体征对灰眉岩鹀鸣唱特征的影响

声信号是鸟类交流的重要方式。鸟类的鸣声特征受到生境的塑造和性选择,也受到发声器官的影响,如种间的比较研究发现,体重大的鸟类鸣声频率低,喙短的鸟类鸣声频宽大。在种内是否也存在类似的规律,目前的结论还不一致。2012年6月,在北京小龙门地区(40°00'N,115°26'E)测量了17只灰眉岩鹀(Emberiza godlewskii)的形态参数以及鸣声的频率特征,未发现体重或喙长与鸣声的最高频率、最低频率、峰频或频宽存在显著的相关性。本研究的结果支持在小型雀形目鸟类中,体型对繁殖期鸣唱频率特征的影响不显著。     

Phylogenetic review of tonal sound production in whales in relation to sociality

Background  

It is widely held that in toothed whales, high frequency tonal sounds called 'whistles' evolved in association with 'sociality' because in delphinids they are used in a social context. Recently, whistles were hypothesized to be an evolutionary innovation of social dolphins (the 'dolphin hypothesis'). However, both 'whistles' and 'sociality' are broad concepts each representing a conglomerate of characters. Many non-delphinids, whether solitary or social, produce tonal sounds that share most of the acoustic characteristics of delphinid whistles. Furthermore, hypotheses of character correlation are best tested in a phylogenetic context, which has hitherto not been done. Here we summarize data from over 300 studies on cetacean tonal sounds and social structure and phylogenetically test existing hypotheses on their co-evolution.     

Unveiling the environmental drivers of intraspecific body size variation in terrestrial vertebrates

Aim

Whether intraspecific spatial patterns in body size are generalizable across species remains contentious, as well as the mechanisms underlying these patterns. Here we test several hypotheses explaining within-species body size variation in terrestrial vertebrates including the heat balance, seasonality, resource availability and water conservation hypotheses for ectotherms, and the heat conservation, heat dissipation, starvation resistance and resource availability hypotheses for endotherms.

Location

Global.

Time period

1970–2016.

Major taxa studied

Amphibians, reptiles, birds and mammals.

Methods

We collected 235,905 body size records for 2,229 species (amphibians = 36; reptiles = 81; birds = 1,545; mammals = 567) and performed a phylogenetic meta-analysis of intraspecific correlations between body size and environmental variables. We further tested whether correlations differ between migratory and non-migratory bird and mammal species, and between thermoregulating and thermoconforming ectotherms.

Results

For bird species, smaller intraspecific body size was associated with higher mean and maximum temperatures and lower resource seasonality. Size–environment relationships followed a similar pattern in resident and migratory birds, but the effect of resource availability on body size was slightly positive only for non-migratory birds. For mammals, we found that intraspecific body size was smaller with lower resource availability and seasonality, with this pattern being more evident in sedentary than migratory species. No clear size–environment relationships were found for reptiles and amphibians.

Main conclusions

Within-species body size variation across endotherms is explained by disparate underlying mechanisms for birds and mammals. Heat conservation (Bergmann's rule) and heat dissipation are the dominant processes explaining biogeographic intraspecific body size variation in birds, whereas in mammals, body size clines are mostly explained by the starvation resistance and resource availability hypotheses. Our findings contribute to a better understanding of the mechanisms behind species adaptations to the environment across their geographic distributions.     

Relationships of song structure to phylogenetic history,habitat, and morphology in the vireos,greenlets, and allies (Passeriformes: Vireonidae)

Acoustic signals show immense variation among passerines, and several hypotheses have been proposed to explain this diversity. In this study, we tested, for the first time, the relationships of song structure to phylogeny, habitat type, and morphology in the vireos and allies (Vireonidae). Every measure of song structure considered in this study had moderate and significant phylogenetic signal. Furthermore, two song-constraining morphological traits, bill shape and body mass, also exhibited significant phylogenetic signal. Song length showed the largest within-clade similarity; longer songs were highly conserved in part of the greenlet (Hylophilus) clade, whereas shorter songs characterized the remaining seven genera. We found no differences in song structure among vireonids living in different habitat types. However, vireonids with shorter, stouter bills and larger bodies sang songs with lower minimum and maximum peak frequency, compared with species with longer, thinner bills and smaller bodies. We conclude that Vireonidae song evolution is driven partially by phylogenetically conserved morphological traits. Our findings support the phylogenetic signal and morphological constraints hypotheses explaining structural diversity in avian acoustic signals.     

Integrating phylogeny,environment and space to explore variation in macroecological traits of Viperidae and Elapidae (Squamata: Serpentes)

We used eigenvector mapping in space and phylogeny to investigate the relationships among space, phylogeny and environment on body size and range size variation across two groups of venomous snakes – Viperidae and Elapidae – from the New World. Data on species geographic range sizes, maximum body sizes and phylogenetic relationships were compiled from the available literature. The distributional data were also used to calculate the latitudinal and longitudinal midpoint and the environmental centroids for each species. The eigenvectors extracted from the pair wise spatial and phylogenetic distance matrices were integrated with environmental variables into a method of variation partitioning where the variation in each trait was quantitatively attributed to ‘pure’ and/or shared effects of phylogeny, environment and space. Our results showed that variation in body size was predominantly determined by phylogeny in both groups of snakes. For Viperidae, we found that pure ‘effects’ of phylogeny were the strongest, indicating that most of the body size evolution that was phylogenetically determined in this group occurred independently of environment and geographical proximity. Regarding range sizes, pure phylogenetic influences were very low in both groups, whereas the largest single fraction of explained variation corresponded to overlapped influences of the three sets of predictors, especially for Elapidae. Along with this, we found evidence that niche conservatism is an important processes underlying variation in body size and range size in both groups of snakes.     

Does sociality drive the evolution of communicative complexity? A comparative test with ground-dwelling sciurid alarm calls

While sociality has been hypothesized to drive the evolution of communicative complexity, the relationship remains to be formally tested. We derive a continuous measure of social complexity from demographic data and use this variable to explain variation in alarm repertoire size in ground-dwelling sciurid rodents (marmots, Marmota spp.; prairie dogs, Cynomys spp.; and ground squirrels, Spermophilus spp.). About 40% of the variation in alarm call repertoire size was explained by social complexity in the raw data set. To determine the degree to which this relationship may have been influenced by historical relationships between species, we used five different phylogenetic hypotheses to calculate phylogenetically independent contrasts. Less variation was significantly explained in contrast-based analyses, but a general positive relationship remained. Social complexity explained more variation in alarm call repertoire size in marmots, while sociality explained no variation in repertoire size in prairie dogs and no variation in phylogenetically based analyses of squirrels. In most cases, substantial variation remained unexplained by social complexity. We acknowledge that factors other than social complexity, per se, may contribute to the evolution of alarm call repertoire size in sciurid rodents, and we discuss alternative hypotheses. Our measure of social complexity could be used by other researchers to test explicit evolutionary hypotheses that involve social complexity.     

Body size correlates negatively with the frequency of distress calls and songs of Neotropical birds

ABSTRACT The allometric relationship between body size and song frequency has been established in previous studies of temperate and tropical bird communities. However, the relationship between body size and the frequency of distress calls has been examined in only one study of temperate birds. We examined size‐frequency relationships in the distress calls and songs of a Neotropical bird community in northwestern Costa Rica. In 2008 and 2009, we recorded distress calls and determined the body mass of 54 mist‐netted birds representing 38 species, 35 genera, and 14 families. We obtained songs for these same species from sound libraries and commercially available compact discs. For each vocalization, we measured minimum frequency and frequency of maximum amplitude. Larger birds produced lower‐frequency distress calls and songs than smaller birds. Phylogenetically controlled analyses revealed that the frequency of maximum amplitude was negatively correlated with body mass for both distress calls and songs. Minimum frequency was negatively correlated with mass for distress calls, but not songs. Our analyses suggest that the influence of phylogeny on the relationship between frequency characteristics and body size is modest. Pair‐wise comparisons across 37 species revealed that distress calls and songs had similar minimum frequencies, but songs had significantly lower frequencies of maximum amplitude than distress calls. This difference may arise from differences in signal function. Lower‐frequency sounds should transmit farther through forest habitats and songs must often transmit longer distances to reach their intended audience than distress calls. Our results support the general theory that body size is negatively correlated with the frequency of acoustic signals by demonstrating that this pattern holds true for both distress calls and songs in a Neotropical bird community.     

Geographic variation in body size: the effects of ambient temperature and precipitation

Latitudinal trends in body size have been explained as a response to temperature- or water-related factors, which are predictors of primary production. We used the first principal component calculated from three body parameters (weight, body length and the greatest length of the skull) of a sample of mammals from Israel and Sinai to determine those species that vary in size geographically, and whether such variation is related to annual rainfall, average minimum January temperature and average maximum August temperature. We used a conservative approach to discern the effects of precipitation and temperature by applying sequential regression. Variable priorities were assigned according to their bivariate correlation with body size, except for rainfall and its interactions that entered into the model last. Eleven species (Acomys cahirinus, Apodemus mystacinus, Canis lupus, Crocidura suaveolens, Gerbillus dasyurus, Hyaena hyaena, Lepus capensis, Meles meles, Meriones tristrami, Rousettus aegyptius and Vulpes vulpes) of the 17 species examined varied in size geographically. In five of them, rainfall was positively related to body size, while in one species it was negatively related to it. Contrary to the prediction of Bergmann’s rule, mean minimum January temperature was positively related to body size in five species and negatively related to body size in two species (C. suaveolens and G. dasyurus). As predicted by Bergmann’s rule, maximum June temperature was negatively related to body size in three species, and positively so in one (L. capensis). Primary production, particularly in desert and semi-desert areas, is determined mainly by precipitation. The above results indicate that, in our sample, primary production has an important effect on body size of several species of mammals. This is evident from the considerable proportion of the variability in body size explained by rain. However, low ambient temperatures may slow down and even inhibit photosynthesis. Hence, the observed positive relationships between average minimum January temperature and body size in four of the six species influenced by rain further support this conclusion.     

The relationship between geographic range size and life history traits: is biogeographic history uncovered? A test using the Iberian butterflies

The geographic range of a species is influenced by past phylogenetic and biogeographic patterns. However, other historical interactions, including the interplay between life history and geography, are also likely involved. Therefore, the range size of a species can be explained on the basis of niche‐breadth or dispersal related hypotheses, and previous work on European butterflies suggests that both, under the respective guise of ecological specialisation and colonising ability may apply. In the present study, data from 205 species of butterflies from the Iberian peninsula were processed through multiple regression analyses to test for correlations between geographic range size, life history traits and geographic features of the species distribution types. In addition, the percentage of variance explained by the subsets of variables analyzed in the study, with and without control for phylogenetic effects was tested. Despite a complex pattern of bivariate correlations, we found that larval polyphagy was the single best correlate of range size, followed by dispersal. Models that combined both life history traits and geographic characteristics performed better than models generated independently. The combined variables explained at least 39% of the variance. Bivariate correlations between range size and body size, migratory habits or egg size primarily reflected taxonomic patterning and reciprocal correlations with larval diet breadth and adult phenology. Therefore, aspects of niche breadth i.e. potential larval diet breadth emerged as the most influential determinants of range size. However, the relationships between these types of ecological traits and biogeographic history must still be considered when associations between life history and range size are of interest.     

Macroecological explanations for differences in species richness gradients: a canonical analysis of South American birds

Aim To evaluate how spatial variation of species richness in different bird orders responds to environmental gradients and determine which order level trait best predicts these relationships. Location South America. Methods A canonical correlation analysis was performed between the species richness in each of 17 bird orders and eight environmental variables in 374, 220 × 220 km cells. Loadings associated with the first two canonical variables were regressed against six order‐level predictors, including diversification level (number of species in each order), body size, median geographical range size and characteristics included in the model to control Type I error rates (the phylogenetic relationship among orders and levels of local‐scale spatial autocorrelation). Results Richness patterns of 14 bird orders were highly correlated with the first canonical axis, indicating that most orders respond similarly to energy‐water gradients (primarily actual evapotranspiration, minimum temperature and potential evapotranspiration). In contrast, species richness within Trochiliformes, Apodiformes and Galliformes were also correlated with the second canonical variable, representing measures of mesoscale climatic variation (range in elevation within cells, minimum temperature, and the interaction term between them) and landcover (habitat diversity). We also found that total diversification within orders was the best predictor of the loadings associated with the first canonical axis, whereas body size of each order best predicted loadings on the second axis. Conclusion Our results broadly support climatic‐related hypotheses as explanations for spatial variation in species richness of different orders. However, both historical (order‐specific variation in speciation rates) and ecological (dispersal of species that evolved by independent processes into areas amenable to birds) processes can explain the relationship between order level traits, such as body size and diversification level, and magnitude of response to current environment, furnishing then guidelines for a further and deeper understanding of broad‐scale diversity gradients.     

Climate history,human impacts and global body size of Carnivora (Mammalia: Eutheria) at multiple evolutionary scales

Aim One of the longest recognized patterns in macroecology, Bergmann’s rule, describes the tendency for homeothermic animals to have larger body sizes in cooler climates than their phylogenetic relatives in warmer climates. Here we provide an integrative process‐based explanation for Bergmann’s rule at the global scale for the mammal order Carnivora. Location Global. Methods Our database comprises the body sizes of 209 species of extant terrestrial Carnivora, which were analysed using phylogenetic autocorrelation and phylogenetic eigenvector regression. The interspecific variation in body size was partitioned into phylogenetic (P) and specific (S) components, and mean P‐ and S‐components across species were correlated with environmental variables and human occupation both globally and for regions glaciated or not during the last Ice Age. Results Three‐quarters of the variation in body size can be explained by phylogenetic relationships among species, and the geographical pattern of mean values of the P‐component is the opposite of the pattern predicted by Bergmann’s rule. Partial regression revealed that at least 43% of global variation in the mean phylogenetic component is explained by current environmental factors. In contrast, the mean S‐component of body size shows large positive deviations from ancestors across the Holarctic, and negative deviations in southern South America, the Sahara Desert, and tropical Asia. There is a moderately strong relationship between the human footprint and body size in glaciated regions, explaining 19% of the variance of the mean P‐component. The relationship with the human footprint and the P‐component is much weaker in the rest of the world, and there is no relationship between human footprint and S‐component in any region. Main conclusions Bergmannian clines are stronger at higher latitudes in the Northern Hemisphere because of the continuous alternation of glacial–interglacial cycles throughout the late Pliocene and Pleistocene, which generated increased species turnover, differential colonization and more intense adaptive processes soon after glaciated areas became exposed. Our analyses provide a unified explanation for an adaptive Bergmann’s rule within species and for an interspecific trend towards larger body sizes in assemblages resulting from historical changes in climate and contemporary human impacts.     

Biodiversity and body size are linked across metazoans

Body size variation across the Metazoa is immense, encompassing 17 orders of magnitude in biovolume. Factors driving this extreme diversification in size and the consequences of size variation for biological processes remain poorly resolved. Species diversity is invoked as both a predictor and a result of size variation, and theory predicts a strong correlation between the two. However, evidence has been presented both supporting and contradicting such a relationship. Here, we use a new comprehensive dataset for maximum and minimum body sizes across all metazoan phyla to show that species diversity is strongly correlated with minimum size, maximum size and consequently intra-phylum variation. Similar patterns are also observed within birds and mammals. The observations point to several fundamental linkages between species diversification and body size variation through the evolution of animal life.     

Ecological, morphological and phylogenetic correlates of interspecific variation in plasma carotenoid concentration in birds

Carotenoids are important as pigments for bright coloration of animals, and as physiologically active compounds with a wide array of health-related benefits. However, the causes of variation in carotenoid acquisition and physiology among species are poorly known. We measured the concentration of carotenoids in the blood of 80 wild bird species differing in diet, body size and the extent of carotenoid-based traits. Preliminary analyses showed that diet significantly explains interspecific variability in plasma carotenoids. However, dietary influences were apparently overridden by phylogenetic relationships among species, which explained most (65%) of this variability. This phylogenetic effect could be due partly to its covariation with diet, but may also be caused by interspecific differences in carotenoid absorption from food to the blood stream, mediated, for example by endothelial carriers or gut parasites. Carotenoid concentrations also decreased with body size (which may be explained by the allometric relationship between ingestion rate and body mass), and correlated positively with the extent of carotenoid-dependent coloration of plumage and bare parts. Therefore, the acquisition of carotenoids from the diet and their use for both health and display functions seem to be constrained by ecological and physiological aspects linked to the phylogeny and size of the species.     

A comparative test of adaptive hypotheses for sexual size dimorphism in lizards

It is commonly argued that sexual size dimorphism (SSD) in lizards has evolved in response to two primary, nonexclusive processes: (1) sexual selection for large male size, which confers an advantage in intrasexual mate competition (intrasexual selection hypothesis), and (2) natural selection for large female size, which confers a fecundity advantage (fecundity advantage hypothesis). However, outside of several well-studied lizard genera, the empirical support for these hypotheses has not been examined with appropriate phylogenetic control. We conducted a comparative phylogenetic analysis to test these hypotheses using literature data from 497 lizard populations representing 302 species and 18 families. As predicted by the intrasexual selection hypothesis, male aggression and territoriality are correlated with SSD, but evolutionary shifts in these categorical variables each explain less than 2% of the inferred evolutionary change in SSD. We found stronger correlations between SSD and continuous estimates of intrasexual selection such as male to female home range ratio and female home range size. These results are consistent with the criticism that categorical variables may obscure much of the actual variation in intrasexual selection intensity needed to explain patterns in SSD. In accordance with the fecundity advantage hypothesis, SSD is correlated with clutch size, reproductive frequency, and reproductive mode (but not fecundity slope, reduced major axis estimator of fecundity slope, length of reproductive season, or latitude). However, evolutionary shifts in clutch size explain less than 8% of the associated change in SSD, which also varies significantly in the absence of evolutionary shifts in reproductive frequency and mode. A multiple regression model retained territoriality and clutch size as significant predictors of SSD, but only 16% of the variation in SSD is explained using these variables. Intrasexual selection for large male size and fecundity selection for large female size have undoubtedly helped to shape patterns of SSD across lizards, but the comparative data at present provide only weak support for these hypotheses as general explanations for SSD in this group. Future work would benefit from the consideration of alternatives to these traditional evolutionary hypotheses, and the elucidation of proximate mechanisms influencing growth and SSD within populations.     

鲸类c - mos 基因的序列变异性及在系统发生分析中应用的初步研究

通过猪等的c-mos 基因保守区序列设计了用于扩增鲸类c-mos 基因的引物。应用此引物扩增并测定了齿鲸类5 个科12 个种546 bp 的c - mos 基因编码区序列。结果表明鲸类的c-mos 基因遗传变异水平较低。在系统发生重建中, 同科的物种聚为单系, 但不能很好地解决科下亚科间的关系, 提示c-mos 基因仅适于鲸类科级以上阶元的系统发生研究。     

Beyond latitude: Temperature,productivity and thermal niche conservatism drive global body size variation in Odonata

Aim

So far, latitudinal body size clines have been discussed primarily in the context of thermoregulation, sensu Bergmann. However, body size patterns are ambiguous in ectotherms, and this heterogeneity remains poorly understood. We tested whether Bergmann's rule and the resource availability rule, which states that energetic requirements determine species body size, apply to damselflies and dragonflies (Odonata). Furthermore, we hypothesized that the contrasting effects of thermoregulation and resource availability (e.g., productivity) can obscure the overall gradient in body size variation.

Location

Global.

Time period

Contemporary.

Major taxa studied

Odonata.

Methods

Using data for 43% of all odonate species described so far, we tested our hypotheses in phylogenetically and spatially comparative analyses at assemblage and species levels. For the distribution data, we integrated expert range maps and ecoregional ranges based on all available occurrence records. To distinguish between long-term and evolutionarily recent responses of environmental drivers in body size, we constructed a phylogenetically informed classification of all odonate species and decomposed the body size into its phylogenetic and specific components for our subset of species.

Results

We documented a weak positive relationship between body length and latitude but found strong and contrasting effects for temperature between dragonflies and damselflies and consistent positive effects for productivity that explained 35–57% of body size variation. Moreover, we showed a strong phylogenetic signal in sized-based thermoregulation that shaped the distribution of dragonflies, but not of damselflies.

Main conclusions

We concluded that temperature, productivity and conservatism in size-based thermoregulation synergistically determine the distribution of ectotherms, while the taxon-specific importance of these factors can lead to contrasting and weak latitude–size relationships. Our results reinforce the importance of body size as a determinant of species distributions and responses to climate change.     

Phylogenetic comparative methods and the geographic range size – body size relationship in new world terrestrial carnivora

Most recent papers avoid describing macroecological relationships and interpreting then without a previous control of non-independence in data caused by phylogenetic patterns in data. In this paper, we analyzed the geographic range size – body size relationship for 70 species of New World terrestrial Carnivora (fissipeds) using various phylogenetic comparative methods and simulation procedures to assess their statistical performance. Autocorrelation analyses suggested a strong phylogenetic pattern for body size, but not for geographic range size. The correlation between the two traits was estimated using standard Pearson correlation across species (TIPS) and four different comparative methods: Felsenstein's independent contrasts (PIC), autoregressive method (ARM), phylogenetic eigenvector regression (PVR) and phylogenetic generalized least-squares (PGLS). The correlation between the two variables was significant for all methods, except PIC, in such a way that ecological mechanisms (i.e., minimum viable population or environmental heterogeneity- physiological homeostasis), could be valid explanations for the relationship. Simulations using different O-U processes for each trait were run in order to estimate true Type I errors of each method. Type I errors at 5% were similar for all phylogenetic methods (always lower than 8%), but equal to 13.1% for TIPS. PIC usually performs better than all other methods under Brownian motion evolution, but not in this case using a more complex combination of evolutionary models. So, recent claims that using independent contrasts in ecological research can be too conservative are correct but, on the other hand, using simple across-species correlation is too liberal even under the more complex evolutionary models exhibited by the traits analyzed here.     

Geographic body size gradients in tropical regions: water deficit and anuran body size in the Brazilian Cerrado

A recent interspecific study found Bergmann's size clines for Holarctic anurans and proposed an explanation based on heat balance to account for the pattern. However, this analysis was limited to cold temperate regions, and exploring the patterns in warmer tropical climates may reveal other factors that also influence anuran body size variation. We address this using a Cerrado anuran database. We examine the relationship between mean body size in a grid of 1° cells and environmental predictors and test the relative support for four hypotheses using an AIC-based model selection approach. Also, we considered three different amphibian phylogenies to partition the phylogenetic and specific components of the interspecific variation in body size using a method analogous to phylogenetic eigen vector regression (PVR). To consider the potential effects of spatial autocorrelation we use eigenvector-based spatial filters. We found the largest species inhabiting high water deficit areas in the northeast and the smallest in the wet southwest. Our results are consistent with the water availability hypothesis which, coupled with previous findings, suggests that the major determinant of interspecific body size variation in anurans switches from energy to water towards the equator. We propose that anuran body size gradients reflect effects of reduced surface to volume ratios in larger species to control both heat and water balance.     

What Makes Vocalisation Frequency an Unreliable Signal of Body Size in Birds? A Study on Black Swans

In many animal species, the frequency (pitch) of vocalisations correlates negatively with body size and may thus signal competitive ability. However, this relationship is absent in other species. Understanding why this difference exists across species may help to explain some of the diversity of vocal communication systems. We assessed whether vocalisation frequency signals body size in black swans (Cygnus atratus), and how this is affected by (i) variation in frequency within individuals and (ii) size variation across individuals. Frequency was correlated with body size and mass, with slopes close to the allometry expected if the birds were maximising sound radiation, but the explained variation in frequency was low. Within‐individual variation in vocalisation frequency was greater in male than female swans, and the reliability of frequency as a signal of size in males was correspondingly lower. A review of the literature on the relationship between the frequency of avian vocalisations and body size also showed smaller effect sizes for more variable vocalisations (birdsongs), than for simpler vocalisations. Vocalisation frequency was more reliably correlated with body size when the sexes were pooled (creating a larger range of variation in size) than when the relationship was examined for either sex separately, although male and female data followed the same allometric line. These results show that variation in frequency within individuals and low variation in size across individuals reduce the reliability of vocalisation frequency as a signal of body size, which helps to understand differences among species in the signal value of vocalisation frequency.     

Localization of a sum of acoustic signals in air by the northern fur seal]

The localization of a sum of acoustic signals by two northern fur seals in air depending on sound parameters was investigated using the method of instrumental conditioned reflexes with food reinforcement. It was found that sound perception of northern fur seal proceeds by the binaural mechanism. The time/intensity interchange coefficient was 570 microseconds/dB for series of clicks (with amplitude maximum at 1 kHz) and 250 microseconds/dB for tonal impulses with a frequency of 1 kHz. With click amplitudes being equal, the number of approaches of the animal to the source of the first signal reached a 75% level at a delay of the second signal 0.07 ms (the minimum delay); with a delay of 6 ms (the maximum delay) and more, the fur seal, probably hears two separate signals. The minimum delay depended little on the duration of tonal impulses (with a frequency of 1 kHz) and was 0.3-0.7 ms; the maximum delay was 9-11 ms for tonal impulses with a duration of 3 ms and 37-40 ms with impulse duration 20 ms. The precedence effect became apparent at a greater delay for smooth fronts of impulses than for rectangular fronts.