Costs of sleeping in Greives, Timothy J.; Kingma, Sjouke A.; Kranstauber, Bart ...
Functional ecology,
October 2015, Letnik:
29, Številka:
10
Journal Article
Recenzirano
Odprti dostop
Summary
Circadian (i.e. daily) regulation of behaviours is thought to provide fitness benefits to organisms by enabling them to anticipate diel changes in the environment, such as sunrise.
A common ...behaviour among socially monogamous songbirds that usually takes place in the early mornings is extra‐pair mating, that is copulating with partners outside of the social pair bond.
Thus, variation in when individuals begin their daily activity may influence their reproductive success; early risers may be better able to gain copulations and guard their partners, thus minimizing their risk of being cuckolded compared with late risers. Sexual selection may thus play an important role in shaping circadian behaviours, but this assumption has yet to be tested in free‐living animals.
Here, we experimentally weakened endogenous circadian rhythmicity, and thus, anticipation of dawn in male great tits (Parus major) in the wild through the subcutaneous administration of implants filled with melatonin shortly before egg‐laying began in this population. Melatonin is a hormone released during the dark phase at night and is one important cue animals use to entrain their circadian clock.
Experimental individuals delayed the onset of daily activity compared with controls and were more likely to be cuckolded compared with control males. Manipulation did not alter other behavioural traits observed; no difference between treatments was observed in activity levels during the day or in the end time of daily activity.
These results strongly support the assumption that selection, particularly sexual selection, shapes the circadian phenotypes of wild vertebrates which enable anticipation of important and predictive diel changes in an individual's biotic and abiotic environment.
Lay Summary
Maternal egg hormones in the mating context Ruuskanen, Suvi; Groothuis, Ton G. G.; Baugh, Alexander T. ...
Functional ecology,
02/2018, Letnik:
32, Številka:
2
Journal Article
Recenzirano
Odprti dostop
Animal personality traits emerge developmentally from the interaction of genetic and early environmental factors. Maternal hormones, such as androgens (testosterone, T and androstenedione, A4), ...transferred to embryos and egg yolks may simultaneously organize multiple behavioural and physiological traits. Although previous studies demonstrated an association between the mother's personality and yolk androgen levels, the independent effects of the male partner's personality and pair combination remains unknown.
We test this association using an ecological model species for personality research, the great tit (Parus major) using multiple approaches: (1) a wild population, (2) a randomly mated captive population and (3) an experimental study with (dis)assortatively mated pairs from lines selected for fast exploration/boldness or slow exploration/shyness.
Egg androgen concentrations were associated with variation in female personality traits, and the experimental data suggested that this is independent of male personality: Experimental females from the slow‐shy line tended to have higher egg T concentrations than females from the fast‐bold line, with no effect of male personality. Shy females from the wild population had higher egg A4 concentration than bold females. However, in the correlative data yolk hormones were linked with male personality, as well as the interaction between female and male traits: Male handling responsiveness correlated negatively with egg A4 concentration in wild birds. In randomly mated birds, pairs that were mated assortatively for personality had lower egg T concentrations than disassortatively mated pairs.
Given that egg androgens are known mediators of avian personality, our results suggest that maternal hormones might contribute to the heritability of personality, may be sensitive to the social context of mating, and act as key drivers of individual differences.
A plain language summary is available for this article.
Plain Language Summary
Behaviour under conditions of mild stress shows consistent patterns in all vertebrates: exploratory behaviour, boldness, aggressiveness covary in the same way. The existence of highly consistent ...individual variation in these behavioural strategies, also referred to as personalities or coping styles, allows us to measure the behaviour under standardized conditions on birds bred in captivity, link the standardized measurements to the behaviour under natural conditions and measure natural selection in the field. We have bred the great tit (Parus major), a classical model species for the study of behaviour under natural conditions, in captivity. Here, we report a realized heritability of 54±5% for early exploratory behaviour, based on four generations of bi-directional artificial selection. In addition to this, we measured hand-reared juveniles and their wild-caught parents in the laboratory. The heritability found in the mid-offspring-mid-parent regression was significantly different from zero. We have thus established the presence of considerable amounts of genetic variation for personality types in a wild bird.
Highlights ► We tested for a link between personality and corticosterone responses in great tits. ► Artificial selection on a composite personality score resulted in differences in CORT responses. ► ...The slow-shy line had higher stress-induced levels than the fast-bold line. ► In non-selected birds exploratory behavior did not co-vary with CORT levels. ► Selection on personality structure drives a correlated response in HPA reactivity.
Many putative Batesian mimics only approximately resemble their supposed models, and such "imperfect" mimics are readily distinguished from defended species by humans and other vertebrates. One ...explanation for the existence of imperfect mimics is that the most important predators of many mimics have very different sensory and cognitive abilities from those of a typical vertebrate. In such circumstances, selection for more accurate mimicry, as perceived by humans, may be reduced. Little is known, however, about how invertebrate predators perceive and respond to mimicry in insect prey. Here, we investigate the foraging behavior of the crab spider Synema globosum, an important predator of flower-visiting insects at our field site, which frequently encounters both Batesian mimics (hoverflies-Diptera: Syrphidae) and their models (bees and wasps-Hymenoptera). In the field, we found that spiders can distinguish among dipteran and hymenopteran prey taxa, frequently attacking some models and mimics, but avoiding others. Laboratory experiments suggest that some apparently accurate mimic taxa are more likely to be avoided when spiders have prior experience of an aversive wasp model. Avoidance by spiders of black and yellow striped artificial prey suggests visual cues play a role in prey selection, but there was no evidence that olfactory cues are used to identify dangerous or noxious species. Overall, our results provide some support for the hypothesis that invertebrate predator behavior can generate selection on visual signals in putative Batesian mimics.
Our study tested whether two European bird‐specialized ticks, Ixodes arboricola and I. frontalis, can act as vectors in the transmission cycles of Borrelia burgdorferi s.l. The ticks have contrasting ...ecologies but share songbird hosts (such as the great tit, Parus major) with the generalist I. ricinus which may therefore act as a bridging vector. In the first phase of the experiment, we obtained Borrelia‐infected ornithophilic nymphs by exposing larvae to great tits that had previously been exposed to I. ricinus nymphs carrying a community of genospecies (Borrelia garinii, valaisiana, afzelii, burgdorferi s.s., spielmanii). Skin samples showed that birds selectively amplified B. garinii and B. valaisiana. The spirochetes were transmitted to the ornithophilic ticks and survived moulting, leading to infection rates of 16% and 27% in nymphs of I. arboricola and I. frontalis respectively. In the second phase, pathogen‐free great tits were exposed to the Borrelia‐infected ornithophilic nymphs. None of these ticks were able to infect the birds, as indicated by the tissue samples. Analysis of xenodiagnostic I. ricinus larvae found no evidence for co‐feeding or systemic transmission of B. burgdorferi s.l. These outcomes do not support the occurrence of enzootic cycles of Borrelia burgdorferi s.l. involving songbirds and their specialized ornithophilic ticks.
Anthropogenic pollution is known to negatively influence an organism's physiology, behaviour, and fitness. Epigenetic regulation, such as DNA methylation, has been hypothesized as a potential ...mechanism to mediate such effects, yet studies in wild species are lacking. We first investigated the effects of early-life exposure to the heavy metal lead (Pb) on DNA methylation levels in a wild population of great tits (Parus major), by experimentally exposing nestlings to Pb at environmentally relevant levels. Secondly, we compared nestling DNA methylation from a population exposed to long-term heavy metal pollution (close to a copper smelter), where birds suffer from pollution-related decrease in food quality, and a control population. For both comparisons, the analysis of about one million CpGs covering most of the annotated genes revealed that pollution-related changes in DNA methylation were not genome wide, but enriched for genes underlying developmental processes. However, the results were not consistent when using binomial or beta binomial regression highlighting the difficulty of modelling variance in CpGs. Our study indicates that post-natal anthropogenic heavy metal exposure can affect methylation levels of development related genes in a wild bird population.
BACKGROUND: Variation in early nutrition is known to play an important role in shaping the behavioural development of individuals. Parental prey selection may have long-lasting behavioural ...influences. In birds foraging on arthropods, for instance, the specific prey types, e.g. spiders and caterpillars, matter as they have different levels of taurine which may have an effect on personality development. Here we investigated how naturally occurring variation in the amounts of spiders and caterpillars, provisioned to nestlings at day 4 and 8 after hatching, is related to the response to handling stress in a wild passerine, the great tit (Parus major). Broods were cross-fostered in a split-brood design allowing us to separate maternal and genetic effects from early rearing effects. Adult provisioning behaviour was monitored on day four and day eight after hatching using video recordings. Individual nestlings were subjected to a handling stress test at an age of 14 days, which is a validated proxy for exploratory behaviour as an adult. RESULTS: Variation in handling stress was mainly determined by the rearing environment. We show that, contrary to our predictions, not the amount of spider biomass, but the amount of caterpillar biomass delivered per nestling significantly affected individual performance in the stress test. Chicks provisioned with lower amounts of caterpillars exhibited a stronger stress response, reflecting faster exploratory behaviour later on in life, than individuals who received larger amounts of caterpillars. CONCLUSIONS: These results suggest that natural variation in parental behaviour in wild birds modulates the developmental trajectories of their offspring's personality via food provisioning. Since parental provisioning behaviour might also reflect the local environmental conditions, provisioning behaviour may influence how nestlings respond to these local environmental conditions.
Identifying the environmental drivers of variation in fitness‐related traits is a central objective in ecology and evolutionary biology. Temporal fluctuations of these environmental drivers are often ...synchronized at large spatial scales. Yet, whether synchronous environmental conditions can generate spatial synchrony in fitness‐related trait values (i.e., correlated temporal trait fluctuations across populations) is poorly understood. Using data from long‐term monitored populations of blue tits (Cyanistes caeruleus, n = 31), great tits (Parus major, n = 35), and pied flycatchers (Ficedula hypoleuca, n = 20) across Europe, we assessed the influence of two local climatic variables (mean temperature and mean precipitation in February–May) on spatial synchrony in three fitness‐related traits: laying date, clutch size, and fledgling number. We found a high degree of spatial synchrony in laying date but a lower degree in clutch size and fledgling number for each species. Temperature strongly influenced spatial synchrony in laying date for resident blue tits and great tits but not for migratory pied flycatchers. This is a relevant finding in the context of environmental impacts on populations because spatial synchrony in fitness‐related trait values among populations may influence fluctuations in vital rates or population abundances. If environmentally induced spatial synchrony in fitness‐related traits increases the spatial synchrony in vital rates or population abundances, this will ultimately increase the risk of extinction for populations and species. Assessing how environmental conditions influence spatiotemporal variation in trait values improves our mechanistic understanding of environmental impacts on populations.
Territorial animals often use signals to advertise territorial occupancy within their larger home ranges. Songbirds are among the best-studied territorial signaling taxa, and when competitors start ...singing during a territorial intrusion, residents usually show elevated spatial and vocal responses. These responses could be used by intruders and distant eavesdroppers to predict future responses or to compare responses across competitors. Yet, the extent to which responses of a resident to a territorial intrusion predict its future responses and its overall spatial behavior (home range) within a neighborhood is less well understood. We used wild great tits (
Parus major
) as a model species in repeated song playback trials, simulating territorial intrusions combined with radio-tracking before and during playback trials. The time spent close to the loudspeaker in response to an initial simulated intrusion predicted the same response variable during a second simulated intrusion on the next day, whereas singing activity during the first simulated intrusion did not predict singing during the second simulated intrusion. We also show that more explorative males (as determined by a novel environment test) and males with smaller home ranges sang more and spent more time near the loudspeaker in response to both simulated intrusions. Thus, by probing residents, intruders can obtain reliable information about subsequent response probabilities, while eavesdroppers from a distance, who can use auditory information only, would not receive sufficient predictive information. Our findings also suggest that males with larger home ranges are more tolerant toward intruders, which could reflect a trade-off between tendencies to respond strongly and to range widely. The lack of predictability of singing activity with regard to responses to future intrusions might explain why territorial animals continuously exchange vocal signals and regularly foray into neighboring territories, as a way to obtain regular information updates.
Significance Statement
Animals use experience from interactions with conspecifics in their future decision making, such as mate choice and strategies for conflict resolution. The value of such information depends in part on the predictability of the future behavior of that conspecific. In songbirds, territorial individuals respond to intruders by approach and signaling. Here, we tested in radio-tagged great tits (
Parus major
) if territorial responses are predictable and are affected by individual and environmental factors. We show that the time spent near the simulated intruder was more predictable than singing activity and that birds with larger home ranges showed weaker responses. These findings suggest that information based on such spatial responses is more useful for future decision making, as compared to vocal information, and that distant eavesdroppers will thus receive less reliable information. Limited predictability may explain why territorial animals continuously exchange vocal signals and foray into neighboring territories, providing opportunities for regular information updates.
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