Ethology最新文献

Sexual Selection has been studied predominantly from a functional perspective with relatively limited investigation of the mechanistic basis of female choice. In this study, we evaluated female choice and larvae production in response to attractive or less attractive males and concurrently examined the protein profile in the brains of females, using the mealworm beetle Tenebrio molitor as a model system. Females were found to prefer males with high levels of pheromones, which requires the secretion of juvenile hormone (JH). Male attractiveness was enhanced using the JH analog methoprene, resulting in less female rejection and higher mating frequency and offspring production. Importantly, reproductive success was not due to differences in testis size or sperm production, or viability. Out of the 1833 proteins detected in the brain, only 32 were differentially expressed in females mating with attractive versus less attractive males. These proteins involved memory, metabolism, olfactory detection, reproduction, and movement. Although some brain proteins have been linked to mate choice in vertebrates, most of the differentially expressed molecules found in this study have not been previously reported concerning mate choice.

The parasitic nest flies Philornis spp. are ectoparasites associated with a large number of Neotropical bird species. Little is known about how flies locate birds' nests and how parents respond to native or subcutaneous parasitic flies. Here, we used blue-black grassquits (Volatinia jacarina) to test (i) if parental care in early egg and nestling stages could predict parasitism status in late nestling stages and (ii) if parental care differed between parasitized and non-parasitized nests. In general, the proportion of time parents were on the nest (both incubation and nestling periods) did not predict later Philornis parasitism status. These results suggest that flies do not use the presence of parents at the nest to locate nestlings. Parents visited the nest to feed nestlings more frequently in parasitized nests, suggesting that parents compensate for presumed nestling energy loss due to Philornis parasitism. Parents also spent more time on nest maintenance in parasitized nests, which may be an attempt to remove larvae from nest walls or repair the nest damaged by larvae displacement. Finally, the time spent brooding did not vary with parasitism status. Grassquit responses to Philornis parasitism provide a new perspective relative to the evolution of effective defense strategies against native parasites.

Species have different requirements for the habitat in which they live, depending on various biotic and abiotic factors. For sedentary predators such as antlion larvae, both factors are essential. In this study, we examined the preferred habitat choice concerning two abiotic factors, i.e., substrate and illumination, in two pit-building antlions, Euroleon nostras and Myrmeleon formicarius, to determine whether choice changes during con- or heterospecific interactions. Both species preferred medium sand grains, i.e., 230–540 μm but differed in their choice of illumination. E. nostras preferred shade, while M. formicarius chose the illuminated part of the container. However, the choice changed, especially for M. formicarius during interactions with another individual. Abiotic factors took precedence over biotic factors in the choice of E. nostras when interactions were involved. M. formicarius avoided interactions and built pits in less suitable conditions when suitable locations were already occupied. The results can be applied to the species' natural habitat and life traits. We can confirm that E. nostras is a more competitive species when it comes to providing the most suitable abiotic conditions in the habitat for pit construction.

Composite scores, where the results of two or more measures are combined, are commonly used in many fields, including ethology. Composite scores can simplify the analysis and interpretation of data while capturing the salient features of the underlying latent variable(s) approximated by the score. Here we outline four approaches for constructing composite scores in ethological studies: ad hoc (AH) assignment, discriminant analysis (DA), principal components analysis (PCA), and partial least squares (PLS). We give examples of each using previously published data from a study of responses of lone star ticks (Amblyomma americanum) to several deterrent phytochemicals. In most cases, researchers construct AH composite scores by subjectively assigning weights and signs to the behavioral components; unity weighting constrains weights to −1 or 1 on standardized variables. Because the weights and signs of the coefficients are subjectively assigned, AH scores may generate a spurious result. DA can be used to construct composite behavioral scores when there are clearly defined treatments or preference tests using distinct stimuli. The DA score created consists of orthogonal variables that capture the variability in the behavioral measures most closely aligned with the differences among treatment or stimuli variables. This approach assumes that subjects discriminate treatment or stimuli differences, but may not manifest clear overt behavior that they are able to do so; it reduces dimensionality, usually to a single axis, representing the underlying latent variable of interest. The PCA approach is similar to DA except that the composite score is created independently of treatment or stimuli variables. Thus, this method can be used to investigate possible relationships between a composite score and any relevant independent variable, perhaps measured asynchronously with the behaviors. PLS is a multivariate method related to DA and PCA and is also used to create latent orthogonal variables. However, these new variables are constructed to maximize correlation with one or more continuous independent variables. Creation of a composite score requires the researcher to consider not only the method used to create it, but, at an earlier stage in the research, which behaviors should be components and how best to measure them.

Learning can occur via trial and error; however, learning from conspecifics is faster and more efficient. Social animals can easily learn from conspecifics, but how do less social species learn? In particular, birds provide astonishing examples of social learning of vocalizations, while vocal learning from conspecifics is much less understood in mammals. We present a hypothesis aimed at solving an apparent paradox: how can harbor seals (Phoca vitulina) learn their song when their whole lives are marked by loose conspecific social contact? Harbor seal pups are raised individually by their mostly silent mothers. Pups' first few weeks of life show developed vocal plasticity; these weeks are followed by relatively silent years until sexually mature individuals start singing. How can this rather solitary life lead to a learned song? Why do pups display vocal plasticity at a few weeks of age, when this is apparently not needed? Our hypothesis addresses these questions and tries to explain how vocal learning fits into the natural history of harbor seals, and potentially other less social mammals. We suggest that harbor seals learn during a sensitive period within puppyhood, where they are exposed to adult males singing. In particular, we hypothesize that, to make this learning possible, the following happens concurrently: (1) mothers give birth right before male singing starts, (2) pups enter a sensitive learning phase around weaning time, which (3) coincides with their foraging expeditions at sea which, (4) in turn, coincide with the peak singing activity of adult males. In other words, harbor seals show vocal learning as pups so they can acquire elements of their future song from adults, and solitary adults can sing because they have acquired these elements as pups. We review the available evidence and suggest that pups learn adult vocalizations because they are born exactly at the right time to eavesdrop on singing adults. We conclude by advancing empirical predictions and testable hypotheses for future work.

Communal nesting behaviour of small mammals is thought to function mainly as a method of thermoregulation. However, this behaviour is also observed during the non-winter season when there are no obvious thermoregulatory benefits. Siberian flying squirrels (Pteromys volans) nest communally during the non-winter season. This may facilitate mating, but other functions such as thermoregulation have not been sufficiently studied. Therefore, we examined whether communal nesting of P. volans during the non-winter season plays a role in thermoregulation in addition to mating. In the event that communal nesting in the non-winter season has any function other than mating, we expected an increase in non-mating groups consisting of only-males during the nurturing period (duration of mother squirrel and cubs living together) because females rearing their young do not participate in communal nesting. In Obihiro, Hokkaido, Japan, during the non-winter season (May–October) between 2019 and 2021, we captured P. volans in 252 nests by using nest boxes. The occurrence of male-only groups showed a tendency to increase during the nurturing period. Moreover, the number of mixed-sex groups increased between August and October each year; these changes in communal nesting during the non-winter season were unrelated to the variation in air temperature or precipitation. These results suggest that during the non-winter season, communal nesting of P. volans is related to reproductive behaviour. Additional studies are needed to determine how communal nesting during the non-winter season enhances the reproductive success of male and female P. volans.

In animals where both males and females have high costs associated with reproduction, it is not rare that both sexes evaluate their potential mate conditions to make the most beneficial choice according to their preferences. Parasite-mediated selection theories predict that individuals would evaluate the ability of their potential mates to resist parasites and decide whether to accept or reject mating based on that information. These studies of parasite-mediated sexual selection had been carried out through the traditional sex roles perspectives. Our study species in this article is one with indirect sperm transfer, the pseudoscorpion Lustrochernes argentinus, and we evaluated mating on the health condition (infected or not) of both males and females. Our hypothesis is that the presence of gregarines in potential mates influences mate choice and for that, we analyzed (1) if gregarine-infected individuals suffer a higher proportion of rejection by their uninfected partners and (2) if spermatophore use success is lower when any of the individuals are infected. We tested this in a behavioral laboratory trial, comparing rejection by the male and the female and spermatophore use in four experimental groups. We found that both males and females suffer a higher probability of rejection when infected with gregarines; the maximum probability of sperm uptake success is when both individuals are healthy.

Parental care is a critical component of many breeding systems that enhances both parent and offspring fitness. It is widely recognized that parental care varies in quality and quantity in response to variation in offspring need, parental condition, and ecological context. One context that has been underexplored, however, is the presence of extensive parental care at night, with many parental care studies focused on diurnal care. To fully understand the evolution of parental care, both diurnal and nocturnal care must be accounted for. Here, we show that nocturnal parental care exists in the clownfish Amphiprion percula, with males and females actively caring for offspring at night throughout embryo development and during hatching within a laboratory setting. At night, as during the day, males continue to be the dominant caregiver and both parents increase care as embryos mature. However, females provide substantially more care at night than during the day. We also document three new parental care behaviors at night that are not seen during the day: vigorous fanning, vigorous mouthing, and anemone biting. These behaviors are particularly frequent during hatching, and they may serve to assist the hatching process by helping embryos transition from the benthic to the pelagic environment. This study contributes to our understanding of parental care, demonstrating the importance of considering nocturnal care if we are to gain a complete understanding of the evolution of parental care.

Mate choice is a key component of reproductive biology. Females often prefer certain males but do females modulate their reproductive investment depending on whether they are mated with their preferred partner? We investigated this question in great tits (Parus major) where we subjected 36 females to a six-choice mate preference test. Male morphological traits and the female's own characteristics did not influence the preference females expressed. We however found that females spent more time near more exploratory males. We then paired females with one of the males in indoor aviaries, and subsequently monitored their reproductive investment (through measurement of plasma 17β-oestradiol concentrations, first egg date, clutch size and egg size). Females that were mated with a male for which they had a strong preference laid their first clutch significantly earlier in the season than females paired with a male they less preferred. Our results show that mate preference influences reproductive investment in great tits, thereby linking mate choice to bird reproductive decisions.

It is assumed that males increase their reproductive performance by mating with the highest number of females. However, in some species males are reproductively constrained, being able to mate only a few times. In these cases, it is expected that males choose the highest quality females available. One factor that can change female quality is parasitism, however, many empirical studies fail to find conclusive support for a non-parasitized female preference. This might be due to the fact that behavioral tests in many studies are made in a controlled environment or use indirect measures of mate choice. Using a natural-environment approach, we tested whether the mate choice of the golden orb-web spider Trichonephila clavipes male is affected by the presence of the parasite in the female. We hypothesize that males will prefer to establish on webs of non-parasitized females and will attempt to mate and copulate more with non-parasitized females over parasitized ones. For this, we conducted field observations for 76 h. We found that males prefer to establish on non-parasitized female webs than on parasitized ones. However, there was no difference between the number of attempts to mate and copulations of parasitized and non-parasitized females. It seems that males can distinguish between parasitized and non-parasitized females, but once they establish on a female web, they are resistant to leave. One possible explanation is that some males stay on a parasitized female web to avoid competition with other males. Therefore, it is possible that mating with parasitized females represents a “making the best of a bad job” mating tactic in T. clavipes.