Thierry Lodé

Multiple paternity in Rana dalmatina, a monogamous territorial breeding anuran

Polyandry and sperm competition in anurans have rarely been documented. We investigated the genetic paternity inferred from allozyme variations in 650 tadpoles from four natural ponds in a territorial breeding anuran, Rana dalmatina. Multiple paternity was demonstrated, although R. dalmatina is regarded as a monogamous species. Polyandrous mating was not a common event, occurring only in 17.9% of clutches, with no significant differences among clutches. The proportions of tadpoles fathered by a second male did not significantly differ among ponds, showing that multipaternity was not restricted to a single site. Such a polyandry may result from synchronous multiple amplexus and should reduce the heterozygote deficit related to the breeding-pond fidelity usually exhibited by most anurans.

What type of amphibian tunnel could reduce road kills

Abstract Increased traffic volumes worldwide are con-tributing to amphibian declines, and measures to reducethe occurrence of road kills are needed. One possiblemeasure is the construction of underpasses throughwhich animals can pass under roads, but little is knownabout whether amphibians will choose tunnels if givena choice or about their preferences for different tunneltypes. We tested the preferences of three anuran speciesfor two kinds of concrete amphibian tunnels currentlyused in France. One was a tunnel lined with soil, theother a bare concrete pipe. The animals could use thetunnels or bypass them over a grassy area. Water frogs Rana esculenta and common toads Bufo bufo showed apreference for the tunnels, whereas agile frogs Ranadalmatina avoided them. Among the individuals thatchose either of the tunnels, all species showed a signifi-cant preference for the tunnel lined with soil. Theseresults indicate that species differ in their preferencesand in their likelihood of using underpasses when givena choice. This highlights the fact that there is no uniquesolution to the problem, and underpasses are only oneof the possible mitigation measures that need to beassessed.Keywords Amphibian tunnels,

Sex-biased predation by polecats influences the mating system of frogs

In agile frogs, Rana dalmatina, an increase in male–biased operational sex ratio and in male abundance results in the emergence of alternative male mating behaviour in the form of searching. As a consequence, females are coerced into mating with multiple males, which in turn increases the level of conflict between the sexes. Selective predation on males by the European polecat, Mustela putorius, decreases the occurrence of polyandry. In ponds visited by polecats, the sex ratio is less male biased than in ponds where polecats are absent. As a result most males call to attract females and fewer males actively search for females. Females are able to choose between calling males and mate with a single male. Thus, predation by polecats is found to influence sex ratio, male abundance and sexual conflict in a frog mating system, restricting the opportunity for multiple mating.

Frog alien species: a way for genetic invasion?

European water frogs are characterized by anthropic introductions and Rana ridibunda may be considered as an invasive species. As such translocations may result in introgression of exotic genes in native populations, i.e. genetic pollution, we studied genetic characteristics (on 11 allozymic loci) of natural versus introduced water frogs. Our study contributed to (1) disclose 3 genetic markers allowing the identification of exotic frogs; (2) quantify the proportion of exotic frogs found in natural populations; and (3) suggest how genetic pollution may arise in these frogs.

Variations in male calls and responses to an unfamiliar advertisement call in a territorial breeding anuran, Rana dalmatina: evidence for a “dear enemy” effect

Focusing on the male advertisement call in Rana dalmatina, this study addresses two issues: (i) there is a large variability in call characteristics among males (fundamental frequency range: 571–865 Hz, number of pulses: 8–87) and (ii) males are able to discriminate between neighbouring and unfamiliar conspecifics. In response to an unfamiliar acoustic stimulus, call advertisement presented the longest duration. In contrast, the response to a familiar conspecific call did not show any significant difference from solitary vocalisations. Emphasising the existence of a discrimination, this result may be regarded as a “dear enemy effect”. This decremental reply may result from habituation to a neighbours call, constituting a learning process. Thus, we suggest call familiarity may enhance conspecific tolerance, reducing the expensive energetic cost of defence interactions for this territorial breeding species.

Polecat predation on frogs and toads at breeding sites in western France

Surveys of eight radiotracked polecats (Mustela putorius) showed that they caught mainly male terrestrial anurans at spawning sites. Agile frogs Rana dalmatina formed 77.5%, whereas common toads Bufo bufo represented only 14.6% of preyed anurans. Throughout the breeding period, male anurans were found to be predominant, representing 64.8% of available agile frog and 60.7% of common toad populations in the four ponds studied. The number of male frogs was significantly higher in two ponds which were not exploited by polecats in 1990. Polecats preyed selectively on anuran males (electivity index D = 0.34 in agile frogs and D = 0.50 in toads). Thus, the intensive predation of polecats at spawning sites can influence the sex-ratio of anuran populations.

Time budget as related to feeding tactics of European polecat Mustela putorius

The time budget of five male and four female European polecats was studied in western France through radiotracking surveys. Their activity level averaged 7 h and 31 min without any significant differences between males and females. However two phases, foraging and travelling, were not similarly distributed in both sexes. Despite a strong sexual dimorphism, females spent more time foraging than males. Travelling, i.e. time devoted to linear movements was more important in males than females. Variations in activity phase duration were correlated with the proportions of food categories, suggesting that the dispersion of available resources directly influenced polecat activity. The exploitation of prey showing an aggregative distribution such as anurans led to a decrease in general activity whereas the consumption of rodents, which were more regularly distributed, was correlated to the foraging activity. Mating and breeding also affected the activity duration. Thus it seems that the time budget of polecats resulted from a compromise between social organization and trophic constraints.

Social partner discrimination based on sounds and scents in Asian small-clawed otters (Aonyx cinereus)

Ability to discriminate familiar conspecifics is an essential competence in any group-living species, ensuring socio-spatial cohesion, but in many animals, such as mustelids, the relative importance of the different communicative modalities for discrimination is poorly understood. In otters, there is evidence of intra-specific variation in physical appearance and in feces chemical profile, but the potential for acoustic identity coding as well as for identity decoding in visual, acoustic and olfactive domains remains unexplored. We investigated the acoustic structure of contact calls in five captive groups of small-clawed otters and found that it is possible to reliably assign one particular call to a given adult male caller. Females discriminated between familiar and unfamiliar adult males based on their sound (playback) and smell (feces) but not based on their picture, suggesting abilities to memorize and use acoustic and olfactive signatures in their daily social life.

Implications of an individualistic lifestyle for species conservation: lessons from jealous beasts

Polecat populations show a very low genetic diversity and a high inbreeding coefficient. Furthermore, the estimate of effective population size is alarmingly low. Polecats Mustela putorius populations are structured into scattered breeding sub-units usually made up of one male and two females, according to a polygynous mating system. Because a strict spatio-temporal segregation was observed between males and females, we propose to call individualistic such species. We suggest that the solitary habits of individualistic species may result in or worsen a high inbreeding and exacerbate their conservation issue, a crucial perspective for critically endangered species such as the European mink.

Variations in call and morphology in male water frogs: taxonomic and evolutionary implications

In Anurans, the specific mate recognition system (SMRS), which contributes to prezygotic isolation, is mainly based on morphological and call features. This is why such criteria are used by zoologists for taxonomic identification. In hybridogenetic water frogs (Rana ridibunda, R. lessonae, R. perezi, R. kl. grafi and R. kl. esculenta), hybridization opens up the question of the efficiency of these criteria for taxon identification and of the specific recognition system in this context. Variation in both morphological and call features revealed both significant mean differences among taxa but also large overlapping among individuals belonging to different taxa. Thus, using call or morphometrical features in order to identify water frogs may be hazardous. Moreover, species differ poorly in their specific mate recognition system, facilitating hybridization events, and therefore suggesting that postzygotic mechanisms may be prevalent over prezygotic mechanisms.