Information transfer about food locations is not a benefit of group living in the solitary foraging striped mouse ( Rhabdomys pumilio )

The benefits of group living have primarily been investigated in species which form permanent groups. There are, however, several species that forage alone but still form groups that share the same territory and nest. One of these group-living solitary foragers is the striped mouse (Rhabdomys pumilio) from the Succulent Karoo in South Africa. I performed field experiments on this species to investigate the hypothesis that mice benefit from group living by exchanging information in social groups about the location and availability of food sources. Presenting additional food sources in the field altered individual foraging decisions. A mouse that found food at one location visited it again the next day; other mice of the same group did not arrive, however. Establishment of permanent feeding stations for 1week affected individual foraging even 1week after termination of feeding, a result demonstrating the strong effect trapping can have on the behaviour of study species. Results from this study suggest that information transfer about good food sources was of little importance in the evolution of group living in the striped mous

Parental and Alloparental Care in a Polygynous Mammal

We studied maternal, paternal, and alloparental care in striped mice (Rhabdomys pumilio), which nest and breed communally in the succulent karoo, South Africa. A total of 18 triads, each consisting of 2 adult female littermates and an unfamiliar adult male, were set up under natural weather conditions. We expected that relationships within captive triads that breed communally would be egalitarian, and that all individuals would participate in the rearing of offspring, but we assumed that the degree of caregiving behavior would vary between mothers, fathers, and alloparents, because individuals obtain different fitness benefits. Social interactions in the triads were predominantly amicable and in the majority of triads, both females produced litters in a communal nest. All 3 adults in a triad participated in care of the offspring, with mothers spending 43%, fathers 26%, and alloparents 24% of observations in caregiving activities. Our results indicate that sisters can form stable cooperative relationships, but members of a communal nest allocate their caregiving to individual offspring according to potential trade-offs between direct and indirect fitness benefits. Large amounts of paternal care can occur in a polygynous species, which contrasts with the common belief that paternal care is a characteristic of monogam

The nasty neighbour in the striped mouse (Rhabdomys pumilio) steals paternity and elicits aggression

Background Territoriality functions to monopolize access to resources including mates, but is costly in terms of energy and time investment. Some species reduce these costs by being less aggressive towards their neighbours than towards unfamiliar strangers, the so called dear enemy phenomenon. However, in other species individuals are more, not less aggressive towards their neighbours. It has been hypothesised that this is due to the fact that neighbours can impose a greater threat than strangers, but this has not been tested previously. Results We tested aggression in wild group-living male striped mice in a neutral test arena and demonstrate that breeders are more aggressive than non-breeding philopatrics, and that more aggression occurs during the breeding than during the non-breeding season. Male breeders were significantly more aggressive towards their neighbours than towards strangers, leading to the prediction that neighbours are the most important competitors for paternity. Using a molecular parentage analysis we show that 28% of offspring are sired by neighbouring males and only 7% by strangers. Conclusions We conclude that in male striped mice the main function of male aggression is defending paternity against their territorial neighbours

Resilience to droughts in mammals: a conceptual framework for estimating vulnerability of a single species

The frequency and severity of droughts in certain areas is increasing as a consequence of climate change. The associated environmental challenges, including high temperatures, low food, and water availability, have affected, and will affect, many populations. Our aims are to review the behavioral, physiological, and morphological adaptations of mammals to arid environments, and to aid researchers and nature conservationists about which traits they should study to assess whether or not their study species will be able to cope with droughts. We provide a suite of traits that should be considered when making predictions about species resilience to drought. We define and differentiate between general adaptations, specialized adaptations, and exaptations, and argue that specialized adaptations are of little interest in establishing how nondesert specialists will cope with droughts. Attention should be placed on general adaptations of semidesert species and assess whether these exist as exaptations in nondesert species. We conclude that phenotypic flexibility is the most important general adaptation that may promote species resilience. Thus, to assess whether a species will be able to cope with increasing aridity, it is important to establish the degree of flexibility of traits identified in semidesert species that confer a fitness advantage under drying conditions

Skeletogenesis and sequence heterochrony in rodent evolution, with particular emphasis on the African striped mouse, Rhabdomys pumilio (Mammalia)

Data documenting skeletal development in rodents, the most species-rich ‘order' of mammals, are at present restricted to a few model species, a shortcoming that hinders exploration of the morphological and ecological diversification of the group. In this study we provide the most comprehensive sampling of rodent ossification sequences to date, with the aim of exploring whether heterochrony is ubiquitous in rodent evolution at the onset of skeletal formation. The onset of ossification in 17 cranial elements and 24 postcranial elements was examined for eight muroid and caviomorph rodent species. New data are provided for two non-model species. For one of these, the African striped mouse, Rhabdomys pumilio, sampling was extended by studying 53 autopodial elements and examining intraspecific variation. The Parsimov method of studying sequence heterochrony was used to explore the role that changes in developmental timing play in early skeletal formation. Few heterochronies were found to diagnose the muroid and caviomorph clades, suggesting conserved patterning in skeletal development. Mechanisms leading to the generation of the wide range of morphological diversity encapsulated within Rodentia may be restricted to later periods in development than those studied in this work. Documentation of skeletogenesis in Rhabdomys indicates that intraspecifc variation in ossification sequence pattern is present, though not extensive. Our study suggests that sequence heterochrony is neither pivotal nor prevalent during early skeletal formation in rodent

Skeletogenesis and sequence heterochrony in rodent evolution, with particular emphasis on the African striped mouse, <i>Rhabdomys pumilio</i> (Mammalia)

Data documenting skeletal development in rodents, the most species-rich ‘order’ of mammals, are at present restricted to a few model species, a shortcoming that hinders exploration of the morphological and ecological diversification of the group. In this study we provide the most comprehensive sampling of rodent ossification sequences to date, with the aim of exploring whether heterochrony is ubiquitous in rodent evolution at the onset of skeletal formation. The onset of ossification in 17 cranial elements and 24 postcranial elements was examined for eight muroid and caviomorph rodent species. New data are provided for two non-model species. For one of these, the African striped mouse, Rhabdomys pumilio, sampling was extended by studying 53 autopodial elements and examining intraspecific variation. The Parsimov method of studying sequence heterochrony was used to explore the role that changes in developmental timing play in early skeletal formation. Few heterochronies were found to diagnose the muroid and caviomorph clades, suggesting conserved patterning in skeletal development. Mechanisms leading to the generation of the wide range of morphological diversity encapsulated within Rodentia may be restricted to later periods in development than those studied in this work. Documentation of skeletogenesis in Rhabdomys indicates that intraspecifc variation in ossification sequence pattern is present, though not extensive. Our study suggests that sequence heterochrony is neither pivotal nor prevalent during early skeletal formation in rodents.Facultad de Ciencias Naturales y Muse

Developmental mechanisms of stripe patterns in rodents

Mammalian color patterns are among the most recognizable characters found in nature and can have a profound impact on fitness. However, little is known about the mechanisms underlying their formation and subsequent evolution. Here we show that, in the African striped mouse (Rhabdomys pumilio), periodic dorsal stripes result from underlying differences in melanocyte maturation, which give rise to spatial variation in 6hair color,and we identify the transcription factor Alx3 as a regulator of this process.In 7embryonic dorsal skin, patterned expression of Alx3 foreshadows pigment stripes and acts 8to directly repress Mitf, a master regulator of melanocyte differentiation, giving rise to 9light-colored hair. Moreover, Alx3 is also upregulated in the light stripes of chipmunks, 10which have independently evolved a similar dorsal pattern.Our results reveal a 11previously unappreciated mechanism for modulating spatial variation in hair color and provide new insight into the ways in which phenotypic novelty evolves.Organismic and Evolutionary Biolog

Alternative Reproductive Tactics

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Confusion Effect

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