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 evolution and socio-ecology of two populations of the Vlei Rat, Otomys irroratus.

Thesis (Ph.D.)-University of Natal, Durban, 1993.This work investigated two important evolutionary processes - speciation and adaptive variation - in two chromosomally-distinct allopatric Natal Midlands populations of the vlei rat Otomys irroratus. The two populations, at Kamberg and Karkloof, differ in the presence of a tandem fusion between chromosomes seven and 12 in the Kamberg karyotype. Speciation studies considered possible reproductive isolating mechanisms. In studies of adaptive variation, socio-ecological characteristics of both populations were investigated. Data on breeding and postnatal development provided evidence of post-zygotic barriers. Interpopulation pairs had reduced breeding success compared to intrapopulation pairs, and some hybrids died before weaning. Surviving hybrids had reduced growth rates, and almost all were sterile. In tests of pre-mating reproductive isolation, ethological barriers were emphasized. Individuals preferred same-population mates, suggesting the existence of mate recognition, which was achieved by means of population-specific courtship behaviour and communication, particularly olfactory, tactile and visual cues. No evidence of population-specific acoustic signals was found, although acoustic cues were associated with agonistic interaction, complementing other communicatory cues to promote increased aggression during interpopulation pairings. Laboratory studies of behaviour and morphology and field work (trapping and habitat assessment) provided information about socio-ecological parameters. The Kamberg habitat was harsher than the Karkloof one, as revealed by differences in seasonal and spatial availability of food and·cover. Cover was the key determinant of the level of sociability of both populations. Sparse, patchy cover selected for a partially communal social system in Kamberg o. irroratus: females were intrasexually tolerant and males were intrasexually highly aggressive. This, in conjunction with male-biased sexual dimorphism, implied that mating was polygynous. Abundant, uniform cover selected for a dispersed social system in Karkloof o. irroratus: females were intrasexually less tolerant than males. Ritualized aggression between males and a low degree of male-biased sexual dimorphism suggested that male may have overlapping home ranges in nature and that mating is promiscuous. Females possibly mated with dominant males, however. Contrasting social systems suggest that adaptation to local environmental circumstances has occurred in allopatry, and that Kamberg and Karkloof o. irroratus are undergoing adaptive speciation. Post-zygotic and pre-mating reproductive barriers appear to have evolved independently in both populations, and could potentially impede gene flow between the populations should they become sympatric. The presence of the tandem fusion in the Kamberg karyotype which, together with genetically-determined factors, may have caused hybrid sterility, suggests that this population is a chromosomally-determined incipient sibling species

Editorial: Proximate and ultimate approaches to behavior in a changing world

[Extract] Tinbergen's (1963) classic four questions for the study of animal behavior have been applied across a range of study species and contexts and provide a solid foundation for understanding species' responses to rapid environmental change. Tinbergen's (1963) proximate questions include understanding the mechanisms (causation) and development (ontogeny) of behavior, while the ultimate questions include understanding the function (adaptive significance) and evolution of behavior. Integrating proximate and ultimate approaches to understanding behavior in an increasingly human-dominated world gives insights into broader conservation and management strategies for mitigating the negative effects on animal species. The current collection of research reports provides insights into how a changing world affects different species, and provides some context for Tinbergen's focus. The contributors to this special issue demonstrate a varied and diverse approach to this topic, highlighting the inclusive nature of Tinbergen's approach to the study of animal behavior. While broad-scale conclusions cannot be drawn, the range of topics showcases how different experts are tackling these questions from a variety of angles

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

Problem solving in animals: proposal for an ontogenetic perspective

Problem solving, the act of overcoming an obstacle to obtain an incentive, has been studied in a wide variety of taxa, and is often based on simple strategies such as trial-and-error learning, instead of higher-order cognitive processes, such as insight. There are large variations in problem solving abilities between species, populations and individuals, and this variation could arise due to differences in development, and other intrinsic (genetic, neuroendocrine and aging) and extrinsic (environmental) factors. However, experimental studies investigating the ontogeny of problem solving are lacking. Here, we provide a comprehensive review of problem solving from an ontogenetic perspective. The focus is to highlight aspects of problem solving that have been overlooked in the current literature, and highlight why developmental influences of problem-solving ability are particularly important avenues for future investigation. We argue that the ultimate outcome of solving a problem is underpinned by interacting cognitive, physiological and behavioural components, all of which are affected by ontogenetic factors. We emphasise that, due to the large number of confounding ontogenetic influences, an individual-centric approach is important for a full understanding of the development of problem solving