that if the color was correlated to one or more indices of male quality, the color displayed on the claws of male L. uruguayensis could be under sexual selection. We found L. uruguayensis claw color varies substantially among the individuals we photographed. However, we did not find a correlation between claw color and indices of quality; neither brightness nor hue correlated to the indices of quality we measured. Our findings suggest that claw color in L. uruguayensis is unlikely to have evolved to signal quality, but may instead function as a species identity or as a non-indicator sexual signal.
Group living is widespread across diverse taxa, and the mechanisms underlying collective decision-making in contexts of variable role division are critical for understanding the dynamics of group stability. While studies on collective behavior in small animals such as fish and insects are well-established, similar research on large wild animals remains challenging due to the limited availability of sufficient and systematic field data. Here, we aimed to explore the collective decision-making pattern and its sexual difference for the dimorphic Tibetan antelopes Pantholops hodgsonii (chiru) in Xizang Autonomous Region, China, by analyzing individual leadership distribution, as well as the joining process, considering factors such as calving stages and joining ranks. The distinct correlations of decision participants' ratio with group size and decision duration underscore the trade-off between accuracy and speed in decision-making. Male antelopes display a more democratic decision-making pattern, while females exhibit more prompt responses after calving at an early stage. This study uncovers a partially shared decision-making strategy among Tibetan antelopes, suggesting flexible self-organization in group decision processes aligned with animal life cycle progression.
The nonlinearity and fear hypothesis predicts that highly aroused vocal mammals and birds produce vocalizations (notably alarm calls and screams) which contain a variety of nonlinear phenomena (NLP). Such vocalizations often sound "noisy" because vocal production systems are over-blown when animals are highly aroused. While much is known about the conditions under which animals produce vocalizations containing NLP and how species respond to them, there is little research about the heritability of such behavioral traits. Using the quantitative genetic animal model, we estimated the genetic basis of "noise" in alarm calls produced by females and found significant heritability in call entropy-our measure of the noisiness. About 9% of the variance in noisiness can be accounted for by genetic differences. Taken together, these findings suggest that the degree to which marmots produce noisy calls is modestly heritable and can be thus subject to further evolution via natural selection.
How ecological and evolutionary factors affect small mammal diversity in arid regions remains largely unknown. Here, we combined the largest phylogeny and occurrence dataset of Gerbillinae desert rodents to explore the underlying factors shaping present-day distribution patterns. In particular, we analyzed the relative contributions of ecological and evolutionary factors on their species diversity using a variety of models. Additionally, we inferred the ancestral range and possible dispersal scenarios and estimated the diversification rate of Gerbillinae. We found that Gerbillinae likely originated in the Horn of Africa in the Middle Miocene and then dispersed and diversified across arid regions in northern and southern Africa and western and central Asia, forming their current distribution pattern. Multiple ecological and evolutionary factors jointly determine the spatial pattern of Gerbillinae diversity, but evolutionary factors (evolutionary time and speciation rate) and habitat filtering were the most important in explaining the spatial variation in species richness. Our study enhances the understanding of the diversity patterns of small mammals in arid regions and highlights the importance of including evolutionary factors when interpreting the mechanisms underlying large-scale species diversity patterns.
Bite force is an important performance indicator of individual fitness that is closely related to food acquisition, male competition, and mating selection. It is also affected by a variety of factors and different mechanisms. Therefore, it is relatively difficult to understand the evolutionary driving forces of changes in bite force. In this study, the driving factors affecting the bite force of wild-derived red junglefowl (Gallus gallus jabouillei) were investigated from the aspects of morphological indicators and physiological characteristics. Results showed that the bite force of wild-derived red junglefowl was directly related to sex, showing obvious sexual differences. However, there was no correlation between the plasma testosterone level and bite force. The bite force of males was significantly greater than that of females, and the body index (i.e., PC1 of five body measures, namely body mass, body length, wing length, tail length, and tarsus length), the grasp index (i.e., tomial length × bill width) of males were significantly greater than those of females. Sexual selection may have played a key role in the evolution of bite force in the red junglefowl. Future studies should examine other key factors affecting changes in bite force to verify the correlation between secondary sexual characteristics and bite force in red junglefowls.
Insects are suitable model organisms for functional morphology research, especially in the context of exaptation, when the same morphological trait represents an advantage in disparate niches. Phylogenetically distant groups of pygmy grasshoppers (Orthoptera: Tetrigidae) have various pronotal projections defining their general appearance and body shape. However, body shape has never been related to niche occupation in these insects, thus the aim of this study is to investigate the relationship between pronotum shape and macrohabitat adaptation in Scelimeninae, a group of Asian and Papuan tetrigids encompassing amphibious and corticolous (bark-dwelling) representatives. With the use of geometric morphometrics and phylogenetic comparative methods, two morphological and functional groups were distinguished, with the body shape exhibiting a significant phylogenetic signal. The first group consists of elongated amphibious taxa (Scelimenini tribe) with highly uniform pronotum morphology, likely due to a strong selection for streamlined body shape. Stouter corticolous taxa (Discotettigini tribe) exhibit more conspicuous body shape variability, possibly increasing camouflage efficiency in tree bark habitats. Ecological divergence associated with macrohabitat adaptation may thus have been the primary driver of speciation in this insect group, but the evolutionary constraints leading to this divergence are still to be identified.
Oaks (Quercus spp.) provide an important food source for many wildlife species throughout the fall and winter. Most research evaluating oak masting patterns and the subsequent behavioral responses of wildlife focuses on the annual temporal scale. However, patterns in masting at the seasonal temporal scale may be important for wildlife behavior. We designed a study quantifying seasonal oak masting patterns of 3 oak species (water oak, Q. nigra; laurel oak, Q. laurifolia; and swamp chestnut oak, Q. michauxii) and linking those patterns to visitation and feeding behavior of 3 primary consumers (white-tailed deer, Odocoileus virginianus; gray squirrel, Sciurus carolinensis; and raccoon, Procyon lotor). We used seed traps to monitor the seasonal masting pattern of 205 trees in the fall of 2021 and 2022 and used camera traps concurrently to monitor wildlife behavior associated with a subset of 30 trees. Seasonal masting patterns differed between oak species both within a season and across years, and the timing of mast varied within oak species across years. White-tailed deer tended to visit swamp chestnut oak as the number of acorns increased and consumed their acorns. Gray squirrels and raccoons tended to visit laurel oak and consume water oak acorns with gray squirrels being more likely to consume as the number of acorns increased. Our results indicate that evaluating acorn production at multiple temporal scales may be necessary to fully understand oak masting relationships with wildlife. Furthermore, differences in wildlife behavior based on oak species may have important implications for oak regeneration.
Maternal care in crayfish has been extensively studied, but little is known of its response to environmental factors. We studied the duration of maternal care and its association with the juvenile development of marbled crayfish Procambarus virginalis in adverse environmental conditions. We exposed females with developmental stage 3 juveniles to environments of low water volume (LW) with food provided, low water volume with no feed (starvation) (LWS), and low water volume without feeding plus an intruder (red swamp crayfish male) (LWSI). A control group with standard water level/feed conditions was included for comparison. Groups were monitored for up to 90 days. The LWS group showed significantly prolonged maternal care (~65 days) as indicated by an extended attachment phase, delayed moulting of mothers (~53 days), and retarded juvenile development. In the LWSI group, conflict precluded extended maternal care. Low use of shelter and feeding was evident under all stress conditions. The results showed that crayfish females modify maternal care in accordance with conditions, providing a longer period of safety for offspring under adverse circumstances. It is possible that the expression of maternal pheromones can manipulate the developmental rate in juveniles, a topic for future research.
Male fiddler crabs own an enlarged claw which is a weapon and an ornament. The enlargement of this claw begins from the juvenile stage and continues throughout life. Males may voluntarily lose (i.e., autotomize) this claw. After several molts males may regenerate a new claw, called leptochelous, which acquires a similar length but a lower muscle mass area than the original one, called brachychelous. In some species, regenerated claws develop permanently as leptochelous, the population having 2 discrete claw morphologies. Other species present morphological variations with leptochelous and brachychelous being 2 ends of a continuum. In the species Leptuca uruguayensis, we studied the morphological variation of this enlarged claw, whether it may be caused by its regeneration at different male sizes, and its consequences on mating success. We found that claws could not be discriminated as discrete morphs, suggesting a morphological continuum from brachychelous to leptochelous. Regenerated claws in the laboratory were initially small and proportional to body size, although a field experiment confirmed that claw size is recovered after several molts. Morphological variation may be caused by energetic limitations where males of different sizes must differently trade-off between restitution of claw length (ornament function) or claw muscle area (weapon function). Fiddler crabs use 2 mating tactics with different levels of female choice. However, regardless of the mating tactic, leptochelous males were at a disadvantage at high densities, although not at low densities, suggesting that the consequences of autotomy and regeneration on mating success may depend on the social context.
Same-sex mounts provide male juvenile golden snub-nosed monkeys (Rhinopithecus roxellana) with opportunities to practice heterosexual copulatory skills and are often followed by grooming (post-mounting grooming, PMG). We hypothesized that juveniles acted as the mountee and provided mounting opportunities to receive grooming from their peer mounter. Here, we observed same-sex mounts among male juveniles (N = 5) in a captive group of R. roxellana in Shanghai Wild Animal Park, China, from November 2014 to June 2015. Among 1,044 mounts recorded, 45.40% were accompanied by PMG initiated by the mounter and only 3.74% were followed by PMG initiated by the mountee. Mountees were more likely to receive PMG when they performed a mounting solicitation than when they did not, or when they were mounted for a longer time (even if they did not solicit). Over a long timeframe (1 month), mountee’s tended to choose partners who groomed them more often than others after mounting, regardless of how long the grooming lasted. However, whether the mounter groomed the mountee did not predict the mounting direction in their subsequent mount. Our results suggest that, in the context of same-sex mounts, juveniles provide mounting opportunities to receive grooming from peers on a long-term, rather than on a short-term basis. This study provides the first evidence that juveniles’ same-sex mounting strategy may be associated with the grooming market in nonhuman primates, which necessitates further investigation with large free-ranging groups due to the limited sample size of individuals and the captive setting of the current study.
Captive breeding and stocking are commonly employed strategies for enhancing fisheries and conserving endangered fish species. However, hatchery-raised fish often exhibit reduced performance in the wild, displaying alterations in physiological, morphological, and behavioral traits. We tested for differences in swimming capacity and metabolic traits between wild and hatchery-reared individuals of the Spanish toothcarp (Aphanius iberus) from 2 different populations. Furthermore, we experimentally tested if these changes translated into fitness differences after their stocking into the wild. There were significant differences in swimming capacity and metabolic traits between wild and hatchery-reared individuals and also between the 2 populations. Captive-bred individuals displayed consistently lower metabolic rates than wild individuals from the same population (30-76% lower). Critical swimming speed rather differed between the 2 populations. Sex-specific differences were observed in maximum and standard metabolic rates, with wild individuals and females generally exhibiting higher values but with some exceptions. During a 3-month experiment, survival rates did not significantly differ between wild and captive-bred fish. Captive-bred individuals started smaller but exhibited rapid growth during the experiment. Initially, larger captive-bred fish had lower body conditions than their wild counterparts, but these differences progressively diminished. In summary, captive-bred individuals of this fish species showed lower metabolic rates, although the differences with wild individuals slightly depended on sex and size.
Organisms inhabiting arid environments face challenges to obtain dietary water. To prevent desiccation, some organisms possess unique adaptations to harvest water from infrequent and unpredictable rainfall, including several squamates (snakes and lizards). While most squamates consume precipitation as it pools in the environment, a small number engage in behaviors to enhance water collection by capturing precipitation from their own skin, referred to as rain-harvesting behavior (RHB). Details of this behavior remain unclear, particularly the sequence of behaviors associated with RHB. We developed a method to simulate rainfall to observe RHB in prairie rattlesnakes (Crotalus viridis) in situ and recorded 72 events in 94 snakes, the most robust sampling of RHB to date. Using video analysis, we describe the postures and kinematics of RHB and develop the first illustrated ethogram of this behavior for any vertebrate. Our results demonstrate that RHB contains fixed and variable patterns useful in cross-species comparisons and in exploring proximate causes of the behavior. In addition, we describe novel features of RHB including suspended head drinking, body levering, and drinking from neighboring snakes. Our results reveal RHB to be an intricate suite of movements and actions, some of which allude to acute sensory abilities of these animals that warrant further study. Furthermore, observations of RHB at dens and rookeries suggest a potential, novel benefit of snake aggregation is the formation of large, communal surfaces for rain harvesting. We suggest that the extremely elongated body plan of snakes may be well-suited for a rapidly deployed, modular rain-harvesting system effective at capitalizing on fleeting rainstorms characteristic of arid ecosystems of the world.
When constraints on antipredator coloration shift over the course of development, it can be advantageous for animals to adopt different color strategies for each life stage. Many caterpillars in the genus Papilio exhibit unique ontogenetic color sequences: for example, early instars that masquerade as bird feces, with later instars possessing eyespots. I hypothesize that larvae abandon feces masquerade in favor of eyespots due to ontogenetic changes in signaler size. This ontogenetic pattern also occurs within broader seasonal shifts in background color and predator activity. I conducted predation experiments with artificial prey to determine how potential signaling constraints (specifically size and season) shape predation risk, and consequently the expression of ontogenetic color change in Papilio larvae. Seasonally, both predation and background greenness declined significantly from July to September, though there was little evidence that these patterns impacted the effectiveness of either color strategy. Caterpillar size and color strongly affected the attack rate of avian predators: attacks increased with prey size regardless of color, and eyespotted prey were attacked more than masquerading prey overall. These results may reflect a key size-mediated tradeoff between conspicuousness and intimidation in eyespotted prey, and raise questions about how interwoven aspects of behavior and signal environment might maintain the prevalence of large, eyespotted larvae in nature.
Abstract We investigated the effects of heat stress on the responsiveness to vibrational cues, our measure of perceptual ability, in Myrmeleon bore antlion larvae (Neuroptera: Myrmeleontidae). We reared these trap-building predatory larvae under 2 heat stress regimes (mild, 30°C, and harsh, 36°C), and after they progressed from one instar stage to another, we tested their perceptual ability in common unchallenging conditions. We hypothesized that exposure to the harsh heat stress regime would impose costs resulting in handicapped vibration responsiveness. We found that the harsh heat stress regime generated more stressful conditions for the larvae, as evidenced by increased mortality and postponed molting, and the loss of body mass among larger larvae. Furthermore, among the individuals who remained alive, those originating from the harsh heat stress regime were characterized by higher vibration responsiveness. Our results suggest 2 not mutually exclusive scenarios. Costly heat stress conditions can sieve out individuals characterized by poor perceptual ability or surviving individuals can attempt to hunt more efficiently to compensate for the physiological imbalance caused by heat stress. Both of these mechanisms fit into the ongoing debate over how adaptation and plasticity contribute to shaping insect communities exposed to heat stress.
Parents adjust their reproductive investment over their lifespan based on their condition, age, and social environment, creating the potential for inter-generational effects to differentially affect offspring physiology. To date, however, little is known about how social environments experienced by parents throughout development and adulthood influence the effect of parental age on the expression of life-history traits in the offspring. Here, I collected data on Drosophila melanogaster offspring traits (i.e., body weight, water content, and lipid reserves) from populations where either mothers, fathers both, or neither parents experienced different social environments during development (larval crowding) and adulthood. Parental treatment modulated parental age effects on offspring lipid reserves but did not influence parental age effects on offspring water content. Importantly, parents in social environments where all individuals were raised in uncrowded larval densities produced daughters and sons lighter than parental treatments which produced the heaviest offspring. The peak in offspring body weight was delayed relative to the peak in parental reproductive success, but more strongly so for daughters from parental treatments where some or all males in the parental social environments were raised in crowded larval densities (irrespective of their social context), suggesting a potential father-to-daughter effect. Overall, the findings of this study reveal that parental ecological history (here, developmental and adult social environments) can modulate the effects of parental age at reproduction on the expression of offspring traits.
Migratory birds likely evolved from residents as a consequence of intraspecific competition for limiting resources followed by dispersal of such individuals to novel sites that had previously not been occu-pied by migrant conspecifics(Alerstam and H?gstedt 1982).
Sexual conflict is common in animals, and female sexual cannibalism represents an extreme form of sexual conflict. Males in many species have evolved a variety of strategies to circumvent or decrease the risk of female sexual cannibalism. Opportunistic mating, by which a male mates with a female when she is disturbed or when she is feeding or undertaking moulting, is one of such kinds of strategies, and widely occurs in many animals, especially in spiders. However, whether the occurrence of male opportunistic mating depends on the intensity of female sexual cannibalism remains largely unexplored. We predicted a positive correlation between them. In this study, we tested this prediction by performing a series of mating trials in the laboratory using 3 species of web-building spiders with different intensities of female sexual cannibalism: Nephila pilipes, Nephilengys malabarensis, and Parasteatoda tepidariorum. We found that the occurrence of male opportunistic mating was positively, though not statistically significantly, correlated with the intensity of female sexual cannibalism, thus supporting our hypothesis. All together, we provide evidence that male opportunistic mating may have evolved to respond to the selection pressure posed by female sexual cannibalism.
Symbiotic relationships in marine environments are not fixed and can change throughout the animal's life. This study investigated the ontogeny of symbiosis of the spider crab Libinia ferreirae with the host medusa Lychnorhiza lucerna. We described the type of relationship, the temporal correlation among species, and food habits. More than 50% of the sampled crabs were symbionts, most in early life stages. The highest number of crabs found in a single medusa was 11. Symbiosis was observed throughout most of the year but was more evident in warm periods. The crab has many benefits in this relationship with a medusa. One is the use of food resources captured by the medusa, primarily copepods. Because the crab steals the medusa's food, it is a kleptoparasitic relationship. There is a niche partition between symbiont and the free-living crabs as they occupy different habitats and use nonoverlapping food resources. Previous research reported that symbiosis first developed during the crab's last larval phase (megalopa) when crab and medusa are in the same habitat. Observation of the crab's behavior shows that symbiosis occurs when the crab can grab to the medusa when the host touches the sea bottom. The crab also took advantage of water currents, releasing itself from the substrate and then drifting toward the medusa. The symbiotic relationship that crabs have with the medusa provides then with a nursery, food resources, shelter, dispersion, and decreased competition with free-living adult crabs, all essential for the crab's survival.
The coexistence of numerous species within a community results from how those species use available resources. Babblers are one of the major groups of Malaysian insectivorous birds, which frequently forage in dense vegetation cover and have a high level of sympatry. Therefore, examining the diet, prey selection, and niche segregation of babblers can be challenging. In this study, we used high-throughput sequencing to investigate potential dietary overlap or segregation among 10 babbler species of the 4 genera of the family Pellorneidae and Timaliidae: Pellorneum, Malacopteron, Stachyris, and Cyanoderma in central peninsular Malaysia. We tested the hypothesis that trophically similar species may differ in resource use to avoid competitive exclusion. We identified 81 distinct arthropod taxa from fecal samples, belonging to 71 families representing 13 orders, which were predominantly from 16 dipteran, 13 lepidopteran, and 10 coleopteran families. Of all the prey taxa consumed, 45% were found to be distinct across the 10 babbler species, and ˂35% were shared simultaneously by ≥3 babbler species, indicating minimal dietary overlap. The black-throated babbler Stachyris nigricollis and moustached babbler Malacopteron magnirostre had the most generalist tendencies because they consumed a greater variety of prey taxa. Small dietary overlap values (Ojk) and a relatively wide range of food resources suggest that dietary segregation occurred among the studied babblers. The great diversity of prey consumed revealed the presence of dietary flexibility among the sympatric insectivorous birds, thus reducing any active dietary competition and facilitating the coexistence through niche partitioning.
