Rafael Márquez

Advertisement calls of Bolivian species of Hyla (Amphibia, Anura, Hylidae)

The advertisement calls of 18 species of Hyla occurring in Bolivia are described. Information on the calling behavior of each species is provided. A characteristic audiospectrogram and oscillogram are presented for each species as well as information about the spectral and temporal features of the calls. Numerical characteristics of the sounds are used to generare a phenogram of the mating calls. Call characteristics agree with the currently accepted phylogeny of South American species of Hyla. Some species with similar calls may breed synchronously and syntopically

Female choice in the midwife toads (Alytes obstetricans and A. cisternasii)

A previous study reported that large males had greater mating success than small males in two species of midwife toads. A behavioural mechanism that would explain such a pattern is sought. Dominant frequency is inversely correlated with male size in Alytes obstetricans and A. cisternasii. In both cases, two-speaker playback tests with synthetic calls show that females have a significant preference for calls with low frequencies. The results shows that female preference may impose directional sexual selection upon a static acoustic character that is correlated with male size. Male Alytes tend their eggs on land, but male size is not correlated with hatching success. Therefore female preference for larger males does not appear to directly increase female fitness.

Iberian Wolf Howls: Acoustic Structure, Individual Variation, and a Comparison with North American Populations

Abstract We present a detailed description of the acoustic structure of howls emitted by Iberian wolves and a comparison with published descriptions of North American wolf howls. We recorded and analyzed 176 howls emitted by 11 wolves held in captivity in social groups of 1–5 individuals. Our sample included solo howls as well as howls included in choruses. Iberian wolf howls are long (1.1- to 12.8-s) harmonic sounds, with a mean fundamental frequency between 270 and 720 Hz. Our results revealed striking similarities between Iberian and North American wolf howls in all variables analyzed except for the number of discontinuities in the frequency of the howl, which was lower for Iberian wolves. Using discriminant function analysis we could assign 84.7% of howls to the correct individual. Variables related to fundamental frequency (mean and maximum) and the coefficient of fundamental modulation best discriminate individuals. We suggest that Iberian wolves could use howls for individual recognition.

Intensity of female preference quantified through playback setpoints : call frequency versus call rate in midwife toads

We quantify and compare female preference for two different acoustic parameters of the male advertisement call in two species of midwife toads where females select mates based on call characteristics. The parameters compared were: call repetition rate, a highly variable parameter associated with male–male competition, and call dominant frequency, a parameter with low variability related to male size. We also tested whether intensity of female preference was similar when the alternate choices were perceived at high overall intensities (close range) or lower overall intensities (long range). We use ‘Playback setpoints’ a new experimental protocol based on two-speaker playback tests with the female placed in a ferret wheel (treadmill) that keeps her equidistant from the two speakers. The protocol measures preference as a trade-off with perceived call intensity: the ‘a priori’ preferred parameter is not broadcast initially, and the female initially walks towards the speaker emitting the inferior parameter. When the female walks towards this speaker the intensity of the opposite speaker is gradually increased until the female turns around and starts her approach towards the ‘a priori’ preferred parameter. At this point the differences in sound intensity between the speakers are measured, and the difference is considered to be a measure of female preference. Our results show that female preference for call repetition rate is significantly more intense than that for dominant frequency. Similarly, we find that female preference intensity is higher when stimuli are broadcast at higher overall intensity indicating that females are more selective at close range.

Reproductive biology of Pelobates cultripes (Anura: Pelobatidae) in Central Spain

We studied the mating system of a population of western spadefoot toads Pelobates cultripes for a single season. The breeding season lasted 35 days, during which there were four periods of arrival at the breeding pond. Only males arrived at the breeding site in the first peak; additional males and females arrived in subsequent peaks. Minimum temperature and rainfall influenced activity, and maximum temperature was correlated with recruitment and total number of toads that remained in the pond. The breeding sex ratio was slightly male-biased (1.15:1), whereas average operational sex ratio was more strongly male-biased (average 2.97:1). Males migrating early to the breeding pond were larger than males that migrated late. Males remained in the pond longer than females, and fighting between males was observed

Call Timing in Male-Male Acoustical Interactions and Female Choice in the Midwife Toad Alytes obstetricans

Abstract Male midwife toads emit a short, tonal advertisement call. Previous studies have shown that two nearby males engaged in acoustical competition (duet) increase their calling rate. We address the question of whether acoustical competition is expressed in the temporal adjustment of the calls of nearby calling males. One male emits its calls typically immediately after the emission of a nearby male with an approximate phase angle of 80°. Variation in timing of calls is correlated with the size of the calling male (as inferred by call frequency). Playback experiments with females show that the timing of calls between interacting males can influence the choice of a mate. Females prefer duets of males calling with a phase angle of 180° rather than 90° and prefer males responding to calls over males initiating the duets.

Nonoptimal propagation of advertisement calls of midwife toads in Iberian habitats

This study compares the efficiency of transmission of the advertisement calls of two species of midwife toads, Alytes cisternasii and A. obstetricans, in both native and non-native habitats in the Iberian Peninsula. Recorded calls of both species and pure tones were broadcast at ten sites native to either the relatively small A. cisternasii or the larger A. obstetricans. A large variation in the patterns of excess attenuation between localities was observed for calls measured at distances of 0.5 to 8 m from a loudspeaker. However, attenuation rates were higher for calls of both species in habitats of A. obstetricans relative to habitats of A. cisternasii. The calls of A. obstetricans experienced lower attenuation rates than those of A. cisternasii in both conspecific and heterospecific localities. Thus, although A. cisternasii occupies habitats more favorable for sound transmission, its advertisement call spectrum is not optimized for these habitats; the calls of A. obstetricans suffer less attenuation in A. cisternasii habitats. This result argues against the notion that spectral features of the calls are adapted to enhance transmission efficiency in natural habitats, and suggests that differences in call dominant frequency between the two species result from constraints imposed by selection on body size.

Sexual Size Dimorphism and Age in the Midwife Toads Alytes obstetricans and A. cistemasii

We studied sexual size dimorphism is in two breeding populations of midwife toads (Alytes obstetricans and Alytes cisterasii) from which skeletochronological data provide information on individual age. The population values show that females are larger than males in both species (A. obstet- ricans, SVLmale = 41.74 mm, SVLfemale = 49.69 mm; A. cisternasii, SVLmale = 35.79, SVLfeale = 38.58). The values obtained for population size dimorphism (Ln(xmale)-Ln(xfemale) -0.174 for A. obstetricans and -0.074 for A. cisternasii) are are higher than the age-specific values (range -0.126 to -0.055 for A. obstet- ricans; -0.101 to -0.043 for A. cisterasii). Differences between age-specific and population dimorphism values are particularly marked in A. obstetricans, where the age distribution of the sample of males and females differ the most. This result suggests that caution should be used when considering population data on size dimorphism to test evolutionary hypotheses about the evolution of this phenomenon. The dimorphism values obtained for the two species are not markedly different from those obtained from other temperate anurans without male parental care. This result does not support the prediction of the invest- ment hypothesis (Williams, 1966; Trivers, 1972) that male parental care may act as a limitation on sexual selection on male size.

Advertisement calls of six species of anurans from Bali, Republic of Indonesia

We describe quantitatively the advertisement calls of six species of anurans from Bali and the release call of three of these. The advertisement calls of three of the species and the three release calls have not been described previously to the best of our knowledge. This is the first study that describes calls from anurans of the island of Bali. Advertisement call characteristics are discussed in light of within‐individual and between‐individual variation. For the three species with previously published accounts of their advertisement calls we compare the data obtained in Bali with other accounts. While Bufo melanostictus did not show a substantial difference in advertisement calls from Coorg (India), the calls of Balinese Fejervarya (Limnonectes) limnocharis show substantial differences with those recorded in Coorg (India). Furthermore, the Balinese recordings of Polypedates leucomystax are similar to recordings obtained by other authors in Negros (Philippines), the Malaysian part of Borneo, and from one of the morphs present in peninsular Malaysia, while being clearly different from recordings of populations from Thailand, Polillo (Philippines), and from the other morph recorded in Malaysia.

Male reproductive success in two midwife toads, Alytes obstetricans and A. cisternasii

SummaryOne population of the midwife toad species Alytes obstetricans and one of A. cisternasii were studied in Spain for two consecutive reproductive seasons. Males that were most successful at hatching a high proportion of their clutch did not obtain more matings. On the other hand, in both species larger body size conferred a significant reproductive advantage on males. These results are explained mainly by the increased number of mates obtained by larger males, probably as a result of female choice. The selection gradients for body size in males (regressions of reproductive success on body size) were not significantly different within species between years nor between species within the same period of time. Hatching success (proportion of the eggs hatched) was not correlated with male body size in A. obstetricans. Hatching success in A. cisternasii was weakly negatively correlated with male body size in 1988.