Abstract
New Caledonian crows exhibit considerable variation in tool making between populations. Here, we present the first study of the species’ genetic structure over its geographical distribution. We collected feathers from crows on mainland Grande Terre, the inshore island of Toupéti, and the nearby island of Maré where it is believed birds were introduced after European colonisation. We used nine microsatellite markers to establish the genotypes of 136 crows from these islands and classical population genetic tools as well as Approximate Bayesian Computations to explore the distribution of genetic diversity. We found that New Caledonian crows most likely separate into three main distinct clusters: Grande Terre, Toupéti and Maré. Furthermore, Toupéti and Maré crows represent a subset of the genetic diversity observed on Grande Terre, confirming their mainland origin. The genetic data are compatible with a colonisation of Maré taking place after European colonisation around 1900. Importantly, we observed (1) moderate, but significant, genetic differentiation across Grande Terre, and (2) that the degree of differentiation between populations on the mainland increases with geographic distance. These data indicate that despite individual crows’ potential ability to disperse over large distances, most gene flow occurs over short distances. The temporal and spatial patterns described provide a basis for further hypothesis testing and investigation of the geographical variation observed in the tool skills of these crows.
Highlights
New Caledonian crows (Corvus moneduloides) are omnivorous forest birds endemic to the French Territory of New Caledonia
Population Delimitation and Genetic Diversity Clustering analysis conducted on the whole dataset indicates that the most likely number of distinct genetic entities is K = 3, approximately representing the islands of Grande Terre, Mareand Toupeti
We conducted the first study of the population genetic structure of the tool-using New Caledonian crow over its geographical range
Summary
New Caledonian crows (Corvus moneduloides) are omnivorous forest birds endemic to the French Territory of New Caledonia. They live on only two of the larger islands of New Caledonia: Grande Terre and Mare [1] (figure 1). Crows stand out amongst nonhuman animals because of their ability to both manufacture and use tools in seemingly sophisticated ways to extract small prey from vegetation. They are the only species other than humans known to create and use hook tools [2]. They produce two distinct types of hook tool: those made from live twigs and similar stick-like material [2,3], and those made from the barbed edges of Pandanus spp. leaves [2,4]
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