Relative fitness of alternative male reproductive tactics in a mammal varies between years

1. In many species, males can use different behavioural tactics to achieve fertilization, so called alternative reproductive tactics (ARTs). Few field studies have measured fitness consequences of ARTs under varying environmental conditions. 2. Here we describe fitness consequences of three phenotypically plastic ARTs in the African striped mouse (Rhabdomys pumilio), and show that relative fitness of ARTs differs between years. Each year represents a different generation. 3. For the generation living under high population density tactics differed in relative fitness in accordance with the theory of conditional strategies, with highly successful territorial breeding males having 10 times higher success than solitary roaming males and 102 times higher success than adult natally philopatric males. 4. For the generation living under intermediate population density the territorial breeding and roaming tactics yielded similar fitness which would be in agreement with the theory of mixed strategies. No philopatric males occurred. 5. For the generation living under low population density roaming was the only tactic used and some roamers had very high fitness. 6. The main prediction of status dependent selection for conditional strategies is a correlation between fitness and status, often measured as body mass, but we did not find this correlation within tactics when more than one tactic was expressed in the population. 7. Female distribution seems to have an effect on which reproductive tactics male chose: female defence polygyny when females are clumped (interference competition), but a searching tactic when females are dispersed (scramble competition). In contrast to predictions arising from theory on scramble competition, male body mass was important in determining fitness only in the year when females were dispersed, but not in other years. 8. Our results indicate that the differentiation between conditional and mixed strategies is not an absolute one. In many other species environmental conditions might fluctuate temporally and spatially so that the normally sub-optimal tactic yields similar fitness to the (usually) dominant tactic, or that only a single tactic prevails. 9. We suggest the term single strategy, independent of current fitness consequences, for systems where tactics are not genetically determined, in contrast to genetically determined alternative strategies

Female home range size is regulated by resource distribution and intraspecific competition: a long-term field study

The size of an individual’s home range is an important feature, influencing reproduction and survival, but it can vary considerably among both populations and individuals. The factors accounting for such variation are still poorly understood, and comprehensive long-term field studies considering various environmental factors that influence home range size are rare. We investigated the effects of seasonality, availability of food, cover, number of direct neighbours and the relative individual body mass on home range sizes in 125 adult female striped mice, Rhabdomys pumilio, in South Africa from 2004 to 2008. We used radiotelemetry to estimate home range sizes, trapping to determine the number of direct neighbours, and plant surveys in every home range to determine availability of food and cover. Home ranges were smaller when food quantity was high, many territorial neighbours were present, females had a relatively small body mass and during the nonbreeding season. We conclude that the availability of food resources and intraspecific competition are the main factors influencing home range size in female striped mice. Females enlarged their home ranges when territorial neighbours were few, and there was a significant positive correlation between home range size and quantity of food plants. This indicates that home range size might not reflect the minimal trade-off between access to resources that allow for a female’s survival and lowest cost for defending and foraging in that area. Instead, we propose a hypothesis for future research that female striped mice occupy areas several times larger than needed to improve their fitness by providing resources for future offspring

Building Babies - Chapter 16

In contrast to birds, male mammals rarely help to raise the offspring. Of all mammals, only among rodents, carnivores, and primates, males are sometimes intensively engaged in providing infant care (Kleiman and Malcolm 1981). Male caretaking of infants has long been recognized in nonhuman primates (Itani 1959). Given that infant care behavior can have a positive effect on the infant’s development, growth, well-being, or survival, why are male mammals not more frequently involved in “building babies”? We begin the chapter defining a few relevant terms and introducing the theory and hypotheses that have historically addressed the evolution of paternal care. We then review empirical findings on male care among primate taxa, before focusing, in the final section, on our own work on paternal care in South American owl monkeys (Aotus spp.). We conclude the chapter with some suggestions for future studies.Deutsche Forschungsgemeinschaft (HU 1746/2-1) Wenner-Gren Foundation, the L.S.B. Leakey Foundation, the National Geographic Society, the National Science Foundation (BCS-0621020), the University of Pennsylvania Research Foundation, the Zoological Society of San Dieg

How Attractive Is the Girl Next Door? An Assessment of Spatial Mate Acquisition and Paternity in the Solitary Cape Dune Mole-Rat, Bathyergus suillus

Behavioural observations of reproduction and mate choice in wild fossorial rodents are extremely limited and consequently indirect methods are typically used to infer mating strategies. We use a combination of morphological, reproductive, spatial, and genetic data to investigate the reproductive strategy of a solitary endemic species, the Cape dune mole-rat Bathyergus suillus. These data provide the first account on the population dynamics of this species. Marked sexual dimorphism was apparent with males being both significantly larger and heavier than females. Of all females sampled 36% had previously reproduced and 12% were pregnant at the time of capture. Post-partum sex ratio was found to be significantly skewed in favour of females. The paternity of fifteen litters (n = 37) was calculated, with sires assigned to progeny using both categorical and full probability methods, and including a distance function. The maximum distance between progeny and a putative sire was determined as 2149 m with males moving between sub-populations. We suggest that above-ground movement should not be ignored in the consideration of mate acquisition behaviour of subterranean mammals. Estimated levels of multiple paternity were shown to be potentially as high as 26%, as determined using sibship and sire assignment methods. Such high levels of multiple paternity have not been found in other solitary mole-rat species. The data therefore suggest polyandry with no evidence as yet for polygyny

Neural Circuits Underlying Rodent Sociality: A Comparative Approach

All mammals begin life in social groups, but for some species, social relationships persist and develop throughout the course of an individual’s life. Research in multiple rodent species provides evidence of relatively conserved circuitry underlying social behaviors and processes such as social recognition and memory, social reward, and social approach/avoidance. Species exhibiting different complex social behaviors and social systems (such as social monogamy or familiarity preferences) can be characterized in part by when and how they display specific social behaviors. Prairie and meadow voles are closely related species that exhibit similarly selective peer preferences but different mating systems, aiding direct comparison of the mechanisms underlying affiliative behavior. This chapter draws on research in voles as well as other rodents to explore the mechanisms involved in individual social behavior processes, as well as specific complex social patterns. Contrasts between vole species exemplify how the laboratory study of diverse species improves our understanding of the mechanisms underlying social behavior. We identify several additional rodent species whose interesting social structures and available ecological and behavioral field data make them good candidates for study. New techniques and integration across laboratory and field settings will provide exciting opportunities for future mechanistic work in non-model species

The fitness of dispersing spotted hyaena sons is influenced by maternal social status

Life history theory predicts that mothers should provide their offspring with a privileged upbringing if this enhances their offspring's and their own fitness. In many mammals, high-ranking mothers provide their offspring with a privileged upbringing. Whether dispersing sons gain fitness benefits during adulthood from such privileges (a 'silver spoon' effect) has rarely been examined. In this paper, we show that in the complex, female-dominated society of spotted hyaenas, high-born sons grew at higher rates, were more likely to disperse to clans offering the best fitness prospects, started reproducing earlier and had a higher reproductive value than did lower-born sons. This illustrates the evolutionary importance of maternal effects even in societies in which male size or fighting ability does not influence fitness. By demonstrating for the first time in a non-human mammal that maternal status influences immigration patterns, the study also advances our understanding of two key ecological and evolutionary processes, dispersal and habitat selection

Prolactin and Upstream Migration of the Amphidromous Teleost, Ayu Plecoglossus altivelis

Changes in mRNA levels of prolactin (PRL) during the upstream migration were examined in fry of the amphidromous fish, ayu Plecoglossus altivelis. Quantification of mRNA has been done with real-time PCR and expressed as whole body or pituitary contents depending the body size of fry. PRL mRNA levels of ayu caught in seawater of the coastal area remained low during early spring. Prior to the start of the upstream migration, the fish caught in the coastal area in mid spring showed increased levels of PRL mRNA. There were further increases in PRL levels in the fish caught in the river. Analysis of proportions revealed that there were significant differences among PRL mRNA in the fish caught in different environmental salinities. Body weight showed a positive relation with PRL mRNA in ayu caught in seawater. A landlocked population of ayu, which migrates from lake to river, showed no significant change in PRL mRNA levels before and after upstream migration. Results in this study indicate the importance of up-regulation of PRL gene expression of ayu during the upstream migration from seawater to fresh water. There is a possible relationship between body size and PRL in the early developmental stage of ayu in seawater, but not in the fish in fresh water

Functions of Intermittent Locomotion in Mustached Tamarins (Saguinus mystax)

Many animals interrupt their moving with brief pauses, which appear to serve several different functions. We examined the function of such intermittent locomotion in wild living mustached tamarins (Saguinus mystax), small arboreal New World primates that form mixed-species groups with saddleback tamarins (Saguinus fuscicollis). We investigated how different environmental and social factors affect pausing during locomotion and used these data to infer the function of this behavior. As measures of intermittent locomotion, we used percentage of time spent pausing and pause rate. We considered 3 possible functions that are not mutually exclusive: increased endurance, route planning, and antipredator vigilance. Mustached tamarins spent on average (mean ± SE) 55.1 ± 1.0% of time pausing, which makes effective resource exploitation more time consuming and needs to be outweighed by correspondingly large benefits. Percentage of time spent pausing decreased in larger mixed-species groups vs. smaller mixed-species groups and decreased with height and in monkeys carrying infants. It was not affected by sex, age, spatial arrangement, or single-species group size. Pause rate increased in individuals traveling independently compared to those traveling in file, but was not affected by other factors. The group size effect in mixed-species groups lends support to the notion that pausing during locomotion is an antipredator tactic that can be reduced in the increased safety of larger groups, but other results suggest that additional functions, particularly route planning, are also of great importance. Benefits in terms of predator confusion and group movement coordination are also likely to play a role and remain a topic for further research

Desperately Seeking Supersymmetry [SUSY]

In this article we try to clarify why supersymmetry [SUSY] and supersymmetric grand unified theories [SUSY GUTs] are the new standard model of particle physics, i.e. the standard by which all other theories and experiments are measured.Comment: 69 pages, 15 figures, new references adde

The influence of refuge sharing on social behaviour in the lizard Tiliqua rugosa

Refuge sharing by otherwise solitary individuals during periods of inactivity is an integral part of social behaviour and has been suggested to be the precursor to more complex social behaviour. We compared social association patterns of active versus inactive sheltering individuals in the social Australian sleepy lizard, Tiliqua rugosa, to empirically test the hypothesis that refuge sharing facilitates social associations while individuals are active. We fitted 18 neighbouring lizards with Global Positioning System (GPS) recorders to continuously monitor social associations among all individuals, based on location records taken every 10 min for 3 months. Based on these spatial data, we constructed three weighted, undirected social networks. Two networks were based on empirical association data (one for active and one for inactive lizards in their refuges), and a third null model network was based on hypothetical random refuge sharing. We found patterns opposite to the predictions of our hypothesis. Most importantly, association strength was higher in active than in inactive sheltering lizards. That is, individual lizards were more likely to associate with other lizards while active than while inactive and in shelters. Thus, refuge sharing did not lead to increased frequencies of social associations while lizards were active, and we did not find any evidence that refuge sharing was a precursor to sleepy lizard social behaviour. Our study of an unusually social reptile provides both quantitative data on the relationship between refuge sharing and social associations during periods of activity and further insights into the evolution of social behaviour in vertebrates