摘要: Little Terns Sternula albifrons are estuarine birds extensively using increasingly urbanized coastal areas. Given the increased exposure of these ecosystems to anthropogenic activities, it is crucial to study the ecology of this species and interactions with human stressors to establish management measures. We collected regurgitates (n = 182) and blood samples (n = 48) to study Little Terns' diet, health condition and isotopic niche, and individually tracked breeding adults (n = 9, during 2021 and 2022) at 2 sandy beaches 21 km apart and located within Ria Formosa Natural Park, Algarve, Portugal. Although both areas are adjacent to foraging coastal marine areas and an estuarine lagoon system with saltpans, they differ in human disturbance. We also compared breeding success and adult health measures between these 2 colonies. The main prey for both populations were Sand Smelts Atherina spp. and Gobies Pomatoschistus spp., and no differences in delta 13C and delta 15N stable isotopic values between colonies were found. Tracking data revealed that individuals foraged in the surroundings of their breeding colonies. Entrance Channels and Ocean were the most frequently used habitats for foraging by individuals from the less disturbed colony. Adults from the more disturbed colony foraged mostly in Entrance Channels. Overall, all individuals tended to forage during daytime. There were no differences in health measures of individuals between colonies, though breeding success at the most disturbed colony was comparably lower. It is important to protect both breeding areas and adjacent foraging habitats for Little Terns, particularly given the expected increasing pressure from human activities on coastal areas worldwide.

摘要: Adaptation to different environments can lead to local adaptations that facilitate morphological divergence between closely related taxa, potentially leading to speciation. Quantifying habitat variation can thus provide valuable insights into evolutionary processes. Arboreal dwarf chameleons of the genus Bradypodion exhibit 3 distinct ecomorphological forms: forest, shrub, and little brown chameleons (LBCs). It is assumed these ecomorphs are the result of convergence among species that are in similar habitats regardless of ancestry, or in some cases, morphological conservatism and retention of an ancestral form that is adapted to a shared habitat type. If so, then the habitat of different ecomorphs would differ in vegetation structure. Our results show that vegetation structure in fynbos/grassy habitats is characterized by significantly narrower perches than shrubby habitats, but both have a largely vertical perch orientation. In contrast, forests have significantly fewer vertical perches than fynbos/grassy habitats with significantly thicker diameter perches. Accordingly, LBC and shrub species used more vertically oriented perches than forest species, suggesting that perch use corresponds with the most widely available perch angles. Although LBC chameleons used the smallest diameter perches, when corrected for body size, there was no difference in perch diameter among ecomorphs. These results suggest that the body size of LBC chameleons is constrained by the prevalence of small-diameter perches in their habitat. Species in habitats with wider perches attain larger body size. These findings support the notion that variation in perch structure is critical for phenotypic convergence that has resulted in the 3 Bradypodion ecomorphs.

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摘要: The brood-parasitic brown-headed cowbird (Molothrus ater) has one of the shortest incubation periods of any bird. Brown-headed cowbird eggs, and those of other avian brood parasites, tend to be more spherical due to their greater relative width. The traditional explanation for this egg shape is that it, combined with the thicker eggshells, resists host puncture-ejection. However, very few North American hosts of the brown-headed cowbird actually engage in puncture-ejection and therefore wider eggs may instead provide greater contact with a host's brood patch during incubation, especially in large host nests. We tested whether greater egg width increased mean temperature and reduced temperature variation in brown-headed cowbirds by inserting temperature probes into brown-headed cowbird and house sparrow (Passer domesticus) eggs and placing them into red-winged blackbird (Agelaius phoeniceus) nests. House sparrow eggs are similar in appearance and in length to cowbird eggs, but are not as wide. We found no significant relationship between brown-headed cowbird egg width and mean incubation temperature. However, brown-headed cowbird eggs experienced less temperature variation than house sparrow eggs, and within brown-headed cowbird eggs, more spherical eggs experienced less temperature variation when accounting for differences in width. These results suggest that brown-headed cowbirds may have short incubation periods in part because their eggs exhibit less temperature variation over the course of incubation. The brown-headed cowbird's egg shape may contribute to its accelerated embryonic development rate relative to host eggs of similar size, which explains its ability to hatch in a variety of host nests.

摘要: Different habitat types exert particular challenges to ecological performance, ultimately having a strong influence on the evolution of morphology. Although it is well known that external morphology can evolve under the selective pressure of habitat structure, the evolutionary response of internal morphological traits remains vastly unexplored. Here, we test for morphological divergence between arenicolous and nonarenicolous species in a clade of tropidurid lizards, considering external morphological proportions and limb muscle dimensions. We found that arenicolous species seem to have evolved internal and external morphological adaptations that separate them from other habitat specialists. Moreover, comparative analyses suggested that the traits that differed the most between arenicolous and nonarenicolous lizards might have evolved divergently towards different optima. Additionally, the axis of higher morphological divergence between arenicolous and nonarenicolous species represented an important proportion of the morphological diversity within our sample, indicating that the hypothetical adaptive divergence of internal and external traits has contributed significantly to phenotypic diversity. Our results show that evolutionary associations between morphology and habitat use can be detected on both external body proportions and muscle morphology. Moreover, they highlight the emergent importance of internal anatomical traits in ecomorphological studies, especially when such traits are directly involved in determining functional performance.

摘要: Aposematism is an antipredator strategy in which conspicuous coloration acts as a warning of chemical defenses to potential predators. Evidence suggests that aposematism largely functions under positive frequency-dependent selection, which is thought to maintain uniformity of aposematic signals. Many studies of aposematic organisms have found evidence that color signals and defenses are positively correlated, indicating a quantitatively honest aposematic signal. Dendrobatid poison frogs represent a well-studied group of aposematic organisms that in addition to exhibiting a diversity of color signals also display unique defensive behaviors. Few studies have examined if both behavior and coloration act as quantitative honest signals of alkaloid defenses in poison frogs. We aimed to determine if coloration and behavior are quantitatively honest signals in the green and black poison frog (Dendrobates auratus) among 6 populations from Costa Rica. We (1) evaluated antipredator displays by using behavioral assays in the field, (2) assessed frog conspicuousness and pattern using digital images, and (3) quantified alkaloid profiles from frog skin secretions. We found that Pacific populations are less conspicuous in coloration, had greater quantities of alkaloids, and more frequently performed body-raising defensive behaviors when compared with Caribbean populations. Our results do not support the hypothesis that aposematic traits in D. auratus are quantitatively honest. Rather, our results suggest that phenotypic differences among populations may represent different phenotypic optima for advertising unprofitability to predators based on local environmental conditions, leading to the diversification of aposematic signals in this species.

摘要: Accurate estimations of animal population size are pivotal for implementing management strategies properly. Recapture technique based on sounds as a specimen identification mark has barely been used for marine mammals. However, inferring abundance estimates from acoustic methods could enhance the accuracy and precision of population size assessments. Here, we tested the possibility of using signature whistles as individual marks for estimating the size of common bottlenose dolphin (Tursiops truncatus) populations. Data were continuously collected for 326 days in 2015-2016, by using a fixed acoustic device located in the Sicily Strait (Italy). The SIGID method was applied to identify Signature Whistles Types (SWTs) over 7,000 h of recordings. Eighty SWTs were detected as long as their stereotyped fundamental frequency contours were repeated in bouts of at least 6 renditions. The mean SWTs monthly recording rate resulted in 0.19 (Standard deviation = 0.16), with 20 SWTs recorded over 5 or more different encounters (until a maximum of 30 encounters). The Jolly-Seber model (with POPAN formulation) was run in Mark software to estimate the population size. The estimated population size resulted in 171 bottlenose dolphins (95% confidence interval = 137-215). Even if the detection and identification of signature whistles required crucial precautions, and animals could be detected differently from visual techniques, the population size estimate obtained was comparable with previous results based on physical marks data. These outcomes demonstrated that signature whistles can be considered a strongly effective tool for integrating traditional mark-recapture techniques with finely estimated dolphins' population abundances.

摘要: Paternal predation risk can program offspring phenotypes via maternal responses and epigenetic marks of spermatozoa. However, the processes and consequences of this experience in biparental species are unknown. Here, we examined how preconception and postconception paternal cat odor (CO) exposure affects anxiety-like behavior and antipredator response in Brandt's voles (Lasiopodomys brandtii). We found that preconception paternal CO exposure inhibited maternal investment when offspring were raised by mothers alone, while postconception exposure increased paternal investment towards the offspring raised by both parents. The increased paternal behavior may be associated with an increasing grooming behavior received from their mates, which alleviated the anxiety-like behavior in CO-exposed males. Both paternal experiences increased the levels of anxiety-like behavior in adolescent offspring but differentially altered adult phenotypes. Specifically, adult females from preconception CO-exposed fathers spent less time in defensive concealing, whereas the offspring of postconception CO-exposed fathers showed more in response to acute cat urine exposure. Correspondingly, baseline corticosterone levels were decreased and increased in these offspring, respectively. Our results indicate that in biparental species, paternal predation risk exposure affects offspring phenotypes in pathway-dependent and age-specific manners and that only the presence of both parents can elicit adaptive responses to a high predation-risk environment.

摘要: Dietary specialists consume specific prey items, and they are often morphologically and behaviorally specialized to feed efficiently on those prey animals. Among specialist snakes, consumption of terrestrial arthropods is relatively rare. Because most terrestrial arthropods possess hardened sclerites and appendages, it is possible that snakes that feed on arthropods would show specialized prey-handling behavior. In this study, we describe prey-handling behavior of a snake feeding on terrestrial arthropods, which hitherto has not been well documented. We focused on Rhabdophis chiwen, which mainly feeds on earthworms, but also consumes lampyrine firefly larvae, sequestering cardiotonic steroids from them in its defensive organs, called nucho-dorsal glands. When feeding on earthworms, snakes showed size-dependent selection of swallowing direction, but this tendency was not observed when feeding on firefly larvae. Manipulation of firefly larvae did not seem to be efficient, probably because they possess sclerites and appendages such as legs that impede smooth handling. Although fireflies are an essential food for R. chiwen as a toxin source, our results showed that the snake is not adept at handling firefly larvae compared to earthworms, implying that dietary specialization does not necessarily accompany behavioral specialization. We discuss possible reasons for this inconsistency.

摘要: Animals living in syntopy share acoustic space. Asian horned frogs are well known for their sympatric distribution, but little is known about their strategies to avoid acoustic niche competition. This study focused on three sympatric Boulenophrys frog species from southern China-B. nanlingensis, B. ombrophila, and B. shimentaina, with the former two species call in similar frequencies but breed in different seasons. First, we checked the call variation during the change of individual body size and the ambient air temperature in three species. We have found call frequencies were the most static parameters in each species that were associated with body size and contributed most to species identification. Temporal call parameters shift with temperature but are mostly influenced by low temperatures. Second, we checked the interactions between the environment and call properties. The calling site preferences of each species corresponded well with the prediction of the acoustic adaptation hypothesis (in view of higher frequency better transmission in open habitat), and species with similar call frequencies have some aspects of common calling sites. Third, we checked the species-species interaction by using playback tests with male B. nanlingensis. Results from playback experiments showed species that call at similar frequencies could hardly share the same habitat during the same season. These findings expanded the knowledge of acoustic coexistence in closely related anuran species and provided insights into the vocal behavior of Asian horned frogs.