Extraordinary large brains in tool-using New Caledonian crows

gerd knaebe

The centipede fauna was very poor, altogether represented by four species, only Lithobius curtipes being shared by all sites. The myriapod communities from the swampy alder woods (Ribeso nigri Alnetum) at Biebrza and in the Bia³owieŜa Primeval Forest were mainly under the influence of fertility soil parameters (available and total phosphorus contents) while the assemblage from an alder swamp at Narew was largely affected by soil humidity. Apparently, the community from an ash-alder alluvial wood (Fraxino-Alnetum) sampled in the Bia³owieŜa Primeval Forest mostly depended on soil pH. Comparing all available information, the structure of myriapod assemblages seems to be quite similar even over distant regions in Central Europe.

We show here that relative size of the neostriatum and whole brain distinguish the true and borderline categories in birds using tools to obtain food or water. From two sources, the specialized literature on tools and an innovation data base gathered in the short note sections of 68 journals in 7 areas of the world, we collected 39 true (e.g. use of probes, hammers, sponges, scoops) and 86 borderline (e.g. bait fishing, battering and dropping on anvils, holding with wedges and skewers) cases of tool use in 104 species from 15 parvorders. True tool users have a larger mean residual brain size (regressed against body weight) than do users of borderline tools, confirming the distinction in the literature. In multiple regressions, residual brain size and residual size of the neostriatum (one of the areas in the avian telencephalon thought to be equivalent to the mammalian neocortex) are the best predictors of true tool use reports per taxon.

We tested the hypothesis that sexual selection for complex motor displays has selected for larger brains across the Pipridae. We found that display complexity positively predicts relative brain weight (adjusted for body size) after controlling for phylogeny in 12 manakin species and a closely related flycatcher. This evidence suggests that brain size has evolved in response to sexual selection to facilitate aspects of display such as motor, sensorimotor, perceptual, and cognitive abilities. We show, for the first time, that sexual selection for acrobatic motor behaviour can drive brain size evolution in avian species and, in particular, a family of suboscine birds. © 2015 S.

Furthermore, motor diversity constitutes a proximate link between diet generalism and innovativeness. Acrobatic display behaviour is sexually selected in manakins (Pipridae) and can place high demands on many neural systems.

The presence of saprophagous millipede species showed a clear succession in parallel with mine-site development, but there is no species with true pioneer behaviour. Centipedes – with Lamyctes emarginatus as a true pioneer – as predators behave less predictably; Geophilomorphs, hunting in the subsoil, are the last to invade. After 50 years of development of mine-site woodlands, five species of millipedes and six species of centipedes, though common in adjacent reference woodlands, had not yet colonised the mine sites.

Comparisons between myriapod assemblages at mine sites in Upper and Lower Lusatia that had different soil and age conditions revealed that myriapods are good indicators of biological soil quality and are reliable and easy to use. Using soil sampling and subsequent heat extraction of animals, four alder stands in the wetlands of the Biebrza, Narew and Bia³owieŜa national parks, north-eastern Poland, were surveyed for millipedes and centipedes. Among 12 millipede species revealed, Xestoiulus laeticollis, Polydesmus complanatus and Craspedosoma rawlinsii occurred and predominated in all alder woods.

Especially at sites that passed three investigations already, major changes become discernible. If the temporal variation goes in the same direction throughout the time series, it is considered a trend.

A key component of the model is the possibility that the association between cognition (ie, brain size) and innovativeness is not causal. Rather, it arises as a consequence of correlated evolution because both cognition and diet generalism evolve in response to environmental variability.

By these standards, a vulture breaking an egg by hitting it with a stone uses a tool, but a gull dropping an egg on a rock does not. This distinction between true and borderline (or proto-tool) cases has been criticized for its arbitrariness and anthropocentrism.

We draw attention to the high degree of inconsistency among empirical findings relating interindividual variation in innovativeness to interindividual variation in learning performance. We go on to propose a model that reconciles the possible (but perhaps controversial) existence of positive associations between cognition and innovation at the cross-taxon level with inconsistent associations at the within-species level.

Innovation rate is the best predictor of borderline tool use distribution. Despite the strong concentration of true tool use cases in Corvida and Passerida, independent constrasts suggest that common ancestry is not responsible for the association between tool use and size of the neostriatum and whole brain.

gerd knaebe

Leave a Reply

Your email address will not be published. Required fields are marked *