摘要: For songbirds, the post-fledging period is critical for development and survival, as young must learn to get food, practice flying, and identify predators to become independent from their parents and disperse or migrate. Obligate avian brood parasites, like cuckoos and cowbirds, lay eggs in nests of other bird species that provide parental care until the parasite's young become independent. The information on the post-fledging period in songbirds is limited due to the difficulty in following and observing fledglings and it is even scarcer for brood parasites. We studied the behavior, survival, and age of independence of Shiny Cowbird (Molothrus bonariensis) fledglings raised by 2 hosts that differ markedly in body size: the House Wren (Troglodytes aedon) and the Chalk-Browed Mockingbird (Mimus saturninus). We radio-tracked individuals from a few days before they left the nest until they disappeared from the natal territory. We found: (1) chicks left the nest when they were 11-15 days of age and the age of fledgling did not differ between the 2 host species, (2) after leaving the nest, they spent most of the time perched in a hidden place without begging but as they grew, the proportion of time perched without begging decreased and begging in hidden and exposed places increased, (3) we observed approaches between adult parasitic females and young in host territories, (4) young abandoned the host territory and joined conspecific flocks when they were 35-39 days of age, and (5) the estimated post-fledging survival was between 12.5% and 20.8%.

摘要: Animal species exhibit a wide range of coloration and patterns, which are under strong selection and often linked to individual quality, influencing mate choice, recognition, signaling, and interspecific interactions such as predator avoidance. In amphibians, coloration can vary based on individual traits as well as environmental conditions, including the coloration of their environment. In this study, we described the dorsal coloration (body coloration reticulated by dark patches) in 676 Western spadefoot toads (Pelobates cultripes) from the French Atlantic coast, comparing color variations across different substrates. In addition, we assessed color change in 18 toads transferred between bright and dark substrates. We demonstrated that the dorsal coloration varies based on capture locations (beach vs. inland) and associated substrate types (bright vs. dark), suggesting background color matching. We showed more pronounced effects in females, which might reflect varying predation risks. Experimentally, we showed that individuals can rapidly adjust their coloration to match the substrate within 24 h. Rapid color changes in response to substrate type indicate significant pigmentation plasticity. Bright individuals from sandy substrates showed less dorsal background (body) color change than dark inland individuals, while patch coloration responded differently depending on the substrate of origin. These findings highlight the complex interactions between substrate type, sex, and pigmentation plasticity. These interactions have potential costs and benefits, which might be linked to melanin production, which warrant further investigation.

摘要: Eyespots have been shown to perform an anti-predator function by intimidating predators. However, whether predators are deterred by the eyespots' mimicking eyes of higher-order predators, or by the conspicuousness of the spots, is still being debated. The anti-predator mechanism of eyespots, which involves the predator's visual perception and cognition, urges to be examined. To explore the eye mimicry hypothesis and conspicuous signal hypothesis, we designed prey with deceptive eyespots eliciting 2-dimensional (2D) or 3-dimensional (3D) visual illusions for domestic chicks (as predators). For 2D visual illusion, we provided prey with occluded eyespots for chicks. Chicks can complete the occluded eyespots into a full 2D concentric circle by the amodal completion mechanism, that is, one of visual illusion. For 3D visual illusion, we created the crescent-shaped sparkles on the eyespots to simulate a visually 3D eye. Our result indicated that (1) 2D: chicks hesitated more when facing preys with occluded eyespots than facing preys with broken eyespots and (2) 3D: compared to prey with no-sparkle eyespots, chicks spent more time approaching prey with sparkle eyespots and were more likely to approach them tangentially. Thus, the visual illusion perceived by chicks would impact the anti-predation effectiveness of eyespots. Eyespots that more closely resemble the real eyes, especially those with 3-dimensionality, provided more effective protection. Our study supported the eye mimicry hypothesis from the perspective of visual illusion.

摘要: Sleeping site selection is essential for understanding primate behavioral ecology and survival. Identifying where species sleep helps determine priority areas and critical resources for targeted conservation efforts. However, observing sleeping sites at night is challenging, especially for species sensitive to human disturbance. Thermal infrared imaging (TIR) with drones is increasingly used for detecting and counting primates, yet it has not been utilized to investigate ecological strategies. This study investigates the sleeping site selection of the Critically Endangered black-shanked douc langur (Pygathrix nigripes) in Cat Tien National Park, Vietnam. Our aim is to assess the feasibility of using a TIR drone to test sleeping site selection strategies in non-nesting primates, specifically examining hypotheses related to predation avoidance and food proximity. Between January and April 2023, we conducted 120 drone flights along 22 transects (similar to 1-km long) and identified 114 sleeping sites via thermal imaging. We established 116 forest structure plots along 29 transects in non-selected sites and 65 plots within douc langur sleeping sites. Our observations reveal that douc langurs selected tall and large trees that may provide protection against predators. Additionally, they selected sleeping sites with increased access to food, such as Afzelia xylocarpa, which serves as a preferred food source during the dry season. These results highlight the effective use of TIR drones for studying douc langur sleeping site selection with minimal disturbance. Besides offering valuable insights into habitat selection and behavioral ecology for conservation, TIR drones hold great promise for the noninvasive and long-term monitoring of large-bodied arboreal species.

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: 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: 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.

摘要: Individual phenological life-history variations in the context of seasonal conditions are well documented in fishes and birds. However, amphibians, a group heavily affected by habitat loss and fragmentation, have received relatively little attention regarding research on life-history adaptations. Here we present 3 years of data on the timing of reproductive activity in a suburban European green toad (Bufotes viridis) population. We found annually consistent patterns of reproductive activity and investigated whether these were caused by allochrony or individual attributes. Body size (a proxy for age), body condition, and sex significantly affected the timing of reproductive activity. However, most individuals showed considerable overlap in their reproductive timeframe, refuting the existence of allochronic subpopulations. Our findings may indicate life-history adaptations in the direction of a faster lifestyle in response to hazardous environments. We propose to focus further research efforts on phenological variations in the context of environmental conditions, and that phenological variations should be considered more strongly in amphibian conservation efforts.

摘要: Artificial light at night (ALAN) is a common anthropogenic disturbance, which alters animal behavior. However, little is known about the impact of the spectral composition of ALAN and co-occurring predation risk on the behavior of aquatic organisms. We experimentally investigated how ALAN of different spectra (cool white LED and HPS light) affects the behavior and foraging of Gammarus jazdzewskii (Amphipoda) on chironomid prey, both as a single stressor and in combination with an olfactory predation cue. Gammarids exposed to ALAN in the absence of predation cues consumed less, compared with darkness, mainly due to their lower activity. Moreover, gammarids showed a stronger response to LED light, spending more time in the shelter and increasing prey handling time in this treatment. The addition of predation cues did not enhance the negative impact of ALAN on the foraging success. Gammarids maintained similar consumption levels as in the ALAN treatment without predation cues and in darkness with predation cues. However, gammarids in LED light altered their behavior in response to predation threat: they decreased prey handling time and consumed prey faster, which may have compensated for the higher food demand in stressful conditions. They also tended to exhibit risky behavior, leaving the shelter and moving towards the lit area, presumably to escape and avoid the combined effects of light and predation cues. Therefore, when assessing the effects of ALAN on organisms, light quality and co-occurring biotic factors should be considered, as predator pressure is common in natural environments.