Tim Halliday

Peahens prefer peacocks with elaborate trains

Abstract Peacocks, Pavo cristatus, defend small display sites and aggregate to form leks. Observations of one lek, consisting of 10 males, showed that there was considerable variance in mating success. The most successful male copulated 12 times whilst the least successful males obtained no copulations. Over 50% of the variance in mating success could be attributed to variance in train morphology; there was a significant positive correlation between the number of eye-spots a male had in his train and the number of females he mated with. Furthermore, analysis of female behaviour provided good evidence that this non-random mating is a result of a female preference. On no occasion did a female mate with the first male that courted her and, on average, females visited three different males. Females thus always reject some potential mates. For 10 out of 11 sequences ending in a successful copulation, the male ‘chosen’ at the end of a sequence had the highest eye-spot number among the males visited. These data support Darwins hypothesis that the peacocks train has evolved, at least in part, as a result of a female preference.

Multiple mating by females: a perspective from quantitative genetics

References Baerends, G. P. & Baerends-van Roon, J.M. 1950. An introduction to the study of the ethology of eiehlid fishes. Behaviour Suppl., 1, 1-242. Fabricius, E. 1953. Aquarium observations on the spawning behaviour of the char, Salmo alpinus. Rept. Inst. Freshwater Res., Drottningholm, 34, 1448. Fabricius, E. & Gustafson, K. J. 1954. Further aquarium observations on the spawning behaviour of the char, Salmo alpinus L. Rep. Inst. Freshwater Res., Drottningholm, 35, 58-104. Jones, J. W. & Ball, J. N. 1954. The spawning behaviour of brown trout and salmon. Br. J. Anim. Behav., 2, 103114. Jones, J. W. & King, G. M. 1949. Experimental observations on the spawning behaviour of the Atlantic salmon (Salmo salar Linn.). Proc. Zool. Soc. Lond., 119, 33-48. Matsushima, T., Kitamura, S., Takei, K., Satou, M., Okumoto, N. & Ueda, K. 1986. An electromyographic study of sexual behavior in him~ salmon (landlocked sockeye salmon, Oncorhynehus nerka). Zool. Set., 3, 563-567. Newcombe, C. P. & Hartman, G. F. 1980. Visual signals in the spawning behaviour of rainbow trout. Can. J. ZooL, 58, 1751-1757. Rowland, W. J. 1982. Mate choice by male sticklebacks, Gasterosteus aeuleatus. Anita. Behav., 30, 1093-1098. Rowland, W. J. & Sevenster, P. 1985. Sign stimuli in the threespine stickleback (Gasterosteus aeuleatus): a reexamination and extension of some classic experiments. Behaviour, 93, 241-257. Satou, M., Oka, Y., Fujita, I., Yamaguchi, K., Nagai, T., Koyama, Y., Shirahata, S. & Ueda, K. 1980. Effect of preoptic lesions on male reproductive behavior in the him~ salmon, land-locked Oneorhynchus nerka. In: Integrative Control Functions of the Brain, VoL 3 (Ed. by M. Ito, N. Tsukahara, K. Kubota & K. Yagi), pp. 333 335. Tokyo: Kodansha/Amsterdam: Elsevier. Satou, M., Oka, Y., Kusunoki, M., Matsushima, T., Kato, M., Fujita, I. & Ueda, I~. 1984. Telencephalic and preoptic areas integrate sexual behavior in him6 salmon (landlocked red salmon, Oneorhynehus nerka): results of electrical brain stimulation experiments. Physiol. Behav., 33, 441-447. Satou, M. & Ueda, K. 1982. Brain mechanisms of salmon sexual behavior. In: Mechanisms of Sexual Behavior (Ed. by E. Ohnishi & T. Hidaka), pp. 5 19. Tokyo: Sangyo-Tosho. Schultz, L. P. & students. 1935. The breeding activities of the little redfish, a landlocked form of the sockeye salmon, Oneorhynchus nerka. Mid-Pacific Magazine, Jan.-Mareh, 67-77. Tautz, A.F. & Groot, C. 1975. Spawning behavior of chum salmon (Oneorhynehus keta) and rainbow trout (Salmo gairdneri). J. Fish. Res. lid Can., 32, 633-642. Tinbergen, N. 1951. The Study of Instinet. London: Oxford University Press.

Competitive mate searching in male common toads, Bufo bufo

Abstract The reproductive behaviour of a population of individually marked toads Bufo bufo was studied at a pond where males outnumbered females by between four and five to one. There was intense competition between the males for mates and only 20·5 % of them bred successfully. Of the successful males, 38·5 % got mates by fighting and displacing other males from the backs of females (takeovers). Larger males enjoyed greater reproductive success because they were stronger and better able to achieve takeovers. When competing for females, some males searched at the spawn site while others searched away from spawn. The numbers searching in the two areas can be predicted by a model which assumes that unpaired males distribute themselves so that there is a spatial ESS, where individuals have equal expectations of finding a female both at and away from the spawning ground.

Multiple mating in a lekking bird: why do peahens mate with more than one male and with the same male more than once?

SummaryApproximately 50% of marked peahens (Pavo cristatus) mate more than once with lek males. Some females mate with more than one male, others copulate repeatedly with the same male. The frequency of courtship also shows marked variation. Some females repeatedly engage males in courtship interactions after they have succesfully copulated with them. The likelihood of mating with more than one male increases if a female first mates with a non-preferred (unsuccessful male). There is a non-significant tendency for females to copulate with a more successful male when remating. Peahens may mate with a non-preferred male first if they do not encounter a successful male during their initial period of choice, perhaps because the most successful male on a lek was courting another female and/or was defended by another female. There are more aggressive interactions between females in front of preferred males. Preferred males receive more repetitive courtship behaviour and repeated matings. Dominant females are more likely to engage in repetitive courtship and matings. The number of times a female initiates courtship on any one day increases with the number of other females actively courting males at a lek site on that day. We suggest that there is competition amongst females for access to preferred males and that dominant females try to monopolise these males by repeatedly engaging them in courtship interactions. We discuss the implications of these observations for the idea that female may gain directly from mate choice in a species where males contribute nothing but gametes to their offspring.

Ground Water Chemistry Changes before Major Earthquakes and Possible Effects on Animals

Prior to major earthquakes many changes in the environment have been documented. Though often subtle and fleeting, these changes are noticeable at the land surface, in water, in the air, and in the ionosphere. Key to understanding these diverse pre-earthquake phenomena has been the discovery that, when tectonic stresses build up in the Earth’s crust, highly mobile electronic charge carriers are activated. These charge carriers are defect electrons on the oxygen anion sublattice of silicate minerals, known as positive holes, chemically equivalent to O− in a matrix of O2−. They are remarkable inasmuch as they can flow out of the stressed rock volume and spread into the surrounding unstressed rocks. Travelling fast and far the positive holes cause a range of follow-on reactions when they arrive at the Earth’s surface, where they cause air ionization, injecting massive amounts of primarily positive air ions into the lower atmosphere. When they arrive at the rock-water interface, they act as •O radicals, oxidizing water to hydrogen peroxide. Other reactions at the rock-water interface include the oxidation or partial oxidation of dissolved organic compounds, leading to changes of their fluorescence spectra. Some compounds thus formed may be irritants or toxins to certain species of animals. Common toads, Bufo bufo, were observed to exhibit a highly unusual behavior prior to a M6.3 earthquake that hit L’Aquila, Italy, on April 06, 2009: a few days before the seismic event the toads suddenly disappeared from their breeding site in a small lake about 75 km from the epicenter and did not return until after the aftershock series. In this paper we discuss potential changes in groundwater chemistry prior to seismic events and their possible effects on animals.

Reproductive stage and history affect the phonotactic preferences of female midwife toads, Alytes muletensis

We investigated whether the reproductive stage or reproductive history of females affects their preferences for male calls that differ in frequency. We repeatedly tested gravid female midwife toads prior to and immediately after mating, and during ovulation. When females were ovulating they were much more consistent in their choice of call than when they were gravid but not ovulating. When females had recently mated they still showed positive phonotaxis, but did not reliably discriminate between alternative calls. This study is the first to test gravid female anurans repeatedly at different stages in their reproductive cycle (ovulating or not; pre- and postmating). It highlights the need to treat with caution the results from population-based preference studies in which individuals are tested only once, and in which variation in reproductive state is not taken into account. Copyright 2000 The Association for the Study of Animal Behaviour.

Selective Phonotaxis by Males in the Majorcan Midwife Toad

Males are expected to exhibit mating preferences when there is high variance in the quality of females or when males are limited to a small number of matings. In the Majorcan midwife toad, Alytes muletensis, the male performs parental care by carrying the eggs wrapped in a string around his hind legs. Both sexes possess courtship vocalizations which they use to advertise receptivity. We looked for evidence of male mating preferences in a phonotaxis arena in which males were presented with two alternative synthetic female calls. We predicted that males should prefer to mate with large females because of maternal effects on egg size, and that this preference would be manifest by selective phonotaxis toward low frequency calls. We also predicted that males should prefer high intensity calls as indicators of the energetic or motivational state of the female. Contrary to our prediction, males did not exhibit a preference for low frequency calls. The results suggest that there is stabilizing selection on call frequency and directional selection on call intensity.

Resolving the Phylogeny of the European Newts

The European newts have been the subject of several phylogenetic analyses, using a variety of character sets, from biochemical to ethological. As a result, the European newts have probably been subjected to more diverse and intense phylogenetic analysis than any other vertebrate genus in the world. The various techniques used have yielded conflicting results, but recent analyses that combine different kinds of data promise a resolution of the problem.

SUCCESS BREEDS SUCCESS IN MATING MALE REED FROGS (HYPEROLIUS MARMORATUS)

Studies of the distribution of mating success among males in frog choruses typically seek to identify specific phenotypic attributes that confer a higher mating success on certain individual males. These attributes invariably relate to competition among males: either direct competition in the form of aggression, or competition to attract and be chosen by females. In this paper, we present evidence that an additional factor may operate in frog choruses. We show that individual males who mate on a given night enjoy a higher probability of being successful on the next night, and we suggest that this is because successful mating enables males to conserve energy.

Ecology: A declining amphibian conundrum

Worldwide declines in amphibian populations have caused so much concern over the past ten years that a special committee was set up to investigate them. One of the conclusions that this group came to was that there seems to be no single cause that can explain this. But a new study shows that, for frogs and toads in Panama and Australia at least, a pathogen -- the chytrid fungus -- is responsible.