Factors affecting male and female reproductive success in a chipmunk (Tamias sibiricus) with a scramble competition mating system

Pet cat personality linked to owner-reported predation frequency

The domestic cat, Felis catus, is one of the most popular and widespread domestic animals. Because domestic cats can reach high population densities and retain at least some tendency to hunt, their overall impact on wildlife can be severe. Domestic cats have highly variable predation rates depending on the availability of prey in their environment, their owners' practices, and individual cat characteristics. Among these characteristics, cat personality has recently been hypothesized to be an important factor contributing to variations in the hunting activity of cats. In this study, we surveyed 2508 cat owners living in France about their cats' personalities, using the Feline Five personality framework, and the frequency with which cats bring home prey. Personality traits were analyzed using factor analysis and related to predation frequency using cumulative logit models. For both birds and small mammals, cats with high levels of extraversion or low levels of neuroticism had significantly higher frequencies of prey return. Owners whose cats had low levels of agreeableness or high levels of dominance reported a significantly lower frequency of bird return. Personality differences therefore seem to contribute to the high variability in predation rates among domestic cats. We also found that the owner-reported prey return frequencies were significantly higher for cats spending more time outdoors, for non-pedigree cats, and for owners living in rural or suburban areas as opposed to urban areas. By contrast, we did not detect an effect of cat sex or age on their reported prey return rates.

A meta-analysis of sex differences in animal personality: no evidence for the greater male variability hypothesis

The notion that men are more variable than women has become embedded into scientific thinking. For mental traits like personality, greater male variability has been partly attributed to biology, underpinned by claims that there is generally greater variation among males than females in non-human animals due to stronger sexual selection on males. However, evidence for greater male variability is limited to morphological traits, and there is little information regarding sex differences in personality-like behaviours for non-human animals. Here, we meta-analysed sex differences in means and variances for over 2100 effects (204 studies) from 220 species (covering five broad taxonomic groups) across five personality traits: boldness, aggression, activity, sociality and exploration. We also tested if sexual size dimorphism, a proxy for sex-specific sexual selection, explains variation in the magnitude of sex differences in personality. We found no significant differences in personality between the sexes. In addition, sexual size dimorphism did not explain variation in the magnitude of the observed sex differences in the mean or variance in personality for any taxonomic group. In sum, we find no evidence for widespread sex differences in variability in non-human animal personality.

Diversification, Introgression, and Rampant Cytonuclear Discordance in Rocky Mountains Chipmunks (Sciuridae: Tamias)

Evidence from natural systems suggests that hybridization between animal species is more common than traditionally thought, but the overall contribution of introgression to standing genetic variation within species remains unclear for most animal systems. Here, we use targeted exon-capture to sequence thousands of nuclear loci and complete mitochondrial genomes from closely related chipmunk species in the Tamias quadrivittatus group that are distributed across the Great Basin and the central and southern Rocky Mountains of North America. This recent radiation includes six overlapping, ecologically distinct species (T. canipes, T. cinereicollis, T. dorsalis, T. quadrivittatus, T. rufus, and T. umbrinus) that show evidence for widespread introgression across species boundaries. Such evidence has historically been derived from a handful of markers, typically focused on mitochondrial loci, to describe patterns of introgression; consequently, the extent of introgression of nuclear genes is less well characterized. We conducted a series of phylogenomic and species-tree analyses to resolve the phylogeny of six species in this group. In addition, we performed several population genomic analyses to characterize nuclear genomes and infer coancestry among individuals. Furthermore, we used emerging quartets-based approaches to simultaneously infer the species tree (SVDquartets) and identify introgression (HyDe). We found that, in spite of rampant introgression of mitochondrial genomes between some species pairs (and sometimes involving up to three species), there appears to be little to no evidence for nuclear introgression. These findings mirror other genomic results where complete mitochondrial capture has occurred between chipmunk species in the absence of appreciable nuclear gene flow. The underlying causes of recurrent massive cytonuclear discordance remain unresolved in this group but mitochondrial DNA appears highly misleading of population histories as a whole. Collectively, it appears that chipmunk species boundaries are largely impermeable to nuclear gene flow and that hybridization, while pervasive with respect to mtDNA, has likely played a relatively minor role in the evolutionary history of this group.

Male energy reserves, mate-searching activities, and reproductive success: alternative resource use strategies in a presumed capital breeder

Sexual selection studies often focus on morphological traits that are important only in the later stages of mate acquisition. Comparatively little is known about traits that lead to mate acquisition, such as mate-searching activities. We experimentally manipulated body condition (i.e., the energy reserves) in male puff adders (Bitis arietans) prior to the mating season using supplemental feeding in the field, and used radio-telemetry and DNA paternity analyses to characterize the relationships between male energy reserves, mating activities, and reproductive success. We found that male mobility is a strongly sexually selected trait because males that travelled further in search of females have higher female encounter rates and reproductive success. However, supplemental feeding did not have a significant effect on mating activities or reproductive success, because control snakes compensated by foraging more often during the mating season. The time invested in foraging by control snakes did not come at the costs of decreased mating activities or opportunity compared to fed snakes, because the latter spent the spare time resting. Our experimental field research directly demonstrates the link between male mobility and reproductive success, identifying the ultimate mechanism leading to the evolution of prolonged male mate-searching activities in snakes, and indicates that male puff adders, presumed capital breeders, adjust their breeding tactics according to resource availability.

Within- and between-year variations of reproductive strategy and cost in a population of Siberian chipmunks

Reproduction costs depend on the general life-history strategies employed by organisms for resource acquisition, the decision rules on resource allocation, and the resource availability. Although the predictability of resource availability is expected to influence the breeding strategy, the relationship between predictability and strategy has rarely been investigated at the population level. One reason is that, while the resource availability is commonly variable in space and time, their predictability is generally assumed constant. Here, we addressed the temporal variation of the breeding strategy and its associated survival cost in a hibernating population of Tamias sibiricus, in which food resources vary in their availability between years and in their predictability within years. Based on 11 years of mark-recapture data, we used multi-event modelling to investigate seasonal variations in reproduction costs of female chipmunks that breed twice a year (spring and summer). In summer, during which a large variety and quantity of resources is available (income breeding strategy), the proportion of breeding females was consistent across years and reproduction yielded no mortality cost. In contrast, in spring, the proportion of breeding females was positively correlated with the amount of resources available for hibernation (partial capital breeding strategy). Spring reproduction yielded no immediate cost, but induced a delayed mortality cost over the next winter if future unknown conditions were unfavorable. Our findings highlight complex temporal reproductive patterns in a short-lived species: not only does the modality of resource acquisition vary among seasons, but also the decision rule to breed and its associated cost.

Inter-annual and inter-individual variations in survival exhibit strong seasonality in a hibernating rodent

Most research on the demography of wild animal populations has focused on characterizing the variation in the mortality of organisms as a function of intrinsic and environmental characteristics. However, such variation in mortality is difficult to relate to functional life history components (e.g. reproduction, dispersal, hibernation) due to the difficulty in monitoring biological processes at a sufficiently fine timescale. In this study, we used a 10-year individual-based data set with an infra-annual timescale to investigate both intra- and inter-annual survival patterns according to intrinsic and environmental covariates in an introduced population of a small hibernating rodent, the Siberian chipmunk. We compared three distinct periods related to particular life history events: spring reproduction, summer reproduction and hibernation. Our results revealed strong interactions between intrinsic and temporal effects. First, survival of male chipmunks strongly decreases during the reproduction periods, while survival is high and equal between sexes during hibernation. Second, the season of birth affects the survival of juveniles during their first hibernation, which does not have long-lasting consequences at the adult stage. Third, at an inter-annual scale, we found that high food resource availability before hibernation and low chipmunk densities specifically favour subsequent winter survival. Overall, our results confirm that the well-known patterns of yearly and inter-individual variation of mortality observed in animals are themselves strongly variable within a given year, suggesting that they are associated with various functional components of the animals' life history.

Seasonal variation in infestations by ixodids on Siberian chipmunks: effects of host age, sex, and birth season

In mammalian hosts, macroparasite aggregation is highly heterogeneous over space and time and among individuals. While the exact causes of this heterogeneity remain unclear, it has mainly been attributed to individual differences in exposure and susceptibility. Although some extrinsic (e.g., parasite availability) and intrinsic (e.g., sex or age) factors are well known to affect infestation patterns, the joint and possibly interacting effects of these factors are poorly understood. Here, we study the infestation of hard ticks (mainly Ixodes ricinus) in a small rodent, the Siberian chipmunk (Tamias sibiricus), introduced to an oak-hornbeam forest in France. We investigate the seasonal variation in infestation according to the sex, age, birth season (spring-born or summer-born), and body weight of individual hosts while controlling for interannual variability. During the 10-year study period, 3421 tick count events were recorded involving 1017 chipmunks monitored by the capture-mark-recapture procedure. Our results reveal a male-biased parasitism in the Siberian chipmunk, which is not consistent among individuals born in different seasons. This sex bias is observed among spring-born juveniles from July to the beginning of hibernation. For adults, this difference becomes apparent along the reproduction period (May-September) for summer-born adults only. These complex interactions between sex, age, and birth season suggest overall that the seasonal variation of tick load is critically linked to the reproductive behavior of this small ground sciurid.

Rates of agonism among female primates: a cross-taxon perspective

Agonism is common in group-living animals, shaping dominance relationships and ultimately impacting individual fitness. Rates of agonism vary considerably among taxa, however, and explaining this variation has been central in ecological models of female social relationships in primates. Early iterations of these models posited a link to diet, with more frequent agonism predicted in frugivorous species due to the presumed greater contestability of fruits relative to other food types. Although some more recent studies have suggested that dietary categories may be poor predictors of contest competition among primates, to date there have been no broad, cross-taxa comparisons of rates of female-female agonism in relation to diet. This study tests whether dietary variables do indeed predict rates of female agonism and further investigates the role of group size (i.e., number of competitors) and substrate use (i.e., degree of arboreality) on the frequency of agonism. Data from 44 wild, unprovisioned groups, including 3 strepsirhine species, 3 platyrrhines, 5 colobines, 10 cercopithecines, and 2 hominoids were analyzed using phylogenetically controlled and uncontrolled methods. Results indicate that diet does not predict agonistic rates, with trends actually being in the opposite direction than predicted for all taxa except cercopithecines. In contrast, agonistic rates are positively associated with group size and possibly degree of terrestriality. Competitor density and perhaps the risk of fighting, thus, appear more important than general diet in predicting agonism among female primates. We discuss the implications of these results for socio-ecological hypotheses.