Personalities and risk taking behaviour

Since behavioural biologists found evidence that behaviour of individuals is much less flexible than previously thought (R’eale et al. 2007) evolutionary and theoretical biologists developed theories how personalities evolve and how different personality traits coexist in one population (Dingemanse et al. 2010). In this thesis I collect empirical evidence for the model that Wolf et al. 2007 introduced. His model suggests that personality traits are related to differences in risk-taking behaviour. Variation in individual prospects should co vary with risk taking behaviour causing some individuals to show risk prone and other risk aversive behaviour types. I found evidence for this theory in the Namibian rock Agama (Carter et al. 2010), Bluegill-sunfish (Wilson et al. 2009), sticklebacks(Bell. 2006) and wild fiddler crabs (Reaney et al. 2007), but not in great tits (Van Oers et al. 2004), European house crickets (Wilson et al. 2010) and sticklebacks (Bell 2006). In other words there are studies that show a correlation in the occurrence of risky-personality traits within a species, but other studies don’t. This thesis concludes that the relation between different risk-taking behavioural traits is not yet clear. The ecological context influences the correlation between risky-behavioural traits and future research has to provide answers on a more quantitative basis.

Research Report 1: Sanderlings passing by the central Dutch Wadden Sea

De begeleider en/of auteur heeft geen toestemming gegeven tot het openbaar maken van de scriptie. The supervisor and/or the author did not authorize public publication of the thesis.

Sensory ecology of Ruffs (Philomachus pugnax): Why feed by day on night-active worms?

De begeleider en/of auteur heeft geen toestemming gegeven tot het openbaar maken van de scriptie. The supervisor and/or the author did not authorize public publication of the thesis.  

Sex-specific growth in chicks of the sexually dimorphic Black-tailed Godwit

Sexual size dimorphism (SSD) is common in birds and has been linked to various selectiveforces. Nevertheless, the question of how and when the sexes start to differentiatefrom each other is poorly studied. This is a critical knowledge gap, as sex differences ingrowth may cause different responses to similar ecological conditions. In this study, wedescribe the sex-specific growth – based on body mass and five morphometric measurements– of 56 captive Black-tailed Godwit Limosa limosa limosa chicks raised under ad libitumfood conditions, and conclude that all six growth curves are sex-specific. Femalesare the larger sex in terms of body mass and skeletal body size. To test whether sex-specificgrowth leads to sex-specific susceptibility to environmental conditions, we comparedthe age-specific sizes of male and female chicks in the wild with those of Black-tailedGodwits reared in captivity. We then tested for a relationship between residual growthand relative hatching date, age, sex and habitat type in which the wild chicks were born.Early-hatched chicks were relatively bigger and in better condition than late-hatchedchicks, but body condition and size were not affected by natal habitat type. Femalechicks deviated more negatively from the sex-specific growth curves than male chicks forbody mass and total-head length. This suggests that the growth of the larger females ismore susceptible to limiting environmental conditions. On average, the deviations ofwild chicks from the predicted growth curves were negative for all measurements, whichsuggests that conditions are limiting in the current agricultural landscape. We argue thatin estimating growth curves for sexually dimorphic species, it is critical first to makeaccurate sex and age determinations

On the Pruning Experiment of HINOKI (Chamaecyparis abtusa ENDL.) by Randomized Block Design. : Part I. On the Growth during Two Years after Pruning

I 緒言　II 試験地の設定　III 枝打後2年間の成長量　IV 総括　参考文献　ResumeFor the purpose of investigating the influence of pruning on the growth of HINOKI (Chamaecyparis obtusa ENDL), the author established five test areas as shown in the table in Kasuya Experimental Forest attached to the Agricultural Department of Kyushu University, in February 1960. (TABLE) In March 1962, the growths in tree height, diameter at breast height, diameter at 3.2 m height (in Test Area No. 1) or at 5.2 m height (in the other test areas) above the ground and stem volume were measured. The results obtained are summarized as follows. 1) In Test Area No. 1, the growths in the diameter at breast height, diameter at 3.2 m height above the ground and stem volume decreased in proportion to the increase of the degree of pruning, but the growth in tree height was reduced only in case of 80 per cent pruning of tree height. 2) In Test Area No. 2, the growths in each component decreased in proportion to the increase of the degree of pruning. 3) In Test Area No. 3, the diameter at breast height, diameter at 5.2 m height above the ground and stem volume decreased in proportion to the increase of the degree of pruning, but the influence of pruning on the growth in tree height was not observed. 4) In Test Area No. 4, no influence of pruning was observed. 5) In Test Area No. 5, the growths in the diameter at breast height and stem volume decreased in proportion to the increase of the degree of pruning, and the growth in the diameter at 52 m height above the ground was reduced only in case of 80 per cent pruning of tree height. But the growth in tree height was not influenced by pruning

Natal habitat and sex-specific survival rates result in a male-biased adult sex ratio

The adult sex ratio (ASR) is a crucial component of the ecological and evolutionary forces shaping the dynamics of a population. Although in many declining populations ASRs have been reported to be skewed, empirical studies exploring the demographic factors shaping ASRs are still rare. In this study of the socially monogamous and sexually dimorphic Black-tailed Godwit (Limosa limosa limosa), we aim to evaluate the sex ratio of chicks at hatch and the subsequent sex-specific survival differences occurring over 3 subsequent life stages. We found that, at hatch, the sex ratio did not deviate from parity. However, the survival of pre-fledged females was 15–30% lower than that of males and the sex bias in survival was higher in low-quality habitat. Additionally, survival of adult females was almost 5% lower than that of adult males. Because survival rates of males and females did not differ during other life-history stages, the ASR in the population was biased toward males. Because females are larger than males, food limitations during development or sex-specific differences in the duration of development may explain the lower survival of female chicks. Differences among adults are less obvious and suggest previously unknown sex-related selection pressures. Irrespective of the underlying causes, by reducing the available number of females in this socially monogamous species, a male-biased ASR is likely to contribute to the ongoing decline of the Dutch godwit population

Generational shift in spring staging site use by a long-distance migratory bird

In response to environmental change, species have been observed altering their migratory behaviours. Few studies, however, have been able to determine whether these alterations resulted from inherited, plastic or flexible changes. Here, we present a unique observation of a rapid population-level shift in migratory routes—over 300 km from Spain to Portugal—by continental black-tailed godwits Limosa limosa limosa. This shift did not result from adult godwits changing staging sites, as adult site use was highly consistent. Rather, the shift resulted from young godwits predominantly using Portugal over Spain. We found no differences in reproductive success or survival among individuals using either staging site, indicating that the shift resulted from developmental plasticity rather than natural selection. Our results therefore suggest that new migratory routes can develop within a generation and that young individuals may be the agents of such rapid changes

Misidentification errors in reencounters result in biased estimates of survival probability from CJS models: Evidence and a solution using the robust design

Misidentification of marked individuals is unavoidable in most studies of wild animal populations. Models commonly used for the estimation of survival from such capture–recapture data ignore misidentification errors potentially resulting in biased parameter estimates. With a simulation study, we show that ignoring misidentification in Cormack–Jolly–Seber (CJS) models results in systematic positive biases in the estimates of survival and in spurious declines of survival over time. We developed an extended robust design capture mark–resight (RDM) model that includes correct identification parameters to get unbiased survival estimates when resighting histories are prone to misidentification. The model assumes that resightings occur repeatedly within a season, which in practice is often the case when resightings of colour-marked individuals are collected. We implemented the RDM model in a state-space formulation and also an approximate, but computationally faster, model (RDMa) in JAGS and evaluated their performances using simulated and empirical capture–resight data on black-tailed godwits Limosa limosa. The CJS models applied to simulated data under an imperfect identification scenario data produced strongly positively biased estimates of survival. For a range of degrees of correct identification probabilities, the RDM model provided unbiased and accurate estimates of survival, reencounter and correct-identification probabilities. The RDMa model performed well for large datasets (>25 individuals), with high resighting (>0.3) and high correct identification (>0.7) probabilities. For the empirical data, the CJS model estimated average juvenile survival at 0.997% and adult survival at 0.939% and also detected a strong decline in adult survival over time at a rate of −0.14 ± 0.029. In contrast, the RDMa model estimated a probability of correct identification of 0.94, annual juvenile survival at 0.234%, adult at 0.834% and less strong decline over time (−0.046 ± 0.016). We conclude that estimates of survival probabilities obtained from data that include misidentification errors and analysed with standard CJS model are unlikely to be correct. The bias in survival increases with the magnitude of misidentification errors, which is inevitable as datasets become longer. Since misidentification due to tag misreads is common in empirical data, we recommend the use of the here presented RDM model to provide unbiased parameter estimates