Larger is not better: no mate preference by European common frog (Rana temporaria) males

In explosive breeding frogs, high intrasexual competition between males leads to a sexual coercion ruled mating system, where males presumably evolved preferences for specific female traits. We tested these preferences in the European Common Frog by excluding intrasexual competition. We hypothesized that all males show preferences towards larger female body size, due to higher fecundity. Our results did not show any preference considering female body size, neither in the attempt to amplex a female nor during the formation of pairs. Additionally, we witnessed a high failure rate of male mating attempts, which hints at high mating costs and offers an explanation for the lack of preferences in males. Nonetheless, we observed a non-random mating pattern in successfully formed pairs, where in the absence of size dimorphism females were on average larger than males. This indicates a different mechanism for selection which is independent from male mating preference or scramble competition.

Individual contributions to group chorus dynamics influence access to mating opportunities in wood frogs

A limitation in bioacoustic studies has been the inability to differentiate individual sonic contributions from group-level dynamics. We present a novel application of acoustic camera technology to investigate how individual wood frogs' calls influence chorus properties, and how variation influences mating opportunities. We recorded mating calls and used playback trials to gauge preference for different chorus types in the laboratory. Males and females preferred chorus playbacks with low variance in dominant frequency. Females preferred choruses with low mean peak frequency. Field studies revealed more egg masses laid in ponds where males chorused with low variance in dominant frequency. We also noted a trend towards more egg masses laid in ponds where males called with low mean frequency. Nearest-neighbour distances influenced call timing (neighbours called in succession) and distances increased with variance in chorus frequency. Results highlight the potential fitness implications of individual-level contributions to a bioacoustic signal produced by groups.

What lies beneath? Population dynamics conceal pace-of-life and sex ratio variation, with implications for resilience to environmental change

Life-history and pace-of-life syndrome theory predict that populations are comprised of individuals exhibiting different reproductive schedules and associated behavioural and physiological traits, optimized to prevailing social and environmental factors. Changing weather and social conditions provide in situ cues altering this life-history optimality; nevertheless, few studies have considered how tactical, sex-specific plasticity over an individual's lifespan varies in wild populations and influences population resilience. We examined the drivers of individual life-history schedules using 31 years of trapping data and 28 years of pedigree for the European badger (Meles meles L.), a long-lived, iteroparous, polygynandrous mammal that exhibits heterochrony in the timing of endocrinological puberty in male cubs. Our top model for the effects of environmental (social and weather) conditions during a badger's first year on pace-of-life explained <10% of variance in the ratio of fertility to age at first reproduction (F/α) and lifetime reproductive success. Conversely, sex ratio (SR) and sex-specific density explained 52.8% (males) and 91.0% (females) of variance in adult F/α ratios relative to the long-term population median F/α. Weather primarily affected the sexes at different life-history stages, with energy constraints limiting the onset of male reproduction but playing a large role in female strategic energy allocation, particularly in relation to ongoing mean temperature increases. Furthermore, the effects of social factors on age of first reproduction and year-to-year reproductive success covaried differently with sex, likely due to sex-specific responses to potential mate availability. For females, low same-sex densities favoured early primiparity; for males, instead, up to 10% of yearlings successfully mated at high same-sex densities. We observed substantial SR dynamism relating to differential mortality of life-history strategists within the population, and propose that shifting ratios of 'fast' and 'slow' life-history strategists contribute substantially to population dynamics and resilience to changing conditions.