Journal of Ethology最新文献

Field and experimental evidence shows that anuran adults selecting spawning habitats make flexible, context-dependent choices based on multiple biotic and abiotic factors. Despite the empirical evidence, few formal theories explain the context-dependent selection of spawning habitats by anurans. To fill this gap, we develop a mathematical model to analyze the interacting effects of multiple biotic and abiotic factors on anuran spawning habitat selection. Our model considers the effects of habitat quality (e.g., resource levels, heterospecific predator abundances, and other abiotic conditions), spawning timing within a reproductive season, strength of conspecific competition among juveniles, and strength of conspecific predation of early hatching on late hatching juveniles. The model predicts that while early-spawning adults generally favor better-quality habitats, late-spawning adults may not necessarily prefer better-quality habitats. Predation of late-hatching juveniles by early-hatching juveniles promotes the avoidance of better-quality habitats by late-spawning adults. Stronger competition among juveniles of the same developmental age increases the preference of late-spawning adults toward better-quality habitats. These predictions are in broad agreement with empirical evidence. Our model demonstrates that the tension between habitat quality and negative conspecific interactions among juveniles drives the context-dependent selection of spawning habitats by anuran adults.

The Anatolian mole rat (Nannospalax xanthodon) is a mammal known for its specialized adaptations to a subterranean existence. Here, we present a field observation of an N. xanthodon individual exhibiting an unusual escape behavior in response to the risk of predation from a domesticated mammal. Faced with this imminent danger, the mole rat displayed a capacity for aquatic locomotion, successfully swimming across a river to escape the predator. This observation challenges our current understanding of the antipredator repertoire in N. xanthodon and underscores the potential for stress-induced behavioral plasticity in subterranean mammals.

Roads provide attractive but dangerous habitats for a wide variety of wild animals, including granivorous species feeding on road-spilled grains. The survival of those animals would imply risk-taking behaviors toward vehicles. We investigated these behaviors in a southern Tunisian crested lark (Galerida cristata) population, by using the flight and tolerance distances of flushed birds as assessments of motivation to take risks. Crested larks foraging on the roadside tolerated more risk compared to those foraging in road-free areas, which could reflect possible habituation of roadside individuals to road traffic. Moreover, crested larks tolerated closer approaches when they were in larger flocks, probably due to increased risk dilution and/or scramble competition. Finally, the studied birds took more risks in summer compared to winter, which could result from reduced time available for foraging during the hot season, or reflect a possible age effect since summer birds included many less-experienced fledglings, among other possible explanations. In sum, our findings highlight that roadside life imposes behavioral adjustments on seed-eating birds, and that seasonal effects may greatly affect birds’ behavioral responses to road-associated threats.

Sexual dimorphism and male combat are observed in many species. Often, the outcome of male combat affects the outcome of subsequent combats, mating success, number of sperm, and fitness of the male’s offspring. Also, the quantity and quality of sperm may be regulated by winning or losing, depending on species ecology and mating system. However, very few studies have experimentally examined the influence of fight outcomes on male offspring fitness. We studied male combat in the giant mealworm (Zophobas atratus) in which males bite each other’s hind legs. We hypothesized that subsequent fitness could differ between winners and losers in the escalated male combat of this species. We measured several fitness traits including the number of eggs laid by mated females, and the number of hatches sired by uncontested males, winners, and losers in escalated and non-escalated combat, and compared the fitness of each winner and loser to that of an uncontested male. We also measured mating duration. The numbers of eggs and the percentages of hatched eggs of losers in the escalated combat were significantly reduced compared to that of the uncontested males. This reduction may be due to injuries from escalated leg- biting fights and a result of the sperm amount of the uncontested males being greater than that of the loser males.

Studies show that the common cuckoo exhibits a strong vocal response to rival playback. In this study, we aimed to assess if males would more eagerly vocally defend their home ranges a day after a simulated rival encounter. At 48 sites in Poland, we conducted a playback experiment where we played 20 calls repeated 5 times with a 5-min break between each series. Using the automatic analysis software Kaleidoscope Pro, we detected cuckoo calls in two datasets, directly after the experiment and the day after. Our results show that even though cuckoos respond to rival calls, this response is short-lived.

Despite acoustic signals playing a fundamental role on animal behavior and reproduction, our understanding of the mechanisms driving their evolution is still scarce. Due to the high cost of signaling, several adaptive bioacoustics hypotheses have been proposed to explain call design. While Acoustic Adaptation Hypothesis (AAH) postulates the habitat influence on shaping acoustic signals, Morphological Adaptation Hypothesis (MAH) emphasizes the constraints that animal structure imposes to their calls. Yet, when testing those hypotheses, phylogenetic comparative methods have been scarcely applied so far. Here we evaluated the AAH and MAH in 163 anurans (i.e., Brazilian species of the family Hylidae), based on a broad review of the dominant frequency of their advertisement calls. Comparative methods revealed a negative relationship between dominant frequency and body size, supporting the MAH. AAH was partly rejected, as vegetation density, habitat type and calling microhabitat did not affect species’ dominant frequency. However, species calling from higher perches had higher dominant frequencies, partially supporting habitat effect on call features. Our results not only highlight the role of morphology on shaping Hylidae call design, but also arise questions about scale effect, behavioral strategies and other sound propagation characteristics while testing AAH in frogs.

Changes in the animals’ environment often impact on their behavior and the way they communicate. Particularly in spiders, living on webs or not is a determining factor. While the Lycosidae family predominantly comprises wandering spiders, only a few species inhabit webs. Aglaoctenus oblongus (C.L. Koch 1847) challenges this norm, as it has been found both in webs and wandering, suggesting a previously undocumented mixed strategy. This study aims to: (1) describe the sexual behavior of A. oblongus under laboratory conditions and (2) utilize phenological data to elucidate when and where mating occurs. Sexual encounters were observed within and outside webs, with minimal differences noted between them. Courtship was characterized by groping and leg shaking performed by the males. Copulation was lengthy (near to seven hours), featuring an irregular pattern of palpal insertions, and culminating in a backward dismount. Individuals showed a mixed life history, with the spiders most often found in webs being females with eggs. Both sexes were found throughout the year, with a peak in autumn. We compare the sexual characteristics of this species with that of A. lagotis (also belonging to the Sosippinae subfamily), the only other wolf spider studied to date that exclusively inhabits webs.

Death feigning is hypothesized to be an anti-predator behavior in which prey is temporarily immobilized in response to external stimuli. While death feigning may be an effective predator-defense strategy, there may be trade-offs in terms of energy and time for finding food and/or mating. The duration of death feigning is regulated by the balance of various selection pressures, and its duration is influenced by many internal and environmental factors. However, little is known about the factors that influence arousal from death-feigning behavior. Sex pheromones are important semiochemicals that affect reproductive success and may influence the duration of death-feigning behavior. In this study, we aimed to investigate the effects of sex pheromones on the death-feigning behavior of the sweet potato weevil (Cylas formicarius) by conducting laboratory experiments. The results showed that males had a significantly shorter death-feigning duration in the presence of sex pheromones because it aroused them from their death-feigning behavior, but females were unaffected. This is the first study to show that sex pheromones alter death-feigning behavior. The results of this study elucidate the factors influencing predator-avoidance behavior and reveal the impact of death-feigning behavior on prey reproduction under predation pressure.

To compensate for mineral deficiencies in food sources, numerous ungulate species use various methods, such as salt licking, soil ingestion, and gnawing on antlers or bones. While osteophagia, the act of gnawing on antlers or bones, is well-documented in cervid species, it has only been observed in sika deer (Cervus nippon) on Mageshima Island in southern Japan despite their widespread distribution. This study aimed to provide an initial account of the observations of osteophagia in sika deer from central Japan. One of the 15 camera traps deployed in the Hakone Nature Forest of Tamagawa University for wildlife monitoring serendipitously captured multiple instances of adult female sika deer gnawing on a four-tined antler on July 9th and 16th in 2018. These occurrences coincided with the fawning season of the species during which mineral deficiencies in the diet are prevalent, suggesting that osteophagia serves as a response to nutrient deficiencies in the diet of sika deer in central Japan. Thus, systematic surveys may yield additional evidence of this behavior in sika deer across diverse geographical areas given the absence of studies on osteophagia in sika deer conducted in other regions. Digital video images related to the article are available at http://www.momo-p.com/showdetail-e.php?movieid=momo240508cn01a.