Hyla Arborea Research Articles

Integrating regional-scale connectivity in habitat restoration: An application for amphibian conservation in eastern France

Habitat restoration is one way of reducing landscape fragmentation, which is seen as a threat to biodiversity. It consists in renovating disused or degraded habitat patches or in creating new habitat patches in suitable areas. Currently, most restoration measures draw on the local knowledge of experts for selecting the best locations. For amphibian metapopulations like the European tree frog (Hyla arborea), the search for such locations must include regional-scale connectivity in order to maintain their viability.We set up a systematic and cumulative protocol for adding new habitat patches to a pond network. Graph modelling is used to include regional-scale connectivity as a criterion to be maximized. Successive locations are tested systematically and connectivity is compared before and after the virtual addition of each new pond. The location that increases connectivity most is identified.The results show that the priority areas identified by the model are similar to those suggested by local experts from a wildlife conservation association. The two approaches are complementary because they are applied on two different scales. The patch addition method can identify strategic areas for improving global connectivity by taking into account the regional scale. Experts’ knowledge can target the precise location within the identified area for creating new habitats based on local factors of the surrounding context. In addition, our method can be also used to prioritize locations already decided on by landscape managers. Consequently, this protocol appears to be a useful tool for guiding habitat restoration in the field.

Range-wide sex-chromosome sequence similarity supports occasional XY recombination in European tree frogs (Hyla arborea).

In contrast with mammals and birds, most poikilothermic vertebrates feature structurally undifferentiated sex chromosomes, which may result either from frequent turnovers, or from occasional events of XY recombination. The latter mechanism was recently suggested to be responsible for sex-chromosome homomorphy in European tree frogs (Hyla arborea). However, no single case of male recombination has been identified in large-scale laboratory crosses, and populations from NW Europe consistently display sex-specific allelic frequencies with male-diagnostic alleles, suggesting the absence of recombination in their recent history. To address this apparent paradox, we extended the phylogeographic scope of investigations, by analyzing the sequences of three sex-linked markers throughout the whole species distribution. Refugial populations (southern Balkans and Adriatic coast) show a mix of X and Y alleles in haplotypic networks, and no more within-individual pairwise nucleotide differences in males than in females, testifying to recurrent XY recombination. In contrast, populations of NW Europe, which originated from a recent postglacial expansion, show a clear pattern of XY differentiation; the X and Y gametologs of the sex-linked gene Med15 present different alleles, likely fixed by drift on the front wave of expansions, and kept differentiated since. Our results support the view that sex-chromosome homomorphy in H. arborea is maintained by occasional or historical events of recombination; whether the frequency of these events indeed differs between populations remains to be clarified.

Stronger transferability but lower variability in transcriptomic‐ than in anonymous microsatellites: evidence from Hylid frogs

A simple way to quickly optimize microsatellites in nonmodel organisms is to reuse loci available in closely related taxa; however, this approach can be limited by the stochastic and low cross-amplification success experienced in some groups (e.g. amphibians). An efficient alternative is to develop loci from transcriptome sequences. Transcriptomic microsatellites have been found to vary in their levels of cross-species amplification and variability, but this has to date never been tested in amphibians. Here, we compare the patterns of cross-amplification and levels of polymorphism of 18 published anonymous microsatellites isolated from genomic DNA vs. 17 loci derived from a transcriptome, across nine species of tree frogs (Hyla arborea and Hyla cinerea group). We established a clear negative relationship between divergence time and amplification success, which was much steeper for anonymous than transcriptomic markers, with half-lives (time at which 50% of the markers still amplify) of 1.1 and 37 My, respectively. Transcriptomic markers are significantly less polymorphic than anonymous loci, but remain variable across diverged taxa. We conclude that the exploitation of amphibian transcriptomes for developing microsatellites seems an optimal approach for multispecies surveys (e.g. analyses of hybrid zones, comparative linkage mapping), whereas anonymous microsatellites may be more informative for fine-scale analyses of intraspecific variation. Moreover, our results confirm the pattern that microsatellite cross-amplification is greatly variable among amphibians and should be assessed independently within target lineages. Finally, we provide a bank of microsatellites for Palaearctic tree frogs (so far only available for H. arborea), which will be useful for conservation and evolutionary studies in this radiation.

First-generation linkage map for the European tree frog (Hyla arborea) with utility in congeneric species.

BackgroundWestern Palearctic tree frogs (Hyla arborea group) represent a strong potential for evolutionary and conservation genetic research, so far underexploited due to limited molecular resources. New microsatellite markers have recently been developed for Hyla arborea, with high cross-species utility across the entire circum-Mediterranean radiation. Here we conduct sibship analyses to map available markers for use in future population genetic applications.FindingsWe characterized eight linkage groups, including one sex-linked, all showing drastically reduced recombination in males compared to females, as previously documented in this species. Mapping of the new 15 markers to the ~200 My diverged Xenopus tropicalis genome suggests a generally conserved synteny with only one confirmed major chromosome rearrangement.ConclusionsThe new microsatellites are representative of several chromosomes of H. arborea that are likely to be conserved across closely-related species. Our linkage map provides an important resource for genetic research in European Hylids, notably for studies of speciation, genome evolution and conservation.Electronic supplementary materialThe online version of this article (doi:10.1186/1756-0500-7-850) contains supplementary material, which is available to authorized users.

Evolutionary trend for metamery reduction and gonad shortening in Anurans revealed by comparison of gonad development.

The gonads develop as the metameric mesodermal structures at the ventral surface of the mesonephroi. To study the evolutionary trends for anuran gonads, we performed comparative analysis of three species from the basal paraphyletic group - Archaeobatrachia (Bombina bombina, Xenopus laevis, Pelobates fuscus) and five species from more derived monophyletic Neobatrachia group (Hyla arborea, Bufotes viridis, Rana dalmatina, Rana arvalis, Rana temporaria). Light and scanning electron microscopy analysis showed that in Archaeobtrachia the undifferentiated gonads and ovaries, but not the testes, have pronounced external metamery. In contrast, Neobatrachia lacked external gonadal metamery and the internal metamery was well pronounced in the ovaries, but only rudimentary in the testes. There was also a difference in the site of genital ridge formation between these two groups. In Archaeobatrachia, the genital ridges developed along almost the entire length of mesonephroi, while in Neobatrachia they were limited to the anterior parts of the mesonephroi. A transient form was observed in P. fuscus, where the gonads formed along the anterior half of the mesonephroi. There was also an evolutionary trend for gradual postero-anterior shortening of the gonadal anlagen. In summary, our study indicates that among anurans there is an evolutionary trend for the gradual loss of metamery and shortening of the gonad.

Conservation phylogeography: does historical diversity contribute to regional vulnerability in European tree frogs (Hyla arborea)?

Documenting and preserving the genetic diversity of populations, which conditions their long-term survival, have become a major issue in conservation biology. The loss of diversity often documented in declining populations is usually assumed to result from human disturbances; however, historical biogeographic events, otherwise known to strongly impact diversity, are rarely considered in this context. We apply a multilocus phylogeographic study to investigate the late-Quaternary history of a tree frog (Hyla arborea) with declining populations in the northern and western part of its distribution range. Mitochondrial and nuclear polymorphisms reveal high genetic diversity in the Balkan Peninsula, with a spatial structure moulded by the last glaciations. While two of the main refugial lineages remained limited to the Balkans (Adriatic coast, southern Balkans), a third one expanded to recolonize Northern and Western Europe, loosing much of its diversity in the process. Our findings show that mobile and a priori homogeneous taxa may also display substructure within glacial refugia ('refugia within refugia') and emphasize the importance of the Balkans as a major European biodiversity centre. Moreover, the distribution of diversity roughly coincides with regional conservation situations, consistent with the idea that historically impoverished genetic diversity may interact with anthropogenic disturbances, and increase the vulnerability of populations. Phylogeographic models seem important to fully appreciate the risks of local declines and inform conservation strategies.

Retinoic acid homeostasis regulates meiotic entry in developing anuran gonads and in Bidder’s organ through Raldh2 and Cyp26b1 proteins

The vitamin A (retinol) and its metabolites such as retinoic acid (RA) affect vertebrate gametogenesis. The level of RA in cells relies on the balance between its synthesis and degradation. The sex-dependent equilibrium is reached in different ways in various species. It is known that RA induces meiosis in developing gonads in mouse, chicken and urodel amphibians, but its role in anuran amphibians has not been studied. Here we show in six anuran species (Xenopus laevis, Bombina bombina, Hyla arborea, Bufo viridis, Rana arvalis and Rana temporaria) that cultured undifferentiated gonads were insensitive to RA treatment, but the RA induced ectopic meiosis in cultured larval testes. In larval testes of all studied species, the exogenous RA induced leptotene phase of I meiotic prophase in gonia, but only in H. arborea and B. viridis gonia progressed to zygotene phase. In the cultured developing ovaries, exogenous RA led to increase in the number of oocytes as compared to the control. Inhibition of either RA synthesis or RA-receptors prevented meiotic entry in larval gonads of all species. Exogenous RA rescued this inhibitory effect demonstrating that the balance in RA homeostasis plays a key role in meiotic entry in anuran gonads. The localization of two enzymes, Raldh2 and Cyp26b1, which antagonistically control RA levels and whose abundance suggests the sites of RA synthesis and degradation respectively, showed two distinct expression patterns specific for (i) X. laevis, H. arborea, R. arvalis, R. temporaria and (ii) B. bombina, B. viridis. Thus, RA, in correlation with specific expression patterns of Raldh2 and Cyp26b, induces meiosis during gonad development in anurans. In addition, in B. viridis, RA signalling seems important for development of the Bidder’s organ containing oocytes both in males and females.

Non-invasive measurement of frog skin reflectivity in high spatial resolution using a dual hyperspectral approach.

BackgroundMost spectral data for the amphibian integument are limited to the visible spectrum of light and have been collected using point measurements with low spatial resolution. In the present study a dual camera setup consisting of two push broom hyperspectral imaging systems was employed, which produces reflectance images between 400 and 2500 nm with high spectral and spatial resolution and a high dynamic range.Methodology/Principal FindingsWe briefly introduce the system and document the high efficiency of this technique analyzing exemplarily the spectral reflectivity of the integument of three arboreal anuran species (Litoria caerulea, Agalychnis callidryas and Hyla arborea), all of which appear green to the human eye. The imaging setup generates a high number of spectral bands within seconds and allows non-invasive characterization of spectral characteristics with relatively high working distance. Despite the comparatively uniform coloration, spectral reflectivity between 700 and 1100 nm differed markedly among the species. In contrast to H. arborea, L. caerulea and A. callidryas showed reflection in this range. For all three species, reflectivity above 1100 nm is primarily defined by water absorption. Furthermore, the high resolution allowed examining even small structures such as fingers and toes, which in A. callidryas showed an increased reflectivity in the near infrared part of the spectrum.Conclusion/SignificanceHyperspectral imaging was found to be a very useful alternative technique combining the spectral resolution of spectrometric measurements with a higher spatial resolution. In addition, we used Digital Infrared/Red-Edge Photography as new simple method to roughly determine the near infrared reflectivity of frog specimens in field, where hyperspectral imaging is typically difficult.

Observations on the Herpetofauna of the Builavânturariţa Massif (Southern Carpathians, Romania )

Abstract The results of herpetological investigations in the Buila-Vânturariţa massif (Southern Carpathians, Romania) and its surrounding areas are reported here. 19 amphibian and reptile species were identified (Salamandra salamandra, Triturus cristatus, Ichthyosaura alpestris, Lissotriton vulgaris, Bombina variegata, Bufo bufo, B. viridis, Hyla arborea, Rana temporaria, R. dalmatina, Pelophylax ridibundus, P. lessonae, Emys orbicularis, Lacerta agilis, L. viridis, Podarcis muralis, Zootoca vivipara, Zamenis longissimus, Natrix natrix) and are presented together with distribution and ecological data.

Maintenance of Ancestral Sex Chromosomes in Palearctic Tree Frogs: Direct Evidence from Hyla orientalis

Contrasting with the situation found in birds and mammals, sex chromosomes are generally homomorphic in poikilothermic vertebrates. This homomorphy was recently shown to result from occasional X-Y recombinations (not from turnovers) in several European species of tree frogs (Hyla arborea, H. intermedia and H. molleri). Because of recombination, however, alleles at sex-linked loci were rarely diagnostic at the population level; support for sex linkage had to rely on multilocus associations, combined with occasional sex differences in allelic frequencies. Here, we use direct evidence, obtained from anatomical and histological analyses of offspring with known pedigrees, to show that the Eastern tree frog (H. orientalis) shares the same pair of sex chromosomes, with identical patterns of male heterogamety and complete absence of X-Y recombination in males. Conservation of an ancestral pair of sex chromosomes, regularly rejuvenated via occasional X-Y recombination, seems thus a widespread pattern among Hyla species. Sibship analyses also identified discrepancies between genotypic and phenotypic sex among offspring, associated with abnormal gonadal development, suggesting a role for sexually antagonistic genes on the sex chromosomes.

Impact assessment of a high-speed railway line on species distribution: Application to the European tree frog (Hyla arborea) in Franche-Comté

The aim of the present work is to assess the potential long-distance effect of a high-speed railway line on the distribution of the European tree frog (Hyla arborea) in eastern France by combining graph-based analysis and species distribution models. This combination is a way to integrate patch-level connectivity metrics on different scales into a predictive model. The approach used is put in place before the construction of the infrastructure and allows areas potentially affected by isolation to be mapped. Through a diachronic analysis, comparing species distribution before and after the construction of the infrastructure, we identify changes in the probability of species presence and we determine the maximum distance of impact. The results show that the potential impact decreases with distance from the high-speed railway line and the largest disturbances occur within the first 500 m. Between 500 m and 3500 m, the infrastructure generates a moderate decrease in the probability of presence with maximum values close to −40%. Beyond 3500 m the average disturbance is less than −10%. The spatial extent of the impact is greater than the dispersal distance of the tree frog, confirming the assumption of the long-distance effect of the infrastructure. This predictive modelling approach appears to be a useful tool for environmental impact assessment and strategic environmental assessment. The results of the species distribution assessment may provide guidance for field surveys and support for conservation decisions by identifying the areas most affected.

CHANGES IN ACOUSTIC PARAMETERS IN THE COURSE OF THE MATING CALL OF MALE HYLA ARBOREA SAVIGNYI (AMPHIBIA: ANURA)

ABSTRACT Each segment (formerly “note) in the mating call of the treefrog Hyla arborea savignyi has two main concentrated bands of energy in the low part of the frequency spectrum and often another one in the upper part. In each segment fall time greatly exceeds rise time. During calling, males change some segment characteristics: dominant frequencies I, II and III become higher; segment duration and fall time become longer; rise time and the interval between segments become shorter. The changing of acoustic characteristics in the course of the mating call is probably a distinct feature of the calling behaviour of H. a. savignyi males that (like pausing between calls) might conceivably serve to avoid monotony.

Gonadal Sex Differentiation in Frogs: How Testes Become Shorter than Ovaries

Testis differentiation in anuran amphibians is the result of two opposing processes: degeneration of the distal part, and development of the proximal part, which becomes a functional male gonad. Undifferentiated gonad differentiates directly into a testis without a transition phase. We described the morphology of developing testes in Rana temporaria and Hyla arborea, and made careful histology and ultrastructure in Pelophylax lessonae. The developing testis was divided into 10 stages (I-III, undifferentiated gonad, IV-X, testis). The earliest morphological symptoms of testis differentiation were observed in 4- to 5-week-old tadpoles at Gosner stage 27-28. At that time an undifferentiated gonad, composed of 6-9 metameres, differentiates into a testis. The proximal metameres (2-3 in the right gonad and 3-4 in the left one) differentiate into a functional testis, while the distal ones degenerate. The difference between left and right gonad size is maintained until adulthood (stage X). Degeneration of the distal part progresses along the posterior-anterior gradient and starts at stage IV. It affects first the germ cells with accompanying precursor Sertoli cells, and then the mesenchymal cells and fibroblasts. Finally the external epithelium forms a "sleeve" around the almost empty distal part. The total length of the testes stays the same until stage VIII at Gosner stage 41 (age 74-148 days). Active spermatogenesis starts at stage IX (juveniles after their first hibernation), during which the distal part eventually disappears and the proximal part starts growing considerably due to progressing spermatogenesis.

Population genetics in a fragmented population of the European tree frog (Hyla arborea)

Habitat degradation and fragmentation are known to be major threats for population persistence in European amphibians. The European tree frog Hyla arborea has suffered from dramatic population declines in the last decades and has therefore been categorised as threatened in many Red Data lists. In the region of Hannover (Germany), the European tree frog has a fragmented distribution. The aim of our study was to infer the genetic consequences of habitat fragmentation in this area by examining genetic variation and population structure. DNA samples from 193 individuals from 11 sampling sites (10 sampling sites located 2 to 32 km apart from each other near Hannover and for comparison one sampling site 140 km northeast) were analysed with eight highly polymorphic microsatellite loci. Bayesian analyses indicated that the tree frog occurrences near Hannover were fragmented into four genetically distinct clusters according to their geographical distribution. Pairwise genetic distances between sampling sites varied between 0 and 0.23 (FST) and 0 and 0.48 (Dest) and indicated high to moderate gene flow within genetic clusters and nearly absent gene flow among genetic clusters. Moreover, we identified a potential source population within the region for an introduced population in the southwest of Hannover. Our data suggest that the genetic structure is influenced in part by isolation by distance and in part by lack of habitat or migration barriers. Habitat fragmentation should by counteracted by targeted conservation measures in areas where gaps in distribution and genetic fragmentation have been revealed.

Sexual dimorphism of AMH, DMRT1 and RSPO1 localization in the developing gonads of six anuran species

In vertebrates, several genes which are differentially expressed in various species, have been implicated in sex determination and gonadal differentiation. We used immunolocalization to study the expression pattern of three proteins AMH, DMRT1, RSPO1 involved in the sexual differentiation of gonads. The pattern of AMH, DMRT1 and RSPO1 expression was analyzed in X. laevis and in five other divergent anuran species: Bombina bombina, Bufo viridis, Hyla arborea, Rana arvalis and Rana temporaria during gonadal development. The pattern of expression of AMH in the developing testes of six studied anuran species was similar to that described for other vertebrates. AMH was strongly expressed in differentiating Sertoli cells. Interestingly, in B. viridis, R. arvalis and R. temporaria, AMH was also expressed in ovaries. In all studied species, DMRT1 was highly expressed in the developing testes, in both the somatic and germ cells. It was also expressed at low level in ovaries in all studied species, with the exception of H. arborea. RSPO1 was expressed in the developing ovaries, especially in the somatic cells, and was almost undetectable in developing testes in all examined anurans. These developmental expression patterns strongly suggest an involvement of AMH and DMRT1 in the development of male gonads and of RSPO1 in the female gonads. The differences in the expression patterns of these proteins in the gonads of different species might reflect the diversity of gonadal development patterns in anurans resulting from long lasting and diverged paths of their evolution.

Within- and among-population impact of genetic erosion on adult fitness-related traits in the European tree frog Hyla arborea

Assessing in wild populations how fitness is impacted by inbreeding and genetic drift is a major goal for conservation biology. An approach to measure the detrimental effects of inbreeding on fitness is to estimate correlations between molecular variation and phenotypic performances within and among populations. Our study investigated the effect of individual multilocus heterozygosity on body size, body condition and reproductive investment of males (that is, chorus attendance) and females (that is, clutch mass and egg size) in both small fragmented and large non-fragmented populations of European tree frog (Hyla arborea). Because adult size and/or condition and reproductive investment are usually related, genetic erosion may have detrimental effects directly on reproductive investment, and also on individual body size and condition that in turn may affect reproductive investment. We confirmed that the reproductive investment was highly size-dependent for both sexes. Larger females invested more in offspring production, and larger males attended the chorus in the pond more often. Our results did not provide evidence for a decline in body size, condition and reproductive effort with decreased multilocus heterozygosity both within and among populations. We showed that the lack of heterozygosity-fitness correlations within populations probably resulted from low inbreeding levels (inferior to ca. 20% full-sib mating rate), even in the small fragmented populations. The detrimental effects of fixation load were either low in adults or hidden by environmental variation among populations. These findings will be useful to design specific management actions to improve population persistence.

A Review of a Rare Type of Anomaly in Amphibians, Tail Duplication and Bifurcation, with Description of Three New Cases in European Species (Triturus dobrogicus,Triturus carnifex, andHyla arborea)

Abstract We review the natural occurrence of tail duplications and tail bifurcations in amphibians as well as experimental studies that induced tail duplications. For natural populations, we found 10 publications that mention tail duplications or bifurcations in a total of 24 individual larval amphibians belonging to 15 species, mainly from Europe and South America. Nineteen publications describe the incidence for 34 individual postlarval urodeles from 12 species from North America, Europe, and Asia. Here we add three new observations: a subadult female Triturus dobrogicus with a duplicated tail and an adult female Triturus carnifex with a bifurcated tail from Hungary, and a tadpole of Hyla arborea with a bifurcated tail tip from Greece. The causes of tail duplications in wild amphibians remain unknown. Similar tail anomalies have been obtained in the laboratory when parts of the chorda dorsalis were destroyed, when tar is injected into the tail, or when the lumbar region is irradiated.

The economic efficiency of conservation measures for amphibians in organic farming – Results from bio-economic modelling

This paper presents a whole farm bio-economic modelling approach for the assessment and optimisation of amphibian conservation conditions applied at the example of a large scale organic farm in North-Eastern Germany. The assessment focuses mainly on the habitat quality as affected by conservation measures such as through specific adapted crop production activities (CPA) and in-field buffer strips for the European tree frog (Hyla arborea), considering also interrelations with other amphibian species (i.e. common spadefoot toad (Pelobates fuscus), fire-bellied toad (Bombina bombina)). The aim of the approach is to understand, analyse and optimize the relationships between the ecological and economic performance of an organic farming system, based on the expectation that amphibians are differently impacted by different CPAs.The modelling system consists of a set of different sub-models that generate a farm model on the basis of environmentally evaluated CPAs. A crop-rotation sub-model provides a set of agronomically sustainable crop rotations that ensures overall sufficient nitrogen supply and controls weed, pest and disease infestations. An economic sub-model calculates the gross margins for each possible CPA including costs of inputs such as labour and machinery. The conservation effects of the CPAs are assessed with an ecological sub-model evaluates the potential negative or positive effect that each work step of a CPA has on amphibians. A mathematical programming sub-model calculates the optimal farm organization taking into account the limited factors of the farm (e.g. labour, land) as well as ecological improvements. In sequential model runs, the habitat quality is to be improved by the model, while the highest possible gross margin is still to be achieved.The results indicate that the model can be used to show the scope of action that a farmer has to improve habitat quality by reducing damage to amphibian population on its land during agricultural activities. Thereby, depending on the level of habitat quality that is aimed at, different measures may provide the most efficient solution. Lower levels of conservation can be achieved with low-cost adapted CPAs, such as an increased cutting height, reduced sowing density and grubbing instead of ploughing. Higher levels of conservation require e.g. grassland-like managed buffer strips around ponds in sensible areas, which incur much higher on-farm conservation costs.

Condition-dependent ways to manage acoustic signals under energetic constraint in a tree frog

Because resources needed to produce sexual displays are limited, courting males are expected to face trade-offs between investing in display properties selected by females and investing in the amount of display. This should be particularly the case in species with energetically expensive displays and high intrasexual competition through endurance rivalry like chorusing anurans. Studies that manipulated the energetic constraint in calling anurans have led to conflicting results, potentially due to nonsimultaneous assessment of call properties selected by females and the calling activity (i.e., the total number of calls emitted by a male), and/or to the use of different strategies to face display trade-offs by males. We investigated display trade-offs in 36 males Hyla arborea (L.) by manipulating their energetic constraint through starvation/feeding experiments while recording their overall call production during 10 consecutive nights. Even when considering simultaneously calling activity and call properties, the energetic constraint does not appear to impact call production. However, when focusing on individual responses, it appears that males cannot maintain both calling activity and within-bout call rate. Big and high-condition males mainly decrease this call property along the experiment, whereas small and low-condition males mainly decrease calling activity. Moreover, males who maintained calling activity the most are those who lost the most condition and, when refed, starved males only increased calling activity. These results suggest that calling activity is costlier to maintain than call properties but may confer a greater advantage in mating success, leading to different allocation strategies among males of different conditions.

Cheating for sex: inherent disadvantage or energetic constraint?

In many species, some males gain access to females by cheating, i.e. by exploiting the reproductive investment made by other males. There are two main nonmutually exclusive hypotheses to explain the decision of an individual to switch from the classical reproductive tactic to the parasitic one: the inherent disadvantage and energetic constraint hypotheses. For the first time, we tested and compared these two hypotheses in an experimental design by manipulating food availability of males with different degrees of inherent disadvantage in the caller/satellite system of Hyla arborea. Small males were more likely to be satellites than large individuals as predicted by the inherent disadvantage hypothesis. However, food deprived males were not more likely to be satellites than those that were fed, suggesting that the energetic constraint is not the main process explaining the use of a parasitic reproductive tactic. Moreover, all else being equal, males were more likely to act as satellites if confronted with an attractive competitor than if confronted with an unattractive one. In addition, males had a greater probability of being satellites at the beginning and end of the night, whereas they were more likely to call during the middle of the night. These results could highlight synchronization between male tactics and expected female availability during the course of the night.