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Biomedical subjects

Louis Lefebvre

Publications and source records attributed to Louis Lefebvre.

12 recordsLinked to original sources
PubMed2007

Social learning and innovation are positively correlated in pigeons (Columba livia).

When animals show both frequent innovation and fast social learning, new behaviours can spread more rapidly through populations and potentially increase rates of natural selection and speciation, as proposed by A.C. Wilson in his behavioural drive hypothesis. Comparative work on primates suggests that more innovative species also show more social learning. In this study, we look at intra-specific variation in innovation and social learning in captive wild-caught pigeons. Performances on an innovative problem-solving task and a social learning task are positively correlated in 42 individuals. The correlation remains significant when the effects of neophobia on the two abilities are removed. Neither sex nor dominance rank are associated with performance on the two tasks. Free-flying flocks of urban pigeons are able to solve the innovative food-finding problem used on captive birds, demonstrating it is within the range of their natural capacities. Taken together with the comparative literature, the positive correlation between innovation and social learning suggests that the two abilities are not traded-off.

Animals↗
PubMed2006

Stealing of dunked food in Carib grackles (Quiscalus lugubris).

The use of tool or tool-like food processing behaviours can render animals vulnerable to theft (kleptoparasitism) because (1) large, nutritious items are usually involved, (2) value is added to the food due to long and/or complex handling, and (3) physical control of items is often temporarily lost during handling. In Barbados, Carib grackles (Quiscalus lugubris) immersing items in water before consumption (a behaviour known as food dunking) lose a larger proportion of items to conspecific food thieves than grackles that do not dunk. In this paper, we first show that dunking in Carib grackles functions as a proto-tool food-processing technique that speeds up ingestion. We then examine five potential predictors of kleptoparasitism: only conspecific density and loss of physical control on food were found to influence the probability that birds would be attacked and successfully robbed of food by conspecifics. Grackles could reduce the probability of kleptoparasitism by holding items in the bill while dunking and engaging in head-up displays. These behaviours were used flexibly depending on variation in the risk of kleptoparasitism. We suggest that costs like the ones incurred from theft might limit the profitability and frequency of tool and proto-tool food processing behaviours, creating a context where counter-strategies might be selected.

Analysis of Variance↗
PubMed2006

Large brains and lengthened life history periods in Odontocetes.

Previous work on primates and birds suggests that large brains require longer periods of juvenile growth, leading to reproductive constraints due to delayed maturation. However, longevity is often extended in large-brained species, possibly compensating for delayed maturation. We examined the relationship between brain size and life history periods in cetaceans, a large-brained mammalian order that has been largely ignored. We looked at males and females of twenty-five species of Odontocetes, using independent contrasts and multiple regressions to disentangle possible phylogenetic effects and inter-correlations among life history traits. We corrected all variables for body size allometry and separated life span into adult and juvenile periods. For females and both sexes combined, gestation, time to sexual maturity, time as an adult and life span were all positively associated with residual brain size in simple regressions; in multiple regressions, maximum life span and time as an adult were the best predictors of brain size. Males showed few significant trends. Our results suggest that brain size has co-evolved with extended life history periods in Odontocetes, as it has in primates and birds, and that a lengthened adult period could have been an important component of encephalization in cetaceans.

Animals↗
PubMed2005

Brain size, innovative propensity and migratory behaviour in temperate Palaearctic birds.

The evolution of migration in birds remains an outstanding, unresolved question in evolutionary ecology. A particularly intriguing question is why individuals in some species have been selected to migrate, whereas in other species they have been selected to be sedentary. In this paper, we suggest that this diverging selection might partially result from differences among species in the behavioural flexibility of their responses to seasonal changes in the environment. This hypothesis is supported in a comparative analysis of Palaearctic passerines. First, resident species tend to rely more on innovative feeding behaviours in winter, when food is harder to find, than in other seasons. Second, species with larger brains, relative to their body size, and a higher propensity for innovative behaviours tend to be resident, while less flexible species tend to be migratory. Residence also appears to be less likely in species that occur in more northerly regions, exploit temporally available food sources, inhabit non-buffered habitats and have smaller bodies. Yet, the role of behavioural flexibility as a response to seasonal environments is largely independent of these other factors. Therefore, species with greater foraging flexibility seem to be able to cope with seasonal environments better, while less flexible species are forced to become migratory.

Analysis of Variance↗
PubMed2005

Big brains, enhanced cognition, and response of birds to novel environments.

The widely held hypothesis that enlarged brains have evolved as an adaptation to cope with novel or altered environmental conditions lacks firm empirical support. Here, we test this hypothesis for a major animal group (birds) by examining whether large-brained species show higher survival than small-brained species when introduced to nonnative locations. Using a global database documenting the outcome of >600 introduction events, we confirm that avian species with larger brains, relative to their body mass, tend to be more successful at establishing themselves in novel environments. Moreover, we provide evidence that larger brains help birds respond to novel conditions by enhancing their innovation propensity rather than indirectly through noncognitive mechanisms. These findings provide strong evidence for the hypothesis that enlarged brains function, and hence may have evolved, to deal with changes in the environment.

Animals↗
PubMed2005

Behavioral drive or behavioral inhibition in evolution: subspecific diversification in Holarctic passerines.

Behavioral changes have long been hypothesized to be an important driver of evolutionary diversification in animals, as they expose individuals to new environmental pressures and thus favor evolutionary divergence. There have been few empirical tests of this hypothesis, however, and the mechanisms linking behavioral changes and diversification processes remain controversial. We show here that Holarctic passerines with large brain size relative to body size, a character correlated with a high propensity for behavioral changes, generally have experienced more extensive subspecific diversification. This effect appears to be largely independent of other well-known mechanisms thought to promote diversification. As suggested by path analysis, relative brain size seems to affect diversification directly rather than indirectly through its presumed effect on range expansion, which is consistent with the original formulation of the behavioral drive hypothesis. Thus, the results support the long-held, intuitive hypothesis that behavioral changes facilitate evolutionary diversification.

Animals↗
PubMed2004

Distraction sneakers decrease the expected level of aggression within groups: a game-theoretic model.

Hawk-dove games have been extensively used to predict the conditions under which group-living animals should defend their resources against potential usurpers. Typically, game-theoretic models on aggression consider that resource defense may entail energetic and injury costs. However, intruders may also take advantage of owners who are busy fighting to sneak access to unguarded resources, imposing thereby an additional cost on the use of the escalated hawk strategy. In this article we modify the two-strategy hawk-dove game into a three-strategy hawk-dove-sneaker game that incorporates a distraction-sneaking tactic, allowing us to explore its consequences on the expected level of aggression within groups. Our model predicts a lower proportion of hawks and hence lower frequencies of aggressive interactions within groups than do previous two-strategy hawk-dove games. The extent to which distraction sneakers decrease the frequency of aggression within groups, however, depends on whether they search only for opportunities to join resources uncovered by other group members or for both unchallenged resources and opportunities to usurp.

Aggression↗
PubMed2004

Loss-of-imprinting of Peg1 in mouse interspecies hybrids is correlated with altered growth.

Previous studies have shown that loss-of-imprinting (LOI) is a regular occurrence in interspecies hybrids of the genus Peromyscus. Furthermore, evidence was presented that indicated that LOI is involved in a placental hybrid dysgenesis effect resulting in abnormal placental growth and thus possibly in speciation. We show here that LOI of the strictly paternally expressed gene Peg1 (also called Mest) occurs in F1 hybrids between Mus musculus (MMU) and M. spretus (MSP). Peg1 LOI is correlated with increased body weight and increased weight of two of the organs tested, kidney and spleen. X-gal staining of tissues derived from Peg1(+/-) x MSP F1 mice, carrying a maternal LacZ knock-in allele of Peg1, demonstrates that LOI is stochastic in that it affects different tissues to variable extents and that, even within one tissue, not all cells are similarly affected. Furthermore, this expression from the maternal allele does not necessarily follow the endogenous paternal Peg1 expression pattern. Our results indicate that LOI occurs in interspecies hybrids in the genus Mus and that altered growth is a frequent outcome of LOI.

Animals↗
PubMed2004

Brains, innovations and evolution in birds and primates.

Several comparative research programs have focused on the cognitive, life history and ecological traits that account for variation in brain size. We review one of these programs, a program that uses the reported frequency of behavioral innovation as an operational measure of cognition. In both birds and primates, innovation rate is positively correlated with the relative size of association areas in the brain, the hyperstriatum ventrale and neostriatum in birds and the isocortex and striatum in primates. Innovation rate is also positively correlated with the taxonomic distribution of tool use, as well as interspecific differences in learning. Some features of cognition have thus evolved in a remarkably similar way in primates and at least six phyletically-independent avian lineages. In birds, innovation rate is associated with the ability of species to deal with seasonal changes in the environment and to establish themselves in new regions, and it also appears to be related to the rate at which lineages diversify. Innovation rate provides a useful tool to quantify inter-taxon differences in cognition and to test classic hypotheses regarding the evolution of the brain.

Animals↗
PubMed1985

Parturition in non-human primates: pain and auditory concealment.

Descriptions of parturition are reviewed for 88 individuals in 29 species of captive and wild non-human primates. Mild or severe discomfort, in the form of straining, stretching, arching, grimacing, writhing, shaking, doubling up, eye closure and restlessness is reported in 69 cases. Silence and utterance of moderate-level vocalizations are reported in 21 and 43 cases, respectively. The overall pattern indicates that parturition in non-human primates is characterized by a significant degree of pain and discomfort, while vocal responses to pain are generally subdued. We suggest that analgesia is the mechanism, and concealment of the parturient female the adaptive significance behind this blocking of vocal pain responses.

Animals↗