Tolerant mothers: aggression does not explain solitary living in the bush Karoo rat.

Many mammal species are thought to adopt solitary living owing to mothers becoming intolerant of adult offspring and the occurrence of social intolerance between adults. However, field studies on how solitary mammals interact are rare. Here we show that solitary living can occur without social intolerance.

Quick Guide to Evolutionary Medicine in Neuroimmunomodulation: Why "Evolved for the Benefit of the Species" Is Not a Valid Argument.

Background: Evolutionary medicine builds on evolutionary biology and explains why natural selection has left us vulnerable to disease. Unfortunately, several misunderstandings exist in the medical literature about the levels and mechanisms of evolution. Reasons for these problems start from the lack of teaching evolutionary biology in medical schools.

Cognitive performance is linked to survival in free-living African striped mice.

Cognition is shaped by evolution and is predicted to increase fitness. However, the link between cognition and fitness in free-living animals is unresolved. We studied the correlates of cognition and survival in a free-living rodent inhabiting an arid environment.

Harshness is not stress.

We must differentiate between stressful and harsh environments to understand animals' resilience to global change. Harshness is not stress. Stressful environments activate the physiological stress response to increase energy availability, while harsh environments inhibit the physiological stress response to save energy.

Seasonal changes in problem-solving in wild African striped mice.

Innovative problem-solving ability is a predictor of whether animals can successfully cope with environmental changes. These environmental changes can test the limits of animals, for example when energy availability decreases seasonally and, hence, problem-solving performance decreases because less energy is available for cognitive processes. Here, we investigated: (1) how problem-solving performance changed between seasons that differed significantly in food availability; (2) whether these changes were related to environmentally induced physiological changes in blood glucose and ketone levels, indicators of energy availability; and (3) whether individual variation in problem-solving was related to sex differences.

Corona, Climate Change, and Evolved Human Behavior.

Most scientists agree that we have to restrict climate change, but there is much frustration that we are failing. The Corona Crisis exemplifies how human behavior is constrained by its evolution, cognition, and resource availability, explaining why we do not act to avoid climate change for the benefit of future generations.

Do alternative reproductive tactics predict problem-solving performance in African striped mice?

In changing environments, animals face unexpected problems to solve. Not all individuals in a population are equally able to solve new problems. It still remains unclear what factors (e.

Seasonal variation in telomere dynamics in African striped mice.

Telomere shortening has been used as an indicator of aging and is believed to accelerate under harsh environmental conditions. This can be attributed to the fact that telomere shortening has often been regarded as non-reversible and negatively impacting fitness. However, studies of laboratory mice indicate that they may be able to repair telomere loss to recover from environmental harshness, as indicated by recent studies in hibernating rodents.

Fat content of striped mice decreases during the breeding season but not during the food-restricted dry season.

Individuals that are capable of accumulating appropriate fat stores are assumed to have selective advantages when food becomes scarce. Similarly to species from temperate zones, some species inhabiting arid areas accumulate fat stores prior to periods of food limitation. Yet, we have little knowledge concerning seasonal variation in body composition and the relationship between fat store size and disappearance risk in species from arid habitats.

Elevated basal corticosterone levels increase disappearance risk of light but not heavy individuals in a long-term monitored rodent population.

According to the cort-fitness hypothesis, glucocorticoid levels correlate negatively with fitness. However, field studies found mixed support for this hypothesis, potentially because the association between glucocorticoids and fitness might depend on prevailing environmental conditions. Based on the long-term monitoring of a natural rodent population, we tested whether individuals with elevated corticosterone levels were more likely to disappear, accounting for individual condition and among-year variation in food availability, population density and predation pressure.

Daily energy expenditure of males following alternative reproductive tactics: Solitary roamers spend more energy than group-living males.

In many species, males follow alternative reproductive tactics (ARTs), where one tactic (called bourgeois) has much higher reproductive success than alternative tactics followed by males with lower competitive ability. The extent to which ARTs differ in energetic costs is unknown, but it is important to understand the fitness payoffs of ARTs. We studied male African striped mice (Rhabdomys pumilio) which follow one of three ARTs: heavy bourgeois males defend harems of females and have 10 times higher reproductive success than smaller roamers, which have ten times higher reproductive success than philopatric males, which remain in their natal group and are the smallest males.

Density feedbacks mediate effects of environmental change on population dynamics of a semidesert rodent.

Population dynamics are the result of an interplay between extrinsic and intrinsic environmental drivers. Predicting the effects of environmental change on wildlife populations therefore requires a thorough understanding of the mechanisms through which different environmental drivers interact to generate changes in population size and structure. In this study, we disentangled the roles of temperature, food availability and population density in shaping short- and long-term population dynamics of the African striped mouse, a small rodent inhabiting a semidesert with high intra- and interannual variation in environmental conditions.

Seasonal variation in energy expenditure in a rodent inhabiting a winter-rainfall desert.

Animals that spend more energy than they obtain risk entering allostatic overload, reducing survival and fitness. They are predicted to adjust their daily energy expenditure (DEE) during periods of food scarcity. Adjustments of DEE to changes in food availability have been well-studied in species in temperate zones during winter, but less so in species enduring seasonal droughts.

The neoteny-helper hypothesis: When to expect and when not to expect endocrine mechanisms to regulate allo-parental care?

Family groups with helpers occur in several species of fish, birds and mammals. In such cooperatively breeding species all group members help with raising the offspring, i.e.

Intra-specific variation in social organization of Strepsirrhines.

Strepsirrhines, that is, lemurs, galagos, and lorises, are considered basal primates, making them important to understand the evolution of primate sociality. Apart from some lemurs, they are nocturnal and solitary living, though the view of their sociality nature has changed with field studies being completed. We conducted a review of the primary literature about the social organization (group composition) of strepsirrhines, with the aim to determine whether intra-specific variation in social organization (IVSO) occurs and to determine how many species are pair-living, group-living, or solitary living.

African striped mice.

Mallarino et al. introduce the African striped mouse, which is being used in a number of fields of research, including animal behavior, evolutionary developmental biology, and chronobiology.

Active and explorative individuals are often restless and excluded from studies measuring resting metabolic rate: Do alternative metabolic rate measures offer a solution?

It has often been proposed that bolder, more explorative or more active individuals also have a higher resting metabolic rate (RMR), indicating metabolic costs of these personality types. However, such individuals might often be restless and thus excluded from RMR datasets, leading to a significant sampling bias. We tested (1) whether such a bias occurs when animals are measured for a relatively common but short time period of 3h, and if so, (2) whether alternative measures of metabolic rate, that allow the incorporation of non-resting individuals, would reveal associations between metabolism and personality.