Are personality differences in a small iteroparous mammal maintained by a life-history trade-off?

Abstract

Despite increasing interest, animal personality is still a puzzling phenomenon. Several theoretical models have been proposed to explain intraindividual consistency and interindividual variation in behaviour, which have been primarily supported by qualitative data and simulations. Using an empirical approach, I tested predictions of one main life-history hypothesis, which posits that consistent individual differences in behaviour are favoured by a trade-off between current and future reproduction. Data on life-history were collected for individuals of a natural population of grey mouse lemurs (Microcebus murinus). Using open-field and novel-object tests, I quantified variation in activity, exploration and boldness for 117 individuals over 3 years. I found systematic variation in boldness between individuals of different residual reproductive value. Young males with low current but high expected future fitness were less bold than older males with high current fecundity, and males might increase in boldness with age. Females have low variation in assets and in boldness with age. Body condition was not related to boldness and only explained marginal variation in exploration. Overall, these data indicate that a trade-off between current and future reproduction might maintain personality variation in mouse lemurs, and thus provide empirical support of this life-history trade-off hypothesis.

Experimental evidence for adaptive personalities in a wild passerine bird

“…The behavioural literature holds various examples of correlations between future assets and risk-taking behaviour that are in line with predictions and found in other species/taxa than great tits (e.g. mammals: [20], birds: [57], fish: [21]). Although such studies do not ultimately allow for confirmation of theoretical predictions because of their non-experimental nature, they do imply that the proposed evolutionary mechanisms revealed in great tits (i.e.…”

“…The idea that individual variation in future fitness expectations would lead to the evolutionary emergence of personality through asset protection has, however, also been criticized because long-term individual differentiation should only emerge in situations where assets and risky behaviour mutually reinforce each other by means of positive feedback mechanisms [19]. Descriptive studies have provided examples of correlations between future assets and risk-taking behaviour that are consistent with predictions of Wolf et al's model [20,21] but these patterns warrant experimental validation. In the current study, we therefore describe manipulations that are known to affect future fitness expectations and explicitly investigate long-term rather than direct (e.g.…”

Senescence or selective disappearance? Age trajectories of body mass in wild and captive populations of a small-bodied primate

“…Longevity is slightly male-biased in our captive study population [19,45] but strongly female-biased in the wild [30]. Roaming by males during the mating season [41] coincides with increased male mortality and, along with an age-associated increase in risk taking by males [46], probably drives the overall sex bias in longevity in the wild [30]. Should this also induce male-biased selective disappearance, wild males that survive to old age may be of exceptionally high quality, whereas the condition of long-lived captive males might be relatively low.…”

“…Selective mortality is presumably more rapid in the wild than in captivity, because weak individuals may more easily succumb to environmental hazards. Wild males had a slightly higher BM than females in their last season of life, which may indicate that female survival depends more on condition, whereas random external mortality may affect males more owing to their risky behaviours [30,46]. BM throughout life was positively associated with lifespan in captivity, indicating that selective disappearance of low-quality individuals operated there also at a longer timescale.…”

Retirement investment theory explains patterns in songbird nest-site choice

“…In such systems, the risk to total fitness is that of adult mortality, which is traded off with some parameter of reproduction such that older animals become more risky with their own lives for the potential reward of reduced risk to their current nest or offspring [11,14]. In our study system, the fitness trade-off is between success of the nest and survival of the fledglings that might emerge from that nest, and the risk-tolerance threshold is associated with adult females facing a timelimited breeding season.…”