Le comportement social des urodèles

in Cahiers d'Ethologie (1999), 19

It could be misleading to consider that the social behaviour of newts and salamanders is simple and can be generalized. Indeed, individuals are faced with external and internal conditions which are ... [more ▼]

It could be misleading to consider that the social behaviour of newts and salamanders is simple and can be generalized. Indeed, individuals are faced with external and internal conditions which are extremely variable. In response to these factors, they may respond in a particular way. The behavioural variations, called alternative tactics, allow individuals to improve their fitness, i.e. to ensure the survival of their genes. They can be exhibited in reaction to a large range of factors such as the mere presence or density of competitors, the operational sex-ratio, the behaviour and kinship of the other individuals, the abiotic characteristics of the environment, the experience of the individuals involved. These alternative tactics are favoured in urodeles. Indeed, although the main process of fertilization is internal, they breed by means of a spermatophore deposited in the external environment. Each species of newts and salamanders exhibits specific behavioural patterns as they developed and evolved in particular environments which have exerted selective pressures on the individuals and in this way on the species. As a consequence, the understanding of patterns of behaviour requires that we know the environment in which they appeared. The main occurrence of parental care and territoriality in terrestrial environments may be explained by the features of these habitats in which eggs could not survive without protection, and in which adults may defend areas of particular interest and communicate by means of pheromones. All of these characteristics show that we have to study the behaviour of individuals of different species under several conditions. Without such an analysis, it would be difficult to understand biodiversity. [less ▲]

The modulation of movement as a behavioral adaptation to extreme environments in the newt Triturus alpestris cyreni

in Journal of Herpetology (1998), 32

Pédomorphose facultative chez Triturus alpestris : comparaison des structures d'âge des tritons métamorphes et pédomorphes

Conference (1998)

La pédomorphose est définie comme la rétention de caractères subadultes ancestraux chez le descendant adulte. Ce processus hétérochronique est relativement répandu au sein des urodèles. Ainsi, les adultes ... [more ▼]

La pédomorphose est définie comme la rétention de caractères subadultes ancestraux chez le descendant adulte. Ce processus hétérochronique est relativement répandu au sein des urodèles. Ainsi, les adultes reproducteurs, dénommés "pédomorphes", conservent les fentes branchiales larvaires. Chez le Triton alpestre, sujet de notre étude, la pédomorphose est facultative en ce sens que les deux traits d'histoire de vie - la métamorphose et la pédomorphose - existent. Certaines populations ne présentent que des individus métamorphes, tandis que d'autres présentent un mélange des deux formes. La pédomorphose était souvent associée à des milieux stables et froids d'altitude. Mais différentes populations ont aussi été découvertes dans des milieux instables de basse altitude. La présence d'animaux pédomorphes dans ce type de milieu ne paraissait dès lors pas adaptative. L'objectif de cette étude a été d'étudier les structures d'âge de deux populations où cohabitent tritons pédomorphes et métamorphes : une population peuplant un lac profond (le lac de la Cabane) situé à 1950 mètres d'altitude dans les Alpes-de-Haute-Provence (France) et une autre habitant une petite mare située à une altitude de 600 mètres à Parana, en Toscane (Italie). L'âge des animaux a été déterminé par squelettochronologie sur phalange et humérus. Au total, nous avons pu déterminer l'âge de 116 adultes de la population française et 128 de la population italienne. Nos résultats montrent une différence de trait d'histoire de vie nette entre les populations de haute et de basse altitude. Ainsi, au lac de la Cabane les structures d'âge des animaux métamorphes et pédomorphes sont identiques, tant en ce qui concerne les mâles que les femelles. La taille des animaux est elle aussi identique. Par contre, à Parana, les pédomorphes atteignent leur maturité sexuelle très jeunes : à un an chez les mâles et à un ou deux ans chez les femelles. Les métamorphes ne deviennent, par contre, matures que plus tardivement : les mâles, à 2-3 ans, et les femelles à 4-5 ans. La pédomorphose ne dure que peu de temps car les pédomorphes peuvent se métamorphoser. Les pédomorphes de cette population sont plus petits que les métamorphes. Chez le Triton alpestre, des cas de populations pédomorphiques ne sont constatés que dans les péninsules italiennes et balkaniques, laissant ainsi supposer une base génétique. Ayant montré que le succès des pédomorphes et leur trait d'histoire de vie, en l'occurrence leur structure d'âge, diffèrent entre les populations, nous pouvons considérer la pédomorphose comme une stratégie alternative influencée par différents facteurs environnementaux. Seules les populations ayant un potentiel génétique pour la pédomorphose peuvent répondre aux pressions de l'environnement, lesquelles, selon leurs caractéristiques, peuvent mener à des patrons de pédomorphose de différents types. En cas de catastrophe ou de colonisation de nouveaux milieux, la pédomorphose par progenèse permet une augmentation rapide de la population. Par contre dans des systèmes d'altitude, où une maturité précoce est peut-être impossible, l'avantage d'une stratégie pédomorphe peut être recherché, par exemple, au niveau des niches alimentaires ou spatiales, ce qui constitue un autre volet de notre étude. [less ▲]

Influence of the temperature on the tail-beat frequency of the fanning movement in the Alpine newt, Triturus alpestris cyreni

Poster (1998)

Un cas de néoténie dans un bâtiment désaffecté, chez le Triton alpestre, Triturus alpestris apuanus (Salamandridae)

in Alytes (1997), 15

A population of Triturus alpestris apuanus of the Apuane Alps (Tuscany , Italy) was studied during July 1994. The particularity of this population is that it breeds in an artificial site, in the dark and ... [more ▼]

A population of Triturus alpestris apuanus of the Apuane Alps (Tuscany , Italy) was studied during July 1994. The particularity of this population is that it breeds in an artificial site, in the dark and under cover, in a deserted building. Moreover some neotenic newts were discovered. The recent colonization and the instability of this biotope indicate a form of labile neoteny, appearing and disappearing spontaneously. [less ▲]

Etude comparée du comportement de cour de Triturus alpestris alpestris (Laurenti, 1768) et Triturus alpestris cyreni (Wolterstorff, 1932) : approche évolutive.

Book published by Cahiers d'Ethologie (1996)

The species concept in the animal world is very abstract. With diverse methods scientists try to place boundaries between species. But this is generally theoretical. Indeed species are in continuous ... [more ▼]

The species concept in the animal world is very abstract. With diverse methods scientists try to place boundaries between species. But this is generally theoretical. Indeed species are in continuous evolution, located more regularly between two evolutionary categories than inside a well-defined one. In this study we are interested by the courtship of two allopatric subspecies of the Alpine newt, Triturus alpestris alpestris and T. a. cyreni. We investigate the behaviour of two closely related taxa, in experimental conditions, to display the basis of behaviour evolution and isolating mechanisms prominently. We have identified 24 behaviours in the male display and principally 3 in the female (negative, static, positive). Sexual encounter will be divided in four stages: orientation during which animals are meeting, fan and lean-in exhibition phases during which the male displays and the spermatophore transfer sequence where the male deposits a spermatophore and displays also. The qualitative differences between subspecies are weak and concern principally amplitude of movements. From a qualitative level some differences were underlined. So T. a. alpestris touches the female with its snout frequently, whereas T. a. cyreni whips more often. The two subspecies do not use the same tactic with a non-responsive female. Indeed the T. a. alpestris male can easily enter in spermatophore transfer phase without the positive response of female. In order to attract the latter, he executes worm-like movements: in this way he lures a negative female. On the contrary, T. a. cyreni rarely deposits a spermatophore when the female is not receptive. It therefore makes very little use of the lure system. The analysis of male behaviours in relation with female response have allowed us to establish a model which assumes that some behaviours are exhibited by the male only when its motivation and that of the female go beyond a particular level. Some stereotyped behaviours (e.g. distal fan) concern movements whose amplitude is variable. We think that this movement modulation could be the foundation of a behaviour evolution and isolating mechanism. The female is indeed sensitive to these variations: in this way communication is possible between transmitter and receiver. The new variants problem is thus resolved. The fanning frequencies vary with temperature. They are weak at low temperatures. We consider this modulation as an adaptation to extreme and unpredictable habitats, e.g. in high altitude lakes and temporary ponds. The observed behavioural differences are in a lower level than between separate species, like T. helveticus and T. vulgaris. Moreover sperm transfer is likely between the two taxa. In conclusion the present data confirm the existence of two distinct subspecies T. a. alpestris and T. a. cyreni as detected by previous authors using allozyme and osteological analysis. [less ▲]

The courtship behaviour of two subspecies of the Alpine newt, Triturus a. alpestris and T. a. cyreni (Amphibia, Caudata): an evolutionary perspective

Poster (1996)