The uniqueness of Daubentonia

The aberrant features of the genus Daubentonia, such as the superficially rodent-like dentition, the globose and foreshortened brain case, and the filiform third manual digit have long been known. But the current assessment of the genus as lemuriform, and within that group as closest to the indriids, depends upon greater weight being placed upon other characteristics such as the cranial arterial pattern, the molariform teeth, and the developmental characteristics of the dentition. Prior multivariate morphometric studies have shown that though the shoulder structure of Daubentonia is uniquely different from that of all other primates, the structure of its pelvis may not be especially different from that of many relatively non-specialized primates. A large series of studies have been summated here in which many different anatomical regions (shoulder, arm, forearm, forelimb as a whole, pelvis, femur, hindlimb as a whole, forelimb and hindlimb combined, and total bodily proportions including limbs, trunk, and head) have been characterized osteometrically in a wide range of primate genera. The resulting data sets have been studied by discriminant function analyses. The differences that have been found are large enough that it can be confidently asserted that in its postcranial skeleton, Daubentonia is more different from the primates as a whole than is any other primate genus. These differences are big enough that their statistical and biological significance is not at all in doubt, notwithstanding the very small numbers of available specimens of this rare genus. They are so great that functional implications exist though they cannot, in our present state of knowledge of the habits of the genus, be ascribed with any certainty. They are so great indeed, paralleling the enormous differences of Daubentonia from other primates in its dentition, skull and cheiridia, that we may prefer to keep open minds about its taxonomic placement.     

Was the Oligo‐Miocene Australian metatherian Yalkaparidon a ‘mammalian woodpecker’?

One of the most striking examples of convergent evolution within mammals is the suite of anatomical specializations shared by the primate Daubentonia of Madagascar and the marsupial Dactylopsila of Australia and New Guinea. Having last shared a common ancestor over 125 million years ago, these two genera have independently evolved extremely similar adaptations for feeding on xylophagous (wood-boring) insect larvae. These include enlarged incisors to gouge holes in wood, cranial modifications to strengthen the skull against the stresses generated by wood gouging and elongate manual digits that are used as probes to extract the larvae. Elsewhere in the world, the same ecological niche is filled by birds (woodpeckers or morphologically convergent forms) that use their beaks for wood gouging. An extinct group of eutherian mammals, the apatemyids, exhibit very similar craniodental and postcranial adaptations to Daubentonia and Dactylopsila and presumably also occupied the woodpecker niche. A qualitative analysis of characters of the skull and dentition of the enigmatic Oligo-Miocene Australian metatherian Yalkaparidon – specifically its combination of very large, open-rooted incisors, zalambdodont molars and features to strengthen the skull against rostral bending – supports the hypothesis that it is probably a fourth 'mammalian woodpecker'. Discovery of the (as yet unknown) manus of Yalkaparidon will test this hypothesis by revealing whether any of its digits are elongate.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 97 , 1–17.     

Percussive Foraging: Stimuli for Prey Location by Aye-Ayes (Daubentonia madagascariensis)

Aye-ayes (Daubentonia madagascariensis) use the thin middle finger to tap on wood in search of subsurface cavities containing insect larvae. When a cavity is located, they gnaw away wood until the prey can be extracted. Previous researchers suggested that acoustical cues reveal cavity location. We designed five studies to identify the cavity features that provide acoustical cues. When cavities were backfilled with gelatin or acoustical foam, excavation was still successful, suggesting that the reverberation of sound in air-filled cavities is not necessary for detection. Moreover, when the density of cavity content was varied, there was no difference in excavation frequency. On the other hand, a one-dimensional break in the subsurface wood was an effective stimulus for excavation. These studies suggest that a simple interface beneath the surface is sufficient to elicit excavation and that neither prey nor cavity nor even small air pockets are necessary to elicit the behavior. These results raise provocative questions as to how the aye-aye manages to forage efficiently.     

Patterns and laterality of hand use in free-ranging aye-ayes (<Emphasis Type="Italic">Daubentonia madagascariensis</Emphasis>) and a comparison with captive studies

We observed hand use in free-ranging aye-ayes (Daubentonia madagascariensis) on an island in the Mananara River, eastern Madagascar. The results were compared with those of two conflicting studies on hand laterality in captive aye-ayes. We argue that patterns of hand preference in wild aye-ayes are comparable to those of captive animals and that discrepancies between studies are—at least partly—caused by different ways of collecting and processing data. Aye-ayes fit Level 2 of the categories of hand laterality described by McGrew and Marchant (Yearb Phys Anthropol 40:201–232, 1997), with some individuals showing significant hand preference, but with the proportion of right- to left-preferent animals being very close to 1:1. We observed hand preference to be consistent for two of the most frequent behaviors, tapping and probing with fingers. Reaching and holding objects in hands is rare in aye-ayes, and the patterns of hand use in aye-ayes are therefore not directly comparable with those of other prosimians in which laterality has been studied. We detected no effect of sex on hand preference and were unable to determine whether there is an effect of age. The posture adopted by the animals did not influence hand preference.     

Two misconceptions of phylogeny and classification

A recent contribution embodies the assumptions that organisms may be excluded from relationship with others on the basis of autopomorphy, and that its position in a classification is an inherent characteristic of an organism. Both of these assumptions are fallacious.     

Commentary on two misconceptions of phylogeny and classification

A recent brief communication criticizes a morphometric study of the structure of Daubentonia (Oxnard, 1981). The criticisms are invalid because they apply to the concept of the detailed character state in a localized anatomical region, a type of morphological information different than the broad measurement that embodies many characters. The criticisms themselves display, moreover, exactly those problems of prior assumption that the underlying philosophy of multivariate morphometric studies as used by Oxnard (1981) tries to eliminate.     

A note on the diet and feeding behavior of the aye-ayeDaubentonia madagascariensis

In the course of a 4-day expedition to the island of Nosy Mangabe in northeastern Madagascar, two aye-ayes were separately sighted, observed feeding and moving, and photographed. These observations confirm recent reports of the continued existence of aye-ayes on the island following the translocation of nine individuals from the mainland in 1967. An adult male aye-aye was seen feeding on the gall-like growths covering much of the bark surface of an Afzelia bijugatree and eating the insects these contained. The same individual also fed briefly on shoots of the bamboo Bambusa vulgaris.     

Feeding sites for extractive foraging by the aye-aye,Daubentonia madagascariensis

The aye-aye, Daubentonia madagascariensis, uses its middle digit to tap on woody sources in search of subsurface cavities containing prey. The acoustical properties of these cavities are thought to be important to this percussive foraging, but the contributions of cavity size, configuration, and contents to efficient prey capture are not known. The purpose of this study was to characterize these cavities and their residents. An analysis of foraged trees at two sites in Madagascar revealed that many of the foraged cavities are mines bored by large cerambycid beetle larvae. Apparently cerambycids, as well as inquiline residents of their mines, are major targets of aye-aye foraging behavior. The larvae bore extended mines that course approximately parallel to the long axes of the trees in which they reside. The orientation and large size of the mines offer an acoustical trail that the aye-aye may follow to its prey. © 1995 Wiley-Liss, Inc.