Current Zoology最新文献

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%.

Portschinskia Semenov is a rare genus of bot flies whose larvae are obligate parasites of pikas and murine rodents, crucial for understanding the evolutionary biology of Oestridae. However, limited information on their adult biology and early immature stages has hindered the progress. Here, we provided the first documentation of adult oviposition, behavior, and morphology of newly hatched first instars of P. magnifica Pleske. Using confocal laser scanning microscopy and scanning electron microscopy, we characterized the ultrastructure of egg and first-instar larva, identifying key traits facilitating attachment. Eggs were deposited individually or in groups, and glued on non-host surfaces with white adhesive substances, without specialized attachment organ. Newly hatched first instars were circled with an anterior spinose band on each body segment except the anal division, awaited hosts in an upright position, and anchored to the egg shell by their anal division, likely supported by curved spines originating from the peritreme of the posterior spiracles. Evolutionary analyses of reproductive behavior across the 4 bot fly subfamilies reveal at least 3 times independent evolution of oviposition on non-host surfaces in Portschinskia or the Hypodermatinae clade as a sister group to Ochotonia, Gasterophilus pecorum (Fabricius) (Gasterophilinae), and Cuterebrinae. In contrast, species in the Oestrinae are larviparous, depositing first instars directly onto hosts. Our findings shed light on oviposition behavior and early immature morphology of the rare genus Portschinskia, offering insights into reproductive strategies and evolutionary adaptations of bot flies.

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.

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.

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.

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.

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.

The study of temperament and behavioral syndromes in insects is still in its early stage, and research conducted to date has mainly focused on locomotor activity and thanatosis. Dung beetles have been the subject of extensive behavioral studies; however, very few studies have addressed the expression of temperament. Those doing so only looked at subsocial and sexual horn dimorphic species, suggesting subsociality and/or sexual horn-dimorphism as possible facilitators of temperament expression. To test this assumption, we conducted a temperament study in a hornless, non-subsocial species, namely Geotrupes mutator (Marsham, 1802). We set up laboratory tests to evaluate 3 behaviors (activity, thanatosis, and distress calls) through the measurement of 7 distinct behavioral traits (3 activity-, 1 thanatosis-, and 3 call-related traits). We found high levels of individual repeatability in all activity- and thanatosis-related traits. We also identified behavioral differences between individuals, which may reflect differences in temperament. Statistical analyses revealed a negative correlation between activity and thanatosis. These results show that the temperament and behavioral syndromes related to activity and thanatosis may also be expressed in dung beetle species that are neither subsocial nor sexual horn dimorphic. By contrast, we only found one of 3 sound-related traits tested (frequency) to be clearly repeatable. Males and females presented a different structure of the stridulatory apparatus, suggesting that morphology may affect the frequency of sounds emitted. These results indicate that certain sound traits might not be good descriptors of individual temperament revealing the need for future research addressing the role of bioacoustics.

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.

Vocal individuality is essential for social discrimination but has been poorly studied in animals that produce communal signals (duets or choruses). Song overlapping and temporal coordination make the assessment of individuality in communal signals more complex. In addition, selection may favor the accurate identification of pairs over individuals by receivers in year-round territorial species with duetting and long-term pair bonding. Here, we studied pair and individual vocal signatures in the polyphonal duets of rufous horneros Furnarius rufus, a Neotropical bird known for its long-term pair bonds. Hornero partners engage in duets to deter territorial intruders and protect their partnership year-round and can discern duets from neighbors versus strangers. Using a dataset of 471 duets from 43 pairs in 2 populations, we measured fine-scale acoustic features across different duet levels (e.g., complete duets to non-overlapping syllable parts) and analysis levels (pair or individual). Permuted linear discriminant function analyses classified pairs and individuals more accurately than expected by chance (means: 45% and 47% vs. 4 and 2%). Pair identity explained more variance in the multivariate acoustic features of duets than individual or population identities. The initial frequency of the duet showed strong potential for encoding pair identity. The acoustic traits contributing most to individual vocal signatures varied between sexes, which might facilitate the simultaneous assessment of duetters' identities by receivers. Our study indicates that vocal individuality may exist even in species with intricate and innate communal signals and elucidates the mechanisms employed by horneros in their social discrimination ability.