Since it is clear that studies involving species of Hylodes are critical to better understanding frog communication, we investigate how the Brazilian torrent frog Hylodes japi communicates intraspecifically. Hylodes japi was recently described as endemic to the montane Atlantic forest of Serra do Japi, in southeastern Brazil [26]. This small frog is mainly diurnal, however it may also exhibit crepuscular and nocturnal reproductive activity [26, 27]. The species is rheophilic, has territorial males and an elaborate courtship behavior, as do other members of the family Hylodidae. The reproductive biology of H. japi is associated with fast-flowing montane streams where males construct underwater chambers for egg deposition; the tadpoles are exotrophic [26]. Our goals were to: (1) characterize visual displays and acoustic signals performed by males and females of H. japi, and to identify their respective roles and associated behavioral contexts; (2) investigate communication during their elaborate courtship ritual, including analyzing potential multimodal compositions and their roles; and (3) characterize the ways by which a sender male controls signal emission according to the position of the receiver male. We discuss the behavioral diversity in the family Hylodidae in light of current knowledge on visual signaling in Neotropical torrent frogs.
Among hylodids, the currently known repertoire of visual displays is most complex in H. japi (Table 3). In fact, Hylodes japi has one of the most diverse repertoires of visual displays known within the order Anura. The five new visual displays that we described and categorized here correspond to 20.8% of the visual displays recognized for members of the family Hylodidae and around 13.5% for anurans. We trust that our results on visual communication are not an exception among hylodids (and anurans in general), but a consequence of the time invested to understand the behaviors. Among hylodids, the most studied species have more diverse repertoires, such as C. schmidti, H. phyllodes, and H. japi ([21, 34, 37]; present study; see Table 3). For Hylodes species, some behaviors, such as arm lifting and arm waving, are only distinguishable via video analysis. Moreover, other visual displays are performed only during specific situations, making them difficult to observe (because they are rarely executed). Head snaking, for example, was recorded only twice among all studies on hylodids; during courtship, once in H. phyllodes [34] and in the present study. The accepted male is the only individual that performs head snaking and only during courtship. From the set of information presented here, it is plausible to expect that the complexity observed in the visual communication of H. japi is similarly widespread within the family Hylodidae, or at least among Hylodes species. Complexity of the visual communication system may be a pattern for the Brazilian torrent frogs (Hylodes species), and most likely as a phylogenetic trait of the genus. Neotropical torrent frogs (i.e. hylodids) still deserve attention, since new studies on their communication have potential to help clarify behavioral patterns and multimodal compositions, and even uncover other new behaviors. Behavioral patterns tend to be similar within families and within genera [2].
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The Grimsel Pass is a low one, only a little over 7,000 feet, but for this reason, and because it lies directly between extensive areas of perpetual snow, which give rise to some of the finest glaciers in Switzerland, it has been extensively ice-ground and presents a scene of savage grandeur which is often absent from higher passes. Everywhere the rocks are ground into huge domes or smooth slopes or rounded hollows, and these ice-ground contours extend to at least a thousand feet higher, above which level the mountains rise in sharp peaks or serrated ridges. The descent towards the Grimsel Hospice is very grand, owing to the enormous surfaces of smooth ice-ground rocks of the hardest gneiss, which plunge down at a very high angle for nearly a thousand feet into the curious little enclosed valley, with its two small rock-basin lakes in which the hospice is situated. Here we see an example of the effects of a kind of eddy in the old ice streams to which I think sufficient attention has not been paid. The torrent from the Aar glacier comes in from the west, but before reaching the Hospice turns off abruptly through a narrow gorge into the main valley, running at first nearly north. But looked at from above, this gorge is invisible, and it seems as if the valley from the glacier continued through the two small lakes further to the east. It is evident that when this district was buried deep in ice very little of it could escape through the gorge, but must have flowed over the higher slopes, while the portion in the valley, fed by ice-streams from nearly opposite directions, would acquire a slow eddying motion which [[p. 176]] would greatly aid its grinding power, and thus account for the land-locked valley and the two small rock-basin lakes.
It is, however, after passing through the narrow gorge between the hamlets of Inner and Outer Urweid, with its picturesque waterfall which the coach road passes by tunnelling under it, that we approach the most remarkable feature of the district. The valley rapidly widens, with a perfectly flat bottom, till at Innertkirchen it becomes nearly a mile wide. Here, on the right, the united waters of the Gadmen and Genthal valleys form a junction with the Aar, issuing out of a narrow gorge between lofty rocks; but the most striking object is the barrier of the Kirchet which extends quite across the valley, rising abruptly to the height of 500 feet above it, and appearing entirely to dam the course of the foaming torrent which has now become a good sized river. Passing along the high road, which by three great zigzags mounts up the steep ascent, the entrance to the gorge is imperceptible; and it is not till having crossed the hill and descended on the other side into the wide alluvial plain of Meiringen that the stream is again [[p. 177]] seen as a considerable and rapidly flowing river. It has passed through the hill by the celebrated Aarschlucht, one of the most remarkable gorges in Europe, which is now rendered easily accessible by a wooden platform suspended a few feet above the surface of the water, and extending for about two-thirds of the total length of the gorge, or nearly half a mile.
On entering the gorge we are struck by its extreme narrowness, usually not more than six or eight feet, often not more than four, and in some places even less; its great depth, from 200 to 300 feet, and its remarkable uniformity of width not perceptibly increasing upwards. The sides are cut away in curves or hollows such as would be caused by tumultuous eddying waters; the walls frequently overhang and then recede again, so that it is only here and there that they are sufficiently vertical to enable us to catch a glimpse of the sky, and wherever we do so we see that the upper edges of the chasm are little, if any, farther apart than are the rock-walls between which we walk. The whole surface of the rock--a hard crystalline limestone--is evidently water-worn, never presenting surfaces due to fracture except perhaps where a lateral stream enters by a picturesque cascade falling over a vertical rock, and where the gorge opens out so that daylight and sunlight freely enter it. The artificial causeway finishes where a dry lateral gorge, with a steeply rising floor of earth and vegetable débris, affords an exit to the plateau and the road from Meiringen. This short lateral gorge is of especial interest, because it reproduces in almost every detail the features of the main gorge, being about the same average width, having similar walls of hollow curvilinear form, and being equally narrow to the very top. This lateral gorge is, however, quite dry, and even in the wettest seasons can hardly have more than a trickle of water because it has no catchment basin, opening out as it does on the top of the bossy limestone rocks of the narrow ridge of the Kirchet. Hence we reach the important conclusion that this gorge could not have been formed by water derived from ordinary streams, unless at a period so remote that the whole surface contours of the district were very different from what they are now. The only explanation that seems to accord with the facts is, that we have here the result of the action of sub-glacial torrents acting throughout the whole period during which the area was buried in ice. Thus only are we able to explain the fact of the almost uniform narrowness of the gorge from bottom to top, since during the process of its formation the rock-walls would be preserved from ordinary denuding agencies, and be kept at a nearly uniform temperature. Hence we have the actual surface as it was left by the glacial waters, and its extreme narrowness together with the luxuriant vegetation which covers the plateau and fringes the edges of the chasm, aided also by the comparatively mild climate of the lower valley, have [[p. 178]] preserved for us one of the most curious and instructive products of the great ice-age. This view of the origin of the gorge is adopted by Professor Bonney, who, in his paper read before the Royal Geographical Society in 1893, says, "This chasm has been sawn by the sub-glacial torrent, while the ice itself has moulded every rock on the barrier into billowy undulations." I may, therefore, take it for granted that this view is held by most geologists who have attended to the subject, and it appears to me to be the only reasonable one; yet it is so important, and leads to conclusions so entirely opposed to the views expressed by Professor Bonney in the same paper, that it seems advisable to ascertain whether any collateral evidence can be obtained in support of it. 2ff7e9595c
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